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2017

Chromatin organization revealed by nanostructure of irradiation induced γH2AX, 53BP1 and Rad51 foci
J. Reindl, S. Girst, D.W.M. Walsh, C. Greubel, B. Schwarz, C. Siebenwirth, G.A. Drexler, A.A. Friedl and G. Dollinger; Scientific Reports 7 (2017) 40616.
Abstract: The spatial distribution of DSB repair factors γH2AX, 53BP1 and Rad51 in ionizing radiation induced foci (IRIF) in HeLa cells using super resolution STED nanoscopy after low and high linear energy transfer (LET) irradiation was investigated. 53BP1 and γH2AX form IRIF with same mean size of (540 ± 40) nm after high LET irradiation while the size after low LET irradiation is significantly smaller. The IRIF of both repair factors show nanostructures with partial anti-correlation. These structures are related to domains formed within the chromatin territories marked by γH2AX while 53BP1 is mainly situated in the perichromatin region. The nanostructures have a mean size of (129 ± 6) nm and are found to be irrespective of the applied LET and the labelled damage marker. In contrast, Rad51 shows no nanostructure and a mean size of (143 ± 13) nm independent of LET. Although Rad51 is surrounded by 53BP1 it strongly anti-correlates meaning an exclusion of 53BP1 next to DSB when decision for homologous DSB repair happened.
BibTeX:
	@article{Reindl2017,
	  author = {Reindl, Judith and Girst, Stefanie and Walsh, Dietrich W. M. and Greubel, Christoph and Schwarz, Benjamin and Siebenwirth, Christian and Drexler, Guido A. and Friedl, Anna A. and Dollinger, Günther},
	  title = {Chromatin organization revealed by nanostructure of irradiation induced γH2AX, 53BP1 and Rad51 foci},
	  journal = {Scientific Reports},
	  year = {2017},
	  volume = {7},
	  pages = {40616},
	  url = {http://www.nature.com/articles/srep40616},
	  doi = {http://doi.org/10.1038/srep40616}
	}
	
The influence of reference radiation photon energy on high-LET RBE: comparison of human peripheral lymphocytes and human--hamster hybrid AL cells
T.E. Schmid, C. Greubel, G. Dollinger and E. Schmid; Radiation and Environmental Biophysics (2017) 1-9.
Abstract: The relative biological effectiveness (RBE) based on the induction of dicentrics in any cell type is principally an important information for the increasing application of high-LET radiation in cancer therapy. Since the standard system of human lymphocytes for measuring dicentrics are not compatible with our microbeam irradiation setup where attaching cells are essential, we used human--hamster hybrid AL cells which do attach on foils and fulfil the special experimental requirement for microbeam irradiations. In this work, the dose--response of AL cells to photons of different energy, 70 and 200 kV X-rays and 60Co γ-rays, is characterized and compared to human lymphocytes. The total number of induced dicentrics in AL cells is approximately one order of magnitude smaller. Despite the smaller α and β parameters of the measured linear--quadratic dose--response relationship, the α/β-ratio versus photon energy dependence is identical within the accuracy of measurement for AL cells and human lymphocytes. Thus, the influence of the reference radiation used for RBE determination is the same. For therapy relevant doses of 2 Gy (60Co equivalent), the difference in RBE is around 20% only. These findings indicate that the biological effectiveness in AL cells can give important information for human cells, especially for studies where attaching cells are essential.
BibTeX:
	@article{Schmid2017,
	  author = {Schmid, T. E. and Greubel, C. and Dollinger, G. and Schmid, E.},
	  title = {The influence of reference radiation photon energy on high-LET RBE: comparison of human peripheral lymphocytes and human--hamster hybrid AL cells},
	  journal = {Radiation and Environmental Biophysics},
	  year = {2017},
	  pages = {1--9},
	  url = {http://link.springer.com/article/10.1007%2Fs00411-016-0680-3},
	  doi = {http://doi.org/10.1007/s00411-016-0680-3}
	}
	
Live cell imaging of mitochondria following targeted irradiation in situ reveals rapid and highly localized loss of membrane potential
D.W.M. Walsh, C. Siebenwirth, C. Greubel, K. Ilicic, J. Reindl, S. Girst, G. Muggiolu, M. Simon, P. Barberet, H. Seznec, H. Zischka, G. Multhoff, T.E. Schmid and G. Dollinger; Scientific Reports 7 (2017) 46684.
Abstract: The reliance of all cell types on the mitochondrial function for survival makes mitochondria an interesting target when trying to understand their role in the cellular response to ionizing radiation. By harnessing highly focused carbon ions and protons using microbeams, we have performed in situ live cell imaging of the targeted irradiation of individual mitochondria stained with Tetramethyl rhodamine ethyl ester (TMRE), a cationic fluorophore which accumulates electrophoretically in polarized mitochondria. Targeted irradiation with both carbon ions and protons down to beam spots of
BibTeX:
	@article{Walsh2017,
	  author = {Walsh, Dietrich W. M. and Siebenwirth, Christian and Greubel, Christoph and Ilicic, Katarina and Reindl, Judith and Girst, Stefanie and Muggiolu, Giovanna and Simon, Marina and Barberet, Philippe and Seznec, Hervé and Zischka, Hans and Multhoff, Gabriele and Schmid, Thomas E. and Dollinger, Guenther},
	  title = {Live cell imaging of mitochondria following targeted irradiation in situ reveals rapid and highly localized loss of membrane potential},
	  journal = {Scientific Reports},
	  year = {2017},
	  volume = {7},
	  pages = {46684},
	  url = {https://www.nature.com/articles/srep46684},
	  doi = {http://doi.org/10.1038/srep46684}
	}
	

2016

Position and time resolution measurements with a microchannel plate image intensifier: A comparison of monolithic and pixelated CeBr3 scintillators
U. Ackermann, S. Eschbaumer, A. Bergmaier, W. Egger, P. Sperr, C. Greubel, B. Löwe, P. Schotanus and G. Dollinger; Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 823 (2016) 56 - 64.
Abstract: Abstract To perform Four Dimensional Age Momentum Correlation measurements in the near future, where one obtains the positron lifetime in coincidence with the three dimensional momentum of the electron annihilating with the positron, we have investigated the time and position resolution of two CeBr3 scintillators (monolithic and an array of pixels) using a Photek IPD340/Q/BI/RS microchannel plate image intensifier. The microchannel plate image intensifier has an active diameter of 40 mm and a stack of two microchannel plates in chevron configuration. The monolithic CeBr3 scintillator was cylindrically shaped with a diameter of 40 mm and a height of 5 mm. The pixelated scintillator array covered the whole active area of the microchannel plate image intensifier and the shape of each pixel was 2.5·2.5·8 mm3 with a pixel pitch of 3.3 mm. For the monolithic setup the measured mean single time resolution was 330 ps (FWHM) at a gamma energy of 511 keV. No significant dependence on the position was detected. The position resolution at the center of the monolithic scintillator was about 2.5 mm (FWHM) at a gamma energy of 662 keV. The single time resolution of the pixelated crystal setup reached 320 ps (FWHM) in the region of the center of the active area of the microchannel plate image intensifier. The position resolution was limited by the cross-section of the pixels. The gamma energy for the pixel setup measurements was 511 keV.
BibTeX:
	@article{Ackermann2016,
	  author = {Ulrich Ackermann and Stephan Eschbaumer and Andreas Bergmaier and Werner Egger and Peter Sperr and Christoph Greubel and Benjamin Löwe and Paul Schotanus and Günther Dollinger},
	  title = {Position and time resolution measurements with a microchannel plate image intensifier: A comparison of monolithic and pixelated CeBr3 scintillators},
	  journal = {Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment},
	  year = {2016},
	  volume = {823},
	  pages = {56 -- 64},
	  url = {http://www.sciencedirect.com/science/article/pii/S016890021630153X},
	  doi = {http://doi.org/10.1016/j.nima.2016.03.110}
	}
	
Four-dimensional positron age-momentum correlation
U. Ackermann, B. Löwe, M. Dickmann, J. Mitteneder, P. Sperr, W. Egger, M. Reiner and G. Dollinger; New Journal of Physics 18 (11) (2016) 113030.
Abstract: We have performed first four-dimensional age-momentum correlation (4D-AMOC) measurements at a pulsed high intensity positron micro beam and determined the absolute value of the three-dimensional momentum of the electrons annihilating with the positrons in coincidence with the positron age in the sample material. We operated two position sensitive detectors in coincidence to measure the annihilation radiation: a pixelated HPGe-detector and a microchannel plate image intensifier with a CeBr 3 scintillator pixel array. The transversal momentum resolution of the 4D-AMOC setup was measured to be about 17 × 10e-3 (FWHM) and was circa 3.5 times larger than the longitudinal momentum resolution. The total time resolution was 540 ps (FWHM). We measured two samples: a gold foil and a carbon tape at a positron implantation energy of 2 keV. For each sample discrete electron momentum states and their respective positron lifetimes were extracted.
BibTeX:
	@article{Ackermann2016a,
	  author = {Ulrich Ackermann and Benjamin Löwe and Marcel Dickmann and Johannes Mitteneder and Peter Sperr and Werner Egger and Markus Reiner and Günther Dollinger},
	  title = {Four-dimensional positron age-momentum correlation},
	  journal = {New Journal of Physics},
	  year = {2016},
	  volume = {18},
	  number = {11},
	  pages = {113030},
	  url = {http://stacks.iop.org/1367-2630/18/i=11/a=113030},
	  doi = {http://doi.org/10.1088/1367-2630/18/11/113030}
	}
	
A New Nanobody-Based Biosensor to Study Endogenous PARP1 In Vitro and in Live Human Cells
A. Buchfellner, L. Yurlova, S. Nüske, A.M. Scholz, J. Bogner, B. Ruf, K. Zolghadr, S.E. Drexler, G.A. Drexler, S. Girst, C. Greubel, J. Reindl, C. Siebenwirth, T. Romer, A.A. Friedl and U. Rothbauer; PLOS ONE 11 (3) (2016) 1-23.
Abstract: Poly(ADP-ribose) polymerase 1 (PARP1) is a key player in DNA repair, genomic stability and cell survival and it emerges as a highly relevant target for cancer therapies. To deepen our understanding of PARP biology and mechanisms of action of PARP1-targeting anti-cancer compounds, we generated a novel PARP1-affinity reagent, active both in vitro and in live cells. This PARP1-biosensor is based on a PARP1-specific single-domain antibody fragment (  15 kDa), termed nanobody, which recognizes the N-terminus of human PARP1 with nanomolar affinity. In proteomic approaches, immobilized PARP1 nanobody facilitates quantitative immunoprecipitation of functional, endogenous PARP1 from cellular lysates. For cellular studies, we engineered an intracellularly functional PARP1 chromobody by combining the nanobody coding sequence with a fluorescent protein sequence. By following the chromobody signal, we were for the first time able to monitor the recruitment of endogenous PARP1 to DNA damage sites in live cells. Moreover, tracing of the sub-nuclear translocation of the chromobody signal upon treatment of human cells with chemical substances enables real-time profiling of active compounds in high content imaging. Due to its ability to perform as a biosensor at the endogenous level of the PARP1 enzyme, the novel PARP1 nanobody is a unique and versatile tool for basic and applied studies of PARP1 biology and DNA repair.
BibTeX:
	@article{Buchfellner2016,
	  author = {Buchfellner, Andrea AND Yurlova, Larisa AND Nüske, Stefan AND Scholz, Armin M. AND Bogner, Jacqueline AND Ruf, Benjamin AND Zolghadr, Kourosh AND Drexler, Sophie E. AND Drexler, Guido A. AND Girst, Stefanie AND Greubel, Christoph AND Reindl, Judith AND Siebenwirth, Christian AND Romer, Tina AND Friedl, Anna A. AND Rothbauer, Ulrich},
	  title = {A New Nanobody-Based Biosensor to Study Endogenous PARP1 In Vitro and in Live Human Cells},
	  journal = {PLOS ONE},
	  year = {2016},
	  volume = {11},
	  number = {3},
	  pages = {1-23},
	  url = {http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0151041},
	  doi = {http://doi.org/10.1371/journal.pone.0151041}
	}
	
Radio frequency elevator for a pulsed positron beam
M. Dickmann, J. Mitteneder, G. Kögel, W. Egger, P. Sperr, U. Ackermann, C. Piochacz and G. Dollinger; Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 821 (2016) 40 - 43.
Abstract: Abstract An elevator increases the potential energy of a particle beam with respect to ground potential without any alteration of kinetic energy and other beam parameters. This elevator is necessary for the implementation of the Munich Scanning Positron Microscope (SPM) at the intense positron source NEPOMUC at the research reactor FRM II in Munich. The principles of the rf elevator for pure electrostatically guided positrons are described. Measurements of beam quality behind the elevator are reported, which confirm that after the implementation of elevator and SPM at NEPOMUC the SPM can be operated at a considerably improved resolution (  0.3 μm) and event rate ( 3.7 kHz) compared to the laboratory based β+-source.
BibTeX:
	@article{Dickmann2016,
	  author = {Marcel Dickmann and Johannes Mitteneder and Gottfried Kögel and Werner Egger and Peter Sperr and Ulrich Ackermann and Christian Piochacz and Günther Dollinger},
	  title = {Radio frequency elevator for a pulsed positron beam},
	  journal = {Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment},
	  year = {2016},
	  volume = {821},
	  pages = {40 -- 43},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168900216300298},
	  doi = {http://doi.org/10.1016/j.nima.2016.03.011}
	}
	
An apparatus for determining an energy deposition of an ion beam
G. Dollinger, K. Parodi, W. Assmann, V. Nitziachristos and S. Kellnberger; Patent, Universität der Bundeswehr München, 85577 Neubiberg and Ludwig-Maximilians-Universität München, 80539 München, EP 2974 771, 2016.
BibTeX:
	@patent{Dollinger2016,
	  author = {Dollinger, Günther and Parodi, Katia and Assmann, Walter and Nitziachristos, Vasilis and Kellnberger, Stephan},
	  title = {An apparatus for determining an energy deposition of an ion beam},
	  type = {Patent},
	  holder = {Universität der Bundeswehr München, 85577 Neubiberg and Ludwig-Maximilians-Universität München, 80539 München},
	  year = {2016},
	  volume = {EP 2974 771},
	  url = {https://register.epo.org/application?number=EP14182487}
	}
	
A position sensitive time of flight detector for heavy ion ERD
S. Eschbaumer, A. Bergmaier and G. Dollinger; Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 371 (2016) 125-131.
Abstract: Abstract A new 2D position sensitive time of flight detector for heavy ion ERD has been developed. The detector features separate time and position measurement in a straight geometry. An electrostatic lens focuses the secondary electrons ejected from a carbon foil onto a channel plate stack maintaining the position information despite the electron momentum distribution. For position readout a 2D Backgammon anode is used. A position resolution of
BibTeX:
	@article{Eschbaumer2016,
	  author = {Eschbaumer, S. and Bergmaier, A. and Dollinger, G.},
	  title = {A position sensitive time of flight detector for heavy ion ERD},
	  booktitle = {The 22nd International Conference on Ion Beam Analysis (IBA 2015)},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms},
	  year = {2016},
	  volume = {371},
	  pages = {125--131},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X15008952},
	  doi = {http://doi.org/10.1016/j.nimb.2015.09.036}
	}
	
Proton Minibeam Radiation Therapy Reduces Side Effects in an In Vivo Mouse Ear Model
S. Girst, C. Greubel, J. Reindl, C. Siebenwirth, O. Zlobinskaya, D. Walsh, K. Ilicic, M. Aichler, A. Walch, J. Wilkens, G. Multhoff, G. Dollinger and T. Schmid; International Journal of Radiation Oncology * Biology * Physics 95 (2016) 234-241.
Abstract: Purpose: Proton minibeam radiation therapy is a novel approach to minimize normal tissue damage in the entrance channel by spatial fractionation while keeping tumor control through a homogeneous tumor dose using beam widening with an increasing track length. In the present study, the dose distributions for homogeneous broad beam and minibeam irradiation sessions were simulated. Also, in an animal study, acute normal tissue side effects of proton minibeam irradiation were compared with homogeneous irradiation in a tumor-free mouse ear model to account for the complex effects on the immune system and vasculature in an in vivo normal tissue model.

Methods and Materials: At the ion microprobe SNAKE, 20-MeV protons were administered to the central part (7.2 x 7.2 mm2) of the ear of BALB/c mice, using either a homogeneous field with a dose of 60 Gy or 16 minibeams with a nominal 6000 Gy (4 x 4 minibeams, size 0.18 x 0.18 mm2, with a distance of 1.8 mm). The same average dose was used over the irradiated area.

Results: No ear swelling or other skin reactions were observed at any point after minibeam irradiation. In contrast, significant ear swelling (up to fourfold), erythema, and desquamation developed in homogeneously irradiated ears 3 to 4 weeks after irradiation. Hair loss and the disappearance of sebaceous glands were only detected in the homogeneously irradiated fields.

Conclusions: These results show that proton minibeam radiation therapy results in reduced adverse effects compared with conventional homogeneous broad-beam irradiation and, therefore, might have the potential to decrease the incidence of side effects resulting from clinical proton and/or heavy ion therapy.

BibTeX:
	@article{Girst2016,
	  author = {Girst, S. and Greubel, C. and Reindl, J. and Siebenwirth, C. and Zlobinskaya, O. and Walsh, D.W.M. and Ilicic, K. and Aichler, M. and Walch, A. and Wilkens, J.J. and Multhoff, G. and Dollinger, G. and Schmid, T.E.},
	  title = {Proton Minibeam Radiation Therapy Reduces Side Effects in an In Vivo Mouse Ear Model},
	  journal = {International Journal of Radiation Oncology * Biology * Physics},
	  year = {2016},
	  volume = {95},
	  pages = {234--241},
	  url = {http://www.sciencedirect.com/science/article/pii/S0360301615265856},
	  doi = {http://doi.org/10.1016/j.ijrobp.2015.10.020}
	}
	
Proton Minibeam Radiotherapy
Stefanie Girst; Dissertation, Universität der Bundeswehr München, 2016.
Abstract: The risk of developing adverse side effects in the normal tissue after radiotherapy is often limiting for the dose that can be applied to the tumor. Proton minibeam radiotherapy, a spatially fractionated radiotherapy method using sub-millimeter proton beams, similar to grid therapy or microbeam radiation radiotherapy (MRT) using X-rays, has recently been invented at the ion microprobe SNAKE in Munich. The aim of this new concept is to minimize normal tissue injuries in the entrance channel and especially in the skin by irradiating only a small percentage of the cells in the total irradiation field, while maintaining tumor control via a homogeneous dose in the tumor, just like in conventional broad beam radiotherapy. This can be achieved by optimizing minibeam sizes and distances according to the prevailing tumor size and depth such that after widening of the minibeams due to proton interactions in the tissue, the overlapping minibeams produce a homogeneous dose distribution throughout the tumor. The aim of this work was to elucidate the prospects of minibeam radiation therapy compared to conventional homogeneous broad beam radiotherapy in theory and in experimental studies at the ion microprobe SNAKE. Treatment plans for model tumors of different sizes and depths were created using the planning software LAP-CERR, to elaborate suitable minibeam sizes and distances for the individual tumors. Radiotherapy-relevant inter-beam distances required to obtain a homogeneous dose in the target volume were found to be in the millimeter range. First experiments using proton minibeams of only 10 µm and 50 µm size (termed microchannels in the corresponding publication Zlobinskaya et al. 2013) and therapy-conform larger dimensions of 100 µm and 180 µm were performed in the artificial human in-vitro skin model EpiDermFT (MatTek). The corresponding inter-beam distances were 500 μm, 1mm and 1.8mm, respectively, leading to irradiation of only a few percent of the cells in the skin tissue, but with significantly increased doses (up to 5000 Gy) compared to the average dose of 2 Gy, which was applied homogeneously in further skin samples for comparison. Gaussian-shaped minibeams of even larger sizes (σ=260 µm and 520 µm, inter-beam distance 1.8mm) were analyzed in further experiments to evaluate the effect of increasing beam sizes as in deeper-lying tissues. Acute side effects were quantified via the MTT tissue viability test and the release of inflammatory proteins into the culture medium and showed improved results for minibeam compared to homogeneous irradiation. Genetic damage, an indicator for secondary tumor induction, was analyzed via the micronucleus test in the epidermal keratinocytes and was less than half for minibeams up to 180 µm size compared to homogeneous fields. Increasing minibeam sizes, i.e. increasing fractions of irradiated skin receiving a dose higher than the average dose of 2 Gy) increased the number of micronuclei per divided cell, but never exceeded the genetic damage induced by a homogeneous dose distribution. A more authentic and representative in-vivo skin model, accounting for higher complexity with blood vessels, further cell types, follicles glands and especially a working immune system, was used in the next step to further examine the side effects of minibeam radiotherapy compared to homogeneous irradiation. The central part of the ear of adult BALB/c mice was irradiated with 20 MeV protons, using an average dose of 60 Gy in a field of 7.2 x 7.2mm². The 4 x 4 minibeams of nominal 6000 Gy had a size of 180x180 µm2 and inter-beam distances of 1.8 mm, as in previous in-vitro skin experiments. Minibeam irradiation induced no ear swelling or other visible skin reaction at any time, while significant ear swelling (up to 4-fold), skin reddening (erythema) and desquamation developed in homogeneously irradiated ears 3-4 weeks after irradiation. Loss of hair and sebaceous glands only occurred in the homogeneous irradiation fields and did not recover during the monitoring phase of 90 days. Taken together all theoretical considerations and experimental findings, proton minibeam radiation therapy appears suitable for the implementation in clinical tumor therapy using protons and/or heavy ions, as it reduces side effects in the normal tissue compared to conventional broad beam irradiation. However, the upper limit of the minibeam size for tissue sparing and the technical feasibility are still to be elucidated as current technologies might have to be improved and adapted for the generation of sub-millimeter proton beams of energies up to 250 MeV at therapy plants.
BibTeX:
	@phdthesis{Girst2016diss,
	  author = {Stefanie Girst},
	  title = {Proton Minibeam Radiotherapy},
	  school = {Universität der Bundeswehr München},
	  year = {2016},
	  url = {http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:706-4569}
	}
	
Double-Strand Break Distributions along high-LET Particle Tracks in Human HeLa Cells
Josef Huber; Masters-Thesis, Universität der Bundeswehr München, 2016.
Abstract: Ionizing radiation finds widespread application in cancer treatment because it induces DNA double-strand breaks (DSB), which are causal to the killing of tumor cells and are ultimately required for a patient’s recovery. Based on its clinical relevance, it is of great importance to study the influence of radiation quality on the number of induced DSB. In previous experiments, the number of observed damage sites in the cell for low-LET X-rays matched well with the number of DSB predicted by simulations. However, for high-LET ionizing radiation, a saturation in the number of damage sites was observed that is less than the predicted number of DSB. The cause of this saturation is attributed to the method of visualizing DSB. It is performed by imaging the distribution of proteins like 53BP1 and γH2AX, which are involved in DSB-signalling and form 1 µm-sized ionizing radiation induced foci (IRIF) at these sites. Due to a decreased spacing between consecutive DSB with increasing LET, single DSB can no longer be resolved within the IRIF. The proteins KU70/80 and DNA-PKcs might be a promising alternative to these conventional damage markers, since one copy each binds to the end of double-stranded DNA immediately after damage induction. Thus, for these proteins significantly smaller IRIF are expected, which might allow the visual- ization of single DSB.
The aim of this work was to count every DSB that is induced by high-LET ionizing radiation in human HeLa cells. For this, the IRIF-formation of DNA-PKcs and KU70/80 was tested and examined. Induction of DSB was achieved by irradiation with α-particles and small angle irradiation at the ion microprobe SNAKE with lithium and carbon ions. Visualization of the target proteins’ distribution in the cell was accom- plished through the method of indirect secondary immunofluorescence staining and imaging was performed with the help of a super-resolution STED-microscope.
In the experiments, no IRIF-formation was detected for primary antibodies specifically targeting KU80 and DNA-PKcs after α-irradiation. The abundant presence of 400000 proteins of each type masked the signal of single proteins bound to double-stranded DNA, indicating that the proteins are not suitable for the counting of single DSB in their indistinguishable collective natural state. DNA-PKcs bound to DSB reportedly undergo phosphorylation at Thr2609, which leads to the dissociation from the DSB. Although this way the expected strong localisation at sites of DSB is lost, it allows for the discrimination of DNA-PKcs proteins that are not involved in damage response. Based on these findings in the relevant literature, the experiments were carried out and IRIF-formation for a primary antibody specific to phosphorylated DNA-PKcs was tested positive after α-particle irradiation. Furthermore, particle tracks were visible after lithium and carbon ion irradiation for samples fixed 2, 3 and 5 minutes post- irradiation. Evaluation of 30 particle tracks for each time point yielded an average number of 2.5±0.4 IRIF per micron after 2 minutes, which increased to 3.2±0.6 IRIF per micron 5 minutes after irradiation for lithium ions with LET=116±10 keV/µm. For carbon ions with LET=500±80 keV/µm , the number of observed IRIF increased from 4.1±0.6 per micron to 4.5±0.7 per micron from 2 to 5 minutes after irradiation. The increase for both ion types can be attributed to a delayed accumulation of protein to a fraction of DSB, which become accessible by changes in the conformation of hete- rochromatin at later times. PARTRAC simulations predict 2.7±0.4 DSB per micron for lithium and 10.2±2.2 DSB per micron for carbon ions. The number of observed IRIF for lithium ions exceeded the number from linear scaling of low-LET X-rays and matched well with the predicted number from PARTRAC. However, the observed number of IRIF for carbon ions was only half the number of the predicted DSB by PARTRAC. Thus, it is concluded that the goal of counting single DSB for high-LET irradiation can only be partly fulfilled: up to LET=116±10 keV/µm , the average spacing between DSB can be resolved by the IRIF-size with diameters from 188±36 nm to 205±49 nm. However, at LET=500±80 keV/µm , the decreased average spacing between consecutive DSB can no longer be resolved and is exceeded by the minimal observed IRIF-diameter of 178±40 nm. PARTRAC takes into account that DSB in close vicinity may not be resolvable and provides a reduced number of observable IRIF, which is derived by assigning all DSB within 150 nm to one observable cluster. This results in a predicted number of 3.3±0.3 observable IRIF per micron for carbon ions, which is matched and partly exceeded by the actual observed number of IRIF per micron. This indicates that the experimental results of this thesis are compatible with PARTRAC simulations.
BibTeX:
	@mastersthesis{Huber2016ma,
	  author = {Huber, Josef},
	  title = {Double-Strand Break Distributions along high-LET Particle Tracks in Human HeLa Cells},
	  school = {Universität der Bundeswehr München},
	  year = {2016}
	}
	
Positron annihilation lifetime spectroscopy study of Kapton thin foils
G.S. Kanda, L. Ravelli, B. Löwe, W. Egger and D.J. Keeble; Journal of Physics D: Applied Physics 49 (2) (2016) 025305.
Abstract: Variable energy positron annihilation lifetime spectroscopy (VE-PALS) experiments on polyimide material Kapton are reported. Thin Kapton foils are widely used in a variety of mechanical, electronic applications. PALS provides a sensitive probe of vacancy-related defects in a wide range of materials, including open volume in polymers. Varying the positron implantation energy enables direct measurement of thin foils. Thin Kapton foils are also commonly used to enclose the positron source material in conventional PALS measurements performed with unmoderated radionuclide sources. The results of depth-profiled positron lifetime measurements on 7.6 μ m and 25 μ m Kapton foils are reported and determine a dominant 385(1) ps lifetime component. The absence of significant nanosecond lifetime component due to positronium formation is confirmed.
BibTeX:
	@article{Kanda2016,
	  author = {Gurmeet S Kanda and Luca Ravelli and Benjamin Löwe and Werner Egger and David J Keeble},
	  title = {Positron annihilation lifetime spectroscopy study of Kapton thin foils},
	  journal = {Journal of Physics D: Applied Physics},
	  year = {2016},
	  volume = {49},
	  number = {2},
	  pages = {025305},
	  url = {http://stacks.iop.org/0022-3727/49/i=2/a=025305},
	  doi = {http://doi.org/10.1088/0022-3727/49/2/025305}
	}
	
Ionoacoustic tomography of the proton Bragg peak in combination with ultrasound and optoacoustic imaging
S. Kellnberger, W. Assmann, S. Lehrack, S. Reinhardt, P. Thirolf, D. Queirós, G. Sergiadis, G. Dollinger, K. Parodi and V. Ntziachristos; Scientific Reports 6 (2016) 29305.
Abstract: Ions provide a more advantageous dose distribution than photons for external beam radiotherapy, due to their so-called inverse depth dose deposition and, in particular a characteristic dose maximum at their end-of-range (Bragg peak). The favorable physical interaction properties enable selective treatment of tumors while sparing surrounding healthy tissue, but optimal clinical use requires accurate monitoring of Bragg peak positioning inside tissue. We introduce ionoacoustic tomography based on detection of ion induced ultrasound waves as a technique to provide feedback on the ion beam profile. We demonstrate for 20 MeV protons that ion range imaging is possible with submillimeter accuracy and can be combined with clinical ultrasound and optoacoustic tomography of similar precision. Our results indicate a simple and direct possibility to correlate, in-vivo and in real-time, the conventional ultrasound echo of the tumor region with ionoacoustic tomography. Combined with optoacoustic tomography it offers a well suited pre-clinical imaging system.
BibTeX:
	@article{Kellnberger2016,
	  author = {Kellnberger, Stephan and Assmann, Walter and Lehrack, Sebastian and Reinhardt, Sabine and Thirolf, Peter and Queirós, Daniel and Sergiadis, George and Dollinger, Günther and Parodi, Katia and Ntziachristos, Vasilis},
	  title = {Ionoacoustic tomography of the proton Bragg peak in combination with ultrasound and optoacoustic imaging},
	  journal = {Scientific Reports},
	  year = {2016},
	  volume = {6},
	  pages = {29305},
	  url = {http://www.nature.com/articles/srep29305},
	  doi = {http://doi.org/10.1038/srep29305}
	}
	
Material selection for hybrid floating gate NAND memory applications
J.G. Lisoni, L. Breuil, P. Blomme, J. Meersschaut, A. Bergmaier, G. Dollinger, G. Van den Bosch and J. Van Houdt; physica status solidi (a) 213 (2) (2016) 237-244.
Abstract: This article discusses the materials aspects involved in the successful integration of hybrid floating gate (HFG) devices for NAND applications. In HFG, a Si(n type)p type) stack replaces the standard poly-Si FG. The high work function metal helps to enlarge the program window by limiting the leakage through the high-k intergate dielectric (IGD); the use of high-k IGD enables to scale the equivalent oxide thickness (EOT) of the HFG cell. Our recent progresses in the understanding of the materials characteristics (IGD crystallinity and HFG-IGD thermal stability) that influence memory performance have allowed to demonstrate that HFG can be a solution to scale planar flash beyond the 20 nm node with the best preferable hybrid floating gate structure being a Ru-based HFG and a 3-layers IGD stack of HfAlOO3HfAlO. Indeed, through the correct selection and combination of materials for process conditions that are relevant in flash memory fabrication flows, we will show that program windows can be suitably engineered. Finally, the materials challenges for keeping acceptable memory retention characteristics are also highlighted.
BibTeX:
	@article{Lisoni2016,
	  author = {Lisoni, Judit G. and Breuil, Laurent and Blomme, Pieter and Meersschaut, Johan and Bergmaier, Andreas and Dollinger, Günther and Van den Bosch, Geert and Van Houdt, Jan},
	  title = {Material selection for hybrid floating gate NAND memory applications},
	  journal = {physica status solidi (a)},
	  year = {2016},
	  volume = {213},
	  number = {2},
	  pages = {237--244},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/pssa.201532829/abstract},
	  doi = {http://doi.org/10.1002/pssa.201532829}
	}
	
Hydrogen analysis depth calibration by CORTEO Monte-Carlo simulation
M. Moser, P. Reichart, A. Bergmaier, C. Greubel, F. Schiettekatte and G. Dollinger; Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 371 (2016) 161-166.
Abstract: Abstract Hydrogen imaging with sub-μm lateral resolution and sub-ppm sensitivity has become possible with coincident proton-proton (pp) scattering analysis (Reichart et al., 2004). Depth information is evaluated from the energy sum signal with respect to energy loss of both protons on their path through the sample. In first order, there is no angular dependence due to elastic scattering. In second order, a path length effect due to different energy loss on the paths of the protons causes an angular dependence of the energy sum. Therefore, the energy sum signal has to be de-convoluted depending on the matrix composition, i.e. mainly the atomic number Z, in order to get a depth calibrated hydrogen profile. Although the path effect can be calculated analytically in first order, multiple scattering effects lead to significant deviations in the depth profile. Hence, in our new approach, we use the CORTEO Monte-Carlo code (Schiettekatte, 2008) in order to calculate the depth of a coincidence event depending on the scattering angle. The code takes individual detector geometry into account. In this paper we show, that the code correctly reproduces measured pp-scattering energy spectra with roughness effects considered. With more than 100 μm thick Mylar-sandwich targets (Si, Fe, Ge) we demonstrate the deconvolution of the energy spectra on our current multistrip detector at the microprobe SNAKE at the Munich tandem accelerator lab. As a result, hydrogen profiles can be evaluated with an accuracy in depth of about 1% of the sample thickness.
BibTeX:
	@article{Moser2016,
	  author = {Moser, M. and Reichart, P. and Bergmaier, A. and Greubel, C. and Schiettekatte, F. and Dollinger, G.},
	  title = {Hydrogen analysis depth calibration by CORTEO Monte-Carlo simulation},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms},
	  year = {2016},
	  volume = {371},
	  pages = {161-166},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X15009428},
	  doi = {http://doi.org/10.1016/j.nimb.2015.09.069}
	}
	
Depletion of Histone Demethylase Jarid1A Resulting in Histone Hyperacetylation and Radiation Sensitivity Does Not Affect DNA Double-Strand Break Repair
C. Penterling, G.A. Drexler, C. Böhland, R. Stamp, C. Wilke, H. Braselmann, R.B. Caldwell, J. Reindl, S. Girst, C. Greubel, C. Siebenwirth, W.Y. Mansour, K. Borgmann, G. Dollinger, K. Unger and A.A. Friedl; PLoS ONE 11 (6) (2016) e0156599.
Abstract: Histone demethylases have recently gained interest as potential targets in cancer treatment and several histone demethylases have been implicated in the DNA damage response. We investigated the effects of siRNA-mediated depletion of histone demethylase Jarid1A (KDM5A, RBP2), which demethylates transcription activating tri- and dimethylated lysine 4 at histone H3 (H3K4me3/me2), on growth characteristics and cellular response to radiation in several cancer cell lines. In unirradiated cells Jarid1A depletion lead to histone hyperacetylation while not affecting cell growth. In irradiated cells, depletion of Jarid1A significantly increased cellular radiosensitivity. Unexpectedly, the hyperacetylation phenotype did not lead to disturbed accumulation of DNA damage response and repair factors 53BP1, BRCA1, or Rad51 at damage sites, nor did it influence resolution of radiation-induced foci or rejoining of reporter constructs. We conclude that the radiation sensitivity observed following depletion of Jarid1A is not caused by a deficiency in repair of DNA double-strand breaks.
BibTeX:
	@article{Penterling2016,
	  author = {Penterling, Corina and Drexler, Guido A. and Böhland, Claudia and Stamp, Ramona and Wilke, Christina and Braselmann, Herbert and Caldwell, Randolph B. and Reindl, Judith and Girst, Stefanie and Greubel, Christoph and Siebenwirth, Christian and Mansour, Wael Y. and Borgmann, Kerstin and Dollinger, Günther and Unger, Kristian and Friedl, Anna A.},
	  title = {Depletion of Histone Demethylase Jarid1A Resulting in Histone Hyperacetylation and Radiation Sensitivity Does Not Affect DNA Double-Strand Break Repair},
	  journal = {PLoS ONE},
	  year = {2016},
	  volume = {11},
	  number = {6},
	  pages = {e0156599},
	  url = {http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0156599},
	  doi = {http://doi.org/10.1371/journal.pone.0156599}
	}
	
Superresolution light microscopy shows nanostructure of carbon ion radiation-induced DNA double-strand break repair foci
R.L. Perez, G. Best, N.H. Nicolay, C. Greubel, S. Rossberger, J. Reindl, G. Dollinger, K.-J. Weber, C. Cremer and P.E. Huber; Faseb 30 (2016) 2767-2776.
Abstract: Carbon ion radiation is a promising new form of radiotherapy for cancer, but the central question about the biologic effects of charged particle radiation is yet incompletely understood. Key to this question is the understanding of the interaction of ions with DNA in the cell’s nucleus. Induction and repair of DNA lesions including double-strand breaks (DSBs) are decisive for the cell. Several DSB repair markers have been used to investigate these processes microscopically, but the limited resolution of conventional microscopy is insufficient to provide structural insights. We have applied superresolution microscopy to overcome these limitations and analyze the fine structure of DSB repair foci. We found that the conventionally detected foci of the widely used DSB marker γH2AX (Ø700–1000 nm) were composed of elongated subfoci with a size of  100 nm consisting of even smaller subfoci elements (Ø40–60 nm). The structural organization of the subfoci suggests that they could represent the local chromatin structure of elementary DSB repair units at the DSB damage sites. Subfoci clusters may indicate induction of densely spaced DSBs, which are thought to be associated with the high biologic effectiveness of carbon ions. Superresolution microscopy might emerge as a powerful tool to improve our knowledge of interactions of ionizing radiation with cells.
BibTeX:
	@article{Perez2016,
	  author = {Ramon Lopez Perez and Gerrit Best and Nils H. Nicolay and Christoph Greubel and Sabrina Rossberger and Judith Reindl and Günther Dollinger and Klaus-Josef Weber and Christoph Cremer and Peter E. Huber},
	  title = {Superresolution light microscopy shows nanostructure of carbon ion radiation-induced DNA double-strand break repair foci},
	  journal = {Faseb},
	  year = {2016},
	  volume = {30},
	  pages = {2767-2776},
	  url = {http://www.fasebj.org/content/30/8/2767},
	  doi = {http://doi.org/10.1096/fj.201500106R}
	}
	
Deuterium microscopy using 17 MeV deuteron-deuteron scattering
P. Reichart, M. Moser, C. Greubel, K. Peeper and G. Dollinger; Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 371 (2016) 178-184.
Abstract: Abstract Using 17 MeV deuterons as a micrometer focused primary beam, we performed deuterium microscopy by using the deuteron-deuteron (dd) scattering reaction. We describe our new box like detector setup consisting of four double sided silicon strip detectors (DSSSD) with 16 strips on each side, each covering up to 0.5 sr solid angle for coincidence detection. This method becomes a valuable tool for studies of hydrogen incorporation or dynamic processes using deuterium tagging. The background from natural hydrocarbon or water contamination is reduced by the factor 150 ppm of natural abundance of deuterium in hydrogen. Deuterium energies of up to 25 MeV, available at the microprobe SNAKE, are ideal for the analysis of thin freestanding samples so that the scattered particles are transmitted to the detector. The differential cross section for the elastic scattering reaction is about the same as for pp-scattering ( 100 mb/sr). The main background due to nuclear reactions is outside the energy window of interest. Deuteron-proton (dp) scattering events give an additional signal for hydrogen atoms, so the H/D-ratio can be monitored in parallel.
BibTeX:
	@article{Reichart2016,
	  author = {Reichart, Patrick and Moser, Marcus and Greubel, Christoph and Peeper, Katrin and Dollinger, Günther},
	  title = {Deuterium microscopy using 17 MeV deuteron-deuteron scattering},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms},
	  year = {2016},
	  volume = {371},
	  pages = {178-184},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X15009489},
	  doi = {http://doi.org/10.1016/j.nimb.2015.09.075}
	}
	
Feinstruktur von BRCA1- und Rad51-Foci nach α-Bestrahlung
Benjamin Schwarz; Masters-Thesis, Ludwig-Maximilians-Universität München, 2016.
Abstract: DNA-Doppelstrangbrüche (DSB) sind kritische Schäden für das Überleben einer Zelle, wobei eine Vielzahl von extra- und intrazellulärer Faktoren zu einem DSB führen können. Aus diesem Grund hat die Natur besonders spezialisierte und dadurch gleichfalls komplexe Methoden zur DSB-Reparatur entwickelt. Einer dieser Prozesse ist die Homologe Rekombination (HR), bei welcher durch ein komplexes Zusammenspiel verschiedenster Proteine, akkumuliert in so genannten Foci, unter Verwendung des homologen Schwesterchromatids, die losen DNA-Enden wieder zusammengefügt werden. Wichtige Schlüsselfunktionen übernehmen dabei die Proteine Rad51 und BRCA1, wobei ihr gesamtes Aufgabenspektrum noch nicht bekannt ist. Die geringe Größe solcher Foci von wenigen 100 nm macht eine Abbildung ihrer inneren Strukturen für herkömmliche Lichtmikroskopie aufgrund der
beugungsbegrenzten Auflösung von 250 nm unmöglich. In dieser Arbeit wurden immunhistochemische Methoden in Kombination mit STED Mikroskopie (STimulated Emission Depletion) verwendet, um die Feinstruktur der Reparaturfoci α-strahlungsinduzierter DSB an Hand von BRCA1 und Rad51 unterhalb der Beugungsgrenze abzubilden und über die Zeit von 24 h zu charakterisieren. Dabei deuten die Ergebnisse der Korrelationsanalyse auf drei Phasen gemeinsamer Aktion am Doppelstrangbruch hin, welche in Early Stage, Processing Stage und Late Stage aufgeteilt werden können. Des Weiteren weisen Intensitätsplots quer durch einzelne Foci gemessen, auf eine lokale Exklusion der beiden Proteine im Zentrum des DSB hin und stärken Hypothesen, welche keinen direkten Protein-Protein-Kontakt beschreiben.

DNA Double-Strand Breaks (DSB) are critical damages for a living cell. A variety of extra- and intracellular factors are able to induce DSB. Therefore, nature developed several specific and complex DSB-Repair mechanisms. One of them is homologous recombination (HR). It depends on a complex interaction between different proteins, accumulating in so called foci. These proteins use the homologous sister chromatid as a template to rejoin the loose DNA ends. The proteins BRCA1 and Rad51 have a key function in HR, but their specific responsibilities are not completely understood yet. The small size of the foci (few 100 nm) rules out a resolution via light microscopy because of the diffraction barrier of 250 nm. During this thesis, immunohistochemistry and STED microscopy (STimulated Emission Depletion) was used to image foci of BRCA1 and Rad51 during the repair of α-radiation induced DSB with a resolution below the diffraction limit. The resulting data of the correlation analysis of BRCA1 and Rad51 imply a subdivision of BRCA1 and Rad51 interaction in 3 phases during HR (early stage, processing stage, late stage). Intensity plots of the localization of BRCA1 and Rad51 show local exclusion within the foci and therefore support predictions of non-existing direct protein interaction.

BibTeX:
	@mastersthesis{Schwarz2016ma,
	  author = {Schwarz, Benjamin},
	  title = {Feinstruktur von BRCA1- und Rad51-Foci nach α-Bestrahlung},
	  school = {Ludwig-Maximilians-Universität München},
	  year = {2016}
	}
	

2015

Time- and energy-resolution measurements of BaF2, BC-418, LYSO and CeBr3 scintillators
U. Ackermann, W. Egger, P. Sperr and G. Dollinger; Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 786 (0) (2015) 5-11.
Abstract: We have investigated the time and energy resolution (TTiming, ∆E/E) of four different scintillator materials BaF2, BC-418, LYSO and CeBr3 at a gamma energy of 511 keV in views of their possible usage for time, energy and position resolution for positron annihilation experiments. The shape of each scintillator was a cylinder with a diameter of 25 mm and a height of 10 mm readout by a Photonis XP2020/URQ photomultiplier tube. The best single time resolution was determined for each photomultiplier–scintillator setup in a three step optimization process. The optimized single time resolutions (FWHM) for BaF2, BC-418, LYSO and CeBr3 were 119 ps, 117 ps, 269 ps and 127 ps, respectively. We measured the energy resolution of the photomultiplier–scintillator setups which show a photopeak in the energy spectrum. The energy resolutions ∆E/E of BaF2, LYSO and CeBr3 were 9.8%, 9.7% and 5.4%, respectively. The overall most promising material for measuring simultaneously time, energy and position resolution for positron annihilation experiments seems to be CeBr3 due to its very good time and energy resolution characteristics.
BibTeX:
	@article{Ackermann2015,
	  author = {Ackermann, Ulrich and Egger, Werner and Sperr, Peter and Dollinger, Günther},
	  title = {Time- and energy-resolution measurements of BaF2, BC-418, LYSO and CeBr3 scintillators},
	  journal = {Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment},
	  year = {2015},
	  volume = {786},
	  number = {0},
	  pages = {5--11},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168900215003101},
	  doi = {http://doi.org/10.1016/j.nima.2015.03.016}
	}
	
Ionoacoustic characterization of the proton Bragg peak with submillimeter accuracy
W. Assmann, S. Kellnberger, S. Reinhardt, S. Lehrack, A. Edlich, P.G. Thirolf, M. Moser, G. Dollinger, M. Omar, V. Ntziachristos and K. Parodi; Medical Physics 42 (2) (2015) 567-574.
Abstract: Purpose: Range verification in ion beam therapy relies to date on nuclear imaging techniques which require complex and costly detector systems. A different approach is the detection of thermoacoustic signals that are generated due to localized energy loss of ion beams in tissue (ionoacoustics). Aim of this work was to study experimentally the achievable position resolution of ionoacoustics under idealized conditions using high frequency ultrasonic transducers and a specifically selected probing beam.

Methods: A water phantom was irradiated by a pulsed 20 MeV proton beam with varying pulse intensity and length. The acoustic signal of single proton pulses was measured by different PZT-based ultrasound detectors (3.5 and 10 MHz central frequencies). The proton dose distribution in water was calculated by Geant4 and used as input for simulation of the generated acoustic wave by the matlab toolbox k-WAVE.

Results: In measurements from this study, a clear signal of the Bragg peak was observed for an energy deposition as low as 10e12 eV. The signal amplitude showed a linear increase with particle number per pulse and thus, dose. Bragg peak position measurements were reproducible within ±30 μm and agreed with Geant4 simulations to better than 100 μm. The ionoacoustic signal pattern allowed for a detailed analysis of the Bragg peak and could be well reproduced by k-WAVE simulations.

Conclusions: The authors have studied the ionoacoustic signal of the Bragg peak in experiments using a 20 MeV proton beam with its correspondingly localized energy deposition, demonstrating submillimeter position resolution and providing a deep insight in the correlation between the acoustic signal and Bragg peak shape. These results, together with earlier experiments and new simulations (including the results in this study) at higher energies, suggest ionoacoustics as a technique for range verification in particle therapy at locations, where the tumor can be localized by ultrasound imaging. This acoustic range verification approach could offer the possibility of combining anatomical ultrasound and Bragg peak imaging, but further studies are required for translation of these findings to clinical application.

BibTeX:
	@article{Assmann2015,
	  author = {Assmann, W. and Kellnberger, S. and Reinhardt, S. and Lehrack, S. and Edlich, A. and Thirolf, P. G. and Moser, M. and Dollinger, G. and Omar, M. and Ntziachristos, V. and Parodi, K.},
	  title = {Ionoacoustic characterization of the proton Bragg peak with submillimeter accuracy},
	  journal = {Medical Physics},
	  year = {2015},
	  volume = {42},
	  number = {2},
	  pages = {567--574},
	  url = {http://scitation.aip.org/content/aapm/journal/medphys/42/2/10.1118/1.4905047},
	  doi = {http://doi.org/10.1118/1.4905047}
	}
	
Live cell imaging at the Munich ion microbeam SNAKE - a status report
G.A. Drexler, C. Siebenwirth, S.E. Drexler, S. Girst, C. Greubel, G. Dollinger and A.A. Friedl; Radiation Oncology 10 (2015) 42.
Abstract: Ion microbeams are important tools in radiobiological research. Still, the worldwide number of ion microbeam facilities where biological experiments can be performed is limited. Even fewer facilities combine ion microirradiation with live-cell imaging to allow microscopic observation of cellular response reactions starting very fast after irradiation and continuing for many hours. At SNAKE, the ion microbeam facility at the Munich 14 MV tandem accelerator, a large variety of biological experiments are performed on a regular basis. Here, recent developments and ongoing research projects at the ion microbeam SNAKE are presented with specific emphasis on live-cell imaging experiments. An overview of the technical details of the setup is given, including examples of suitable biological samples. By ion beam focusing to submicrometer beam spot size and single ion detection it is possible to target subcellular structures with defined numbers of ions. Focusing of high numbers of ions to single spots allows studying the influence of high local damage density on recruitment of damage response proteins.
BibTeX:
	@article{Drexler2015,
	  author = {Drexler, Guido A. and Siebenwirth, Christian and Drexler, Sophie E. and Girst, Stefanie and Greubel, Christoph and Dollinger, Günther and Friedl, Anna A.},
	  title = {Live cell imaging at the Munich ion microbeam SNAKE - a status report},
	  journal = {Radiation Oncology},
	  year = {2015},
	  volume = {10},
	  pages = {42},
	  url = {http://ro-journal.biomedcentral.com/articles/10.1186/s13014-015-0350-7},
	  doi = {http://doi.org/10.1186/s13014-015-0350-7}
	}
	
Improved normal tissue protection by proton and X-ray microchannels compared to homogeneous field irradiation
S. Girst, C. Marx, E. Bräuer-Krisch, A. Bravin, S. Bartzsch, U. Oelfke, C. Greubel, J. Reindl, C. Siebenwirth, O. Zlobinskaya, G. Multhoff, G. Dollinger, T. Schmid and J. Wilkens; Physica Medica 31 (0) (2015) 615-620.
Abstract: The risk of developing normal tissue injuries often limits the radiation dose that can be applied to the tumour in radiation therapy. Microbeam Radiation Therapy (MRT), a spatially fractionated photon radiotherapy is currently tested at the European Synchrotron Radiation Facility (ESRF) to improve normal tissue protection. MRT utilizes an array of microscopically thin and nearly parallel X-ray beams that are generated by a synchrotron. At the ion microprobe SNAKE in Munich focused proton microbeams (“proton microchannels”) are studied to improve normal tissue protection. Here, we comparatively investigate microbeam/microchannel irradiations with sub-millimetre X-ray versus proton beams to minimize the risk of normal tissue damage in a human skin model, in vitro. Skin tissues were irradiated with a mean dose of 2 Gy over the irradiated area either with parallel synchrotron-generated X-ray beams at the ESRF or with 20 MeV protons at SNAKE using four different irradiation modes: homogeneous field, parallel lines and microchannel applications using two different channel sizes. Normal tissue viability as determined in an MTT test was significantly higher after proton or X-ray microchannel irradiation compared to a homogeneous field irradiation. In line with these findings genetic damage, as determined by the measurement of micronuclei in keratinocytes, was significantly reduced after proton or X-ray microchannel compared to a homogeneous field irradiation. Our data show that skin irradiation using either X-ray or proton microchannels maintain a higher cell viability and DNA integrity compared to a homogeneous irradiation, and thus might improve normal tissue protection after radiation therapy.
BibTeX:
	@article{Girst2015,
	  author = {Girst, S. and Marx, C. and Bräuer-Krisch, E. and Bravin, A. and Bartzsch, S. and Oelfke, U. and Greubel, C. and Reindl, J. and Siebenwirth, C. and Zlobinskaya, O. and Multhoff, G. and Dollinger, G. and Schmid, T.E. and Wilkens, J.J.},
	  title = {Improved normal tissue protection by proton and X-ray microchannels compared to homogeneous field irradiation},
	  journal = {Physica Medica},
	  year = {2015},
	  volume = {31},
	  number = {0},
	  pages = {615--620},
	  url = {http://www.sciencedirect.com/science/article/pii/S1120179715000952},
	  doi = {http://doi.org/10.1016/j.ejmp.2015.04.004}
	}
	
The influence of the channel size on the reduction of side effects in microchannel proton therapy
S. Girst, C. Greubel, J. Reindl, C. Siebenwirth, O. Zlobinskaya, G. Dollinger and T.E. Schmid; Radiation and Environmental Biophysics 54 (3) (2015) 335-342.
Abstract: The potential of proton microchannel radiotherapy to reduce radiation effects in the healthy tissue but to keep tumor control the same as in conventional proton therapy is further elucidated. The microchannels spread on their way to the tumor tissue resulting in different fractions of the healthy tissue covered with doses larger than the tumor dose, while the tumor gets homogeneously irradiated. The aim of this study was to evaluate the effect of increasing channel width on potential side effects in the normal tissue. A rectangular 180 × 180 µm2 and two Gaussian-type dose distributions of σ = 260 µm and σ = 520 µm with an interchannel distance of 1.8 mm have been applied by 20-MeV protons to a 3D human skin model in order to simulate the widened channels and to compare the irradiation effects at different endpoints to those of a homogeneous proton irradiation. The number of protons applied was kept constant at all irradiation modes resulting in the same average dose of 2 Gy. All kinds of proton microchannel irradiation lead to higher cell viability and produce significantly less genetic damage than homogeneous proton irradiation, but the reduction is lower for the wider channel sizes. Our findings point toward the application of microchannel irradiation for clinical proton or heavy ion therapy to further reduce damage of normal tissues while maintaining tumor control via a homogeneous dose distribution inside the tumor.
BibTeX:
	@article{Girst2015a,
	  author = {Girst, Stefanie and Greubel, Christoph and Reindl, Judith and Siebenwirth, Christian and Zlobinskaya, Olga and Dollinger, Günther and Schmid, Thomas E.},
	  title = {The influence of the channel size on the reduction of side effects in microchannel proton therapy},
	  booktitle = {Radiation and Environmental Biophysics},
	  journal = {Radiation and Environmental Biophysics},
	  year = {2015},
	  volume = {54},
	  number = {3},
	  pages = {335--342},
	  url = {http://link.springer.com/article/10.1007%2Fs00411-015-0600-y},
	  doi = {http://doi.org/10.1007/s00411-015-0600-y}
	}
	
Free Volume and Gas Permeation in Anthracene Maleimide-Based Polymers of Intrinsic Microporosity
M.M. Khan, V. Filiz, T. Emmler, V. Abetz, T. Koschine, K. Rätzke, F. Faupel, W. Egger and L. Ravelli; Membranes 5 (2) (2015) 214.
Abstract: High free-volume copolymers were prepared via polycondensation with 2,3,5,6,-tetrafluoroterephthalonitrile (TFTPN) in which a portion of the 3,3,3',3'-tetramethyl- 1,1'-spirobisindane (TTSBI) of PIM-1 was replaced with dibutyl anthracene maleimide (4bIII). An investigation of free volume using positron annihilation lifetime spectroscopy (PALS), and gas permeation measurements was carried out for the thin film composite copolymer membranes and compared to PIM-1. The average free volume hole size and the gas permeance of the copolymer membranes increased with decreasing TTSBI content in the copolymer.
BibTeX:
	@article{Khan2015,
	  author = {Khan, Muntazim Munir and Filiz, Volkan and Emmler, Thomas and Abetz, Volker and Koschine, Toenjes and Rätzke, Klaus and Faupel, Franz and Egger, Werner and Ravelli, Luca},
	  title = {Free Volume and Gas Permeation in Anthracene Maleimide-Based Polymers of Intrinsic Microporosity},
	  journal = {Membranes},
	  year = {2015},
	  volume = {5},
	  number = {2},
	  pages = {214},
	  url = {http://www.mdpi.com/2077-0375/5/2/214},
	  doi = {http://doi.org/10.3390/membranes5020214}
	}
	
Correlation of gas permeation and free volume in new and used high free volume thin film composite membranes
T. Koschine, K. Rätzke, F. Faupel, M. Khan, T. Emmler, V. Filiz, V. Abetz, L. Ravelli and W. Egger; Journal of Polymer Science, Part B: Polymer Physics 53 (3) (2015) 213-217.
Abstract: Polymeric gas separation membranes frequently undergo the phenomenon of aging, that is, performance parameters like permeability decrease with storage or usage time. Here, we report on a new approach of reducing aging by incorporation of functionalized multiwalled carbon nanotubes into a polymer of intrinsic microporosity. Free volume and permeability measurements clearly show a reduced aging with incorporation of the carbon nantubes.
BibTeX:
	@article{Koschine2015,
	  author = {Koschine, T. and Rätzke, K. and Faupel, F. and Khan, M.M. and Emmler, T. and Filiz, V. and Abetz, V. and Ravelli, L. and Egger, W.},
	  title = {Correlation of gas permeation and free volume in new and used high free volume thin film composite membranes},
	  journal = {Journal of Polymer Science, Part B: Polymer Physics},
	  year = {2015},
	  volume = {53},
	  number = {3},
	  pages = {213--217},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/polb.23616/abstract;jsessionid=794C1386DED7BBED63EA824F50C74C4F.f03t01},
	  doi = {http://doi.org/10.1002/polb.23616}
	}
	
Erste ortsauflösende Positronen Lebensdauerspektroskopie am Scanning-Positron-Microscope Interface
Johannes Mitteneder; Masters-Thesis, Hochschule München, 2015.
Abstract: Das Scanning-Positron-Microscope (SPM) ist ein Instrument zur zerstörungsfreien Materialuntersuchung mittels der Positronen Lebensdauerspektroskopie. Positronen sind sensitiv für Materialdefekte wie Leerstellen, Versetzungen oder Korngrenzen.
An Defekten variiert die lokale Elektronendichte und damit die mittlere Lebensdauer der Positronen im Probenmaterial.
An der Universität der Bundeswehr wurde das SPM an einer Labor-Positronenquelle betrieben. Für einen höheren Positronenfluss wird das SPM zukünftig durch das SPM-Interface an die Reaktor Positronenquelle NEPOMUC gekoppelt. Durch den höheren Fluss des Positronenstrahls sollen kürzere Messzeiten erreicht werden.
Das SPM-Interface verbessert die Strahleigenschaften, indem es die Divergenz und den Strahldurchmesser des Positronenstrahls verkleinert. Zusätzlich formt das SPM-Interface die Positronenpulse aus dem kontinuierlichen Positronenstrahl von NEPOMUC.
Die Pulsung des Strahls wird als Startsignal für die Lebensdauermessungen benötigt. Damit passt das SPM-Interface den Positronenstrahl von NEPOMUC an die Bedürfnisse des SPM an.
Am SPM sollen ortsauflösende Positronen Lebensdauerspektroskopie Messungen mit einer Ortsauflösung von unter 1 µm und einer Pulsbreite von weniger als 150 ps erreicht werden. Dazu sind mehrere Stufen der Pulsformung und Fokussierung nötig.
Um die projektierten Ziele des SPM zu erreichen, muss am Abschluss des SPM-Interfaces ein Strahldurchmesser kleiner 200 µm und eine Pulsbreite von unter 250 ps (FWHM) erreicht werden. Die hohen Ansprüche an die Strahleigenschaften am Abschluss des SPM-Interfaces dienen außerdem dem effizienten Einkoppeln des Positronenstrahls in das SPM.
Um die Strahleigenschaften am Abschluss des SPM-Interfaces zu bestimmen, wurden mehrere Messungen durchgeführt. Die Messungen liefern die Grundlage für die Planung des weiteren Aufbaus des SPM an der Quelle NEPOMUC.
Für die Vermessungen des Strahlprofils des SPM-Interfaces wurde der Strahl mit einer Micro-Channel-Plate (MCP) direkt beobachtet. Der Bereich der höchsten Intensität des Positronenstrahls ist kreisförmig mit einem Durchmesser von 4mm FWHM. Das Intensitätsprofil ist gaußförmig. Durch eine Abbildung des Strahls mit einer elektrostatischen Linse auf die MCP konnte ein Strahldurchmesser von 2mm FWHM bei einer Brennweite von mm erreicht werden. Mit dieser Messung kann die kinetische Energie der transversalen Bewegung der Positronen auf 70meV abgeschätzt werden.
Ein rundes Strahlprofil mit gaußförmiger Intensität ist die Voraussetzung für die weiteren Messungen. In dieser Arbeit wurde eine Probenkammer zur ortsauflösenden Lebensdauerspektroskopie für das SPM-Interface gebaut. Die Probenkammer fokussiert den gepulsten Strahl mit Hilfe einer magnetischen Linse. Der magnetisch fokussierte Strahl kann durch Scannig-Spulen über eine Probe gerastert werden. Mit Hilfe der Probenkammer sind so ortsauflösende Messungen zur Bestimmung des minimal erreichbaren Strahldurchmessers möglich.
Als Grundlage für die ortsaufgelösten Messungen muss die erreichbare Zeitauflösung bekannt sein. Die Zeitauflösung ergibt sich durch die totale Zeitauflösung des Detektors und der Pulsbreite der erzeugten Positronenpulse. Für Pulsbreiten von unter 250 ps muss der kontinuierliche Positronenstrahl der Quelle NEPOMUC in mehreren Schritten zu Pulsen geformt werden. Dazu werden am SPM-Interface ein Sägezahn-Vorbuncher und zwei Sinus-Buncher sowie ein Chopper genutzt. Zur Bestimmung der Pulsbreite sind alle Pulsungkomponenten einzeln eingestellt und optimiert worden. Der Zeitfokus kann durch geeignete Einstellungen der Buncher- Amplitude und der Driftgeschwindigkeiten auf den Probenort in der Kammer gelegt werden. Durch die 50MHz Frequenz der Pulsung erreichen die Positronen alle vielfache von 20 ns die Probenposition t_n =n 20 ns (n e N). Liegt der Zeitfokus auf der Probe, ist die zeitliche Verteilung der ankommenden Positronen um t_n minimal. Die FWHM der gemessenen zeitlichen Verteilung (für viele Positronen aus mehreren Pulsen), der im SPM-Interface gepulsten Positronen entspricht der Pulsbreite.
Die Pulsbreite T_Puls wurde auf gute (257+/-3) ps bestimmt. Aus dem Vergleich der Zählrate mit und ohne Pulsung an der Probenposition ergibt sich ein Wirkungsgrad der Pulsung von 70%.
Am späteren Aufbau des SPM werden die im SPM-Interface erzeugten Pulse noch einmal gebuncht. Damit können aus den im SPM-Interface vorgeformten Pulsen schärfere Pulse im Bereich von 150 ps erzeugt werden.
Mit der erreichten Pulsbreite sind die Positronen Lebensdauermessungen mit der für das SPM-Interface gebauten Probenkammer möglich. Die Probenkammer erlaubt durch die im Laufe der Arbeit gebaute Hardware und in LabView programmierte Software vollautomatisierte ortsaufgelöste Positronen Lebensdauermessungen. Um mögliche Einstellungen der elektrischen Potenziale in der Kammer sowie für den Strom der fokussierenden magnetischen Linse für die Messungen zu finden, ist der Strahlverlauf in der Probenkammer mit COMSOL Multiphysics® simuliert worden. Vor den Messungen am SPM-Interface ist die Probenkammer auf Vakuumdichtigkeit und Hochspannungsfestigkeit bis 10 kV getestet worden. Die Tests verliefen problemlos, nach einem längeren Abpumpen wurde ein Druck von 1 10^(-6) mbar erreicht.
Aus den Messungen mit der Probenkammer des SPM-Interfaces soll der minimal erreichbare Strahldurchmesser bestimmt werden. Dazu wurden ortsaufgelöste Messungen durchgeführt. Die Probenkammer des SPM-Interfaces erlaubt einen Scan- Bereich von 1,5 x 1,5 mm. Der Scan-Bereich ist dabei weitestgehend frei von Verzeichnungen.
Durch die Geometrie der Probenkammer und die Abschirmung des Detektors sind Messungen mit geringem Untergrund möglich. Als Untergrund zählen alle 511 keV-Quanten, die nicht von einer Annihilation im Probenmaterial stammen. Das Peak zu Untergrund Verhältnis beträgt 1000. Damit ist die Aufnahme guter Einzelspektren ausgewählter Orte der Probe möglich. Mit Hilfe von Line-Scans ist die Ortsauflösung in der Probenkammer zu (180+-10) µm bestimmt. Um diesen Strahldurchmesser zu erreichen, wurde der Positronenstrahl in der Probenkammer mit der magnetischen Linse des zweiten Remoderators des SPM fokussiert. Durch die Verwendung dieser Linse ist am weiteren Aufbau des SPM ein vergleichbar kleiner Strahldurchmesser auf dem zweiten Remoderator möglich. Der Remoderator wirkt als gepulste Positronenquelle für die Positronen Lebensdauermessungen in der Probenkammer des SPM. Mit einem Quellendurchmesser von ca. 200 µm und der schmalen Energieverteilung des remoderierten Strahls sind Strahldurchmesser um 1 µm beim finalen Aufbau des SPM möglich.
Der Aufbau der Probenkammer des SPM-Interfaces sowie die durchgeführten Messungen waren sehr erfolgreich. Die in dieser Arbeit erreichten Ergebnisse erlauben den finalen Aufbau des SPM. Durch die Kenntnis des Strahldurchmessers kann die Positronen-Strahloptik zum Ankoppeln des SPM an das SPM-Interface effektiv ausgelegt werden. Schon mit dem Aufbau der Probenkammer des SPM-Interfaces sind Positronen Lebensdauerspektroskopie Messungen mit guter Orts- und sehr guter Zeitauflösung möglich.
Positronen Lebensdauermessungen mit einer Pulsbreite von 260 ps, einem Strahldurchmesser von 180 µm und mit einr hoher Intensität von 2000 Counts pro Sekunde sind weltweit einzigartig. Sie sind nur am Scanning-Positron-Microscope Interface mit der in dieser Arbeit gebauten Probenkammer des SPM-Interafces der Universität der Bundeswehr an der Positronenquelle NEPOMUC möglich.
BibTeX:
	@mastersthesis{Mitteneder2015ma,
	  author = {Mitteneder, Johannes},
	  title = {Erste ortsauflösende Positronen Lebensdauerspektroskopie am Scanning-Positron-Microscope Interface},
	  school = {Hochschule München},
	  year = {2015}
	}
	
Transport of a high brightness proton beam through the Munich tandem accelerator
M. Moser, C. Greubel, W. Carli, K. Peeper, P. Reichart, B. Urban, T. Vallentin and G. Dollinger; Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 348 (0) (2015) 34-42.
Abstract: Basic requirement for ion microprobes with sub-μm beam focus is a high brightness beam to fill the small phase space usually accepted by the ion microprobe with enough ion current for the desired application. We performed beam transport simulations to optimize beam brightness transported through the Munich tandem accelerator. This was done under the constraint of a maximum ion current of 10 μA that is allowed to be injected due to radiation safety regulations and beam power constrains. The main influence of the stripper foil in conjunction with intrinsic astigmatism in the beam transport on beam brightness is discussed. The calculations show possibilities for brightness enhancement by using astigmatism corrections and asymmetric filling of the phase space volume in the x- and y-direction.
BibTeX:
	@article{Moser2015,
	  author = {Moser, M. and Greubel, C. and Carli, W. and Peeper, K. and Reichart, P. and Urban, B. and Vallentin, T. and Dollinger, G.},
	  title = {Transport of a high brightness proton beam through the Munich tandem accelerator},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms},
	  year = {2015},
	  volume = {348},
	  number = {0},
	  pages = {34--42},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X14009495},
	  doi = {http://doi.org/10.1016/j.nimb.2014.11.068}
	}
	
Nanoscopic exclusion between Rad51 and 53BP1 after ion irradiation in human HeLa cells
J. Reindl, G.A. Drexler, S. Girst, C. Greubel, C. Siebenwirth, S.E. Drexler, G. Dollinger and A.A. Friedl; Physical Biology 12 (6) (2015) 066005.
Abstract: Many proteins involved in detection, signalling and repair of DNA double-strand breaks (DSB) accumulate in large number in the vicinity of DSB sites, forming so called foci. Emerging evidence suggests that these foci are sub-divided in structural or functional domains. We use stimulated emission depletion (STED) microscopy to investigate localization of mediator protein 53BP1 and recombination factor Rad51 after irradiation of cells with low linear energy transfer (LET) protons or high LET carbon ions. With a resolution better than 100 nm, STED microscopy and image analysis using a newly developed analyzing algorithm, the reduced product of the differences from the mean, allowed us to demonstrate that with both irradiation types Rad51 occupies spherical regions of about 200 nm diameter. These foci locate within larger 53BP1 accumulations in regions of local 53BP1 depletion, similar to what has been described for the localization of Brca1, CtIP and RPA. Furthermore, localization relative to 53BP1 and size of Rad51 foci was not different after irradiation with low and high LET radiation. As expected, 53BP1 foci induced by low LET irradiation mostly contained one Rad51 focal structure, while after high LET irradiation, most foci contained >1 Rad51 accumulation.
BibTeX:
	@article{Reindl2015,
	  author = {Judith Reindl and Guido A Drexler and Stefanie Girst and Christoph Greubel and Christian Siebenwirth and Sophie E Drexler and Günther Dollinger and Anna A Friedl},
	  title = {Nanoscopic exclusion between Rad51 and 53BP1 after ion irradiation in human HeLa cells},
	  journal = {Physical Biology},
	  year = {2015},
	  volume = {12},
	  number = {6},
	  pages = {066005},
	  url = {http://stacks.iop.org/1478-3975/12/i=6/a=066005},
	  doi = {http://doi.org/10.1088/1478-3975/12/6/066005}
	}
	
Investigation of EBT2 and EBT3 films for proton dosimetry in the 4–20 MeV energy range
S. Reinhardt, M. Würl, C. Greubel, N. Humble, J. Wilkens, M. Hillbrand, A. Mairani, W. Assmann and K. Parodi; Radiation and Environmental Biophysics 54 (1) (2015) 71-79.
Abstract: Radiochromic films such as Gafchromic EBT2 or EBT3 films are widely used for dose determination in radiation therapy because they offer a superior spatial resolution compared to any other digital dosimetric 2D detector array. The possibility to detect steep dose gradients is not only attractive for intensity-modulated radiation therapy with photons but also for intensity-modulated proton therapy. Their characteristic dose rate-independent response makes radiochromic films also attractive for dose determination in cell irradiation experiments using laser-driven ion accelerators, which are currently being investigated as future medical ion accelerators. However, when using these films in ion beams, the energy-dependent dose response in the vicinity of the Bragg peak has to be considered. In this work, the response of these films for low-energy protons is investigated. To allow for reproducible and background-free irradiation conditions, the films were exposed to mono-energetic protons from an electrostatic accelerator, in the 4–20 MeV energy range. For comparison, irradiation with clinical photons was also performed. It turned out that in general, EBT2 and EBT3 films show a comparable performance. For example, dose–response curves for photons and protons with energies as low as 11 MeV show almost no differences. However, corrections are required for proton energies below 11 MeV. Care has to be taken when correction factors are related to an average LET from depth–dose measurements, because only the dose-averaged LET yields similar results as obtained in mono-energetic measurements.
BibTeX:
	@article{Reinhardt2015,
	  author = {Reinhardt, S. and Würl, M. and Greubel, C. and Humble, N. and Wilkens, J.J. and Hillbrand, M. and Mairani, A. and Assmann, W. and Parodi, K.},
	  title = {Investigation of EBT2 and EBT3 films for proton dosimetry in the 4–20 MeV energy range},
	  journal = {Radiation and Environmental Biophysics},
	  year = {2015},
	  volume = {54},
	  number = {1},
	  pages = {71--79},
	  url = {http://link.springer.com/article/10.1007%2Fs00411-014-0581-2},
	  doi = {http://doi.org/10.1007/s00411-014-0581-2}
	}
	
Sub-micrometer 20 MeV protons or 45 MeV lithium spot irradiation enhances yields of dicentric chromosomes due to clustering of DNA double-strand breaks
T. Schmid, W. Friedland, C. Greubel, S. Girst, J. Reindl, C. Siebenwirth, K. Ilicic, E. Schmid, G. Multhoff, E. Schmitt, P. Kundrát and G. Dollinger; Mutation Research/Genetic Toxicology and Environmental Mutagenesis 793 (2015) 30-40.
Abstract: Abstract In conventional experiments on biological effects of radiation types of diverse quality, micrometer-scale double-strand break (DSB) clustering is inherently interlinked with clustering of energy deposition events on nanometer scale relevant for DSB induction. Due to this limitation, the role of the micrometer and nanometer scales in diverse biological endpoints cannot be fully separated. To address this issue, hybrid human-hamster AL cells have been irradiated with 45 MeV (60 keV/μm) lithium ions or 20 MeV (2.6 keV/μm) protons quasi-homogeneously distributed or focused to 0.5 × 1 μm2 spots on regular matrix patterns (point distances up to 10.6 × 10.6 μm), with pre-defined particle numbers per spot to provide the same mean dose of 1.7 Gy. The yields of dicentrics and their distribution among cells have been scored. In parallel, track-structure based simulations of DSB induction and chromosome aberration formation with PARTRAC have been performed. The results show that the sub-micrometer beam focusing does not enhance DSB yields, but significantly affects the DSB distribution within the nucleus and increases the chance to form DSB pairs in close proximity, which may lead to increased yields of chromosome aberrations. Indeed, the experiments show that focusing 20 lithium ions or 451 protons per spot on a 10.6 μm grid induces two or three times more dicentrics, respectively, than a quasi-homogenous irradiation. The simulations reproduce the data in part, but in part suggest more complex behavior such as saturation or overkill not seen in the experiments. The direct experimental demonstration that sub-micrometer clustering of DSB plays a critical role in the induction of dicentrics improves the knowledge on the mechanisms by which these lethal lesions arise, and indicates how the assumptions of the biophysical model could be improved. It also provides a better understanding of the increased biological effectiveness of high-LET radiation.
BibTeX:
	@article{Schmid2015,
	  author = {Schmid, T.E. and Friedland, W. and Greubel, C. and Girst, S. and Reindl, J. and Siebenwirth, C. and Ilicic, K. and Schmid, E. and Multhoff, G. and Schmitt, E. and Kundrát, P. and Dollinger, G.},
	  title = {Sub-micrometer 20 MeV protons or 45 MeV lithium spot irradiation enhances yields of dicentric chromosomes due to clustering of DNA double-strand breaks},
	  booktitle = {Insights into formation and consequences of chromosome aberrations: Report on the 11th International Symposium on Chromosomal Aberrations (ISCA 11), Rhodes , Greece, September 12-14, 2014},
	  journal = {Mutation Research/Genetic Toxicology and Environmental Mutagenesis},
	  year = {2015},
	  volume = {793},
	  pages = {30--40},
	  url = {http://www.sciencedirect.com/science/article/pii/S1383571815002053},
	  doi = {http://doi.org/10.1016/j.mrgentox.2015.07.015}
	}
	
Determination of the accuracy for targeted irradiations of cellular substructures at SNAKE
C. Siebenwirth, C. Greubel, S. Drexler, S. Girst, J. Reindl, D. Walsh, G. Dollinger, A. Friedl, T. Schmid and G. Drexler; Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 348 (0) (2015) 137-142.
Abstract: In the last 10 years the ion microbeam SNAKE, installed at the Munich 14 MV tandem accelerator, has been successfully used for radiobiological experiments by utilizing pattern irradiation without targeting single cells. Now for targeted irradiation of cellular substructures a precise irradiation device was added to the live cell irradiation setup at SNAKE. It combines a sub-micrometer single ion irradiation facility with a high resolution optical fluorescence microscope. Most systematic errors can be reduced or avoided by using the same light path in the microscope for beam spot verification as well as for and target recognition. In addition online observation of the induced cellular responses is possible. The optical microscope and the beam delivering system are controlled by an in-house developed software which integrates the open-source image analysis software, CellProfiler, for semi-automatic target recognition.
BibTeX:
	@article{Siebenwirth2015,
	  author = {Siebenwirth, C. and Greubel, C. and Drexler, S.E. and Girst, S. and Reindl, J. and Walsh, D.W.M. and Dollinger, G. and Friedl, A.A. and Schmid, T.E. and Drexler, G.A.},
	  title = {Determination of the accuracy for targeted irradiations of cellular substructures at SNAKE},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms},
	  year = {2015},
	  volume = {348},
	  number = {0},
	  pages = {137--142},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X15000865},
	  doi = {http://doi.org/10.1016/j.nimb.2015.01.064}
	}
	
Quantification of water in hydrous ringwoodite
S.-M. Thomas, S.D. Jacobsen, C.R. Bina, P. Reichart, M. Moser, E.H. Hauri, M. Koch-Müller, J.R. Smyth and G. Dollinger; Frontiers in Earth Science 2 (2015) 38/1-10.
Abstract: Ringwoodite, γ-(Mg,Fe)2SiO4, in the lower 150 km of Earth's mantle transition zone (410–660 km depth) can incorporate up to 1.5–2 wt% H2O as hydroxyl defects. We present a mineral-specific IR calibration for the absolute water content in hydrous ringwoodite by combining results from Raman spectroscopy, secondary ion mass spectrometry (SIMS) and proton-proton (pp)-scattering on a suite of synthetic Mg- and Fe-bearing hydrous ringwoodites. H2O concentrations in the crystals studied here range from 0.46 to 1.7 wt% H2O (absolute methods), with the maximum H2O in the same sample giving 2.5 wt% by SIMS calibration. Anchoring our spectroscopic results to absolute H-atom concentrations from pp-scattering measurements, we report frequency-dependent integrated IR-absorption coefficients for water in ringwoodite ranging from 78,180 to 158,880 Lmol−1cm−2, depending upon frequency of the OH absorption. We further report a linear wavenumber IR calibration for H2O quantification in hydrous ringwoodite across the Mg2SiO4-Fe2SiO4 solid solution, which will lead to more accurate estimations of the water content in both laboratory-grown and naturally occurring ringwoodites. Re-evaluation of the IR spectrum for a natural hydrous ringwoodite inclusion in diamond from the study of Pearson et al. (2014) indicates the crystal contains 1.43 ± 0.27 wt% H2O, thus confirming near-maximum amounts of H2O for this sample from the transition zone.
BibTeX:
	@article{Thomas2015,
	  author = {Thomas, Sylvia-Monique and Jacobsen, Steven D. and Bina, Craig R. and Reichart, Patrick and Moser, Marcus and Hauri, Erik H. and Koch-Müller, Monika and Smyth, Joseph R. and Dollinger, Günther},
	  title = {Quantification of water in hydrous ringwoodite},
	  journal = {Frontiers in Earth Science},
	  year = {2015},
	  volume = {2},
	  pages = {38/1-10},
	  url = {http://www.frontiersin.org/earth_and_planetary_materials/10.3389/feart.2014.00038/abstract},
	  doi = {http://doi.org/10.3389/feart.2014.00038}
	}
	
A microbeam slit system for high beam currents
T. Vallentin, M. Moser, S. Eschbaumer, C. Greubel, T. Haase, P. Reichart, T. Rösch and G. Dollinger; Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 348 (0) (2015) 43-47.
Abstract: A new microbeam slit system for high beam currents of 10 μA was built up to improve the brightness transport of a proton beam with a kinetic energy of up to 25 MeV into the microprobe SNAKE. The new slit system features a position accuracy of less than 1 μm under normal operating conditions and less than 2 μm if the beam is switched on and off. The thermal management with a powerful watercooling and potential-free thermocouple feedback controlled heating cables is optimized for constant slit aperture at thermal power input of up to 250 W. The transparent zone is optimized to 0.7 μm due to the use of tungsten formed to a cylindrical surface with a radius r = 100 mm and mechanically lapped surface to minimize small angle scattering effects and to minimize the number of ions passing the slits with low energy loss. Electrical isolation of the slit tip enables slit current monitoring, e.g. for tandem accelerator feedback control. With the ability to transport up to 10 μA of protons with the new microslit system, the brightness B_exp transported into the microprobe was increased by a factor of 2 compared to low current injection using the old slit system.
BibTeX:
	@article{Vallentin2015,
	  author = {Vallentin, T. and Moser, M. and Eschbaumer, S. and Greubel, C. and Haase, T. and Reichart, P. and Rösch, T. and Dollinger, G.},
	  title = {A microbeam slit system for high beam currents},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms},
	  year = {2015},
	  volume = {348},
	  number = {0},
	  pages = {43--47},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X14010313},
	  doi = {http://doi.org/10.1016/j.nimb.2014.12.015}
	}
	

2014

Interphase of a polymer at a solid interface
H.J. Butt, H. Duran, W. Egger, F. Faupel, V. Harmandaris, S. Harms, K. Johnston, K. Kremer, F.Y. Lin, L. Lue, C. Ohrt, K. Rätzke, L. Ravelli, W. Steffen and S.D.B. Vianna; Macromolecules 47 (23) (2014) 8459-8465.
Abstract: Atomistic molecular dynamics simulations of a chemically realistic model of atactic short-chain polystyrene between gold surfaces (111) and positron annihilation lifetime spectroscopy experiments on similar polystyrene thin films on gold were performed. Results from both approaches show that the free volume voids in the film have a slightly smaller average size than in bulk polystyrene. In agreement to that the existence of an interphase of higher density at the polymer-solid substrate interface is shown both by the simulation as well as in the experiment. The average shape of the voids is similar in the bulk and the film.
BibTeX:
	@article{Butt2014,
	  author = {Butt, H. J. and Duran, H. and Egger, W. and Faupel, F. and Harmandaris, V. and Harms, S. and Johnston, K. and Kremer, K. and Lin, F. Y. and Lue, L. and Ohrt, C. and Rätzke, K. and Ravelli, L. and Steffen, W. and Vianna, S. D. B.},
	  title = {Interphase of a polymer at a solid interface},
	  journal = {Macromolecules},
	  year = {2014},
	  volume = {47},
	  number = {23},
	  pages = {8459-8465},
	  url = {http://pubs.acs.org/doi/abs/10.1021/ma501747j},
	  doi = {http://doi.org/10.1021/ma501747j}
	}
	
Interphases in polymer solid-contacts and nanocomposites probed by positron annihilation lifetime spectroscopy
C. Ohrt, T. Koschine, S. Harms, F. Faupel, K. Rätzke, W. Egger, L. Ravelli, L. Willner and G. Schneider; Soft Materials 12 (2014) S135-S141.
Abstract: At polymer-solid contacts with thermoplastic polymers, the chain characteristics can deviate from the bulk on a length-scale of several nanometer in the so-called interphase. Such an interphase depends on the interaction between respective macromolecule and substrate, and affects the free volume in the polymer. Here, we review our experiments on the characterization of the free volume by positron lifetime spectroscopy at planar and curved interfaces. For Teflon AF on silicon, we identify a layer of increased density, corresponding to an interphase width of some 10 nm. PEP based nanocomposites with functionalized silica show no interphase, whereas for functionalized POSS an interphase is detected.
BibTeX:
	@article{Ohrt2014,
	  author = {Ohrt, C. and Koschine, T. and Harms, S. and Faupel, F. and Rätzke, K. and Egger, W. and Ravelli, L. and Willner, L. and Schneider, G.J.},
	  title = {Interphases in polymer solid-contacts and nanocomposites probed by positron annihilation lifetime spectroscopy},
	  journal = {Soft Materials},
	  year = {2014},
	  volume = {12},
	  pages = {S135-S141},
	  url = {http://www.tandfonline.com/doi/abs/10.1080/1539445X.2014.957835},
	  doi = {http://doi.org/10.1080/1539445X.2014.957835}
	}
	
Three-dimensional microscopy of deuterium in tungsten
K. Peeper, M. Moser, P. Reichart, E. Markina, S. Elgeti (Lindig), M. Balden, T. Schwarz-Selinger, M. Mayer and G. Dollinger; Physica Scripta T159 (2014) 014070.
Abstract: The hydrogen isotope retention in tungsten is an important issue for fusion devices. In this paper we study the possibility of using a μ m-focused deuterium beam in order to quantify deuterium distributions in microscopic dimensions. Due to the lack of cross-section data for deuteron-deuteron-scattering (dd-scattering) a validated reference sample is needed. For this purpose we used a15 μ m thick aluminum foil covered by a-C:D-layers that have been deposited in a CD 4 plasma discharge from both sides. At the SNAKE facility of the Munich tandem accelerator we already established a three-dimensional microscopy of hydrogen using protons within an energy range between 17 and 25 MeV. Now, we have tested the possibility for deuteron microscopy. As a first application we analyzed a25 μ m foil implanted with 2.0 × 10 20 atom cm −2 deuterons.
BibTeX:
	@article{Peeper2014,
	  author = {Peeper, K. and Moser, M. and Reichart, P. and Markina, E. and Elgeti (Lindig), S. and Balden, M. and Schwarz-Selinger, Th. and Mayer, M. and Dollinger, G.},
	  title = {Three-dimensional microscopy of deuterium in tungsten},
	  journal = {Physica Scripta},
	  year = {2014},
	  volume = {T159},
	  pages = {014070},
	  url = {http://stacks.iop.org/1402-4896/2014/i=T159/a=014070},
	  doi = {http://doi.org/10.1088/0031-8949/2014/T159/014070}
	}
	
Improvement of the Pulsed Low Energy Positron System (PLEPS) for complex problems in materials science
Luca Ravelli; Dissertation, Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, 2014.
Abstract: This thesis concerns the application and the improvement of the Pulsed Low Energy Positron System (PLEPS) at the high intensity positron source NEPOMUC at the Munich research reactor FRM-II. This system is used for the defect study in complex materials. Positrons are the ideal probe for non-destructive investigations of vacancy-like defects in matter. The combination of positron lifetime spectroscopy with a pulsed, monochromatic positron beam of variable energy conveys information on the type and the concentration of defects down to the sub-ppm range and their depth-profile with nm resolution. Defect structures in two materials were investigated with PLEPS for this thesis. First, we studied strontium titanate (STO), which is a material of great relevance in modern oxide electronics. The cation vacancies (strontium and titanium vacancies, VSr and VTi, respectively) were identified in STO films deposited by Pulsed Laser Deposition (PLD). It was also shown, that in commercially available STO substrates only titanium vacancies with a concentration of (1.26±0.16) ppm could be detected and that upon annealing in the same conditions as for the PLD procedure a 400 nm thick layer of titanium-oxygen divacancies VTi-O was introduced. The second investigation was performed in permanently densified silica glasses. In combination with XRD measurements the structure evolution upon densification was analyzed. In particular, it was demonstrated that the average inter-tetrahedral void radius measured with PLEPS permits to predict the shift of the first sharp diffraction peak of the static structure factor as a function of the density. In the second part of this work, from the experience gained with PLEPS in the course of this thesis, the limits of the apparatus were analyzed, measures to improve the quality of the positron lifetime spectra measured with PLEPS were identified and tested. Comprehensive simulations were performed to understand the structures in the background of the measured lifetime spectra and possible countermeasures were found. Modifications of the pulsing system allowed to a) improve the time resolution of PLEPS to about 250 ps, b) measure precisely positron lifetime longer than 3 ns, which enhances the capabibility of PLEPS for the determination of free volumes in polymer samples and membranes and c) get rid of disturbing structures in the background of the positron lifetime spectra. Thus, PLEPS in combination with the high intensity positron source NEPOMUC can be considered as the most productive pulsed positron beam for defect depth-profiling in materials currently available world-wide.
BibTeX:
	@phdthesis{Ravelli2014diss,
	  author = {Ravelli, Luca},
	  title = {Improvement of the Pulsed Low Energy Positron System (PLEPS) for complex problems in materials science},
	  school = {Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik},
	  year = {2014},
	  url = {http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:706-3513}
	}
	
Erprobung von Szintillator-Detektoren bei tiefen Temperaturen
Johannes Schütze; Masters-Thesis, Universität der Bundeswehr München, 2014.
BibTeX:
	@mastersthesis{Schuetze2014ma,
	  author = {Schütze, Johannes},
	  title = {Erprobung von Szintillator-Detektoren bei tiefen Temperaturen},
	  school = {Universität der Bundeswehr München},
	  year = {2014}
	}
	
PLEPS study of ions implanted RAFM steels
S. Sojak, V. Slugeň, W. Egger, L. Ravelli, M. Petriska, J. Veterníková, M. Stacho and V. Sabelová; Journal of Physics: Conference Series 505 (1) (2014) 012016.
Abstract: Current nuclear power plants (NPP) require radiation, heat and mechanical resistance of their structural materials with the ability to stay operational during NPP planned lifetime. Radiation damage much higher, than in the current NPP, is expected in new generations of nuclear power plants, such as Generation IV and fusion reactors. Investigation of perspective structural materials for new generations of nuclear power plants is among others focused on study of reduced activation ferritic/martensitic (RAFM) steels. These steels have good characteristics as reduced activation, good resistance to volume swelling, good radiation, and heat resistance. Our experiments were focused on the study of microstructural changes of binary Fe-Cr alloys with different chromium content after irradiation, experimentally simulated by ion implantations. Fe-Cr alloys were examined, by Pulsed Low Energy Positron System (PLEPS) at FRM II reactor in Garching (Munich), after helium ion implantations at the dose of 0.1 C/cm(2). The investigation was focused on the chromium effect and the radiation defects resistivity. In particular, the vacancy type defects (monovacancies, vacancy clusters) have been studied. Based on our previous results achieved by conventional lifetime technique, the decrease of the defects size with increasing content of chromium is expected also for PLEPS measurements.
BibTeX:
	@article{Sojak2014,
	  author = {Sojak, S. and Slugeň, V. and Egger, W. and Ravelli, L. and Petriska, M. and Veterníková, J. and Stacho, M. and Sabelová, V.},
	  title = {PLEPS study of ions implanted RAFM steels},
	  journal = {Journal of Physics: Conference Series},
	  year = {2014},
	  volume = {505},
	  number = {1},
	  pages = {012016},
	  editor = {Hugenschmidt, C and Piochacz, C},
	  note = {13th International Workshop on Slow Positron Beam Techniques and Applications (SLOPOS), Tech Univ Munchen, Munich, GERMANY, SEP 15-20, 2013},
	  url = {http://iopscience.iop.org/1742-6596/505/1/012016/},
	  doi = {http://doi.org/10.1088/1742-6596/505/1/012016}
	}
	
A Microbeam Slit System for High Beam Currents
Thomas Vallentin; Masters-Thesis, Universität der Bundeswehr München, 2014.
Abstract: A new microbeam slit system for high beam currents of 10 µA was built up to improve the brightness transport of a proton beam with a kinetic energy of up to 25 MeV into the microprobe SNAKE. The new slit system features a position accuracy of less than 1 µm under normal operating conditions and less than 2 µm if the beam is switched on and off [1]. The thermal management with a powerful watercooling and potential-free thermocouple feedback controlled heating cables is optimized for constant slit aperture. The transparent zone is reduced to 0.7 µm due to the use of mechanically lapped tungsten as slit tip material to reduce small angle scattering effects and to reduce the number of ions passing the slits with low energy loss. The slits feature electrical isolation of the slit tip to make slit current monitoring possible, e.g. for tandem feedback control. With the high possible thermal power input of 250 W we could measure for the first time the high-energy beam brightness B_exp of injected beams with high emittances of eps_in = 2pi mmmrad. The brightness B_exp transported into the microprobe was improved to B_exp = 2 µA/(mm2 mrad2 MeV) and therefore brightness loss through the tandem accelerator was around 25 %. The higher transported brightness B_exp gives the opportunity to achieve the high resolution of the single ion, cell irradiation setup [8, 7] ( 320 nm) also at higher current of I_exp = 100 pA for materials analysis [5].
BibTeX:
	@mastersthesis{Vallentin2014ma,
	  author = {Vallentin, Thomas},
	  title = {A Microbeam Slit System for High Beam Currents},
	  school = {Universität der Bundeswehr München},
	  year = {2014}
	}
	
Structural evolution and medium range order in permanently densified vitreous SiO2
M. Zanatta, G. Baldi, R.S. Brusa, W. Egger, A. Fontana, E. Gilioli, S. Mariazzi, G. Monaco, L. Ravelli and F. Sacchetti; Physical Review Letters 112 (4) (2014) 045501.
Abstract: Positron annihilation lifetime spectroscopy is employed to measure the size of the interstitial void spaces characterizing the structure of a set of permanently densified SiO2 glasses. The average volume of the voids is markedly affected by the densification process and linearly shrinks by almost an order of magnitude after a relative density variation of 22%. In addition, x-ray diffraction shows that this change of density does not modify appreciably the short range order, which remains organized in SiO4 tetrahedra. These results strongly suggest a porous medium description for v-SiO2 glasses where the compressibility and the medium range order are dominated by the density variation of the voids volume up to densities close to that of α-quartz. © 2014 American Physical Society.
BibTeX:
	@article{Zanatta2014,
	  author = {Zanatta, M. and Baldi, G. and Brusa, R. S. and Egger, W. and Fontana, A. and Gilioli, E. and Mariazzi, S. and Monaco, G. and Ravelli, L. and Sacchetti, F.},
	  title = {Structural evolution and medium range order in permanently densified vitreous SiO2},
	  journal = {Physical Review Letters},
	  year = {2014},
	  volume = {112},
	  number = {4},
	  pages = {045501},
	  url = {http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.112.045501},
	  doi = {http://doi.org/10.1103/PhysRevLett.112.045501}
	}
	
The Effects of Ultra-High Dose Rate Proton Irradiation on Growth Delay in the Treatment of Human Tumor Xenografts in Nude Mice
O. Zlobinskaya, C. Siebenwirth, C. Greubel, V. Hable, R. Hertenberger, N. Humble, S. Reinhardt, D. Michalski, B. Röper, G. Multhoff, G. Dollinger, J. Wilkens and T. Schmid; Radiation Research 181 (2) (2014) 177-183.
Abstract: The new technology of laser-driven ion acceleration (LDA) has shown the potential for driving highly brilliant particle beams. Laser-driven ion acceleration differs from conventional proton sources by its ultra-high dose rate, whose radiobiological impact should be investigated thoroughly before adopting current clinical dose concepts. The growth of human FaDu tumors transplanted onto the hind leg of nude mice was measured sonographically. Tumors were irradiated with 20 Gy of 23 MeV protons at pulsed mode with single pulses of 1 ns duration or continuous mode (?100 ms) in comparison to controls and to a dose-response curve for 6 MV photons. Tumor growth delay and the relative biological effectiveness (RBE) were calculated for all irradiation modes. The mean target dose reconstructed from Gafchromic films was 17.4 ± 0.8 Gy for the pulsed and 19.7 ± 1.1 Gy for the continuous irradiation mode. The mean tumor growth delay was 34 ± 6 days for pulsed, 35 ± 6 days for continuous protons, and 31 ± 7 days for photons 20 ± 1.2 Gy, resulting in RBEs of 1.22 ± 0.19 for pulsed and 1.10 ± 0.18 for continuous protons, respectively. In summary, protons were found to be significantly more effective in reducing the tumor volume than photons (P The new technology of laser-driven ion acceleration (LDA) has shown the potential for driving highly brilliant particle beams. Laser-driven ion acceleration differs from conventional proton sources by its ultra-high dose rate, whose radiobiological impact should be investigated thoroughly before adopting current clinical dose concepts. The growth of human FaDu tumors transplanted onto the hind leg of nude mice was measured sonographically. Tumors were irradiated with 20 Gy of 23 MeV protons at pulsed mode with single pulses of 1 ns duration or continuous mode (?100 ms) in comparison to controls and to a dose-response curve for 6 MV photons. Tumor growth delay and the relative biological effectiveness (RBE) were calculated for all irradiation modes. The mean target dose reconstructed from Gafchromic films was 17.4 ± 0.8 Gy for the pulsed and 19.7 ± 1.1 Gy for the continuous irradiation mode. The mean tumor growth delay was 34 ± 6 days for pulsed, 35 ± 6 days for continuous protons, and 31 ± 7 days for photons 20 ± 1.2 Gy, resulting in RBEs of 1.22 ± 0.19 for pulsed and 1.10 ± 0.18 for continuous protons, respectively. In summary, protons were found to be significantly more effective in reducing the tumor volume than photons (P
BibTeX:
	@article{Zlobinskaya2014,
	  author = {Zlobinskaya, O. and Siebenwirth, C. and Greubel, C. and Hable, V. and Hertenberger, R. and Humble, N. and Reinhardt, S. and Michalski, D. and Röper, B. and Multhoff, G. and Dollinger, G. and Wilkens, J.J. and Schmid, T.E.},
	  title = {The Effects of Ultra-High Dose Rate Proton Irradiation on Growth Delay in the Treatment of Human Tumor Xenografts in Nude Mice},
	  booktitle = {Radiation Research},
	  journal = {Radiation Research},
	  year = {2014},
	  volume = {181},
	  number = {2},
	  pages = {177--183},
	  url = {http://www.rrjournal.org/doi/abs/10.1667/RR13464.1},
	  doi = {http://doi.org/10.1667/RR13464.1}
	}
	

2013

Development of a new time and position resolving detector for the pulsed low energy positron system PLEPS
U. Ackermann, W. Egger, P. Sperr, B. Löwe, L. Ravelli, G. Kögel, G. Dollinger and O. Jagutzki; Journal of Physics: Conference Series 443 (1) (2013) 012095.
Abstract: The pulsed low energy positron system PLEPS at the Munich research reactor FRM-II is a user facility for depth resolved positron lifetime measurements. Besides positron lifetime measurements 2D-AMOC (Two Dimensional Age Momentum Correlation) experiments are also possible. 2D-AMOC provides in coincidence the lifetime of the positron and the longitudinal momentum distribution of the annihilated electron. It would be of great scientific concern to measure simultaneously the entire 3D-momentum distribution of the electron annihilating with the positron and the corresponding lifetime of the positron (4D-AMOC). To perform 4D-AMOC measurements a time and position resolving detector is required in coincidence with a pixelated Germanium detector. Therefore a time and spatially resolving detector is currently developed at our institute with envisaged time resolution of 100 ps (FWHM) and a spatial resolution of about 2.6 mm (FWHM) over an area of 12 cm2. First test measurements have been carried out with a 25 mm diameter MCP (Micro Channel Plate) image intensifier and with special delay-line anode readout for the spatial information. Up to now 178 ps (FWHM) time resolution and on average 3.4 mm (FWHM) position resolution have been achieved with BaF2 as scintillator material and a 60Co source.
BibTeX:
	@article{Ackermann2013,
	  author = {Ackermann, U. and Egger, W. and Sperr, P. and Löwe, B. and Ravelli, L. and Kögel, G. and Dollinger, G. and Jagutzki, O.},
	  title = {Development of a new time and position resolving detector for the pulsed low energy positron system PLEPS},
	  journal = {Journal of Physics: Conference Series},
	  year = {2013},
	  volume = {443},
	  number = {1},
	  pages = {012095},
	  url = {http://iopscience.iop.org/1742-6596/443/1/012095/},
	  doi = {http://doi.org/10.1088/1742-6596/443/1/012095}
	}
	
Surfaces of colloidal PbSe nanocrystals probed by thin-film positron annihilation spectroscopy
L. Chai, W. Al-Sawai, Y. Gao, A. Houtepen, P. Mijnarends, B. Barbiellini, H. Schut, L. Van Schaarenburg, M. Van Huis, L. Ravelli, W. Egger, S. Kaprzyk, A. Bansil and S. Eijt; APL Materials 1 (2) (2013) 022111.
Abstract: Positron annihilation lifetime spectroscopy and positron-electron momentum density (PEMD) studies on multilayers of PbSe nanocrystals (NCs), supported by transmission electron microscopy, show that positrons are strongly trapped at NC surfaces, where they provide insight into the surface composition and electronic structure of PbSe NCs. Our analysis indicates abundant annihilation of positrons with Se electrons at the NC surfaces and with O electrons of the oleic ligands bound to Pb ad-atoms at the NC surfaces, which demonstrates that positrons can be used as a sensitive probe to investigate the surface physics and chemistry of nanocrystals inside multilayers. Ab initio electronic structure calculations provide detailed insight in the valence and semi-core electron contributions to the positron-electron momentum density of PbSe. Both lifetime and PEMD are found to correlate with changes in the particle morphology characteristic of partial ligand removal.
BibTeX:
	@article{Chai2013,
	  author = {Chai, L. and Al-Sawai, W. and Gao, Y. and Houtepen, A.J. and Mijnarends, P.E. and Barbiellini, B. and Schut, H. and Van Schaarenburg, L.C. and Van Huis, M.A. and Ravelli, L. and Egger, W. and Kaprzyk, S. and Bansil, A. and Eijt, S.W.H.},
	  title = {Surfaces of colloidal PbSe nanocrystals probed by thin-film positron annihilation spectroscopy},
	  journal = {APL Materials},
	  year = {2013},
	  volume = {1},
	  number = {2},
	  pages = {022111},
	  url = {http://aip.scitation.org/doi/10.1063/1.4818001},
	  doi = {http://doi.org/10.1063/1.4818001}
	}
	
Subdiffusion Supports Joining Of Correct Ends During Repair Of DNA Double-Strand Breaks
S. Girst, V. Hable, G.A. Drexler, C. Greubel, C. Siebenwirth, M. Haum, A.A. Friedl and G. Dollinger; Scientific Reports 3 (2013) 2511.
Abstract: The mobility of damaged chromatin regions in the nucleus may affect the probability of mis-repair. In this work, live-cell observation and distance tracking of GFP-tagged DNA damage response protein MDC1 was used to study the random-walk behaviour of chromatin domains containing radiation-induced DNA double-strand breaks (DSB). Our measurements indicate a subdiffusion-type random walk process with similar time dependence for isolated and clustered DSBs that were induced by 20 MeV proton or 43 MeV carbon ion micro-irradiation. As compared to normal diffusion, subdiffusion enhances the probability that both ends of a DSB meet, thus promoting high efficiency DNA repair. It also limits their probability of long-range movements and thus lowers the probability of mis-rejoining and chromosome aberrations.
BibTeX:
	@article{Girst2013,
	  author = {Girst, S. and Hable, V. and Drexler, G. A. and Greubel, C. and Siebenwirth, C. and Haum, M. and Friedl, A. A. and Dollinger, G.},
	  title = {Subdiffusion Supports Joining Of Correct Ends During Repair Of DNA Double-Strand Breaks},
	  journal = {Scientific Reports},
	  year = {2013},
	  volume = {3},
	  pages = {2511},
	  url = {http://www.nature.com/articles/srep02511},
	  doi = {http://doi.org/10.1038/srep02511}
	}
	
Einfluss der zeitlichen und räumlichen Fokussierung auf die strahlenbiologische Wirksamkeit von Protonen.
Christoph Greubel; Dissertation, Universität der Bundeswehr München, 2013.
Abstract: In dieser Arbeit wurde der Einfluss von auf Nanosekunden gepulster (zeitlich fokussierter) Dosisdeposition, im zweiten Teil von auf Submikrometer (räumlich) fokussierter Dosisdeposition auf die relative biologische Wirksamkeit, RBE, studiert. Die Effekte gepulster Bestrahlung auf Nanosekunden Zeitskala sind vor allem für eine mögliche Anwendung der Laserbeschleunigung von Ionen in der Tumortherapie, welche die Dosisdeposition auf einer Nanosekunden Zeitskala erwarten lässt, von Bedeutung. Zur Untersuchung wurde die Wachstumsverzögerung von zwei menschlichen Plattenepitelkarzinomen aus dem Mund- und Rachenraum, FaDu und XF354, im Mausmodell nach Bestrahlung mit einer Fraktion von nominell 20 Gy gemessen. In Ermangelung geeigneter lasergetriebener Ionenstrahlen wurde hierzu mittels konventioneller Technik am Rasterionenmikroskop SNAKE am Müchener Tandembeschleuniger ein auf 1,3 ns (volle Halbwertsbreite) gepulster 23 MeV Protonenstrahl mit einer Fluenz pro Einzelpuls von bis zu 109 cm-2 präpariert, sowie ein kontinuierlicher Protonenstrahl zur Dosisdeposition auf Millisekunden Zeitskala für direkte Vergleichsmessungen. Die Bestrahlung der maximal 4 mm tiefen und 7 mm im Durchmesser messenden Tumore erfolgt voxelweise, wobei die komplette Fluenz eines Voxels mit einem Nanosekunden Puls appliziert wird. An jedem Punkt im Tumor deponiert mindestens ein Puls eine Dosis zwischen 1,0 Gy und 2,7 Gy. Der RBE für die Wachstumsverzögerung von FaDu Tumoren bezüglich 6 MV Röntgenstrahlung wurde nach kontinuierlicher Dosisdeposition zu 1,10 ± 0,14, nach gepulster Dosisdeposition zu 1,22 ± 0,17 gemessen. Auch für die XF354 Tumore konnte kein signifikanter Unterschied in der Wachstumsverzögerung gemessen werden. Die Messungen zeigen keine Anzeichen für eine geänderte Wirksamkeit von Nanosekunden gepulster Dosisdeposition. Im zweiten Teil der Arbeit wurden die Auswirkungen von räumlich fokussierter Dosisdeposition am Endpunkt der Induktion von dizentrischen Chromosomen und Mikrokernen untersucht. Durch die Submikrometer Fokussierung von niedrig-LET 20 MeV Protonen kann eine räumliche Dosisverteilung generiert werden, welche qualitativ jener von Schwerionen mit hohem LET ähnelt, so dass die Wirkung von dichtionisierender hoch-LET Strahlung modelliert werden kann. Hierzu wurden AL-Zellen mit einer Dosis von jeweils 1,7 Gy in drei verschiedenen Modi bestrahlt: Die Bestrahlung mit Submikrometer fokussierten 20 MeV Protonen folgt einer 5,4 µm x 5,4 µm Matrix, wobei 117 Protonen pro Matrixpunkt appliziert werden. Die Bestrahlung mit 55 MeV Kohlenstoffionen erfolgt im selben Muster mit je einem Ion pro Matrixpunkt. Zufällig verteilte 20 MeV Protonen werden mit einer Fluenz von 4,01 µm-2 appliziert. Der RBE für die Induktion von Mikrokernen steigt durch die Fokussierung der Protonen von 1,28 ± 0,07 nach zufällig verteilter Protonenbestrahlung auf 1,48 ± 0,07 nach fokussierter Protonenapplikation, der RBE für die Induktion von dizentrischen Chromosomen steigt von 1,41 ± 0,14 auf 1,92 ± 0,15. Der von Kohlenstoffionen induzierte RBE ist mit 2,20 ± 0,09 für Mikrokerne und 3,21 ± 0,27 für dizentrische Chromosomen nochmal deutlich höher. Die signifikante Erhöhung der Induktion von Chromosomenaberrationen alleine durch die Fokussierung der Protonen und damit der räumlichen Dosisverteilung zeigt, dass die räumliche Dosisverteilung für den RBE maßgeblich ist. Die Experimente stellen somit die erste experimentelle Bestätigung der Grundannahme des Local Effect Models dar, welches in der Tumortherapie mit schweren Ionen zur Modellierung des RBE für die Dosisplanung verwendet wird. Rechnungen mit dem Local Effect Model III zeigen jedoch, dass dieses den RBE für die Endpunkte der Chromosomenaberrationen für die drei Bestrahlungsmodi zwar qualitativ, nicht aber quantitativ beschreiben kann.
BibTeX:
	@phdthesis{Greubel2013diss,
	  author = {Greubel, Christoph},
	  title = {Einfluss der zeitlichen und räumlichen Fokussierung auf die strahlenbiologische Wirksamkeit von Protonen.},
	  school = {Universität der Bundeswehr München},
	  year = {2013},
	  url = {http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:706-3415}
	}
	
Nonstoichiometry accommodation in SrTiO3 thin films studied by positron annihilation and electron microscopy
D. Keeble, S. Wicklein, L. Jin, C. Jia, W. Egger and R. Dittmann; Physical Review B - Condensed Matter and Materials Physics 87 (19) (2013) 195409.
Abstract: Accommodation of nonstoichiometry in SrTiO3 pulsed laser deposited (PLD) films was investigated using positron annihilation lifetime spectroscopy and (scanning) transmission electron microscopy. Increasing PLD laser fluence changed the stoichiometry from Ti to Sr deficient. Cation vacancy defects were detected, and the concentration ratio of Sr to Ti vacancies, [VSr]/[VTi], was observed to increase systematically in the Sr-deficient region, although no change in the electron microscopy lattice images was detected. Increasing Ti deficiency resulted in the accommodation of SrO layers in planar defects, and in the formation of vacancy cluster defects. A change from VTi to VSr defect positron trapping was also detected.
BibTeX:
	@article{Keeble2013,
	  author = {Keeble, D.J. and Wicklein, S. and Jin, L. and Jia, C.L. and Egger, W. and Dittmann, R.},
	  title = {Nonstoichiometry accommodation in SrTiO3 thin films studied by positron annihilation and electron microscopy},
	  journal = {Physical Review B - Condensed Matter and Materials Physics},
	  year = {2013},
	  volume = {87},
	  number = {19},
	  pages = {195409},
	  url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.87.195409},
	  doi = {http://doi.org/10.1103/PhysRevB.87.195409}
	}
	
Accurate determination of optical bandgap and lattice parameters of Zn 1-xMgxO epitaxial films (0 ≤ x ≤ 0.3) grown by plasma-assisted molecular beam epitaxy on a-plane sapphire
B. Laumer, F. Schuster, M. Stutzmann, A. Bergmaier, G. Dollinger and M. Eickhoff; Journal of Applied Physics 113 (23) (2013) 233512.
Abstract: Zn1-xMgxO epitaxial films with Mg concentrations 0 ≤ x ≤ 0.3 were grown by plasma-assisted molecular beam epitaxy on a-plane sapphire substrates. Precise determination of the Mg concentration x was performed by elastic recoil detection analysis. The bandgap energy was extracted from absorption measurements with high accuracy taking electron-hole interaction and exciton-phonon complexes into account. From these results a linear relationship between bandgap energy and Mg concentration is established for x ≤ 0.3. Due to alloy disorder, the increase of the photoluminescence emission energy with Mg concentration is less pronounced. An analysis of the lattice parameters reveals that the epitaxial films grow biaxially strained on a-plane sapphire.
BibTeX:
	@article{Laumer2013,
	  author = {Laumer, B. and Schuster, F. and Stutzmann, M. and Bergmaier, A. and Dollinger, G. and Eickhoff, M.},
	  title = {Accurate determination of optical bandgap and lattice parameters of Zn 1-xMgxO epitaxial films (0 ≤ x ≤ 0.3) grown by plasma-assisted molecular beam epitaxy on a-plane sapphire},
	  journal = {Journal of Applied Physics},
	  year = {2013},
	  volume = {113},
	  number = {23},
	  pages = {233512},
	  note = {cited By (since 1996)1},
	  url = {http://scitation.aip.org/content/aip/journal/jap/113/23/10.1063/1.4811693},
	  doi = {http://doi.org/10.1063/1.4811693}
	}
	
A position sensitive germanium detector for the measurement of angular deviation of annihilation radiation
B. Löwe, M. Reiner, W. Egger, C. Hugenschmidt and G. Dollinger; Journal of Physics: Conference Series 443 (1) (2013) 012098.
Abstract: To improve electron momentum sensitivity in Coincidence Doppler Broadening Spectroscopy (CDBS) measurements it is envisaged to measure the angular correlation of annihilation radiation along with the energy of both annihilation photons. For this purpose two position sensitive 36-fold pixelated, planar germanium detectors will be utilized. The position sensitivity of one of those detectors has been tested with a collimated gamma source. A data acquisition system consisting of 37 sampling analogue-to-digital converters with PC based online/off-line processing has been installed. A position sensitivity of 1.6 mm has been achieved.
BibTeX:
	@article{Loewe2013,
	  author = {Löwe, B. and Reiner, M. and Egger, W. and Hugenschmidt, C. and Dollinger, G.},
	  title = {A position sensitive germanium detector for the measurement of angular deviation of annihilation radiation},
	  journal = {Journal of Physics: Conference Series},
	  year = {2013},
	  volume = {443},
	  number = {1},
	  pages = {012098},
	  url = {http://iopscience.iop.org/1742-6596/443/1/012098/},
	  doi = {http://doi.org/10.1088/1742-6596/443/1/012098}
	}
	
Study of Positronium formation in nano-channelled silicon as a function of sample temperature
S. Mariazzi, L. Dinoto, L. Ravelli, W. Egger and R. Brusa; Journal of Physics: Conference Series 443 (1) (2013) 012061.
Abstract: Oxidized nanochannel in silicon have been demonstrated to be suitable for positronium (Ps) formation and cooling also at low sample temperature. To investigate the Ps yield and to clarify the Ps formation mechanism we studied, by Positron Annihilation Spectroscopy (PAS), nanochanneled Si p-type samples in the 150-430 K temperature range. Ps yield was found to be constant in the 150-300 K temperature range, then it increases up to ∼50% of its value from 350-400 K. This effect is associated to a decrease of the fraction of positrons annihilating in Si and in the SiO2 layer on the nanochannels surface. This finding is compatible with the thermal decrease of the positive charge distribution at the Si/SiO2 interface limiting e+ reaching the SiO2 layer and to a charge rearrangement at the SiO2 surfaces.
BibTeX:
	@article{Mariazzi2013,
	  author = {Mariazzi, S. and Dinoto, L. and Ravelli, L. and Egger, W. and Brusa, R.S.},
	  title = {Study of Positronium formation in nano-channelled silicon as a function of sample temperature},
	  journal = {Journal of Physics: Conference Series},
	  year = {2013},
	  volume = {443},
	  number = {1},
	  pages = {012061},
	  url = {http://iopscience.iop.org/article/10.1088/1742-6596/443/1/012061/meta;jsessionid=D1DE141D0665C855F0EED9CB9570D8E4.c1.iopscience.cld.iop.org},
	  doi = {http://doi.org/10.1088/1742-6596/443/1/012061}
	}
	
High-accuracy fluence determination in ion beams using fluorescent nuclear track detectors
J.-M. Osinga, M. Akselrod, R. Herrmann, V. Hable, G. Dollinger, O. Jäkel and S. Greilich; Radiation Measurements 56 (2013) 294-298.
Abstract: We present an approach to use Al2O3:C,Mg-based fluorescent nuclear track detectors (FNTDs) and confocal laser scanning microscopy as a semiautomatic tool for fluence measurements in clinical ion beams. The method was found to cover a linear energy transfer (LET) range from at least L∞(Al2O3) = 0.5 keV/μm to 61,000 keV/μm with a detection efficiency ≥99.83% (20 MeV protons) at particle fluences up to at least 5 × 107 per cm2. Our technique allows to determine the spatial fluence distribution on a microscopic scale and enables detailed track-by-track comparison studies between different fluence detectors.
BibTeX:
	@article{Osinga2013,
	  author = {Osinga, J.-M. and Akselrod, M.S. and Herrmann, R. and Hable, V. and Dollinger, G. and Jäkel, O. and Greilich, S.},
	  title = {High-accuracy fluence determination in ion beams using fluorescent nuclear track detectors},
	  booktitle = {Proceedings of the 8th International Conference on Luminescent Detectors and Transformers of Ionizing Radiation (LUMDETR 2012)},
	  journal = {Radiation Measurements},
	  year = {2013},
	  volume = {56},
	  pages = {294--298},
	  url = {http://www.sciencedirect.com/science/article/pii/S1350448713000589},
	  doi = {http://doi.org/10.1016/j.radmeas.2013.01.035}
	}
	
3D-microscopy of hydrogen in tungsten
K. Peeper, M. Moser, P. Reichart, E. Markina, M. Mayer, S. Lindig, M. Balden and G. Dollinger; Journal of Nuclear Materials 438, Supplement (0) (2013) S887-S890.
Abstract: The mapping of hydrogen distributions in 3 dimensions and its correlation with structural features allow further insight into mechanisms of hydrogen trapping in tungsten. We studied hydrogen distributions in 25 μm thick polycrystalline tungsten foils by 3D hydrogen microscopy using a proton-proton-scattering method. Two types of tungsten samples were prepared: (i) at 1200 K annealed foils and using 1.8 MeV implantation energy (ii) at 2000 K annealed foils using 200 eV implantation energy. It has been found that large variations of surface hydrogen contamination occur within different samples. Nevertheless, a statistically significant variation of the hydrogen content across grain boundaries has been observed.
BibTeX:
	@article{Peeper2013,
	  author = {Peeper, K. and Moser, M. and Reichart, P. and Markina, E. and Mayer, M. and Lindig, S. and Balden, M. and Dollinger, G.},
	  title = {3D-microscopy of hydrogen in tungsten},
	  booktitle = {Proceedings of the 20th International Conference on Plasma-Surface Interactions in Controlled Fusion Devices},
	  journal = {Journal of Nuclear Materials},
	  year = {2013},
	  volume = {438, Supplement},
	  number = {0},
	  pages = {S887--S890},
	  url = {http://www.sciencedirect.com/science/article/pii/S0022311513002006},
	  doi = {http://doi.org/10.1016/j.jnucmat.2013.01.192}
	}
	
Geant4 simulation of the effect of backscattered positrons on the lifetime spectra of PLEPS
L. Ravelli, B. Löwe, W. Egger, G. Kögel, P. Sperr and G. Dollinger; Journal of Physics: Conference Series 443 (1) (2013) 012096.
Abstract: The Pulsed Low Energy Positron System (PLEPS) allows the measurement of positron lifetime spectra of very high quality with peak-to-background ratios up to 3 · 104. At those peak-to-background ratios small structures appear in the lifetime spectra due to backscattered positrons. Despite their small overall contribution-less than 2 % of the total events in the spectrum even with backscattering coefficient as high as 40 %-those satellite structures can render the data analysis difficult. To understand the origin of those satellite structures and to further improve the performance of the system, comprehensive simulations of the target chamber of PLEPS have been undertaken. The results reproduce fairly well the background of the lifetime spectrum. It is now possible to identify the origin of the background structures and also plan some additional countermeasures.
BibTeX:
	@article{Ravelli2013,
	  author = {Ravelli, L. and Löwe, B. and Egger, W. and Kögel, G. and Sperr, P. and Dollinger, G.},
	  title = {Geant4 simulation of the effect of backscattered positrons on the lifetime spectra of PLEPS},
	  journal = {Journal of Physics: Conference Series},
	  year = {2013},
	  volume = {443},
	  number = {1},
	  pages = {012096},
	  url = {http://iopscience.iop.org/1742-6596/443/1/012096/},
	  doi = {http://doi.org/10.1088/1742-6596/443/1/012096}
	}
	
Transport behaviour of boron delta-doped diamond
J. Scharpf, A. Denisenko, C. Pakes, S. Rubanov, A. Bergmaier, G. Dollinger, C. Pietzka and E. Kohn; Physica Status Solidi (A) Applications and Materials Science 210 (10) (2013) 2028-2034.
Abstract: The electrical transport properties of two-dimensional (2D) boron-doped delta layers were investigated by a comprehensive analysis of physical, electrochemical and microscopic methods. The boron concentration profile was determined physically by elastic recoil detection (ERD) and compared to the doping (acceptor) profile extracted from capacitance-voltage (CV) measurements, giving a boron concentration of 2-4 × 1013 cm-2. Corresponding field effect transistor (FET) characteristics, based on the boron-doped delta channel concept, measured in electrolyte, show good modulation behaviour but field effect mobilities in the range of 10-2-10 -1 cm2 V-1 s-1 that are far below expected values. High-resolution transmission electron microscopy (HR-TEM) analysis was employed to shed new light on the transport behaviour of boron-doped delta layers, revealing an inhomogeneous and interrupted morphology. Based on this finding, a hypothesis is proposed, modelling the delta layer transport behaviour via hopping and tunnelling processes between boron clusters.
BibTeX:
	@article{Scharpf2013,
	  author = {Scharpf, J. and Denisenko, A. and Pakes, C.I. and Rubanov, S. and Bergmaier, A. and Dollinger, G. and Pietzka, C. and Kohn, E.},
	  title = {Transport behaviour of boron delta-doped diamond},
	  journal = {Physica Status Solidi (A) Applications and Materials Science},
	  year = {2013},
	  volume = {210},
	  number = {10},
	  pages = {2028-2034},
	  note = {cited By (since 1996)0},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/pssa.201300093/abstract},
	  doi = {http://doi.org/10.1002/pssa.201300093}
	}
	
Untersuchung des zeitlichen Verhaltens von Siliziumphotomultipliern
Johannes Schütze; Bachelors-Thesis, Universität der Bundeswehr München, 2013.
Abstract: Diese Bachelorarbeit beschäftigt sich mit der Untersuchung des zeitlichen Verhaltens von Siliziumphotomultipliern (SiPMs). Dazu werden die Zeitauflösungen verschiedener SiPMs der Firma Ketek ermittelt. Der Schwerpunkt liegt dabei auf der Untersuchung des Zeitverhaltens bei unterschiedlichen Versorgungsspannungen. Im Folgenden wird zunächst die Funktionsweise von SiPMs, sowie die Funktionsweise der verwendeten Messelektronik erklärt. Anschließend wird der Ablauf der einzelnen Messmethoden erläutert. Zum Abschluss werden die Ergebnisse dargestellt und es wird auf Besonderheiten, die während der Messungen aufgetreten sind, eingegangen.
BibTeX:
	@mastersthesis{Schuetze2013ba,
	  author = {Schütze, Johannes},
	  title = {Untersuchung des zeitlichen Verhaltens von Siliziumphotomultipliern},
	  school = {Universität der Bundeswehr München},
	  year = {2013}
	}
	
Microstructural examination of reactor pressure vessel steels by positron annihilation point of view
V. Slugeň, H. Hein, S. Sojak, W. Egger, M. Pavúk, J. Veterníková, M. Petriska, V. Sabelová and R. Hinca; Progress in Nuclear Energy 62 (2013) 1-7.
Abstract: This paper presents a comparison of commercially used German and Russian reactor pressure vessel steels from the positron annihilation spectroscopy (PAS) point of view, having in mind knowledge obtained also from other techniques from the last decades. The second generations of Russian RPV steels seems to be fully comparable with German steels and their quality enables prolongation of NPP operating lifetime over projected 40 years. The embrittlement of CrMoV steel is very low due to the dynamic recovery of radiation-induced defects at reactor operating temperatures. © 2012 Elsevier Ltd. All rights reserved.
BibTeX:
	@article{Slugen2013,
	  author = {Slugeň, V. and Hein, H. and Sojak, S. and Egger, W. and Pavúk, M. and Veterníková, J. and Petriska, M. and Sabelová, V. and Hinca, R.},
	  title = {Microstructural examination of reactor pressure vessel steels by positron annihilation point of view},
	  journal = {Progress in Nuclear Energy},
	  year = {2013},
	  volume = {62},
	  pages = {1--7},
	  url = {http://www.sciencedirect.com/science/article/pii/S0149197012001023},
	  doi = {http://doi.org/10.1016/j.pnucene.2012.08.002}
	}
	
PLEPS study of ion implanted and annealed Fe-11.62% Cr alloys
S. Sojak, V. Sluge, W. Egger, L. Ravelli, M. Petriska, S. Stanek, M. Sahul, M. Skarba, P. Priputen, M. Stacho, J. Veterníková, R. Hinca and V. Sabelová; Journal of Physics: Conference Series 443 (1) (2013) 012036.
Abstract: Reduced activation ferritic/martensitic (RAFM) steels are one of the candidate structural materials for application in future nuclear facilities. These steels fulfill demands on radiation, thermal, and mechanical resistance during their operational lifetime. Our experiments were focused on study of microstructural changes of binary Fe-Cr alloys after annealing and irradiation, experimentally simulated by ion implantations. Alloys with 11.62% Cr were examined after helium ion implantations at different doses (0.1; 0.3; 0.5 C/cm2). Thermal annealing, motivated by literature and our previous work in the field of reactor steels [1,2], was performed at temperatures of 400, 475, 525 and 600 °C after implantations with aim to study changes of the defect size/amount. The Pulsed Low Energy Positron System (PLEPS) at FRM II reactor in Garching (Munich) was applied for lifetime studies [3]. Damage introduced into the microstructure caused problems with defect interpretations by the PLEPS technique and therefore SEM was applied as well. Positron lifetimes measured at annealing temperatures in range of 400-525 °C did not show an expected decrease. Only in the case of temperature of 600 °C the mean lifetime (MLT) decreased significantly and assumptions about the defect size decrease were made according to the literature [2].
BibTeX:
	@article{Sojak2013,
	  author = {Sojak, S. and Sluge, V. and Egger, W. and Ravelli, L. and Petriska, M. and Stanek, S. and Sahul, M. and Skarba, M. and Priputen, P. and Stacho, M. and Veterníková, J. and Hinca, R. and Sabelová, V.},
	  title = {PLEPS study of ion implanted and annealed Fe-11.62% Cr alloys},
	  journal = {Journal of Physics: Conference Series},
	  year = {2013},
	  volume = {443},
	  number = {1},
	  pages = {012036},
	  url = {http://iopscience.iop.org/article/10.1088/1742-6596/443/1/012036/meta},
	  doi = {http://doi.org/10.1088/1742-6596/443/1/012036}
	}
	
Thermal annealing influence on ions implanted Fe-Cr model alloys
S. Sojak, V. Slugeň, V. Kršjak, W. Egger, L. Ravelli, M. Petriska, S. Stanček, M. Skarba, P. Priputen, K. Vitázek, M. Stacho, J. Veterníková and V. Sabelová; Materials Science Forum 733 (2013) 274-277.
Abstract: Binary Fe-11.62wt%Cr alloys were investigated in as-received state as well as after a two step helium ion implantation at different energies (100 keV and 250 keV) with doses up to 3.12×1018 cm-2. In order to study changes in alloys in dependence on the temperature, thermal annealing was performed at temperatures of 400, 475, 525 and 600 oC and specimens were afterwards measured by a pulsed low energy positron system (PLEPS). Annealing out of defects at lower temperatures was not as significant as expected, and we also encountered difficulties with defect identification. However, an apparent decrease of defect size was observed in the specimen annealed at a temperature of 600 oC. © (2013) Trans Tech Publications, Switzerland.
BibTeX:
	@article{Sojak2013a,
	  author = {Sojak, S. and Slugeň, V. and Kršjak, V. and Egger, W. and Ravelli, L. and Petriska, M. and Stanček, S. and Skarba, M. and Priputen, P. and Vitázek, K. and Stacho, M. and Veterníková, J. and Sabelová, V.},
	  title = {Thermal annealing influence on ions implanted Fe-Cr model alloys},
	  booktitle = {POSITRON AND POSITRONIUM CHEMISTRY X},
	  journal = {Materials Science Forum},
	  year = {2013},
	  volume = {733},
	  pages = {274--277},
	  editor = {Kristiak, J and Kuriplach, J and Pujari, PK},
	  note = {10th International Workshop on Positron and Positronium Chemistry (PPC-10), Smolenice, SLOVAKIA, SEP 05-09, 2011},
	  url = {http://www.scientific.net/MSF.733.274},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.733.274}
	}
	
Hydrogen microscopy - Distribution of hydrogen in buckled niobium hydrogen thin films
S. Wagner, M. Moser, C. Greubel, K. Peeper, P. Reichart, A. Pundt and G. Dollinger; International Journal of Hydrogen Energy 38 (31) (2013) 13822-13830.
Abstract: Hydrogen absorption in thin metal films clamped to rigid substrates results in mechanical stress that changes the hydrogen's chemical potential by ΔμH(σ) = −1.124σ kJ/molH for σ measured in [GPa]. In this paper we show that local stress relaxation by the detachment of niobium hydrogen thin films from the substrate affects the chemical potential on the local scale: using coincident proton-proton scattering at a proton microprobe, the hydrogen concentration is determined with μm resolution, revealing that hydrogen is not homogenously distributed in the film. The local hydrogen solubility of the film changes with its local stress state, mapping the buckled film fraction. In niobium hydrogen thin films loaded up to nominal concentrations in the two-phase coexistence region, the clamped film fraction remains in the solid solution phase, while the buckles represent the hydride phase. These results are compared to a simple model taking the stress impact on the chemical potential into account.
BibTeX:
	@article{Wagner2013,
	  author = {Wagner, Stefan and Moser, Marcus and Greubel, Christoph and Peeper, Katrin and Reichart, Patrick and Pundt, Astrid and Dollinger, Günther},
	  title = {Hydrogen microscopy - Distribution of hydrogen in buckled niobium hydrogen thin films},
	  journal = {International Journal of Hydrogen Energy},
	  year = {2013},
	  volume = {38},
	  number = {31},
	  pages = {13822--13830},
	  url = {http://www.sciencedirect.com/science/article/pii/S0360319913019137},
	  doi = {http://doi.org/10.1016/j.ijhydene.2013.08.006}
	}
	
Reduced side effects by proton microchannel radiotherapy: Study in a human skin model
O. Zlobinskaya, S. Girst, C. Greubel, V. Hable, C. Siebenwirth, D. Walsh, G. Multhoff, J. Wilkens, T. Schmid and G. Dollinger; Radiation and Environmental Biophysics 52 (1) (2013) 123-133.
Abstract: The application of a microchannel proton irradiation was compared to homogeneous irradiation in a three-dimensional human skin model. The goal is to minimize the risk of normal tissue damage by microchannel irradiation, while preserving local tumor control through a homogeneous irradiation of the tumor that is achieved because of beam widening with increasing track length. 20 MeV protons were administered to the skin models in 10- or 50-μm-wide irradiation channels on a quadratic raster with distances of 500 μm between each channel (center to center) applying an average dose of 2 Gy. For comparison, other samples were irradiated homogeneously at the same average dose. Normal tissue viability was significantly enhanced after microchannel proton irradiation compared to homogeneous irradiation. Levels of inflammatory parameters, such as Interleukin-6, TGF-Beta, and Pro-MMP1, were significantly lower in the supernatant of the human skin tissue after microchannel irradiation than after homogeneous irradiation. The genetic damage as determined by the measurement of micronuclei in keratinocytes also differed significantly. This difference was quantified via dose modification factors (DMF) describing the effect of each irradiation mode relative to homogeneous X-ray irradiation, so that the DMF of 1.21 ± 0.20 after homogeneous proton irradiation was reduced to 0.23 ± 0.11 and 0.40 ± 0.12 after microchannel irradiation using 10- and 50-μm-wide channels, respectively. Our data indicate that proton microchannel irradiation maintains cell viability while significantly reducing inflammatory responses and genetic damage compared to homogeneous irradiation, and thus might improve protection of normal tissue after irradiation.
BibTeX:
	@article{Zlobinskaya2013,
	  author = {Zlobinskaya, O. and Girst, S. and Greubel, C. and Hable, V. and Siebenwirth, C. and Walsh, D.W.M. and Multhoff, G. and Wilkens, J.J. and Schmid, T.E. and Dollinger, G.},
	  title = {Reduced side effects by proton microchannel radiotherapy: Study in a human skin model},
	  booktitle = {Radiation and Environmental Biophysics},
	  journal = {Radiation and Environmental Biophysics},
	  year = {2013},
	  volume = {52},
	  number = {1},
	  pages = {123--133},
	  url = {http://link.springer.com/article/10.1007%2Fs00411-012-0450-9},
	  doi = {http://doi.org/10.1007/s00411-012-0450-9}
	}
	
On the interplay of point defects and Cd in non-polar ZnCdO films
A. Zubiaga, F. Reurings, F. Tuomisto, F. Plazaola, J. García, A. Kuznetsov, W. Egger, J. Zúñiga-Pérez and V. Muñoz-Sanjosé; Journal of Applied Physics 113 (2) (2013) 023512.
Abstract: Non-polar ZnCdO films, grown over m- and r-sapphire with a Cd concentration ranging between 0.8% and 5%, have been studied by means of slow positron annihilation spectroscopy (PAS) combined with chemical depth profiling by secondary ion mass spectroscopy and Rutherford back-scattering. Vacancy clusters and Zn vacancies with concentrations up to 1017 cm-3 and 1018 cm-3, respectively, have been measured inside the films. Secondary ion mass spectroscopy results show that most Cd stays inside the ZnCdO film but the diffused atoms can penetrate up to 1.3 μm inside the ZnO buffer. PAS results give an insight to the structure of the meta-stable ZnCdO above the thermodynamical solubility limit of 2%. A correlation between the concentration of vacancy clusters and Cd has been measured. The concentration of Zn vacancies is one order of magnitude larger than in as-grown non-polar ZnO films and the vacancy cluster are, at least partly, created by the aggregation of smaller Zn vacancy related defects. The Zn vacancy related defects and the vacancy clusters accumulate around the Cd atoms as a way to release the strain induced by the substitutional CdZn in the ZnO crystal.
BibTeX:
	@article{Zubiaga2013,
	  author = {Zubiaga, A. and Reurings, F. and Tuomisto, F. and Plazaola, F. and García, J.A. and Kuznetsov, A.Yu. and Egger, W. and Zúñiga-Pérez, J. and Muñoz-Sanjosé, V.},
	  title = {On the interplay of point defects and Cd in non-polar ZnCdO films},
	  journal = {Journal of Applied Physics},
	  year = {2013},
	  volume = {113},
	  number = {2},
	  pages = {023512},
	  url = {http://aip.scitation.org/doi/10.1063/1.4775396},
	  doi = {http://doi.org/10.1063/1.4775396}
	}
	

2012

A laser-driven nanosecond proton source for radiobiological studies
J. Bin, K. Allinger, W. Assmann, G. Dollinger, G.A. Drexler, A.A. Friedl, D. Habs, P. Hilz, R. Hoerlein, N. Humble, S. Karsch, K. Khrennikov, D. Kiefer, F. Krausz, W. Ma, D. Michalski, M. Molls, S. Raith, S. Reinhardt, B. Roeper, T.E. Schmid, T. Tajima, J. Wenz, O. Zlobinskaya, J. Schreiber and J.J. Wilkens; Applied Physics Letters 101 (24) (2012) 243701.
Abstract: Ion beams are relevant for radiobiological studies and for tumor therapy. In contrast to conventional accelerators, laser-driven ion acceleration offers a potentially more compact and cost-effective means of delivering ions for radiotherapy. Here, we show that by combining advanced acceleration using nanometer thin targets and beam transport, truly nanosecond quasi-monoenergetic proton bunches can be generated with a table-top laser system, delivering single shot doses up to 7Gy to living cells. Although in their infancy, laser-ion accelerators allow studying fast radiobiological processes as demonstrated here by measurements of the relative biological effectiveness of nanosecond proton bunches in human tumor cells.
BibTeX:
	@article{Bin2012,
	  author = {Bin, Jianhui and Allinger, Klaus and Assmann, Walter and Dollinger, Guenther and Drexler, Guido A. and Friedl, Anna A. and Habs, Dieter and Hilz, Peter and Hoerlein, Rainer and Humble, Nicole and Karsch, Stefan and Khrennikov, Konstantin and Kiefer, Daniel and Krausz, Ferenc and Ma, Wenjun and Michalski, Doerte and Molls, Michael and Raith, Sebastian and Reinhardt, Sabine and Roeper, Barbara and Schmid, Thomas E. and Tajima, Toshiki and Wenz, Johannes and Zlobinskaya, Olga and Schreiber, Joerg and Wilkens, Jan J.},
	  title = {A laser-driven nanosecond proton source for radiobiological studies},
	  journal = {Applied Physics Letters},
	  year = {2012},
	  volume = {101},
	  number = {24},
	  pages = {243701},
	  url = {http://link.aip.org/link/doi/10.1063/1.4769372},
	  doi = {http://doi.org/10.1063/1.4769372}
	}
	
Characterization of vacancy-type defects in heteroepitaxial GaN grown by low-energy plasma-enhanced vapor phase epitaxy
A. Calloni, R. Ferragut, A. Dupasquier, H. von Känel, A. Guiller, A. Rutz, L. Ravelli and W. Egger; Journal of Applied Physics 112 (2) (2012) 024510.
Abstract: The defect concentration in thin GaN layers was estimated by means of positron annihilation spectroscopy. Positron lifetime and Doppler broadening of the annihilation radiation were used. A comparative study of GaN films grown with different techniques was performed. Specific attention has been given to the new low energy plasma enhanced vapor phase epitaxy (LEPEVPE) growth technique. A very high Ga vacancy density (10 19 cm -3) was found in a thin GaN layer directly grown by LEPEVPE on a sapphire substrate. However, when a GaN substrate (commercial sample grown by Metal Organic Vapor Phase Epitaxy) is used as a template for LEPEVPE deposition, the vacancy density of the film is low (about 10 16 cm -3). This fact provides evidences that the LEPEVPE technique is able to produce high quality GaN layers.
BibTeX:
	@article{Calloni2012,
	  author = {Calloni, A. and Ferragut, R. and Dupasquier, A. and von Känel, H. and Guiller, A. and Rutz, A. and Ravelli, L. and Egger, W.},
	  title = {Characterization of vacancy-type defects in heteroepitaxial GaN grown by low-energy plasma-enhanced vapor phase epitaxy},
	  journal = {Journal of Applied Physics},
	  year = {2012},
	  volume = {112},
	  number = {2},
	  pages = {024510},
	  url = {http://aip.scitation.org/doi/10.1063/1.4737402},
	  doi = {http://doi.org/10.1063/1.4737402}
	}
	
Recruitment kinetics of DNA repair proteins Mdc1 and Rad52 but not 53BP1 depend on damage complexity
V. Hable, G.A. Drexler, T. Brüning, C. Burgdorf, C. Greubel, A. Derer, J. Seel, H. Strickfaden, T. Cremer, A.A. Friedl and G. Dollinger; PLoS One 7 (7) (2012) e41943.
Abstract: The recruitment kinetics of double-strand break (DSB) signaling and repair proteins Mdc1, 53BP1 and Rad52 into radiation-induced foci was studied by live-cell fluorescence microscopy after ion microirradiation. To investigate the influence of damage density and complexity on recruitment kinetics, which cannot be done by UV laser irradiation used in former studies, we utilized 43 MeV carbon ions with high linear energy transfer per ion (LET = 370 keV/μm) to create a large fraction of clustered DSBs, thus forming complex DNA damage, and 20 MeV protons with low LET (LET = 2.6 keV/μm) to create mainly isolated DSBs. Kinetics for all three proteins was characterized by a time lag period T0 after irradiation, during which no foci are formed. Subsequently, the proteins accumulate into foci with characteristic mean recruitment times τ1. Mdc1 accumulates faster (T0 = 17±2 s, τ1 = 98±11 s) than 53BP1 (T0 = 77±7 s, τ1 = 310±60 s) after high LET irradiation. However, recruitment of Mdc1 slows down (T0 = 73±16 s, τ1 = 1050±270 s) after low LET irradiation. The recruitment kinetics of Rad52 is slower than that of Mdc1, but exhibits the same dependence on LET. In contrast, the mean recruitment time τ1 of 53BP1 remains almost constant when varying LET. Comparison to literature data on Mdc1 recruitment after UV laser irradiation shows that this rather resembles recruitment after high than low LET ionizing radiation. So this work shows that damage quality has a large influence on repair processes and has to be considered when comparing different studies.
BibTeX:
	@article{Hable2012,
	  author = {Hable, Volker and Drexler, Guido A. and Brüning, Tino and Burgdorf, Christian and Greubel, Christoph and Derer, Anja and Seel, Judith and Strickfaden, Hilmar and Cremer, Thomas and Friedl, Anna A. and Dollinger, Günther},
	  title = {Recruitment kinetics of DNA repair proteins Mdc1 and Rad52 but not 53BP1 depend on damage complexity},
	  journal = {PLoS One},
	  year = {2012},
	  volume = {7},
	  number = {7},
	  pages = {e41943},
	  url = {http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0041943},
	  doi = {http://doi.org/10.1371/journal.pone.0041943}
	}
	
Aging and free volume in a polymer of intrinsic microporosity (PIM-1)
S. Harms, K. Rätzke, F. Faupel, N. Chaukura, P. Budd, W. Egger and L. Ravelli; Journal of Adhesion 88 (7) (2012) 608-619.
Abstract: There is a growing market for polymeric gas separation membranes for applications such as air separation and carbon dioxide capture. One of the key properties dominating transport is the free volume between atoms, allowing gas diffusion. However, thin films, in particular, undergo aging, decreasing free volume, and, hence, performance with time. We have measured the change in free volume during aging of thin films of a polymer of intrinsic microporosity (PIM-1) by depth-resolved positron annihilation lifetime spectroscopy. For films with thickness, d, smaller than 1m, aging is nearly complete after 3 months, whereas for films with d>1 μm aging continues even after several months. Aging is thickness-and time-dependent and the free volume diffuses through the film to the free surface.
BibTeX:
	@article{Harms2012,
	  author = {Harms, S. and Rätzke, K. and Faupel, F. and Chaukura, N. and Budd, P.M. and Egger, W. and Ravelli, L.},
	  title = {Aging and free volume in a polymer of intrinsic microporosity (PIM-1)},
	  journal = {Journal of Adhesion},
	  year = {2012},
	  volume = {88},
	  number = {7},
	  pages = {608--619},
	  url = {http://www.tandfonline.com/doi/abs/10.1080/00218464.2012.682902},
	  doi = {http://doi.org/10.1080/00218464.2012.682902}
	}
	
Ultrahigh gain AlGaN/GaN high energy radiation detectors
J.D. Howgate, M. Hofstetter, S.J. Schoell, M. Schmid, S. Schäfer, I. Zizak, V. Hable, C. Greubel, G. Dollinger, S. Thalhammer, M. Stutzmann and I.D. Sharp; physica status solidi (a) 209 (8) (2012) 1562-1567.
Abstract: Due to its remarkable tolerance to high energy ionizing radiation, GaN has recently attracted attention as a promising material for dosimetry applications. However, materials issues that lead to persistent photoconductivity, poor sensitivity, and requirements for large operational voltages have been hurdles to realization of the full potential of this material. Here we demonstrate that the introduction of a two-dimensional electron gas channel, through the addition of AlGaN/GaN heterointerfaces, can be used to create intrinsic amplification of the number of electrons that can be collected from single ionization events, yielding exceptionally large sensitivities in ultralow dose rate regimes. Furthermore, anomalous photo-responses, which severely limit response times of GaN-based devices, can be eliminated using these heterostructures. Measurements using focused monochromatic synchrotron radiation at 1-20 keV, as well as focused 20 MeV protons, reveal that these devices provide the capability for high sensitivity and resolution real time monitoring, which is competitive with and complementary to state-of-the-art detectors. Therefore, AlGaN/GaN heterostructure devices are extremely promising for future applications in fields ranging from high energy physics to medical imaging.
BibTeX:
	@article{Howgate2012,
	  author = {Howgate, J. D. and Hofstetter, M. and Schoell, S. J. and Schmid, M. and Schäfer, S. and Zizak, I. and Hable, V. and Greubel, C. and Dollinger, G. and Thalhammer, S. and Stutzmann, M. and Sharp, I. D.},
	  title = {Ultrahigh gain AlGaN/GaN high energy radiation detectors},
	  journal = {physica status solidi (a)},
	  year = {2012},
	  volume = {209},
	  number = {8},
	  pages = {1562--1567},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/pssa.201228097/abstract},
	  doi = {http://doi.org/10.1002/pssa.201228097}
	}
	
Growth study of nonpolar Zn 1-xMg xO epitaxial films on a-plane bulk ZnO by plasma-assisted molecular beam epitaxy
B. Laumer, F. Schuster, M. Stutzmann, A. Bergmaier, G. Dollinger, S. Vogel, K. Gries, K. Volz and M. Eickhoff; Applied Physics Letters 101 (12) (2012) 122106.
Abstract: Nonpolar Zn 1-x Mg x O epitaxial films were grown by plasma-assisted molecular beam epitaxy on a-plane ZnO substrates. A smooth surface morphology was accomplished under oxygen-rich growth conditions. The benefits of the use of ZnO substrates on the structural properties are reflected by a low-density of threading dislocations. Furthermore, no indications for the generation of basal plane stacking faults are found. The pseudomorphic growth on a-plane ZnO substrates efficiently locks the epitaxial Zn 1-x Mg x O films to the wurtzite structure up to x = 0.25. The Mg concentration is not constant and increases with larger thickness. The optical properties reflect the influence of alloy disorder.
BibTeX:
	@article{Laumer2012,
	  author = {Laumer, B. and Schuster, F. and Stutzmann, M. and Bergmaier, A. and Dollinger, G. and Vogel, S. and Gries, K.I. and Volz, K. and Eickhoff, M.},
	  title = {Growth study of nonpolar Zn 1-xMg xO epitaxial films on a-plane bulk ZnO by plasma-assisted molecular beam epitaxy},
	  journal = {Applied Physics Letters},
	  year = {2012},
	  volume = {101},
	  number = {12},
	  pages = {122106},
	  note = {cited By (since 1996)1},
	  url = {http://scitation.aip.org/content/aip/journal/apl/101/12/10.1063/1.4754076},
	  doi = {http://doi.org/10.1063/1.4754076}
	}
	
Niobium aggregation and vacancylike defect evolution in nanostructured Nb-doped Mg: Their role in the kinetics of the hydride-to-metal phase transformation
C. Macchi, C. Maurizio, R. Checchetto, S. Mariazzi, L. Ravelli, W. Egger, P. Mengucci, N. Bazzanella, A. Miotello, A. Somoza and R. Brusa; Physical Review B - Condensed Matter and Materials Physics 85 (21) (2012) 214117.
Abstract: The structural evolution of nanostructured Nb-doped magnesium film samples and its correlation with the change of the H 2 desorption kinetics after successive H 2 sorption cycles at 623 K was investigated by different techniques. The variation of the dispersed Nb fraction and the Nb clusterization was followed by extended x-ray absorption fine structure (EXAFS), while the progressive Mg nanostructuring was monitored by x-ray diffraction. The presence of vacancylike defects and their evolution was studied using positron annihilation lifetime spectroscopy and Doppler broadening spectroscopies. It was found that, with successive H 2 sorption cycles: (i) the H 2 desorption kinetics progressively becomes slower until stationary conditions are reached and (ii) the Nb dopant atoms, dispersed in the nanocrystalline Mg layers, aggregate, forming nanoclusters. Our results show that the progressive Nb aggregation drives the H 2 desorption kinetics. EXAFS analysis show that fast desorption kinetics is due to the presence of small (∼1 nm) Nb aggregates rather than Nb atoms dispersed into the Mg matrix. With cycling, the Nb aggregates progressively grow, forming larger bcc Nb nanoclusters and the H 2 desorption kinetics becomes slower. In the as-deposited Nb-doped Mg samples, analysis of the positron data reveals the presence of intragranular vacancylike defects and of vacancy clusters which are inferred to be mainly located at the grain boundaries of the nanocrystalline Mg layers. With H 2 cycling: (i) a decrease of the atomic fraction of the intragranular vacancylike defects after the first two sorption cycles was observed, and (ii) an increase of the atomic fraction of vacancy clusters at grain boundaries and the appearance of vacancylike defects located at the interface between the Nb aggregates and the Mg matrix was probed. It was also found that the kinetics follows a nucleation and growth mechanism and, under stationary conditions, the Mg nucleation is controlled by vacancy-decorated bcc Nb nanoclusters rather than by vacancy clusters, as in undoped Mg samples.
BibTeX:
	@article{Macchi2012,
	  author = {Macchi, C. and Maurizio, C. and Checchetto, R. and Mariazzi, S. and Ravelli, L. and Egger, W. and Mengucci, P. and Bazzanella, N. and Miotello, A. and Somoza, A. and Brusa, R.S.},
	  title = {Niobium aggregation and vacancylike defect evolution in nanostructured Nb-doped Mg: Their role in the kinetics of the hydride-to-metal phase transformation},
	  journal = {Physical Review B - Condensed Matter and Materials Physics},
	  year = {2012},
	  volume = {85},
	  number = {21},
	  pages = {214117},
	  url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.85.214117},
	  doi = {http://doi.org/10.1103/PhysRevB.85.214117}
	}
	
High brilliance multicusp ion source for hydrogen microscopy at SNAKE
M. Moser, P. Reichart, W. Carli, C. Greubel, K. Peeper, P. Hartung and G. Dollinger; Nuclear Instruments and Methods in Physics Research Section B 273 (2012) 226-230.
Abstract: In order to improve the lateral resolution of the 3D hydrogen microscopy by proton-proton scattering at the Munich microprobe SNAKE, we have installed a new multicusp ion source for negative hydrogen ions manufactured by HVEE at the Munich 14 MV tandem accelerator that boosts the proton beam brilliance with the potential to reduce the beam diameter at the focal plane of SNAKE. We measured a beam brilliance B = 27 A m -2 rad -2 eV -1 directly behind the ion source that is at the space charge limit for conventional ion sources. After preacceleration to in total 180 keV beam energy we measure a slightly reduced beam brilliance of B = 10 μA mm -2 mrad -2 MeV -1. For injection into the tandem accelerator, the extracted H --current of the multicusp source of 1 mA is reduced to about 10 μA because of radiation safety regulations and heating problems at the object slits of SNAKE. Due to beam oscillations and influences of the terminal stripper of the tandem we measured a reduced beam brilliance of 0.8 μA mm -2 mrad -2 MeV -1 in front of SNAKE at 25 MeV but still being nearly 10 times larger than measured with any other ion source.
BibTeX:
	@article{Moser2012,
	  author = {Moser, M. and Reichart, P. and Carli, W. and Greubel, C. and Peeper, K. and Hartung, P. and Dollinger, G.},
	  title = {High brilliance multicusp ion source for hydrogen microscopy at SNAKE},
	  booktitle = {20th International Conference on Ion Beam Analysis},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2012},
	  volume = {273},
	  pages = {226--230},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X11007257},
	  doi = {http://doi.org/10.1016/j.nimb.2011.07.081}
	}
	
Non-Rutherford backscattering microscopy using 25 MeV protons
K. Peeper, M. Moser, P. Reichart and G. Dollinger; Nuclear Instruments and Methods in Physics Research Section B 273 (2012) 254-257.
Abstract: Protons at energies between 10 and 25 MeV are a very sensitive probe for hydrogen using coincident proton-proton scattering with the possibility for depth profiling samples up to several 100 μm thickness. At the Munich microprobe SNAKE we have developed this method for sensitive 3D hydrogen microscopy [1]. In parallel to sensitive 3D hydrogen microscopy by proton-proton scattering we introduce a non-Rutherford backscattering analysis utilizing 25 MeV protons in order to obtain 3D depth profiles of all major elements. We present energy spectra of backscattered protons at various thin and thick film samples of pure elements which we use as fingerprints to analyse more complex materials like minerals or metals. It is due to the low stopping power of the high energy protons that the depth profiles of several elements do not or do only partially overlap when analysing freestanding samples with thicknesses in the 100 μm range. The merit of our method is that signals of the light elements may not be affected by heavier matrix elements. Analysing thin films smaller than 5 μm we have achieved a mass resolution of ΔA/A≤1/28 for non-overlapping mass signals utilizing a 5 mm thick Si(Li)-detector.
BibTeX:
	@article{Peeper2012,
	  author = {Peeper, K. and Moser, M. and Reichart, P. and Dollinger, G.},
	  title = {Non-Rutherford backscattering microscopy using 25 MeV protons},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2012},
	  volume = {273},
	  pages = {254--257},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X11007324},
	  doi = {http://doi.org/10.1016/j.nimb.2011.07.088}
	}
	
Super resolution microscopy of repair foci after ion irradiation of human HeLa cells
Judith (Seel) Reindl; Masters-Thesis, Ludwigs-Maximilians-Universität München, 2012.
Abstract: High LET (linear energy transfer) irradiation of living cells using heavy ions generates a high amount of DNA double-strand breaks (DSB) in close vicinity to each other along the ion track. Various repair proteins cluster to the damage sites, such as gH2AX and 53BP1, forming so-called repair foci of a gross size of about 1 µm. Due to the fact that one focus covers more than one DSB, a fine-structure within the focus can be expected. First indications for such a fine-structure were found in wide field images of
cells taken one hour after irradiation with 55MeV carbon ions in a 5x5 µm matrix performed at the ion microprobe SNAKE. While a typical focus with the diameter of about 1 µm can be easily resolved using a conventional fluorescence microscope, its substructures cannot be resolved due to the diffraction limit of about 250 nm in conventional fluorescence microscopy. Therefore, for analyzing foci fine-structures systematically, super-resolution microscopy techniques like structured illumination microscopy (SIM), stimulation emission depletion microscopy (STED) or localization microscopy (SPDM) which provide a lateral resolution of about 130 nm (SIM) to 50 nm (SPDM) fwhm are utilized. Since with these techniques the lateral resolution is even better than the z-resolution we used an irradiation configuration, where the cells are irradiated at a small angle to the image plane. Thus, the complete ion track appears as a line within one layer of a 3D microscope image. Due to these improvements the super resolution images clearly indicate a fine-structure when e. g. 53BP1 is stained with two colors.
For quantification of the results the Pearson correlation coefficient is calculated for a pixel wise shift in x-direction as well as in y-direction of one color channel with respect to the other (Van Steensel approach). This proves the existence of a fine-structure of a scale of about 200-230 nm, which becomes obvious by an extra correlation peak with a fwhm of this size. Using the same Van Steensel approach with images where one color marks 53BP1 and the other gH2AX, it can be shown that there is no total correlation of the fine-structure between 53BP1 and gH2AX on the small scale.
Using the product of the difference of the mean (PDM) for 2D profiles the images where one protein is labeled with two colors show large regions with total correlation of the to color channels and only small regions at the rim of the focus with no total correlation. In addition, in the PDM approach two different damage markers each labeled in one color show colocalisation in small regions inside the focus but anticorrelation in the outer regions of the focus. These analysis lead to different results:
first of all a single repair marker seems to cluster systematically to the damage site and not in a random way. Secondly 53BP1 and gH2AX cluster in a different way and therefore no full colocalisation can be reached.
With this experimental and analytical methods it is possible to determine the way of clustering to DSB of one single DNA damage marker to clarify the structure of a DSB and the structure of the chromatin architecture as well as the comparison of two
damage markers to get deeper understanding to the interaction of repair markers and repair proteins and at the end decode the way of DNA repair.
BibTeX:
	@mastersthesis{Reindl2012ma,
	  author = {Reindl, Judith (Seel)},
	  title = {Super resolution microscopy of repair foci after ion irradiation of human HeLa cells},
	  school = {Ludwigs-Maximilians-Universität München},
	  year = {2012}
	}
	
Low LET protons focused to submicrometer shows enhanced radiobiological effectiveness
T.E. Schmid, C. Greubel, V. Hable, O. Zlobinskaya, D. Michalski, S. Girst, C. Siebenwirth, E. Schmid, M. Molls, G. Multhoff and G. Dollinger; Physics in Medicine and Biology 57 (19) (2012) 5889-5907.
Abstract: This study shows that enhanced radiobiological effectiveness (RBE) values can be generated focusing low linear energy transfer (LET) radiation and thus changing the microdose distribution. 20 MeV protons (LET = 2.65 keV µm −1 ) are focused to submicrometer diameter at the ion microprobe superconducting nanoprobe for applied nuclear (Kern) physics experiments of the Munich tandem accelerator. The RBE values, as determined by measuring micronuclei (RBE MN = 1.48 ± 0.07) and dicentrics (RBE D = 1.92 ± 0.15), in human–hamster hybrid (A L ) cells are significantly higher when 117 protons were focused to a submicrometer irradiation field within a 5.4 × 5.4 µm 2 matrix compared to quasi homogeneous in a 1 × 1 µm 2 matrix applied protons (RBE MN = 1.28 ± 0.07; RBE D = 1.41 ± 0.14) at the same average dose of 1.7 Gy. The RBE values are normalized to standard 70 kV (dicentrics) or 200 kV (micronuclei) x-ray irradiation. The 117 protons applied per point deposit the same amount of energy like a 12 C ion with 55 MeV total energy (4.48 MeV u −1 ). The enhancements are about half of that obtained for 12 C ions (RBE MN = 2.20 ± 0.06 and RBE D = 3.21 ± 0.10) and they are attributed to intertrack interactions of the induced damages. The measured RBE values show differences from predictions of the local effect model (LEM III) that is used to calculate RBE values for irradiation plans to treat tumors with high LET particles.
BibTeX:
	@article{Schmid2012,
	  author = {Schmid, T. E. and Greubel, C. and Hable, V. and Zlobinskaya, O. and Michalski, D. and Girst, S. and Siebenwirth, C. and Schmid, E. and Molls, M. and Multhoff, G. and Dollinger, G.},
	  title = {Low LET protons focused to submicrometer shows enhanced radiobiological effectiveness},
	  journal = {Physics in Medicine and Biology},
	  year = {2012},
	  volume = {57},
	  number = {19},
	  pages = {5889-5907},
	  url = {http://stacks.iop.org/0031-9155/57/i=19/a=5889},
	  doi = {http://doi.org/10.1088/0031-9155/57/19/5889}
	}
	
Charakterisierung von Siliziumphotomultipliern
Johannes Schütze and Christoph Hager; Studienarbeit, Universität der Bundeswehr München, 2012.
BibTeX:
	@thesis{SchuetzeHager2012sa,
	  author = {Schütze, Johannes and Hager, Christoph},
	  title = {Charakterisierung von Siliziumphotomultipliern},
	  school = {Universität der Bundeswehr München},
	  year = {2012}
	}
	
Different Chromium Content and Thermal Annealing Influence on Ions Implanted Fe-Cr Model Alloys
S. Sojak, V. Slugeň, V. Kršjak, W. Egger, L. Ravelli, M. Petriska, S. Stanček, M. Skarba, P. Priputen, K. Vitázek, M. Stacho, J. Veterníková and V. Sabelová; Physics Procedia 35 (2012) 80–85.
Abstract: Reduced activation ferritic/martensitic steels (RAFM) represented by binary Fe-Cr alloys, with different chromium content, were studied in as-received state as well as after helium ions implantation. In order to study changes in dependence on the temperature, thermal annealing of He ions implanted Fe-11.62%Cr specimens was performed. Measurements by Pulsed Low Energy Positron System (PLEPS) in Garching, Germany were performed afterwards. Annealing out of defects at lower temperatures was not significant as was expected and some uncertainties are present. Extensive decrease of positron lifetime of defects was observed in specimens annealed at temperature 600 degrees C.
BibTeX:
	@article{Sojak2012,
	  author = {Sojak, S. and Slugeň, V. and Kršjak, V. and Egger, W. and Ravelli, L. and Petriska, M. and Stanček, S. and Skarba, M. and Priputen, P. and Vitázek, K. and Stacho, M. and Veterníková, J. and Sabelová, V.},
	  title = {Different Chromium Content and Thermal Annealing Influence on Ions Implanted Fe-Cr Model Alloys},
	  booktitle = {POSITRON STUDIES OF DEFECTS 2011},
	  journal = {Physics Procedia},
	  year = {2012},
	  volume = {35},
	  pages = {80–85},
	  editor = {Eijt, S and Schut, H},
	  note = {7th International Workshop on Positron Studies of Defects (PSD), Delft Univ Technol, Delft, NETHERLANDS, AUG 28-SEP 02, 2011},
	  url = {http://www.sciencedirect.com/science/article/pii/S1875389212019529},
	  doi = {http://doi.org/10.1016/j.phpro.2012.06.015}
	}
	
Brillanzverlust durch die Kohlenstoffstripperfolie beim Strahltransport im Garchinger Tandembeschleuniger
Benedikt Urban; Bachelors-Thesis, Universität der Bundeswehr München, 2012.
Abstract: Die Verteilung von Wasserstoff in Materialien ist ein technisch äußerst relevanter Forschungsgegenstand der Materialphysik. Am SNAKE können mittels Proton- Proton Streuung Wasserstoffverteilungen in Materialien quantitativ bestimmt werden.
Einzigartig ist, dass Wasserstoffverteilungen an Strukturen im mm-Bereich aufgelöst werden können. Die laterale Auflösung (Strahldurchmesser) des bestehenden Systems beträgt derzeit ca. 1 mm. Um diese zu verbessern, wurde eine hochbrillante Ionenquelle aufgebaut, die bei besserer Strahlqualität gleichen Ionenstrom an der Probe zur Verfügung stellt.
Nach Inbetriebnahme und ersten Messungen wurde festgestellt, dass sich ein erheblicher Verlust der Brillanz einstellt und somit Einbußen bei der Strahlauflösung. Die Brillanz am Experiment ist um einen Faktor 20 schlechter als die Ausgangsbrillanz. Es gilt zu untersuchen, inwieweit eine Steigerung der Brillanz durch Variation des Strahleinschusses in den Beschleuniger möglich ist. Im Rahmen dieser Arbeit soll ein vorhandenes Simulationsprogramm sowie existierende Strahltransportrechnungen auf die Strahleigenschaften der nun hochbrillanten Quelle adaptiert werden. Auf dieser Basis sollen die Transporteigenschaften mit existierenden Messungen verglichen und validiert werden.
Ziel dieser Arbeit ist es, das benötigte Phasenraumvolumen direkt vor der Stripperfolie zu bestimmen, als Folge des nötigen Phasenraums am SNAKE. In einem weiteren Schritt ist es mithilfe des genauen Phasenraumvolumens möglich, die Brillanzverschlechterung aufgrund der Kleinwinkelstreuung beim Umladungsprozess im Inneren des Terminals nachzuvollziehen und den Strahlengang diesbezüglich zu optimieren.
BibTeX:
	@mastersthesis{Urban2012ba,
	  author = {Urban, Benedikt},
	  title = {Brillanzverlust durch die Kohlenstoffstripperfolie beim Strahltransport im Garchinger Tandembeschleuniger},
	  school = {Universität der Bundeswehr München},
	  year = {2012}
	}
	
Design und Simulation eines temperaturstabilisierten Schlitzsystems für den Transport eines hochbrillanten Protonen-Mikrostrahls
Thomas Vallentin; Bachelors-Thesis, Universität der Bundeswehr München, 2012.
Abstract: Die Verteilung von Wasserstoff in Materialien ist ein technisch äußerst relevanter Forschungsgegenstand der Materialphysik. Am Experiment SNAKE können mittels Proton-Proton Streuung Wasserstoffverteilungen in Materialien quantitativ bestimmt
werden. Einzigartig ist, dass Wasserstoffverteilungen an Strukturen im µm-Bereich aufgelöst werden können. Die laterale Auflösung (Strahldurchmesser) des bestehenden Systems beträgt derzeit ca. 1 µm. Um diese zu verbessern wurde eine hochbrilliante Ionenquelle aufgebaut, die bei besserer Strahlqualität gleichen Ionenstrom an der Probe zur Verfügung stellt. Dies führt zur thermischen Überlastung des aktuell verwendeten Mikroschlitzsystems, welches maÿgeblich für die erreichbare Auflösung verantwortlich ist.
Ziel dieser Arbeit ist es mittels Finite-Elemente-Simulationen die Anforderungen an ein neues Mikroschlitzsytem unter maximaler Strahllast zu untersuchen. Das System muss 10 µA Strahlstrom und Protonen mit Energien von bis zu 25 MeV standhalten.
Auf Grund der nötigen Empfindlichkeit des Systems wird besonders auf die Unsicherheitsabschätzung der Randbedingungen eingegangen. Als kritischer Punkt stellte sich die hochgenaue Strahlstrommessung im nano-Ampere Bereich heraus, die bei hohen Temperaturen an den Mikroschlitzen zur Tandemreglung benötigt wird. Als idealer Werkstoff zeigte sich Aluminiumnitrid (AlN), welches eine hohe Wärmeleitfähigkeit von bis zu k = 180W/(mK) und ein gutes Isolationsvermögen mit rho_v = 5 x 10^5
Ohm m bei Schlitztemperaturen Diese Arbeit zeigt, dass die Anforderungen an das neue Mikroschlitzsystem erfüllt werden können. Dabei kann unter Betracht aller Einflussgrößen eine sehr geringe Unschärfe der Objektgröÿe von Durch den Einsatz dieses neu definierten Mikroschlitzsystems wird eine Erhöhung der Auflösungen in den sub-µm-Bereich erwartet.
BibTeX:
	@mastersthesis{Vallentin2012ba,
	  author = {Vallentin, Thomas},
	  title = {Design und Simulation eines temperaturstabilisierten Schlitzsystems für den Transport eines hochbrillanten Protonen-Mikrostrahls},
	  school = {Universität der Bundeswehr München},
	  year = {2012}
	}
	
Induction and repair of DNA double-strand breaks assessed by gamma-H2AX foci after irradiation with pulsed or continuous proton beams
O. Zlobinskaya, G. Dollinger, D. Michalski, V. Hable, C. Greubel, G. Du, G. Multhoff, B. Röper, M. Molls and T.E. Schmid; Radiation and Environmental Biophysics 51 (1) (2012) 23-32.
Abstract: In particle tumor therapy including beam scanning at accelerators, the dose per voxel is delivered within about 100 ms. In contrast, the new technology of laser plasma acceleration will produce ultimately shorter particle packages that deliver the dose within a nanosecond. Here, possible differences for relative biological effectiveness in creating DNA double-strand breaks in pulsed or continuous irradiation mode are studied. HeLa cells were irradiated with 1 or 5 Gy of 20-MeV protons at the Munich tandem accelerator, either at continuous mode (100 ms), or applying a single pulse of 1-ns duration. Cells were fixed 1 h after 1-Gy irradiation and 24 h after 5-Gy irradiation, respectively. A dose–effect curve based on five doses of X-rays was taken as reference. The total number of phosphorylated histone H2AX (gamma-H2AX) foci per cell was determined using a custom-made software macro for gamma-H2AX foci counting. For 1 h after 1-Gy 20-MeV proton exposures, values for the relative biological effectiveness (RBE) of 0.97 ± 0.19 for pulsed and 1.13 ± 0.21 for continuous irradiations were obtained in the first experiment 1.13 ± 0.09 and 1.16 ± 0.09 in the second experiment. After 5 Gy and 24 h, RBE values of 0.99 ± 0.29 and 0.91 ± 0.23 were calculated, respectively. Based on the gamma-H2AX foci numbers obtained, no significant differences in RBE between pulsed and continuous proton irradiation in HeLa cells were detected. These results are well in line with our data on micronucleus induction in HeLa cells.
BibTeX:
	@article{Zlobinskaya2012,
	  author = {Zlobinskaya, O. and Dollinger, G. and Michalski, D. and Hable, V. and Greubel, C. and Du, G. and Multhoff, G. and Röper, B. and Molls, M. and Schmid, T. E.},
	  title = {Induction and repair of DNA double-strand breaks assessed by gamma-H2AX foci after irradiation with pulsed or continuous proton beams},
	  journal = {Radiation and Environmental Biophysics},
	  year = {2012},
	  volume = {51},
	  number = {1},
	  pages = {23--32},
	  url = {http://link.springer.com/article/10.1007%2Fs00411-011-0398-1},
	  doi = {http://doi.org/10.1007/s00411-011-0398-1}
	}
	

2011

Comprehensive comparison of various techniques for the analysis of elemental distributions in thin films
D. Abou-Ras, R. Caballero, C.-H. Fischer, C. Kaufmann, I. Lauermann, R. Mainz, H. Mönig, A. Schöpke, C. Stephan, C. Streeck, S. Schorr, A. Eicke, M. Döbeli, B. Gade, J. Hinrichs, T. Nunney, H. Dijkstra, V. Hoffmann, D. Klemm, V. Efimova, A. Bergmaier, G. Dollinger, T. Wirth, W. Unger, A. Rockett, A. Perez-Rodriguez, J. Alvarez-Garcia, V. Izquierdo-Roca, T. Schmid, P.-P. Choi, M. Müller, F. Bertram, J. Christen, H. Khatri, R. Collins, S. Marsillac and I. Kötschau; Microscopy and Microanalysis 17 (5) (2011) 728-751.
Abstract: The present work shows results on elemental distribution analyses in Cu(In,Ga)Se2 thin films for solar cells performed by use of wavelength-dispersive and energy-dispersive X-ray spectrometry (EDX) in a scanning electron microscope, EDX in a transmission electron microscope, X-ray photoelectron, angle-dependent soft X-ray emission, secondary ion-mass (SIMS), time-of-flight SIMS, sputtered neutral mass, glow-discharge optical emission and glow-discharge mass, Auger electron, and Rutherford backscattering spectrometry, by use of scanning Auger electron microscopy, Raman depth profiling, and Raman mapping, as well as by use of elastic recoil detection analysis, grazing-incidence X-ray and electron backscatter diffraction, and grazing-incidence X-ray fluorescence analysis. The Cu(In,Ga)Se2 thin films used for the present comparison were produced during the same identical deposition run and exhibit thicknesses of about 2 μm. The analysis techniques were compared with respect to their spatial and depth resolutions, measuring speeds, availabilities, and detection limits.
BibTeX:
	@article{Abou-Ras2011,
	  author = {Abou-Ras, D. and Caballero, R. and Fischer, C.-H. and Kaufmann, C.A. and Lauermann, I. and Mainz, R. and Mönig, H. and Schöpke, A. and Stephan, C. and Streeck, C. and Schorr, S. and Eicke, A. and Döbeli, M. and Gade, B. and Hinrichs, J. and Nunney, T. and Dijkstra, H. and Hoffmann, V. and Klemm, D. and Efimova, V. and Bergmaier, A. and Dollinger, G. and Wirth, T. and Unger, W. and Rockett, A.A. and Perez-Rodriguez, A. and Alvarez-Garcia, J. and Izquierdo-Roca, V. and Schmid, T. and Choi, P.-P. and Müller, M. and Bertram, F. and Christen, J. and Khatri, H. and Collins, R.W. and Marsillac, S. and Kötschau, I.},
	  title = {Comprehensive comparison of various techniques for the analysis of elemental distributions in thin films},
	  journal = {Microscopy and Microanalysis},
	  year = {2011},
	  volume = {17},
	  number = {5},
	  pages = {728--751},
	  note = {cited By (since 1996)16},
	  url = {http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8386415&fileId=S1431927611000523},
	  doi = {http://doi.org/10.1017/S1431927611000523}
	}
	
Survival of tumor cells after proton irradiation with ultra-high dose rates
S. Auer, V. Hable, C. Greubel, G.A. Drexler, T.E. Schmid, C. Belka, G. Dollinger and A.A. Friedl; Radiation Oncology 6 (1) (2011) 139.
Abstract: Background Laser acceleration of protons and heavy ions may in the future be used in radiation therapy. Laser-driven particle beams are pulsed and ultra high dose rates of >109 Gy s-1may be achieved. Here we compare the radiobiological effects of pulsed and continuous proton beams. Methods The ion microbeam SNAKE at the Munich tandem accelerator was used to directly compare a pulsed and a continuous 20 MeV proton beam, which delivered a dose of 3 Gy to a HeLa cell monolayer within
BibTeX:
	@article{Auer2011,
	  author = {Auer, Susanne and Hable, Volker and Greubel, Christoph and Drexler, Guido A. and Schmid, Thomas E. and Belka, Claus and Dollinger, Günther and Friedl, Anna A.},
	  title = {Survival of tumor cells after proton irradiation with ultra-high dose rates},
	  journal = {Radiation Oncology},
	  year = {2011},
	  volume = {6},
	  number = {1},
	  pages = {139},
	  url = {http://ro-journal.biomedcentral.com/articles/10.1186/1748-717X-6-139},
	  doi = {http://doi.org/10.1186/1748-717X-6-139}
	}
	
Enhanced kinetics of hydride-metal phase transition in magnesium by vacancy clustering
R. Checchetto, N. Bazzanella, A. Kale, A. Miotello, S. Mariazzi, R. Brusa, P. Mengucci, C. Macchi, A. Somoza, W. Egger and L. Ravelli; Physical Review B - Condensed Matter and Materials Physics 84 (5) (2011) 054115.
Abstract: The relation between vacancies and vacancy clusters evolution and the H2 desorption kinetics was studied in nanocrystalline Mg samples submitted to successive H2 sorption cycles. Vacancy defects were detected by positron annihilation lifetime spectroscopy while the desorption process was monitored measuring the H2 desorption flux. During H 2 sorption cycles, vacancies disappear, the number of vacancy clusters increases, and the crystalline quality of the Mg grains increases. The disappearance of intragranular vacancies is followed by an acceleration of the H2 desorption process. This is attributed to the increase of vacancy clusters at grain boundaries which assist the Mg nucleation in the hydride to metal phase transition. For H2 sorption cycles, the values of vacancy and vacancy cluster concentrations were obtained into the frame of the positron diffusion trapping model and the size of the involved vacancy clusters was evaluated by ab initio calculations of positron annihilation rates in Mg.
BibTeX:
	@article{Checchetto2011,
	  author = {Checchetto, R. and Bazzanella, N. and Kale, A. and Miotello, A. and Mariazzi, S. and Brusa, R.S. and Mengucci, P. and Macchi, C. and Somoza, A. and Egger, W. and Ravelli, L.},
	  title = {Enhanced kinetics of hydride-metal phase transition in magnesium by vacancy clustering},
	  journal = {Physical Review B - Condensed Matter and Materials Physics},
	  year = {2011},
	  volume = {84},
	  number = {5},
	  pages = {054115},
	  url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.84.054115},
	  doi = {http://doi.org/10.1103/PhysRevB.84.054115}
	}
	
Comment on 'Therapeutic application of metallic nanoparticles combined with particle-induced x-ray emission effect'
G. Dollinger; Nanotechnology 22 (24) (2011) 248001.
BibTeX:
	@article{Dollinger2011,
	  author = {Dollinger, G.},
	  title = {Comment on 'Therapeutic application of metallic nanoparticles combined with particle-induced x-ray emission effect'},
	  journal = {Nanotechnology},
	  year = {2011},
	  volume = {22},
	  number = {24},
	  pages = {248001},
	  note = {cited By (since 1996)2},
	  url = {http://iopscience.iop.org/0957-4484/22/24/248001/},
	  doi = {http://doi.org/10.1088/0957-4484/22/24/248001}
	}
	
Spatial Dynamics of DNA Damage Response Protein Foci along the Ion Trajectory of High-LET Particles
G. Du, G.A. Drexler, W. Friedland, C. Greubel, V. Hable, R. Krücken, A. Kugler, L. Tonelli, A.A. Friedl and G. Dollinger; Radiation Research 176 (6) (2011) 706-715.
Abstract: High-linear energy transfer (LET) ion irradiation of cell nuclei induces complex and severe DNA lesions, and foci of repair proteins are formed densely along the ion trajectory. To efficiently discriminate the densely distributed/overlapping foci along the ion trajectory, a focus recognition algorithm called FociPicker3D based on a local fraction thresholding technique was developed. We analyzed high-resolution 3D immunofluorescence microscopic focus images and obtained the kinetics and spatial development of γ-H2AX, 53BP1 and phospho-NBS1 foci in BJ1-hTERT cells irradiated with 55 MeV carbon ions and compared the results with the dynamics of double-strand break (DSB) distributions simulated using the PARTRAC model. Clusters consisting of several foci were observed along the ion trajectory after irradiation. The spatial dynamics of the protein foci supports that the foci clusters are not formed by neighboring foci but instead originate from the DSB cluster damage induced by high-LET radiations.
BibTeX:
	@article{Du2011,
	  author = {Du, Guanghua and Drexler, Guido A. and Friedland, Werner and Greubel, Christoph and Hable, Volker and Krücken, Reiner and Kugler, Alexandra and Tonelli, Laura and Friedl, Anna A. and Dollinger, Günther},
	  title = {Spatial Dynamics of DNA Damage Response Protein Foci along the Ion Trajectory of High-LET Particles},
	  booktitle = {Radiation Research},
	  journal = {Radiation Research},
	  year = {2011},
	  volume = {176},
	  number = {6},
	  pages = {706--715},
	  url = {http://www.bioone.org/doi/10.1667/RR2592.1},
	  doi = {http://doi.org/10.1667/RR2592.1}
	}
	
Layer-resolved study of the Mg to MgH2 transformation in Mg-Ti films with short-range chemical order
S. Eijt, H. Leegwater, H. Schut, A. Anastasopol, W. Egger, L. Ravelli, C. Hugenschmidt and B. Dam; Journal of Alloys and Compounds 509 (SUPPL. 2) (2011) S567-S571.
Abstract: Positron depth-profiling was applied to monitor the effects of hydrogenation on Mg1-yTiy thin films. S-W diagrams and VEPFIT analysis of the depth-profiles demonstrated the homogeneity of most metal and metal hydride films. In contrast, Mg0.90Ti0.10H x films consisted of a double layer, with a thin unloaded Mg 0.90Ti0.10 or Mg-Ti-Pd alloy layer on top of a hydrogenated bottom layer. The metal-to-metal-hydride transformation of Mg domains in the nanoscale phase-segregated Mg-Ti films was monitored exclusively, enabled by the large difference in positron affinity for Mg and Ti. The changes in the Doppler broadening parameters revealed that the metal-insulator transition for fluorite MgH2 is similar to that for rutile MgH 2. Positron lifetime spectroscopy showed the presence of di-vacancies in the metal sub-lattice of as-deposited and hydrogenated Mg-Ti metal films, which may induce the fast hydrogen sorption kinetics of the fluorite MgH 2 phase.
BibTeX:
	@article{Eijt2011,
	  author = {Eijt, S.W.H. and Leegwater, H. and Schut, H. and Anastasopol, A. and Egger, W. and Ravelli, L. and Hugenschmidt, C. and Dam, B.},
	  title = {Layer-resolved study of the Mg to MgH2 transformation in Mg-Ti films with short-range chemical order},
	  journal = {Journal of Alloys and Compounds},
	  year = {2011},
	  volume = {509},
	  number = {SUPPL. 2},
	  pages = {S567-S571},
	  url = {http://www.sciencedirect.com/science/article/pii/S0925838810023911},
	  doi = {http://doi.org/10.1016/j.jallcom.2010.09.157}
	}
	
Study of defects in an electroresistive Au/La2/3Sr 1/3MnO3/SrTiO3(001) heterostructure by positron annihilation
R. Ferragut, A. Dupaquier, S. Brivio, R. Bertacco and W. Egger; Journal of Applied Physics 110 (5) (2011) 053511.
Abstract: Defects in an ultrathin Au/La2/3Sr1/3MnO 3/SrTiO3 (Au/LSMO/STO) heterostructure displaying electroresistive behavior were studied using variable energy positron annihilation spectroscopy. Vacancy-like defects were found to be the dominant positron traps in the LSMO and STO thin perovskite oxides with a number density >1017 cm-3 and 2 × 1017 cm -3 in the STO substrate. High defect density was revealed by strong positron trapping at the Au/LSMO interface. Oxygen deficiency in LSMO would be the main source of these traps. Besides, a low density of sub-nano voids of ∼6Å was found in the substrate and in the thin LSMO/STO films. © 2011 American Institute of Physics.
BibTeX:
	@article{Ferragut2011,
	  author = {Ferragut, R. and Dupaquier, A. and Brivio, S. and Bertacco, R. and Egger, W.},
	  title = {Study of defects in an electroresistive Au/La2/3Sr 1/3MnO3/SrTiO3(001) heterostructure by positron annihilation},
	  journal = {Journal of Applied Physics},
	  year = {2011},
	  volume = {110},
	  number = {5},
	  pages = {053511},
	  url = {http://aip.scitation.org/doi/10.1063/1.3631825},
	  doi = {http://doi.org/10.1063/1.3631825}
	}
	
Anomalous subdiffusion of DNA repair protein foci after ion microirradiation.
Stefanie Girst; Diplomarbeit, Technische Universität München, 2011.
Abstract: DNA repair processes, starting after the irradiation of cell nuclei, can be made visible by tagging DNA repair proteins (here MDC1) with the green fluorescent protein GFP, so that microscopic accumulations of the repair proteins ( at the ion-induced
damages (mostly DNA double-strand breaks) can be observed and analyzed "live" under a fluorescence microscope.
The aim of this work is to determine the dynamics of the MDC1-foci in the nucleus. Living U2OS osteosarcoma cells were irradiated in a 5x5 µm^2 matrix pattern with one carbon ion (43MeV) per point or 32 protons (20 MeV) respectively at the ion microprobe SNAKE at the Munich 14MV Tandem accelerator. The relative movement (i.e. the distance) of neighboring foci within the living cells was monitored over several hours "online" at the irradiation site at SNAKE. This relative measure is more robust against cell movement than absolute position determination. The distribution of the change of distance dl between two foci in a time interval dt is a measure for the underlying diffusion. The square of its standard deviation sigma^2(dt) is in general described by
sigma^2(dt) = G*dt^a, with a = 1 for normal, a The diffusion data gathered in the performed experiments are in agreement with an anomalous subdiffusion. The anomalous diffusion exponent found is a = 0.50 +/- 0.04 for both proton and carbon irradiation on a time scale of dt =10 s till 10 000 s,
indicating that the degree of anomality does not depend on the density of double-strand breaks. The transport coefficient G and thus the apparent and the instantaneous diffusion coefficient, however, were clearly bigger in proton-irradiated cell nuclei
(G = (7+/-2)x10^(-3) µm^2/s^0.5) than in those irradiated with the higher-LET carbon ions (G = (3 +/- 1) x 10^(-3) µm^2/s^0.5). This probably arises from the fact that protons produce isolated double-strand breaks (DSBs) which move faster than the larger number of DSBs that form the foci in a carbon ion track.
BibTeX:
	@mastersthesis{Girst2011da,
	  author = {Girst, Stefanie},
	  title = {Anomalous subdiffusion of DNA repair protein foci after ion microirradiation.},
	  school = {Technische Universität München},
	  year = {2011}
	}
	
Scanning irradiation device for mice in vivo with pulsed and continuous proton beams
C. Greubel, W. Assmann, C. Burgdorf, G. Dollinger, G. Du, V. Hable, A. Hapfelmeier, R. Hertenberger, P. Kneschaurek, D. Michalski, M. Molls, S. Reinhardt, B. Röper, S. Schell, T.E. Schmid, C. Siebenwirth, T. Wenzl, O. Zlobinskaya and J.J. Wilkens; Radiation and Environmental Biophysics 50 (3) (2011) 339-344.
Abstract: A technical set-up for irradiation of subcutaneous tumours in mice with nanosecond-pulsed proton beams or continuous proton beams is described and was successfully used in a first experiment to explore future potential of laser-driven particle beams, which are pulsed due to the acceleration process, for radiation therapy. The chosen concept uses a microbeam approach. By focusing the beam to approximately 100 × 100 μm2, the necessary fluence of 109 protons per cm2 to deliver a dose of 20 Gy with one-nanosecond shot in the Bragg peak of 23 MeV protons is achieved. Electrical and mechanical beam scanning combines rapid dose delivery with large scan ranges. Aluminium sheets one millimetre in front of the target are used as beam energy degrader, necessary for adjusting the depth–dose profile. The required procedures for treatment planning and dose verification are presented. In a first experiment, 24 tumours in mice were successfully irradiated with 23 MeV protons and a single dose of 20 Gy in pulsed or continuous mode with dose differences between both modes of 10%. So far, no significant difference in tumour growth delay was observed.
BibTeX:
	@article{Greubel2011,
	  author = {Greubel, Christoph and Assmann, Walter and Burgdorf, Christian and Dollinger, Günther and Du, Guanghua and Hable, Volker and Hapfelmeier, Alexander and Hertenberger, Ralf and Kneschaurek, Peter and Michalski, Dörte and Molls, Michael and Reinhardt, Sabine and Röper, Barbara and Schell, Stefan and Schmid, Thomas E. and Siebenwirth, Christian and Wenzl, Tatiana and Zlobinskaya, Olga and Wilkens, Jan J.},
	  title = {Scanning irradiation device for mice in vivo with pulsed and continuous proton beams},
	  journal = {Radiation and Environmental Biophysics},
	  year = {2011},
	  volume = {50},
	  number = {3},
	  pages = {339--344},
	  url = {http://link.springer.com/article/10.1007%2Fs00411-011-0365-x},
	  doi = {http://doi.org/10.1007/s00411-011-0365-x}
	}
	
Echtzeitbeobachtung schneller Reaktionskinetiken in lebenden Zellen nach Ionenmikrobestrahlung
Volker Hable; Dissertation, Universität der Bundeswehr München, 2011.
Abstract: Diese Arbeit beschreibt den Aufbau einer Lebendzellmikroskopieumgebung am Rasterionenmikroskop SNAKE, welches am Münchner 14 MV Tandembeschleuniger installiert ist. An dessen Zellbestrahlungsplatz können lebende Zellen mit Protonen und Schwerionen unter Lebendbedingungen mit einer Genauigkeit von ca. 0,5 µm und mit genau definierter Dosis bestrahlt werden. Die nach der Bestrahlung im Zellkern ablaufenden Reparaturvorgänge können durch eine mikroskopische Betrachtung der an der Reparatur beteiligten Proteine analysiert werden. Hierfür ist die Markierung dieser Proteine mittels Fluoreszenzfarbstoffen nötig. Dazu werden die Zellen auf gentechnischem Wege so verändert, dass an Proteine, die an der Reparatur der ioneninduzierten Schäden beteiligt sind, Fluoreszenzproteine (z. B. GFP, green fluorescent protein) angehängt werden. Mikroskopische Proteinanlagerungen an die Schadensorte, sogenannte Foci, können mit dem im Rahmen dieser Arbeit realisierten Aufbau unmittelbar nach und sogar während der Bestrahlung "online“ analysiert werden. Ein kommerziell erhältliches Fluoreszenzmikroskop (Zeiss Axiovert 200M) wurde hierzu am Bestrahlungsplatz angebracht. An dessen Probentisch befinden sich die Zellen während der Bestrahlung und der nachfolgenden Mikroskopie unter optimalen Umgebungsbedingungen in neu entwickelten Zellkulturgefäßen. Erste Experimente an dem neuen Aufbau dienten der Untersuchung von Kinetiken (= zeitlicher Ablauf der Focibildung) der Proteine Mdc1, 53BP1 und Rad52. Nach Applizierung einer mittleren Dosis von 4,4 Gy mit 55 MeV Kohlenstoffionen mit einem linearen Energietransfer LET = 310 keV/µm beginnt Mdc1 nach T0 = 17 ± 2 s mit der Anlagerung an die Schadensorte. Dies geschieht mit einer Zeitkonstante t = 98 ± 11 s. Wird dieselbe Dosis mit 20 MeV Protonen appliziert (LET = 2,65 keV/µm), läuft die Focibildung langsamer ab (T0 = 73 ± 16 s, t = 1050 ± 270 s). Eine höhere Bestrahlungsdosis durch Erhöhung der pro Punkt applizierten Protonen beschleunigt die Kinetik. Die Zeitkonstanten des Proteins 53BP1 weisen keine solch ausgeprägte Abhängigkeit von der Bestrahlungsart auf. Für alle Bestrahlungsbedingungen liegt hier T0 in der Größenordnung von 100 s und t in der Größenordnung von 300 s. Das nur qualitativ betrachtete Reparaturprotein Rad52 zeigt eine deutlich langsamere Kinetik, die allerdings wieder stark von der Dosis und vom LET der Strahlung abhängt. Während bereits ca. zehn Minuten nach Bestrahlung mit 4,7 Gy mit 55 MeV Kohlenstoffionen erste Foci sichtbar werden, dauert deren Erscheinen nach Applizierung von 5,7 Gy durch 20 MeV Protonen (117 Protonen pro Punkt) ca. drei Stunden. Eine Erhöhung der pro Punkt applizierten Protonenzahl auf 256 (und somit der Dosis auf 12 Gy) verkürzt diese Zeit auf ca. eine Stunde. Eine weitere Verdopplung von Protonenzahl und Dosis führt zu einem Sichtbarwerden der Foci nach weniger als zehn Minuten.
BibTeX:
	@phdthesis{Hable2011diss,
	  author = {Hable, Volker},
	  title = {Echtzeitbeobachtung schneller Reaktionskinetiken in lebenden Zellen nach Ionenmikrobestrahlung},
	  school = {Universität der Bundeswehr München},
	  year = {2011},
	  url = {http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:706-2487}
	}
	
Free volume changes on optical switching in azobenzene- polymethylmethacrylate blends studied by a pulsed low-energy positron beam
S. Harms, K. Rätzke, C. Pakula, V. Zaporojtchenko, T. Strunskus, W. Egger, P. Sperr and F. Faupel; Journal of Polymer Science, Part B: Polymer Physics 49 (6) (2011) 404-408.
Abstract: Polymers including chromophores, which can be switched by light, have been studied extensively during the last years due to a host of potential applications which arise from the marked changes in physical properties on switching. Even though there is clear evidence that the free volume has a significant influence on the isomerization kinetics, the question of free volume changes on switching was only addressed recently. Using a pulsed low-energy positron beam the ortho-positronium lifetime τ3 was taken as a very sensitive free volume probe, and no change in free volume was detected on isomerization in an azobenzene-polymethylmethacrylate (PMMA) copolymer containing about 8 wt % of the azobenzene moiety. Here, we report for the first time on free volume changes in an azobenzene-PMMA blend with an azobenzene moiety concentration as high as 40 wt %. Using the same pulsed low-energy positron beam, small but significant changes of τ3 were observed between the structurally relaxed dark and the UV-illuminated states suggesting a decrease in free volume of the order of 10%.
BibTeX:
	@article{Harms2011,
	  author = {Harms, S. and Rätzke, K. and Pakula, C. and Zaporojtchenko, V. and Strunskus, T. and Egger, W. and Sperr, P. and Faupel, F.},
	  title = {Free volume changes on optical switching in azobenzene- polymethylmethacrylate blends studied by a pulsed low-energy positron beam},
	  journal = {Journal of Polymer Science, Part B: Polymer Physics},
	  year = {2011},
	  volume = {49},
	  number = {6},
	  pages = {404--408},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/polb.22201/abstract;jsessionid=4D54F7AB4F5618E0910C9AE9CE32EE19.f04t03},
	  doi = {http://doi.org/10.1002/polb.22201}
	}
	
Free volume distribution at the Teflon AF®/silicon interfaces probed by a slow positron beam
S. Harms, K. Rätzke, V. Zaporojtchenko, F. Faupel, W. Egger and L. Ravelli; Polymer 52 (2) (2011) 505-509.
Abstract: We performed positron annihilation lifetime spectroscopy experiments at Teflon AF®/silicon interfaces as function of the positron implantation energy to determine the free volume hole size distribution in the interfacial region and to investigate the width of the interphase. While no interphase was detected in very short chained solvent-free, thermally evaporated Teflon AF®, an interphase of some tens of nm in extension was observed for high molecular weight spin-coated Teflon AF® films. Influences of the native oxide layer on the data evaluation could be ruled out.
BibTeX:
	@article{Harms2011a,
	  author = {Harms, S. and Rätzke, K. and Zaporojtchenko, V. and Faupel, F. and Egger, W. and Ravelli, L.},
	  title = {Free volume distribution at the Teflon AF®/silicon interfaces probed by a slow positron beam},
	  journal = {Polymer},
	  year = {2011},
	  volume = {52},
	  number = {2},
	  pages = {505--509},
	  url = {http://www.sciencedirect.com/science/article/pii/S0032386110010347},
	  doi = {http://doi.org/10.1016/j.polymer.2010.11.039}
	}
	
Subdiffusion von DNS-Doppelstrangbrüchen unter dem Einfluss von Zellkernverformungen
Michael Haum; Bachelors-Thesis, Universität der Bundeswehr München, 2011.
Abstract: Die Untersuchung von Schäden an biologischem Material durch ionisierende Strahlung stellt immer noch ein großes Forschungsgebiet von Medizin und Biologie dar. Insbesondere die Reparaturvorgänge nach der Schädigung der DNS im Zellkern werfen noch viele offene Fragen auf, dabei vor allem die der gefährlichsten Doppelstrangbrüche (DSB). Für ein besseres Verständnis der raumzeitlichen Dynamik der DSB wurden lebende Zellen am Münchner 14 MV Tandembeschleuniger mit 43 MeV Kohlenstoff-Ionen beschossen, um so die DNS gezielt zu schädigen und die erzeugten DSB über die sich dort gebildeten fluoreszenzmarkierten Reparaturproteincluster („Foci“) zu beobachten.
Für die Analyse der Dynamik wurde die zeitliche Änderung der Abstände benachbarter Foci ( l≈5μm ) herangezogen. Die Standardabweichung der Abstandsänderung über ein Zeitintervall dt kann mit der Gleichung sigma^2= G * dt^a beschrieben werden, die eine Aussage über die Art der Diffusion macht. Es zeigte sich, dass der Diffusionsexponent mit a=0,49±0,05 deutlich kleiner ist als der einer normalen Diffusion ( a=1 ) und der Transportkoeffizient bei G=(1,7± 0,6) x 10^(−3) μm^2/s^0,49 liegt, sodass der Bewegung eine anomale Subdiffusion zugrunde liegt [S. Girst, 2011]. Durch die Betrachtung der Abstände anstelle von absoluten Positionen soll ausgeschlossen werden, dass eine Bewegung oder Deformation der gesamten Zelle unbeabsichtigt
in die Auswertung mit einfließt.
Ziel dieser Arbeit war es zu untersuchen, ob auch bei der Auswertung von größeren Foci-Abständen eine anomale Subdiffusion vorliegt. Hierfür wurden die Abstandsänderungen eines Foci zu seinem übernächsten Nachbarn ( l≈10μm ) herangezogen. Es ergab sich, dass auch hier eine anomale Subdiffusion vorliegt, mit dem Diffusionsexponenten a=0,58± 0,03 und dem Transportkoeffizienten G=(1,6± 0,3) x 10^(−3) μm^2 /s^0,58 . Trotz des größeren Diffusionsexponenten liegt auch nach dieser Auswertung eine anomale Subdiffusion vor, sodass das für kleine Abstände gefundene Ergebnis bestätigt wird. Der größere Diffusionsexponent ist allerdings ein Hinweis darauf, dass sich bei großen Foci-Abständen eine Verformung der Zelle in der Auswertung stärker
bemerkbar macht.
BibTeX:
	@mastersthesis{Haum2011ba,
	  author = {Haum, Michael},
	  title = {Subdiffusion von DNS-Doppelstrangbrüchen unter dem Einfluss von Zellkernverformungen},
	  school = {Universität der Bundeswehr München},
	  year = {2011}
	}
	
Vacancy defects in CdTe thin films
D. Keeble, J. Major, L. Ravelli, W. Egger and K. Durose; Physical Review B - Condensed Matter and Materials Physics 84 (17) (2011) 174122.
Abstract: Vacancy defects have been investigated in a series of CdTe thin films grown by close-space sublimation. Variable-energy positron annihilation lifetime spectroscopy measurements, performed with a high-intensity positron beam, were used to profile polycrystalline films with varying grain size. These were obtained by changing the nitrogen pressure used during deposition. Two vacancy defects were detected, with positron lifetimes of 321(7)ps and 450(30) ps, respectively. Density functional theory calculations support the assignment of the first to the Cd vacancy and provide evidence that the second is the divacancy defect.
BibTeX:
	@article{Keeble2011,
	  author = {Keeble, D.J. and Major, J.D. and Ravelli, L. and Egger, W. and Durose, K.},
	  title = {Vacancy defects in CdTe thin films},
	  journal = {Physical Review B - Condensed Matter and Materials Physics},
	  year = {2011},
	  volume = {84},
	  number = {17},
	  pages = {174122},
	  url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.84.174122},
	  doi = {http://doi.org/10.1103/PhysRevB.84.174122}
	}
	
Suppression of vacancy defects in epitaxial La-doped SrTiO 3 films
D. Keeble, B. Jalan, L. Ravelli, W. Egger, G. Kanda and S. Stemmer; Applied Physics Letters 99 (23) (2011) 232905.
Abstract: Variable energy positron annihilation lifetime spectroscopy of high-mobility La-doped SrTiO 3 grown by molecular beam epitaxy found that the films contained sufficiently low concentrations of Sr vacancies and vacancy cluster defects to allow the observation of positron annihilation events from the perfect lattice. This enabled the concentrations of charged cation vacancies to be estimated, and these were found to be at least an order of magnitude below the La-dopant concentrations.
BibTeX:
	@article{Keeble2011a,
	  author = {Keeble, D.J. and Jalan, B. and Ravelli, L. and Egger, W. and Kanda, G. and Stemmer, S.},
	  title = {Suppression of vacancy defects in epitaxial La-doped SrTiO 3 films},
	  journal = {Applied Physics Letters},
	  year = {2011},
	  volume = {99},
	  number = {23},
	  pages = {232905},
	  url = {http://aip.scitation.org/doi/10.1063/1.3664398},
	  doi = {http://doi.org/10.1063/1.3664398}
	}
	
Differential proton-proton scattering cross section for energies between 1.9 MeV and 50 MeV
M. Moser, P. Reichart, C. Greubel and G. Dollinger; Nuclear Instruments and Methods in Physics Research Section B 269 (20) (2011) 2217-2228.
Abstract: We present a phase shift analysis of differential elastic proton-proton scattering cross sections (dσ/dΩ) pp in the energy range from 1.9 MeV to 50 MeV and laboratory scattering angles θlab= 15-75°. That results in an accurate representation of the experimental data by an analytical function (χred2=1.95). The average statistical error of the resulting data fit is 0.2%. The evaluation is representing the experimental data better than the evaluated cross section by the framework of the R-matrix theory as available from the ENDF database (χred2=6.98). For a fast evaluation we extract an E,θ-matrix for (dσ/dΩ) pp with a negligible interpolation error. These data may be used for data evaluation when using proton-proton scattering for hydrogen detection in material analysis.
BibTeX:
	@article{Moser2011,
	  author = {Moser, M. and Reichart, P. and Greubel, C. and Dollinger, G.},
	  title = {Differential proton-proton scattering cross section for energies between 1.9 MeV and 50 MeV},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2011},
	  volume = {269},
	  number = {20},
	  pages = {2217--2228},
	  note = {12th International Conference on Nuclear Microprobe Technology and Applications},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X1100200X},
	  doi = {http://doi.org/10.1016/j.nimb.2011.02.017}
	}
	
Differential Proton-Proton Scattering Cross Section for energies between 1.9 MeV and 50 MeV
Marcus Moser; Masters-Thesis, Hochschule München, 2011.
Abstract: We present a phase shift analysis of differential elastic proton-proton scattering cross sections (dσ/dO)_pp in the energy range from 1.9 MeV to 50 MeV and laboratory scattering angles θ_lab = 15 . . . 75. It results in an accurate representation of the experimental data by an analytical function for (dσ/dO)_pp (E, θ). The average statistical error of the resulting data fit is 0.2%. For a fast evaluation we extract an [E, θ]-matrix for (dσ/dO)_pp with a negligible interpolation error smaller than 0.02%. This data may be relevant for data evaluation for hydrogen analysis when using proton-proton scattering.
BibTeX:
	@mastersthesis{Moser2011ma,
	  author = {Moser, Marcus},
	  title = {Differential Proton-Proton Scattering Cross Section for energies between 1.9 MeV and 50 MeV},
	  school = {Hochschule München},
	  year = {2011}
	}
	
Eine hochbrillante Multicusp H-/D- Ionenquelle am Münchener Tandembeschleuniger.
Marcus Moser; Studienarbeit, Hochschule München, 2011.
Abstract: Proton-proton scattering at the Munich microprobe SNAKE gives the unique possibility for sensitive 3D hydrogen microscopy [1]. We have installed a new multicusp ion source for negative hydrogen ions manufactured by HVEE [2] at the Munich tandem accelerator. The aim is boosting the proton beam brightness and hence optimizing the microprobe's lateral resolution and its sensitivity in hydrogen detection. The source operates at the space charge limit at its extraction site and therefore enables an optimum emittance of 15-20 Am^(−2)rad^(−2)eV^(−1) and brightness at the principal limit for conventional ion sources. The emittance is two orders of magnitude larger than that of the ECR source that was used before in combination with charge exchange for negative hydrogen production. For injection into the tandem accelerator, the extraction current of up to 1.5 mA H− is reduced to about 10 μA. Thus, we only accelerate the high brightness core of the beam that is further restricted in size and divergence by micro slit systems in front of SNAKE. We present the performance of the installed source and show the beam characteristics at the focal plane of SNAKE. In addition we show first 3D hydrogen microscopy on geological samples with a new multi-strip detector matrix consisting of four 5x5 cm^2, 1 mm thick strip detectors in a configuration parallel to the beam. The new detector setup enables us to use up to 25 MeV of incoming protons stopping all scattered protons from proton-proton scattering in the detector.
BibTeX:
	@thesis{Moser2011sa,
	  author = {Moser, Marcus},
	  title = {Eine hochbrillante Multicusp H-/D- Ionenquelle am Münchener Tandembeschleuniger.},
	  school = {Hochschule München},
	  year = {2011}
	}
	
Konstruktion und Aufbau einer positionierbaren, kollimierten Gammaquelle zur Kalibrierung eines gepixelten Germaniumdetektors für die Positronenannihilation
Ricardo Riedel; Studienarbeit, Universität der Bundeswehr München, 2011.
BibTeX:
	@thesis{Riedel2011sa,
	  author = {Ricardo Riedel},
	  title = {Konstruktion und Aufbau einer positionierbaren, kollimierten Gammaquelle zur Kalibrierung eines gepixelten Germaniumdetektors für die Positronenannihilation},
	  school = {Universität der Bundeswehr München},
	  year = {2011}
	}
	
The effectiveness of 20 MeV protons at nanosecond pulse lengths in producing chromosome aberrations in human-hamster hybrid cells
T.E. Schmid, G. Dollinger, V. Hable, C. Greubel, O. Zlobinskaya, D. Michalski, S. Auer, A.A. Friedl, E. Schmid, M. Molls and B. Röper; Radiation Research 175 (6) (2011) 719-727.
Abstract: Laser accelerated radiotherapy is a potential cancer treatment with proton and carbon-ion beams that is currently under development. Ultra-fast high-energy laser pulses will accelerate ion beams that deliver their dose to a patient in a “pulsed mode” that is expected to differ from conventional irradiation by increasing the dose delivery rate to a tissue voxel by approximately 8 orders of magnitude. In two independently performed experiments at the ion microprobe SNAKE of the 14 MV Munich tandem accelerator, AL cells were exposed either to protons with 1-ns pulse durations or to protons applied over 150 ms in continuous irradiation mode. A slightly but consistently lower aberration yield was observed for the pulsed compared to the continuous mode of proton irradiation. This difference was not statistically significant when each aberration type was analyzed separately (P values between 0.61 and 0.85 in experiment I and P values between 0.32 and 0.64 in experiment II). However, excluding the total aberrations, which were not analyzed as independent radiation-induced effects, the mean ratio of the yields of dicentrics, centric rings and excess acentrics scored together showed (with 95% CI) a significant difference of 0.90 (0.81; 0.98) between the pulsed and the continuous irradiation modes. A similar tendency was also determined for the corresponding RBE values relative to 70 kV X rays. Since the different findings for the comparisons of individual chromosome aberration types and combined comparisons could be explained by different sample sizes with the consequence that the individual comparisons had less statistical power to identify a difference, it can be concluded that 20 MeV protons may be slightly less effective in the pulsed mode.
BibTeX:
	@article{Schmid2011,
	  author = {Schmid, T. E. and Dollinger, G. and Hable, V. and Greubel, C. and Zlobinskaya, O. and Michalski, D. and Auer, S. and Friedl, A. A. and Schmid, E. and Molls, M. and Röper, B.},
	  title = {The effectiveness of 20 MeV protons at nanosecond pulse lengths in producing chromosome aberrations in human-hamster hybrid cells},
	  booktitle = {Radiation Research},
	  journal = {Radiation Research},
	  year = {2011},
	  volume = {175},
	  number = {6},
	  pages = {719--727},
	  url = {http://www.bioone.org/doi/10.1667/RR2465.1},
	  doi = {http://doi.org/10.1667/RR2465.1}
	}
	
Double-strand break-induced transcriptional silencing is associated with loss of tri-methylation at H3K4
D. Seiler, J. Rouquette, V. Schmid, H. Strickfaden, C. Ottmann, G. Drexler, B. Mazurek, C. Greubel, V. Hable, G. Dollinger, T. Cremer and A. Friedl; Chromosome Research 19 (7) (2011) 883-899.
Abstract: Epigenetic alterations induced by ionizing radiation may contribute to radiation carcinogenesis. To detect relative accumulations or losses of constitutive post-translational histone modifications in chromatin regions surrounding DNA double-strand breaks (DSB), we developed a method based on ion microirradiation and correlation of the signal intensities after immunofluorescence detection of the histone modification in question and the DSB marker γ-H2AX. We observed after ionizing irradiation markers for transcriptional silencing, such as accumulation of H3K27me3 and loss of active RNA polymerase II, at chromatin regions labeled by γ-H2AX. Confocal microscopy of whole nuclei and of ultrathin nuclear sections revealed that the histone modification H3K4me3, which labels transcriptionally active regions, is underrepresented in γ-H2AX foci. While some exclusion of H3K4me3 is already evident at the earliest time amenable to this kind of analysis, the anti-correlation apparently increases with time after irradiation, suggesting an active removal process. Focal accumulation of the H3K4me3 demethylase, JARID1A, was observed at damaged regions inflicted by laser irradiation, suggesting involvement of this enzyme in the DNA damage response. Since no accumulation of the repressive mark H3K9me2 was found at damaged sites, we suggest that DSB-induced transcriptional silencing resembles polycomb-mediated silencing rather than heterochromatic silencing.
BibTeX:
	@article{Seiler2011,
	  author = {Seiler, D.M. and Rouquette, J. and Schmid, V.J. and Strickfaden, H. and Ottmann, C. and Drexler, G.A. and Mazurek, B. and Greubel, C. and Hable, V. and Dollinger, G. and Cremer, T. and Friedl, A.A.},
	  title = {Double-strand break-induced transcriptional silencing is associated with loss of tri-methylation at H3K4},
	  journal = {Chromosome Research},
	  year = {2011},
	  volume = {19},
	  number = {7},
	  pages = {883--899},
	  url = {http://link.springer.com/article/10.1007%2Fs10577-011-9244-1},
	  doi = {http://doi.org/10.1007/s10577-011-9244-1}
	}
	
Fe-Cr alloys behavior after helium implantation
V. Slugen, V. Krsjak, W. Egger, M. Petriska, S. Sojak and J. Veternikova; Journal of Nuclear Materials 409 (2) (2011) 163-166.
Abstract: The paper discusses our recent experiments focused on the chromium influence on the microstructural changes of iron based alloys under radiation treatment. Our experimental method - the positron annihilation lifetime spectroscopy (PALS) enables an observation of size and density changes of the vacancy type defects in the material microstructure. These defects have been created by implantation of charged particles (He2+). The cascade collisions in the crystal lattice and following Frenkel pair creation have been considered as possible approximation of the neutron flux damage up to 100 DPA in the region up to 1 μm from the surface.
BibTeX:
	@article{Slugen2011,
	  author = {Slugen, V. and Krsjak, V. and Egger, W. and Petriska, M. and Sojak, S. and Veternikova, J.},
	  title = {Fe-Cr alloys behavior after helium implantation},
	  journal = {Journal of Nuclear Materials},
	  year = {2011},
	  volume = {409},
	  number = {2},
	  pages = {163--166},
	  url = {http://www.sciencedirect.com/science/article/pii/S002231151000499X},
	  doi = {http://doi.org/10.1016/j.jnucmat.2010.09.023}
	}
	

2010

Structural characterization of H plasma-doped ZnO single crystals by positron annihilation spectroscopies
W. Anwand, G. Brauer, T. Cowan, D. Grambole, W. Skorupa, J. Čižek, J. Kuriplach, I. Procházka, W. Egger and P. Sperr; Physica Status Solidi (A) Applications and Materials Science 207 (11) (2010) 2415-2425.
Abstract: Nominally undoped, hydrothermally grown ZnO single crystals have been investigated before and after exposure to remote H plasma. Structural characterizations have been made by various positron annihilation spectroscopies (continuous and pulsed slow positron beams, conventional lifetime). The content of bound hydrogen (H-b) before and after the remote H plasma treatment at the polished side of the crystals was determined at depths of 100 and 600 nm, respectively, using nuclear reaction analysis. At a depth of 100 nm, H-b increased from (11.8 ± 2.5) to (48.7 ± 7.6) × 10 19 cm -3 after remote H plasma treatment, whereas at 600 nm no change in H-b was observed. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
BibTeX:
	@article{Anwand2010,
	  author = {Anwand, W. and Brauer, G. and Cowan, T.E. and Grambole, D. and Skorupa, W. and Čižek, J. and Kuriplach, J. and Procházka, I. and Egger, W. and Sperr, P.},
	  title = {Structural characterization of H plasma-doped ZnO single crystals by positron annihilation spectroscopies},
	  journal = {Physica Status Solidi (A) Applications and Materials Science},
	  year = {2010},
	  volume = {207},
	  number = {11},
	  pages = {2415-2425},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/pssa.200925609/abstract},
	  doi = {http://doi.org/10.1002/pssa.200925609}
	}
	
Study of defects in implanted silica glass by depth profiling Positron Annihilation Spectroscopy
R. Brusa, S. Mariazzi, L. Ravelli, P. Mazzoldi, G. Mattei, W. Egger, C. Hugenschmidt, B. Löwe, P. Pikart, C. Macchi and A. Somoza; Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 268 (19) (2010) 3186-3190.
Abstract: Positron Annihilation Spectroscopy (PAS) performed with continuous and pulsed positron beams allows to characterize the size of the intrinsic nano-voids in silica glass, their in depth modification after ion implantation and their decoration by implanted ions. Three complementary PAS techniques, lifetime spectroscopy (LS), Doppler broadening spectroscopy (DBS) and coincidence Doppler broadening spectroscopy (CDBS) will be illustrated by presenting, as a case study, measurements obtained on virgin and gold implanted silica glass. © 2010 Elsevier B.V. All rights reserved.
BibTeX:
	@article{Brusa2010,
	  author = {Brusa, R.S. and Mariazzi, S. and Ravelli, L. and Mazzoldi, P. and Mattei, G. and Egger, W. and Hugenschmidt, C. and Löwe, B. and Pikart, P. and Macchi, C. and Somoza, A.},
	  title = {Study of defects in implanted silica glass by depth profiling Positron Annihilation Spectroscopy},
	  journal = {Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms},
	  year = {2010},
	  volume = {268},
	  number = {19},
	  pages = {3186-3190},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X10005343},
	  doi = {http://doi.org/10.1016/j.nimb.2010.05.084}
	}
	
Quantitative Analyse der LET- und Strahlungsdosisabhängigkeit von Proteinkinetiken nach Ionenmikrobestrahlung
Christian Burgdorf; Diplomarbeit, Universität der Bundeswehr München, 2010.
Abstract: In dieser Arbeit wurde eine quantitative Analyse von Proteinkinetiken nach Ionenmikrobestrahlung hinsichtlich einer LET- und Strahlungsdosisabhängigkeit durchgeführt.
Zur Auswertung der ablaufenden Reparaturprozesse wurden die mit dem Rasterionenmikroskop SNAKE fluoreszenzmikroskopisch aufgenommenen Zeitserien analysiert. In diesen Zeitserien bildeten sich in bestrahlten Bereichen innerhalb von verschiedenen Zeitintervallen Foci aus. Diese Foci beschreiben Orte, in denen sich die Konzentration von Proteinen erhöht, was mit der Anlagerung von Reparaturproteinen an beschädigten DNA-Sequenzen gleich zusetzen ist. Bei Beobachtung dieser Focibildung wurde des Weiteren deutlich, dass die Foci mit den Bestrahlungsorten kolokalisieren.
In dieser Arbeit wurden die Kinetiken der Proteine MDC1 und 53BP1 mit Hilfe von Helligkeitsmessungen ihrer Foci ausgewertet. Eine entwickelte Modellfunktion wurde an die gemessenen Helligkeitsverläufe angepasst. Die Proteinanlagerung und der Proteinabbau wurden mit Hilfe von zwei Zeitkonstanten Tau_1 und Tau_2 charakterisiert. Eine mögliche zeitliche Verzögerung beim Start des Reparaturvorganges konnte mit einem Zeitoffset T0 modelliert werden.
Zum Abschluss der Helligkeitsmessungen wurden probenübergeifend einzelne Bestrahlungsexperimente zusammengefasst, die unter gleichen biophysikalischen Bedingungen durchgeführt wurden. Die Klassifizierung erfolgte nach der verwendeten Strahlungsart und -dosis sowie nach dem untersuchten Reparaturprotein.
Hinsichtlich einer LET- und Strahlungsdosisabhängigkeit konnten für das Reparaturprotein MDC1 nach 20MeV H+, wie auch bei einer 55MeV C+ Bestrahlung, Abhängigkeiten festgestellt werden. Dabei zeigte sich für die Bestrahlung mit H+, dass die Erhöhung der Strahlungsdosis von 4,8 Gy auf 12,05 Gy (Faktor 2,5) eine Beschleunigung der Anlagerungszeit Tau_1,( 4,8 Gy) = 1052 ± 272 s zu Tau_1,(12,05 Gy) = 522 ± 148 s zur Folge hatte. Das Starten der Reparaturprozesse hingegen war nahezu konstant nach einem Zeitoffset von
T0,(4,8 Gy) = 73 ± 16 s und T0,(12,05 Gy) = 80 ± 11 s.
Für die Zeitkonstanten nach 55MeV C+ Bestrahlung zeigte sich ein ähnliches Bild, wobei deutlich wurde, dass weitaus geringere Strahlungsdosen nötig waren, um vergleichsweise schnelle Reaktionen für die Proteinanlagerung zu erreichen. Die Zeit für den Anlagerungsprozess wurde mit steigender Strahlungsdosis weiter verringert. Bei einer Dosis von 3,1Gy betrug Tau_1,(3,1 Gy) = 218 ± 55 s, die sich bei der Dosis von 4,4 Gy auf Tau_1,(4,4 Gy) = 98 ± 11 s verringerte. Eine signifikante Dosisabhängigkeit für die Offset-Zeiten
T0 konnte nicht bestimmt werden (T0,(3,1 Gy) = 14 ± 4 s, T0,(4,4 Gy) = 17 ± 2 s).
Die Auswertung des zweiten Reparaturproteins 53BP1 erbrachte für die Bestrahlung mit 20MeV H+ keine linearen Dosisabhängigkeiten. Die Werte für die Zeitkonstanten Tau_1 liegen in niedrigen (3,4 Gy) und hohen Strahlungsdosisbereichen (13,7 Gy) nahezu konstant
bei Tau_1,(3,4 Gy) = 237 ± 33 s und Tau_1,(13,7 Gy) = 226 ± 60 s. Für den mittleren Dosisbereich ist mit Tau_1,(6,9 Gy) = 460 ± 100 s die benötigte Zeit für die Proteinanlagerung doppelt so groß. Derselbe Effekt ist auch bei der Offset-Zeit T0 zu erkennen (T0, 3,4 Gy = 118 ± 14 s, T0, 6,9 Gy = 160 ± 12 s, T0, 13,7 Gy = 120 ± 22 s).
Die Auswertung des 53BP1 nach 55 MeVC+ Bestrahlung erbrachte ein Tau_1,(6,3 Gy) = 375 ± 58 s und einen Zeitoffset T0,(6,3 Gy) = 89 ± 8 s. Dabei wurde deutlich, dass sich die Zeitkonstanten für unterschiedliche Strahlungsarten trotz einer ähnlichen applizierten Strahlungsdosis stark unterschieden. Dennoch zeigte sich, wie bei der Untersuchung von MDC1, dass 55MeV C+ bestrahlte 53BP1 Proben eine schnellere Reaktion zeigten.
BibTeX:
	@mastersthesis{Burgdorf2010da,
	  author = {Burgdorf, Christian},
	  title = {Quantitative Analyse der LET- und Strahlungsdosisabhängigkeit von Proteinkinetiken nach Ionenmikrobestrahlung},
	  school = {Universität der Bundeswehr München},
	  year = {2010}
	}
	
Positron annihilation spectroscopy: A technique to probe the molecular level of nanofiltration membranes
A. Cano-Odena, P. Vandezande, K. Hendrix, R. Zaman, K. Mostafa, W. Egger, P. Sperr, J. De Baerdemaeker and I. Vankelecom; JOURNAL MISSING! (2010) 320-322.
BibTeX:
	@conference{Cano-Odena2010,
	  author = {Cano-Odena, A. and Vandezande, P. and Hendrix, K. and Zaman, R. and Mostafa, K. and Egger, W. and Sperr, P. and De Baerdemaeker, J. and Vankelecom, I.F.J.},
	  title = {Positron annihilation spectroscopy: A technique to probe the molecular level of nanofiltration membranes},
	  booktitle = {20th Annual Meeting of the North American Membrane Society and 11th International Conference on Inorganic Membranes 2010, NAMS/ICIM 2010},
	  publisher = {North American Membrane Society ( NAMS )},
	  year = {2010},
	  pages = {320--322}
	}
	
Life cell micro-irradiation
G. Dollinger; Nuclear Physics News 20 (3) (2010) 27-32.
Abstract: A main subject of modern experiments in radiobiology is the detailed investigation of the biological response on a microscopic scale when a living organism is irradiated by ionizing radiation. As known for long, a DNA double strand break (DSB) is one of the most harmful threats that can be induced by ionizing radiation (Figure 1a). Thus, the response of cells to DSBs on a microscopic scale interests in view of cell surveillance strategies. There are already a lot of proteins known that are omnipresent in cell nuclei and that are involved in the repair of DSBs. Some of them cluster around a DSB forming a “repair focus” (Figure 1b). The spatio-temporal development of the repair processes and the interaction of the different proteins within repair pathways are to a large extent still unknown. A precise irradiation of cells by means of a nuclear microprobe, for example, using SNAKE ( S uperconducting N anoscope for A pplied nuclear ( K ern-) physics E xperiments) at the Munich tandem accelerator, is an ideal tool to perform accurate radiobiological experiments and to investigate cell surveillance strategies in general [1].
BibTeX:
	@article{Dollinger2010,
	  author = {Dollinger, G.},
	  title = {Life cell micro-irradiation},
	  journal = {Nuclear Physics News},
	  year = {2010},
	  volume = {20},
	  number = {3},
	  pages = {27--32},
	  note = {cited By (since 1996)0},
	  url = {http://www.nupecc.org/index.php?display=npn/issues},
	  doi = {http://doi.org/10.1080/10619127.2010.506125}
	}
	
Pulsed low-energy positron beams: A useful tool to investigate defect structures in deformed metals and alloys
W. Egger, P. Sperr, G. Kögel and H.-J. Gudladt; Journal of Physics: Conference Series 240 (2010) 012164.
Abstract: To understand in more detail the behaviour of deformed metallic materials, the knowledge of defects and defect distributions at an atomistic level is important. To investigate the plastic zone in front of a crack tip, the positron annihilation lifetime spectroscopy with a pulsed monoenergetic positron beam of variable energy allows the detection of vacancies, dislocations, vacancy clusters and micro voids in the crack surface near region. Moreover, for a given defect type it is possible to determine its concentration. The positron lifetime measurements in samples of different materials (aluminium, copper) showed different defect profiles for crack surfaces produced by monotonic and cyclic deformation. In addition, this technique was able to characterize the kind of damage (monotonic or cyclic) by analysing the different positron lifetimes. © 2010 IOP Publishing Ltd.
BibTeX:
	@article{Egger2010,
	  author = {Egger, W. and Sperr, P. and Kögel, G. and Gudladt, H.-J.},
	  title = {Pulsed low-energy positron beams: A useful tool to investigate defect structures in deformed metals and alloys},
	  journal = {Journal of Physics: Conference Series},
	  year = {2010},
	  volume = {240},
	  pages = {012164},
	  url = {http://iopscience.iop.org/article/10.1088/1742-6596/240/1/012164/meta;jsessionid=43E8EFB1F3F805A71643DA6B40BEEFE9.ip-10-40-1-105},
	  doi = {http://doi.org/10.1088/1742-6596/240/1/012164}
	}
	
Pulsed low-energy positron beams in materials sciences
W. Egger; In: R. Brusa, A. Dupasquier and A.P. Mills jr. (Eds.), Physics with many Positrons , Vol. 174 , p. 419-449 , IOS Press , 2010.
Abstract: Pulsed low-energy positron beams of variable energy are powerful tools for defect profiling in materials. In this lecture we will at first describe two pulsed-beam systems developed over the last two decades: The Pulsed Low Energy Positron System (PLEPS) for depth-resolved defect profiling and the Scanning Positron Microscope (SPM), which in addition offers lateral resolution. We then consider some examples of applications of those pulsed beams to condensed matter problems. Next, the limits of those systems are discussed. Finally, we will give an outlook how pulsing with many positrons may be achieved and used for the purposes of materials sciences by combining existing experimental equipment with a strong positron source. © 2010 by Società Italiana di Fisica.
BibTeX:
	@incollection{Egger2010a,
	  author = {Egger, Werner},
	  title = {Pulsed low-energy positron beams in materials sciences},
	  booktitle = {Physics with many Positrons},
	  publisher = {IOS Press},
	  year = {2010},
	  volume = {174},
	  pages = {419--449},
	  editor = {Brusa, R. and Dupasquier, A. and Mills jr., A. P.},
	  url = {http://ebooks.iospress.nl/publication/26841},
	  doi = {http://doi.org/10.3254/978-1-60750-647-8-419}
	}
	
Positronium formation in porous materials for antihydrogen production
R. Ferragut, A. Calloni, A. Dupasquier, G. Consolati, F. Quasso, M. Giammarchi, D. Trezzi, W. Egger, L. Ravelli, M. Petkov, S. Jones, B. Wang, O. Yaghi, B. Jasinska, N. Chiodini and A. Paleari; Journal of Physics: Conference Series 225 (2010) 012007.
Abstract: Positronium (Ps) formation measurements in several porous materials as: Vycor, germanate Xerogel, Metal-Organic Frameworks MOF-177 and Aerogel with two densities (20 and 150 mg/cm3), were performed by means of a variable energy positron beam provided with a Ge detector and a positron lifetime spectrometer. An efficient formation of cooled Ps atoms is a requisite for the production of antihydrogen, with the aim of a direct measurement of the Earth gravitational acceleration g of antimatter, which is a primary scientific goal of AEGIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy). Porous materials are necessary to form a high yield of Ps atoms as well as to cool Ps through collisions with the inner walls of the pores. The different materials were characterized and produce Ps into the pores. Lifetime measurements give an estimation of the typical pores dimension of the substances. A comparative study of the positron lifetime and the Ps fraction values in the above mentioned materials indicates that silica Aerogel, with the appropriate density, is an excellent candidate for an efficient formation of cold Ps atoms for the AEGIS project. © 2010 IOP Publishing Ltd.
BibTeX:
	@article{Ferragut2010,
	  author = {Ferragut, R. and Calloni, A. and Dupasquier, A. and Consolati, G. and Quasso, F. and Giammarchi, M.G. and Trezzi, D. and Egger, W. and Ravelli, L. and Petkov, M.P. and Jones, S.M. and Wang, B. and Yaghi, O.M. and Jasinska, B. and Chiodini, N. and Paleari, A.},
	  title = {Positronium formation in porous materials for antihydrogen production},
	  journal = {Journal of Physics: Conference Series},
	  year = {2010},
	  volume = {225},
	  pages = {012007},
	  url = {http://iopscience.iop.org/article/10.1088/1742-6596/225/1/012007/meta},
	  doi = {http://doi.org/10.1088/1742-6596/225/1/012007}
	}
	
Free volume and swelling in thin films of poly(N-isopropylacrylamide) end-capped with N-butyltrithiocarbonate
S. Harms, K. Rätzke, F. Faupel, W. Egger, L. Ravello, A. Laschewsky, W. Wang and P. Müller-Buschbaum; Macromolecular Rapid Communications 31 (15) (2010) 1364-1367.
Abstract: The free volume in thin films of poly(N-isopropylacrylamid) end-capped with n-butyltriocarbonate (nbc-PNIPAM) is probed with positron annihilation lifetime spectroscopy (PALS). The PALS measurements are performed as function of energy to obtain depth profiles of the free volume of nbc-PNIPAM films. The range of nbc-PNIPAM films with thicknesses from 40 to 200 nm is focused. With decreasing film thickness the free volume increases in good agreement with an increase in the maximum swelling capability of the nbc-PNIPAM films. Thus in thin hydrogel films the sorption and swelling behavior is governed by free volume. (Figure Presented) © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
BibTeX:
	@article{Harms2010,
	  author = {Harms, S. and Rätzke, K. and Faupel, F. and Egger, W. and Ravello, L. and Laschewsky, A. and Wang, W. and Müller-Buschbaum, P.},
	  title = {Free volume and swelling in thin films of poly(N-isopropylacrylamide) end-capped with N-butyltrithiocarbonate},
	  journal = {Macromolecular Rapid Communications},
	  year = {2010},
	  volume = {31},
	  number = {15},
	  pages = {1364-1367},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/marc.201000067/abstract},
	  doi = {http://doi.org/10.1002/marc.201000067}
	}
	
Identification of vacancy defects in a thin film perovskite oxide
D. Keeble, R. MacKie, W. Egger, B. Löwe, P. Pikart, C. Hugenschmidt and T. Jackson; Physical Review B - Condensed Matter and Materials Physics 81 (6) (2010) 064102.
Abstract: Vacancies are the dominant point defects in perovskite oxides, however, detecting and identifying the nature of vacancy defects in thin films remains challenging. This can be achieved using electron-beam methods but concentrations of several percent are required. Here we use a high-flux positron beam, providing high statistics positron lifetime measurements, to identify vacancies in laser ablated SrTiO3 on SrTiO3. The method is capable of subparts per million sensitivity and when combined with density-functional theory provides local structure information. The positron lifetime spectrum depth profile detects the presence of large vacancy clusters in a surface layer, a uniform distribution of Sr vacancies through the bulk of the film and resolves the interface with the substrate. © 2010 The American Physical Society.
BibTeX:
	@article{Keeble2010,
	  author = {Keeble, D.J. and MacKie, R.A. and Egger, W. and Löwe, B. and Pikart, P. and Hugenschmidt, C. and Jackson, T.J.},
	  title = {Identification of vacancy defects in a thin film perovskite oxide},
	  journal = {Physical Review B - Condensed Matter and Materials Physics},
	  year = {2010},
	  volume = {81},
	  number = {6},
	  pages = {064102},
	  url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.81.064102},
	  doi = {http://doi.org/10.1103/PhysRevB.81.064102}
	}
	
Identification of A- and B-site cation vacancy defects in perovskite oxide thin films
D. Keeble, S. Wicklein, R. Dittmann, L. Ravelli, R. MacKie and W. Egger; Physical Review Letters 105 (22) (2010) 226102.
Abstract: Cation vacancies on both sublattices (VTi, VSr) have been identified in homoepitaxial pulsed laser deposited SrTiO3 films using high intensity variable energy positron annihilation lifetime spectroscopy (PALS) measurements. Film nonstoichiometry was varied by varying laser fluence. PALS showed that on increasing the fluence above the Ti/Sr∼1 value, the concentration ratio [VSr]/[VTi] systematically increased. Reducing the fluence into the Ti-poor region below resulted in additional vacancy cluster defect formation. Vacancy concentrations greater than ∼50ppm were observed in all films. © 2010 The American Physical Society.
BibTeX:
	@article{Keeble2010a,
	  author = {Keeble, D.J. and Wicklein, S. and Dittmann, R. and Ravelli, L. and MacKie, R.A. and Egger, W.},
	  title = {Identification of A- and B-site cation vacancy defects in perovskite oxide thin films},
	  journal = {Physical Review Letters},
	  year = {2010},
	  volume = {105},
	  number = {22},
	  pages = {226102},
	  url = {http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.226102},
	  doi = {http://doi.org/10.1103/PhysRevLett.105.226102}
	}
	
Precise nitrogen depth profiling by high-resolution RBS in combination with angle-resolved XPS
K. Kimura, K. Nakajima, T. Conard, W. Vandervorst, A. Bergmaier and G. Dollinger; Nuclear Instruments and Methods in Physics Research Section B 268 (11-12) (2010) 1960-1963.
Abstract: Nitrogen depth profiling in a high-k gate stack structure, SiON/HfO2/SiON/Si(0 0 1) was performed by high-resolution Rutherford backscattering spectroscopy (HRBS) in combination with angle-resolved X-ray photoelectron spectroscopy (AR-XPS). The nitrogen depth profile is determined so that both the HRBS spectrum and the angular dependence of the XPS yield are reproduced. The obtained nitrogen profile is compared with the result of high-resolution elastic recoil detection (ERD) which is the most reliable technique for depth profiling of light elements. The agreement between the result of the present combination analysis and that of high-resolution ERD is fairly good, showing that the present combination analysis is a promising method for the analysis of light elements.
BibTeX:
	@article{Kimura2010,
	  author = {Kimura, K. and Nakajima, K. and Conard, T. and Vandervorst, W. and Bergmaier, A. and Dollinger, G.},
	  title = {Precise nitrogen depth profiling by high-resolution RBS in combination with angle-resolved XPS},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2010},
	  volume = {268},
	  number = {11-12},
	  pages = {1960-1963},
	  note = {cited By (since 1996)2},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X1000203X},
	  doi = {http://doi.org/10.1016/j.nimb.2010.02.108}
	}
	
Analysis of ultra-Thin HfO2/SiON/Si(001): Comparison of three different techniques
K. Kimura, K. Nakajima, T. Conard, W. Vandervorst, A. Bergmaier and G. Dollinger; Analytical Sciences 26 (2) (2010) 223-226.
Abstract: Composition depth profiling of HfO2 (2.5 nm)/SiON (1.6 nm)/Si(001) was performed by three diffetent analytical techniques: high-resolution Rutherford backscattering spectroscopy (HRBS), angle-resolved X-ray photoelectron spectroscopy (AR-XPS) and high-resolution elastic recoil detection (HR-ERD). By comparing these results we found the following: (1) HRBS generally provides accurate depth profiles. However, care must be taken in backgroud subtraction for depth profiling of light elements. (2) In the standard AR-XPS analysis, a simple exponential formula is often used to calculate the photoelectron escape probability. This simple formula, however, cannot be used for the precise depth profiling. (2) Although HR-ERD is the most reliable technique for the depth profiling of light elements, it may suffer from multiple scattering, which deteriorates the depth resolution, and also may cause a large background.
BibTeX:
	@article{Kimura2010a,
	  author = {Kimura, K. and Nakajima, K. and Conard, T. and Vandervorst, W. and Bergmaier, A. and Dollinger, G.},
	  title = {Analysis of ultra-Thin HfO2/SiON/Si(001): Comparison of three different techniques},
	  journal = {Analytical Sciences},
	  year = {2010},
	  volume = {26},
	  number = {2},
	  pages = {223--226},
	  note = {cited By (since 1996)2},
	  url = {https://www.jstage.jst.go.jp/article/analsci/26/2/26_2_223/_article},
	  doi = {http://doi.org/10.2116/analsci.26.223}
	}
	
A new value for the half-life of 10Be by Heavy-Ion Elastic Recoil Detection and liquid scintillation counting
G. Korschinek, A. Bergmaier, T. Faestermann, U. Gerstmann, K. Knie, G. Rugel, A. Wallner, I. Dillmann, G. Dollinger, C. von Gostomski, K. Kossert, M. Maiti, M. Poutivtsev and A. Remmert; Nuclear Instruments and Methods in Physics Research Section B 268 (2) (2010) 187-191.
Abstract: The importance of 10Be in different applications of accelerator mass spectrometry (AMS) is well-known. In this context the half-life of 10Be has a crucial impact, and an accurate and precise determination of the half-life is a prerequisite for many of the applications of 10Be in cosmic-ray and earth science research. Recently, the value of the 10Be half-life has been the centre of much debate. In order to overcome uncertainties inherent in previous determinations, we introduced a new method of high accuracy and precision. An aliquot of our highly enriched 10Be master solution was serially diluted with increasing well-known masses of 9Be. We then determined the initial 10Be concentration by least square fit to the series of measurements of the resultant 10Be/9Be ratio. In order to minimize uncertainties because of mass bias which plague other low-energy mass spectrometric methods, we used for the first time Heavy-Ion Elastic Recoil Detection (HI-ERD) for the determination of the 10Be/9Be isotopic ratios, a technique which does not suffer from difficult to control mass fractionation. The specific activity of the master solution was measured by means of accurate liquid scintillation counting (LSC). The resultant combination of the 10Be concentration and activity yields a 10Be half-life of T1/2 = 1.388 ± 0.018 (1 s, 1.30%) Ma. In a parallel but independent study (Chmeleff et al. [11]), found a value of 1.386 ± 0.016 (1.15%) Ma. Our recommended weighted mean and mean standard error for the new value for 10Be half-life based on these two independent measurements is 1.387 ± 0.012 (0.87%) Ma.
BibTeX:
	@article{Korschinek2010,
	  author = {Korschinek, G. and Bergmaier, A. and Faestermann, T. and Gerstmann, U.C. and Knie, K. and Rugel, G. and Wallner, A. and Dillmann, I. and Dollinger, G. and von Gostomski, Ch.L. and Kossert, K. and Maiti, M. and Poutivtsev, M. and Remmert, A.},
	  title = {A new value for the half-life of 10Be by Heavy-Ion Elastic Recoil Detection and liquid scintillation counting},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2010},
	  volume = {268},
	  number = {2},
	  pages = {187--191},
	  note = {cited By (since 1996)163},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X09009872},
	  doi = {http://doi.org/10.1016/j.nimb.2009.09.020}
	}
	
Divacancies and the hydrogenation of Mg-Ti films with short range chemical order
H. Leegwater, H. Schut, W. Egger, A. Baldi, B. Dam and S. Eijt; Applied Physics Letters 96 (12) (2010) 121902.
Abstract: We obtained evidence for the partial chemical segregation of as-deposited and hydrogenated Mg1-yTiy films (0≤y≤0.30) into nanoscale Ti and Mg domains using positron Doppler-broadening. We exclusively monitor the hydrogenation of Mg domains, owing to the large difference in positron affinity for Mg and Ti. The electron momentum distribution broadens significantly upon transformation to the MgH2 phase over the whole compositional range. This reveals the similarity of the metal-insulator transition for rutile and fluorite MgH2. Positron lifetime studies show the presence of divacancies in the as-deposited and hydrogenated Mg-Ti metal films. In conjunction with the relatively large local lattice relaxations we deduce to be present in fluorite MgH2, these may be responsible for the fast hydrogen sorption kinetics in this MgH2 phase. © 2010 American Institute of Physics.
BibTeX:
	@article{Leegwater2010,
	  author = {Leegwater, H. and Schut, H. and Egger, W. and Baldi, A. and Dam, B. and Eijt, S.W.H.},
	  title = {Divacancies and the hydrogenation of Mg-Ti films with short range chemical order},
	  journal = {Applied Physics Letters},
	  year = {2010},
	  volume = {96},
	  number = {12},
	  pages = {121902},
	  url = {http://aip.scitation.org/doi/10.1063/1.3368698},
	  doi = {http://doi.org/10.1063/1.3368698}
	}
	
Ordered nanoporous membranes based on diblock copolymers with high chemical stability and tunable separation properties
X. Li, C.-A. Fustin, N. Lefèvre, J.-F. Gohy, S. Feyter, J. Baerdemaeker, W. Egger and I. Vankelecom; Journal of Materials Chemistry 20 (21) (2010) 4333-4339.
Abstract: Block copolymers, having the ability to self-assemble into arrays of well-defined nanostructures, can be turned into thin films. Their application as membrane was so far strongly limited by the fact that these thin films have to be transferred manually onto a porous membrane support, or because of the very strict preparation conditions. A simple method is reported here to directly produce ordered nanoporous membranes on porous supports. Well-ordered membrane structures were prepared via a simple strategy exploiting blending of a block copolymer (PS-b-PEO) with a homopolymer (PAA), involving no thermal or solvent treatment. The membranes could be directly introduced on several types of porous membrane supports via straightforward spin or dip coating of very small amounts of polymer. Moreover, the permeability of the membranes could be readily tuned by removal of the PAA without changing membrane morphology. While already inherently stable in e.g. sodium hypochlorite solutions, the chemical stability of the membranes could be further enhanced via simple UV-radiation, clearly widening their potential application field. © The Royal Society of Chemistry 2010.
BibTeX:
	@article{Li2010,
	  author = {Li, X. and Fustin, C.-A. and Lefèvre, N. and Gohy, J.-F. and Feyter, S.D. and Baerdemaeker, J.D. and Egger, W. and Vankelecom, I.F.J.},
	  title = {Ordered nanoporous membranes based on diblock copolymers with high chemical stability and tunable separation properties},
	  journal = {Journal of Materials Chemistry},
	  year = {2010},
	  volume = {20},
	  number = {21},
	  pages = {4333-4339},
	  url = {http://pubs.rsc.org/en/Content/ArticleLanding/2010/JM/b926774c#!divAbstract},
	  doi = {http://doi.org/10.1039/b926774c}
	}
	
Experimental elucidation of vacancy complexes associated with hydrogen ion-induced splitting of bulk GaN
O. Moutanabbir, R. Scholz, U. Gösele, A. Guittoum, M. Jungmann, M. Butterling, R. Krause-Rehberg, W. Anwand, W. Egger and P. Sperr; Physical Review B - Condensed Matter and Materials Physics 81 (11) (2010) 115205.
Abstract: We present a detailed study of the thermal evolution of H ion-induced vacancy related complexes and voids in bulk GaN implanted under ion-cut conditions. By using transmission electron microscopy, we found that the damage band in as-implanted GaN is decorated with a high density of nanobubbles of ∼1-2nm in diameter. Variable energy Doppler broadening spectroscopy showed that this band contains vacancy clusters and voids. In addition to vacancy clusters, the presence of VGa, VGa -H2, and VGaVN complexes was evidenced by pulsed low-energy positron lifetime spectroscopy. Subtle changes upon annealing in these vacancy complexes were also investigated. As a general trend, a growth in open-volume defects is detected in parallel to an increase in both size and density of nanobubbles. The observed vacancy complexes appear to be stable during annealing. However, for temperatures above 450°C, unusually large lifetimes were measured. These lifetimes are attributed to the formation of positronium in GaN. Since the formation of positronium is not possible in a dense semiconductor, our finding demonstrates the presence of sufficiently large open-volume defects in this temperature range. Based on the Tao-Eldrup model, the average lattice opening during thermal annealing was quantified. We found that a void diameter of 0.4 nm is induced by annealing at 600°C. The role of these complexes in the subsurface microcracking is discussed. © 2010 The American Physical Society.
BibTeX:
	@article{Moutanabbir2010,
	  author = {Moutanabbir, O. and Scholz, R. and Gösele, U. and Guittoum, A. and Jungmann, M. and Butterling, M. and Krause-Rehberg, R. and Anwand, W. and Egger, W. and Sperr, P.},
	  title = {Experimental elucidation of vacancy complexes associated with hydrogen ion-induced splitting of bulk GaN},
	  journal = {Physical Review B - Condensed Matter and Materials Physics},
	  year = {2010},
	  volume = {81},
	  number = {11},
	  pages = {115205},
	  url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.81.115205},
	  doi = {http://doi.org/10.1103/PhysRevB.81.115205}
	}
	
Bimodal range distributions of low-energy carbon ions in tetrahedral amorphous carbon
P. Neumaier, A. Bergmaier, W. Eckstein, R. Fischer, H. Hofsäss, H. Jäger, H. Kröger, C. Ronning and G. Dollinger; EPL 90 (4) (2010) 46002.
Abstract: Range and mixing distributions of carbon ions deposited onto tetrahedral amorphous carbon films at kinetic energies between 22 eV and 692 eV are measured utilizing high-resolution elastic recoil detection. These data are compared to respective calculations based on binary collision approximation as well as to classical molecular-dynamics simulations. The measured range profiles reveal asymmetric, bimodal structures which are not reproduced from theories. The measured mixing distributions approve the measured range distributions, in particular the observed differences between theory and experiment, which have to be considered in subplantation growth models.
BibTeX:
	@article{Neumaier2010,
	  author = {Neumaier, P. and Bergmaier, A. and Eckstein, W. and Fischer, R. and Hofsäss, H. and Jäger, H.U. and Kröger, H. and Ronning, C. and Dollinger, G.},
	  title = {Bimodal range distributions of low-energy carbon ions in tetrahedral amorphous carbon},
	  journal = {EPL},
	  year = {2010},
	  volume = {90},
	  number = {4},
	  pages = {46002},
	  note = {cited By (since 1996)0},
	  url = {http://iopscience.iop.org/article/10.1209/0295-5075/90/46002/meta},
	  doi = {http://doi.org/10.1209/0295-5075/90/46002}
	}
	
Open volume in bioadhesive detected by positron annihilation lifetime spectroscopy
K. Rätzke, M. Wiegemann, M. Shaikh, S. Harms, R. Adelung, W. Egger and P. Sperr; Acta Biomaterialia 6 (7) (2010) 2690-2694.
Abstract: Barnacles attach to a wide variety of surfaces underwater and show substrate-specific adhesion mechanisms. Investigating and understanding these mechanisms is a key for developing new technical adhesives. We expected open volume (porosity) at the sub-nanometre scale to occur in barnacle adhesive. With positron annihilation lifetime spectroscopy (PALS) it is possible to detect porosity at the nanometre scale by determining the lifetime of positrons. This method has not been applied to bioadhesives so far. We showed that PALS is a suitable technique for the investigation of the barnacle base and its adhesive with respect to open volume. The results were interpreted using a standard model adapted from polymers. We thereby estimated pore sizes of 0.5 nm. © 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
BibTeX:
	@article{Raetzke2010,
	  author = {Rätzke, K. and Wiegemann, M. and Shaikh, M.Q. and Harms, S. and Adelung, R. and Egger, W. and Sperr, P.},
	  title = {Open volume in bioadhesive detected by positron annihilation lifetime spectroscopy},
	  journal = {Acta Biomaterialia},
	  year = {2010},
	  volume = {6},
	  number = {7},
	  pages = {2690-2694},
	  url = {http://www.sciencedirect.com/science/article/pii/S1742706109005807},
	  doi = {http://doi.org/10.1016/j.actbio.2009.12.039}
	}
	
In-vacancies in Si-doped InN
C. Rauch, F. Reurings, F. Tuomisto, T. Veal, C. McConville, H. Lu, W. Schaff, C. Gallinat, G. Koblmüller, J. Speck, W. Egger, B. Löwe, L. Ravelli and S. Sojak; Physica Status Solidi (A) Applications and Materials Science 207 (5) (2010) 1083-1086.
Abstract: The introduction of vacancy type point defects by Si doping in InN grown by plasma-assisted molecular beam epitaxy was studied using a monoenergetic positron beam. With the combination of positron lifetime and Doppler broadening measurements, compensating In-vacancy (V In) acceptors were identified in the material. For increasing Si doping an enhanced formation of VIn defects was observed, up to a concentration of c V = 7 × 10 17 cm -3 in the highest doped sample (ne = 6:6 × 10 20 cm -3). A strong inhomogeneity of the defect profile with a significant increase of the V In concentration toward the layer/substrate interface could be detected. Additionally, larger vacancy clusters containing several V In are formed in the proximity of the interface. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
BibTeX:
	@article{Rauch2010,
	  author = {Rauch, C. and Reurings, F. and Tuomisto, F. and Veal, T.D. and McConville, C.F. and Lu, H. and Schaff, W.J. and Gallinat, C.S. and Koblmüller, G. and Speck, J.S. and Egger, W. and Löwe, B. and Ravelli, L. and Sojak, S.},
	  title = {In-vacancies in Si-doped InN},
	  journal = {Physica Status Solidi (A) Applications and Materials Science},
	  year = {2010},
	  volume = {207},
	  number = {5},
	  pages = {1083-1086},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/pssa.200983120/abstract},
	  doi = {http://doi.org/10.1002/pssa.200983120}
	}
	
Irradiation-induced defects in InN and GaN studied with positron annihilation
F. Reurings, F. Tuomisto, W. Egger, B. Löwe, L. Ravelli, S. Sojak, Z. Liliental-Weber, R. Jones, K. Yu, W. Walukiewicz and W. Schaff; Physica Status Solidi (A) Applications and Materials Science 207 (5) (2010) 1087-1090.
Abstract: We use positron annihilation to study 2-MeV 4He + irradiated and subsequently rapid-thermal-annealed InN grown by molecular-beam epitaxy and GaN grown by metal-organic chemical-vapour deposition. The irradiation fluences were in the range 5×10 14-2×10 16 cm -2. In vacancies are introduced in the irradiation at a low rate of 100 cm -1, with their concentration saturating in the mid-1017 cm -3 range at an irradiation fluence of 2×10 15 cm -2. The annealing, performed at temperatures between 425 and 475 °C, is observed to result in an inhomogeneous redistribution of the In vacancies. The behaviour is opposite to GaN, where Ga vacancies are introduced at a much higher rate of 3600 cm -1 showing no detectable saturation. About half of the Ga vacancies are found to recover in the annealing, in agreement with previous studies, while the remaining Ga vacancies undergo no spatial redistribution. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
BibTeX:
	@article{Reurings2010,
	  author = {Reurings, F. and Tuomisto, F. and Egger, W. and Löwe, B. and Ravelli, L. and Sojak, S. and Liliental-Weber, Z. and Jones, R.E. and Yu, K.M. and Walukiewicz, W. and Schaff, W.J.},
	  title = {Irradiation-induced defects in InN and GaN studied with positron annihilation},
	  journal = {Physica Status Solidi (A) Applications and Materials Science},
	  year = {2010},
	  volume = {207},
	  number = {5},
	  pages = {1087-1090},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/pssa.200983111/abstract},
	  doi = {http://doi.org/10.1002/pssa.200983111}
	}
	
Differences in the kinetics of γ-H2AX fluorescence decay after exposure to low and high LET radiation
T.E. Schmid, G. Dollinger, W. Beisker, V. Hable, C. Greubel, S. Auer, A. Mittag, A. Tarnok, A.A. Friedl, M. Molls and B. Röper; International Journal of Radiation Biology 86 (8) (2010) 682-691.
Abstract: Purpose:
In order to obtain more insight into heavy ion tumour therapy, some features of the underlying molecular mechanisms controlling the cellular response to high linear energy transfer (LET) radiation are currently analysed.

Materials and methods:
We analysed the decay of the integrated fluorescence intensity of γ-H2AX (phosphorylated histone H2AX) which is thought to reflect the repair kinetics of radiation-induced DNA double-strand breaks (DSB) using Laser-Scanning-Cytometry. Asynchronous human HeLa cells were irradiated with a single dose of either 1.89 Gy of 55 MeV carbon ions or 5 Gy of 70 kV X-rays.

Results:
Measurements of the γ-H2AX-intensities from 15–60 min resulted in a 16 % decrease for carbon ions and in a 43 % decrease for X-rays. After 21 h, the decrease was 77 % for carbon ions and 85 % for X-rays. The corresponding time-effect relationship was fitted by a bi-exponential function showing a fast and a slow component with identical half-life values for both radiation qualities being 24 ± 4 min and 13.9 ± 0.7 h, respectively. Apparent differences in the kinetics following high and low LET irradiation could completely be attributed to quantitative differences in their contributions, with the slow component being responsible for 47 % of the repair after exposure to X-rays as compared to 80 % after carbon ion irradiation.

Conclusion:
γ-H2AX loss kinetics follows a bi-exponential decline with two definite decay times independent of LET. The higher contribution of the slow component determined for carbon ion exposure is thought to reflect the increased amount of complex DSB induced by high LET radiation.

BibTeX:
	@article{Schmid2010,
	  author = {Schmid, Thomas E. and Dollinger, Günther and Beisker, Wolfgang and Hable, Volker and Greubel, Christoph and Auer, Susanne and Mittag, Anja and Tarnok, Attila and Friedl, Anna A. and Molls, Michael and Röper, Barbara},
	  title = {Differences in the kinetics of γ-H2AX fluorescence decay after exposure to low and high LET radiation},
	  journal = {International Journal of Radiation Biology},
	  year = {2010},
	  volume = {86},
	  number = {8},
	  pages = {682--691},
	  note = {PMID: 20569192},
	  url = {http://informahealthcare.com/doi/abs/10.3109/09553001003734543},
	  doi = {http://doi.org/10.3109/09553001003734543}
	}
	
Relative biological effectiveness of pulsed and continuous 20 MeV protons for micronucleus induction in 3D human reconstructed skin tissue
T.E. Schmid, G. Dollinger, V. Hable, C. Greubel, O. Zlobinskaya, D. Michalski, M. Molls and B. Röper; Radiotherapy and Oncology 95 (1) (2010) 66-72.
Abstract: Background and purpose: Laser accelerated radiotherapy is a prospect for cancer treatment with proton and/or carbon ion beams that is currently under fast development. In principal, ultra fast, high-energy laser pulses will lead to a "pulsed" delivery of the induced ion beam with pulse durations of 1 ns and below, whereas conventional proton beams deriving from a cyclotron or synchrotron apply the dose within 100 ms ("continuous"). Materials and methods: A simulation of both irradiation modes could be established at the Munich tandem accelerator with a 20 MeV proton beam, and a wide-field fast scanning system was implemented that allowed for application of up to 5 Gy per tissue voxel in a single pulse. The relative biological effectiveness (RBE) of pulsed and continuous modes of irradiation with 20 MeV protons relative to the reference radiation 70 kV X-rays was examined in a human tissue model (3D human reconstructed skin, EpiDermFT™) which preserves the three-dimensional geometric arrangement and communication of cells present in tissues in vivo. Using the induction of micronuclei (MN) in keratinocytes as the biological endpoint, the RBE was calculated as the ratio between the dose of 70 kV X-rays and 3 Gy of 20 MeV protons (pulsed or continuous) which produced equal response. Results: For pulsed and continuous 20 MV proton exposures of the human skin model, RBE values of 1.08 ± 0.20 and 1.22 ± 0.15 versus 70 kV X-rays were obtained in a first experiment and 1.00 ± 0.14 and 1.13 ± 0.14 in a second experiment during distinct beam access times, respectively. The ∼10% difference in RBE between the respective irradiation modes in both experiments was associated with large uncertainties which were not statistically significant (p ≈ 0.5). Conclusion: These findings represent an important step on the way towards application of laser-accelerated protons for clinical radiotherapy. Further clinically relevant endpoints in normal and tumor tissue have to be evaluated.
BibTeX:
	@article{Schmid2010a,
	  author = {Schmid, Thomas E. and Dollinger, Günther and Hable, Volker and Greubel, Christoph and Zlobinskaya, Olga and Michalski, Dörte and Molls, Michael and Röper, Barbara},
	  title = {Relative biological effectiveness of pulsed and continuous 20 MeV protons for micronucleus induction in 3D human reconstructed skin tissue},
	  journal = {Radiotherapy and Oncology},
	  year = {2010},
	  volume = {95},
	  number = {1},
	  pages = {66--72},
	  url = {http://www.sciencedirect.com/science/article/pii/S0167814010001623},
	  doi = {http://doi.org/10.1016/j.radonc.2010.03.010}
	}
	
Tumorbestrahlung mit gepulsten und kontinuierlichen Protonen am Mausmodell.
Christian Siebenwirth; Diplomarbeit, Technische Universität München, 2010.
Abstract: Zur Qualifizierung der Tumortherapie mit gepulsten Protonenstrahlen mit Pulsbreiten von 1 ns, wie sie bei der Laserbeschleunigung erzeugt werden, wurden am Münchner 14 MV Tandembeschleuniger menschliche Tumore am Mausmodell mit 20 Gy bestrahlt. Anhand des Parameters der Tumorwachstumsverzögerung wurde überprüft, ob ein Unterschied in der relativen biologischen Wirksamkeit (RBW) zwischen Protonenstrahlung, die ihre Dosis in Pulsen der Breite von 1 ns applizieren, und kontinuierlicher Protonenbestrahlung auftritt.
Da es noch keine laserbeschleunigten Ionenstrahlen in hinreichender Qualität gibt, um eine Tumorbestrahlung durchzuführen, wurde am Rasterionenmikroskop SNAKE ein laserbeschleunigter Protonenstrahl simuliert. Dazu wurde das 5 MHz Pulsungssystem des Tandembeschleunigers verwendet, das ein 23 MeV Protonenstrahl mit einer Pulsbreite von 1 ns erzeugt. Durch die Fokussierung des Strahls an SNAKE auf einen Durchmesser von 100 μm konnte in einem einzelnen Puls eine Ionenstrahldichte von 10^9 Protonen/cm² erreicht werden und so eine Dosis von 20 Gy mit einem Puls im Target deponiert werden. Die Strahlflecke wurden in lateraler Richtung durch Strahlablenkung und Bewegen des Tumors inklusive Maus zu einem homogenen Feld von ca. 1 cm² zusammengesetzt. Die homogene Tiefendosis wurde mittels Aluminiumplättchen als diskrete Energieabsorber kurz vor dem Target verwirklicht. So besaß das homogen bestrahlte Gesamtvolumen eine Tiefe von 4,8 mm und einen Durchmesser von 9 mm. Durch die Realisierung der kontinuierlichen Protonenbestrahlung am selben Gerät, wurden systematische Fehler im Vergleich der beiden Bestrahlungsarten minimiert.
Zur Kontrolle der Protonenfluenz diente ein vor dem Tumor platzierter Gafchromic EBT2 Film, der in Abhängigkeit von der durch die Protonen deponierten Dosis verdunkelt. Damit konnte die Dosis der gepulsten und kontinuierlichen Bestrahlung mit einer relativen Genauigkeit von 3 % rekonstruiert werden.
Es wurden insgesamt 11 XF354 und 12 FaDu Tumore bestrahlt, davon 12 im gepulsten und 11 im kontinuierlichen Modus. Die sich aus der Dosisrekonstruktion ergebende mittlere Tiefendosis lag für die gepulsten Bestrahlungen durchschnittlich bei 17,6 Gy mit einer Breite von 0,2 Gy bzw. für die kontinuierliche Bestrahlung bei 19,6 Gy mit einer Breite von 0,3 Gy. Annähernd die Hälfte des 10 % Dosisunterschieds zwischen gepulst und kontinuierlicher Bestrahlung konnten auf systematische Fehler der Bestrahlungsdurchführung und der Dosisrekonstruktion zurückgeführt werden. Diese sind
in zukünftigen Experimenten einfach zu korrigieren. Die andere Hälfte liegt vermutlich in der Strahlstrommessung begründet und sollte nach näheren Untersuchungen ebenfalls reduziert werden können.
Bei den XF354 Tumoren erreichte ein Tumor je Bestrahlungsmodus das dreifache Bestrahlungsvolumen, das für die Wachstumsverzögerung als Bezugspunkt dient, wobei die Wachstumsverzögerung 103 d für die gepulste und 35 d für die kontinuierliche Bestrahlung ergab. Die übrigen Tumore wurden kontrolliert, wodurch sich wegen der geringen Statistik keine Aussage über eine unterschiedliche RBW treffen lässt. Für die FaDu Tumore konnte eine mittlere Wachstumsverzögerung von (34 ± 4) d aus fünf gepulst bestrahlten und (36 ± 4) d aus vier kontinuierlich bestrahlten nicht kontrollierten Tumoren bestimmt werden.
Die gewonnenen Ergebnisse zeigen keinen signifikanten Unterschied bezüglich der Tumorwachstumsverzögerung von gepulster und kontinuierlicher Protonenbestrahlung.
BibTeX:
	@mastersthesis{Siebenwirth2010da,
	  author = {Siebenwirth, Christian},
	  title = {Tumorbestrahlung mit gepulsten und kontinuierlichen Protonen am Mausmodell.},
	  school = {Technische Universität München},
	  year = {2010}
	}
	

2009

Characterization of ZnO nanostructures: A challenge to positron annihilation spectroscopy and other methods
G. Brauer, W. Anwand, D. Grambole, W. Egger, P. Sperr, I. Beinik, L. Wang, C. Teichert, J. Kuriplach, J. Lang, S. Zviagins, E. Cizmar, C.C. Ling, Y.F. Hsu, Y.Y. Xi, X. Chen, A.B. Djurisic and W. Skorupa; Physica Status Solidi (C) Current Topics in Solid State Physics 6 (11) (2009) 2556-2560.
Abstract: ZnO nanostructures are of special interest for device applications. However, their structural characterization remains an ongoing challenge. This paper reviews recent efforts and latest achievements in this direction. Results comprise PAS in the form of Slow Positron Implantation Spectroscopy (SPIS) and Pulsed Low Energy Positron Lifetime Spectroscopy (PLEPS), Nuclear Reaction Analysis (NRA), Atomic Force Microscopy (AFM), conductive AFM (C-AFM), Nuclear Magnetic Resonance (NMR), Electron Spin Resonance (ESR), Photoluminescence (PL) spectroscopy, and latest theoretical investigations of structure-related and positron properties of selected defects. The fundamental importance of a relationship between fabrication conditions, native defect formation, and resulting optical and electronic properties is demonstrated by getting either inferior (nanorods) or significantly improved (tetrapods) optical properties compared to single crystal samples, depending on the nanostructure fabrication method.
BibTeX:
	@article{Brauer2009,
	  author = {Brauer, Gerhard and Anwand, Wolfgang and Grambole, Dieter and Egger, Werner and Sperr, Peter and Beinik, Igor and Wang, Lin and Teichert, Christian and Kuriplach, Jan and Lang, Jan and Zviagins, Sergei and Cizmar, Erik and Ling, Chi Chung and Hsu, Yuk Fan and Xi, Yan Yan and Chen, Xinyi and Djurisic, Aleksandra B. and Skorupa, Wolfgang},
	  title = {Characterization of ZnO nanostructures: A challenge to positron annihilation spectroscopy and other methods},
	  journal = {Physica Status Solidi (C) Current Topics in Solid State Physics},
	  year = {2009},
	  volume = {6},
	  number = {11},
	  pages = {2556-2560},
	  note = {ICPA 15},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/pssc.200982081/abstract},
	  doi = {http://doi.org/10.1002/pssc.200982081}
	}
	
Probing the Molecular Level of Polyimide-Based Solvent Resistant Nanofiltration Membranes with Positron Annihilation Spectroscopy
A. Cano-Odena, P. Vandezande, K. Hendrix, R. Zaman, K. Mostafa, W. Egger, P. Sperr, J. De Baerdemaeker and I.F.J. Vankelecom; Journal of Physical Chemistry B 113 (30) (2009) 10170–10176.
Abstract: Positron annihilation spectroscopy (PAS) has been performed to link fundamental polymer properties to membrane performance, more specifically for polyimide (PI)-based solvent-resistant nanofiltration membranes. Laboratory-made membranes with well-known properties were applied first to define proper pretreatment conditions for the membrane to allow PAS-analysis and to allow more correct linking of PAS results to membrane properties. This knowledge was then applied to probe the structure of commercial PI-based Starmem membranes.
BibTeX:
	@article{Cano-Odena2009,
	  author = {Cano-Odena, Angels and Vandezande, Pieter and Hendrix, Katrien and Zaman, Rolph and Mostafa, Khaled and Egger, Werner and Sperr, Peter and De Baerdemaeker, Jeremie and Vankelecom, Ivo F. J.},
	  title = {Probing the Molecular Level of Polyimide-Based Solvent Resistant Nanofiltration Membranes with Positron Annihilation Spectroscopy},
	  journal = {Journal of Physical Chemistry B},
	  year = {2009},
	  volume = {113},
	  number = {30},
	  pages = {10170–10176},
	  url = {http://pubs.acs.org/doi/abs/10.1021/jp9012653},
	  doi = {http://doi.org/10.1021/jp9012653}
	}
	
Hydrogen-induced defects in Pd films
J. Cizek, I. Prochazka, O. Melikhova, M. Vlach, N. Zaludova, G. Brauer, W. Anwand, W. Egger, P. Sperr, C. Hugenschmidt, R. Gemma, A. Pundt and R. Kirchheim; Physica Status Solidi (C) Current Topics in Solid State Physics 6 (11) (2009) 2364-2366.
Abstract: Hydrogen absorbed in crystalline solids causes a lattice expansion and the formation of hydride phases. Contrary to free standing bulk samples, thin films are fixed at substrates, which prevent their in-plane expansion. This makes hydrogen-induced expansion of thin films highly anisotropic and leads to the formation of high stresses in hydrogen loaded thin films. As a consequence, lattice defects may be created in thin films loaded with hydrogen. This work reports about defects created by hydrogen loading in epitaxial Pd films deposited on Al(2)O(3) substrates by cold cathode beam sputtering. Hydrogen-induced defects are characterized by positron annihilation spectroscopy performed with variable energy slow positron beams. Extended studies of defect depth profile and its development with increasing concentration of hydrogen are performed by measurement of Doppler broadening of annihilation profile using a continuous positron beam. Selected states are investigated also by positron lifetime spectroscopy on an intense pulsed positron beam. Firstly, the microstructure of virgin films is characterized. Subsequently, the hydrogen concentration in the films is increased step-by-step by electrochemical charging. The development of the film microstructure and the evolution of defects are investigated.
BibTeX:
	@article{Cizek2009,
	  author = {Cizek, Jakub and Prochazka, Ivan and Melikhova, Oksana and Vlach, Martin and Zaludova, Nada and Brauer, Gerhard and Anwand, Wolfgang and Egger, Werner and Sperr, Peter and Hugenschmidt, Christoph and Gemma, Ryota and Pundt, Astrid and Kirchheim, Reiner},
	  title = {Hydrogen-induced defects in Pd films},
	  journal = {Physica Status Solidi (C) Current Topics in Solid State Physics},
	  year = {2009},
	  volume = {6},
	  number = {11},
	  pages = {2364-2366},
	  note = {ICPA 15},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/pssc.200982064/abstract},
	  doi = {http://doi.org/10.1002/pssc.200982064}
	}
	
Nanosecond pulsed proton microbeam
G. Dollinger, A. Bergmaier, V. Hable, R. Hertenberger, C. Greubel, A. Hauptner and P. Reichart; Nuclear Instruments and Methods in Physics Research Section B 267 (12-13) (2009) 2008-2012.
Abstract: We show the preparation of a pulsed 20 MeV proton beam at the Munich tandem accelerator which offers a fluence of more than 1 × 10e9 protons/cm2 being deposited in a beam spot smaller than 100 μm in diameter and within a time span of 0.9 ns fwhm. Such a beam is produced by an ECR type proton source using charge exchange in cesium vapor to obtain a beam of negative hydrogen of high brightness that is bunched, chopped, accelerated and then focused by the superconducting multipole lens of the microprobe SNAKE. Single beam pulses are generated in order to irradiate cell samples or tissue and to measure their biological effect in comparison to continuous proton or X-ray irradiation.
BibTeX:
	@article{Dollinger2009,
	  author = {Dollinger, G. and Bergmaier, A. and Hable, V. and Hertenberger, R. and Greubel, C. and Hauptner, A. and Reichart, P.},
	  title = {Nanosecond pulsed proton microbeam},
	  booktitle = {Proceedings of the 11th International Conference on Nuclear Microprobe Technology and Applications and the 3rd International Workshop on Proton Beam Writing},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2009},
	  volume = {267},
	  number = {12-13},
	  pages = {2008--2012},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X09003310},
	  doi = {http://doi.org/10.1016/j.nimb.2009.03.006}
	}
	
Nature of defects induced by Au implantation in hexagonal silicon carbide single crystals
A. Gentils, M.-F. Barthe, W. Egger and P. Sperr; AIP Conference Proceedings 1099 (2009) 891-895.
Abstract: Pulsed-slow-positron-beam-based positron lifetime spectroscopy was used to investigate the nature of vacancy defects induced by 20 MeV An implantation in single crystals 6H-SiC. Preliminary analysis of the data shows that at lower fluence, below 10(14) cm(-2), a positron lifetime of 220 ps has been obtained: it could be associated with the divacancy V(Si)-V(C) in comparison with the literature. At higher fluence, above 10(15) cm(-2), a positron lifetime of 260-270 ps, increasing with the incident positron energy, has been observed after decomposition of the lifetime spectra. By comparison with lifetime calculations, open-volumes such as quadrivacancy (V(Si)-V(C))(2) clusters could be associated with this value.
BibTeX:
	@article{Gentils2009,
	  author = {Gentils, Aurelie and Barthe, Marie-France and Egger, Werner and Sperr, Peter},
	  title = {Nature of defects induced by Au implantation in hexagonal silicon carbide single crystals},
	  journal = {AIP Conference Proceedings},
	  year = {2009},
	  volume = {1099},
	  pages = {891--895},
	  note = {20th International Conference on Application of Accelerators in Research and Industry, Ft Worth, TX, AUG 10-15, 2008},
	  url = {http://aip.scitation.org/doi/abs/10.1063/1.3120183},
	  doi = {http://doi.org/10.1063/1.3120183}
	}
	
The live cell irradiation and observation setup at SNAKE
V. Hable, C. Greubel, A. Bergmaier, P. Reichart, A. Hauptner, R. Krücken, H. Strickfaden, S. Dietzel, T. Cremer, G. Drexler, A. Friedl and G. Dollinger; Nuclear Instruments and Methods in Physics Research Section B 267 (12-13) (2009) 2090-2097.
Abstract: We describe a new setup at the ion microprobe SNAKE (Superconducting Nanoscope for Applied nuclear (Kern-) physics Experiments) at the Munich 14 MV Tandem accelerator that facilitates both living cell irradiation with sub micrometer resolution and online optical imaging of the cells before and after irradiation by state of the art phase contrast and fluorescence microscopy. The cells are kept at standard cell growth conditions at 37 °C in cell culture medium. After irradiation it is possible to switch from single ion irradiation conditions to cell observation within 0.5 s. First experiments were performed targeting substructures of a cell nucleus that were tagged by TexasRed labeled nucleotides incorporated in the cellular DNA by 55 MeV single carbon ion irradiation. In addition we show first online sequences of short time kinetics of Mdc1 protein accumulation in the vicinity of double strand breaks after carbon ion irradiation.
BibTeX:
	@article{Hable2009,
	  author = {Hable, V. and Greubel, C. and Bergmaier, A. and Reichart, P. and Hauptner, A. and Krücken, R. and Strickfaden, H. and Dietzel, S. and Cremer, T. and Drexler, G.A. and Friedl, A.A. and Dollinger, G.},
	  title = {The live cell irradiation and observation setup at SNAKE},
	  booktitle = {Proceedings of the 11th International Conference on Nuclear Microprobe Technology and Applications and the 3rd International Workshop on Proton Beam Writing},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2009},
	  volume = {267},
	  number = {12-13},
	  pages = {2090--2097},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X09003504},
	  doi = {http://doi.org/10.1016/j.nimb.2009.03.071}
	}
	
Microstructural study of He-implanted Fe-Cr alloys with the use of conventional lifetime technique and pulsed low energy positron beam
V. Kršjak, V. Slugeň, M. Petriska, S. Sojak and W. Egger; Physica Status Solidi (C) Current Topics in Solid State Physics 6 (11) (2009) 2339-2341.
Abstract: Experimental simulation of the radiation damage using He+ implantation has been performed in research of Fe-Cr model alloys. Different chromium content in the studied materials enables investigations of the effect of this element on the microstructure of radiation treated materials. The damaged region was investigated with the positron lifetime techniques with focus on the size and distribution of the defects. Our measurements show that not only pulsed low energy positron beam spectroscopy (PLEPS) but also conventional lifetime spectroscopy can study the behaviour of vacancy type defects induced by implantation of charged particles. Our results show that initial microstructure of low Cr alloys with significant presence of vacancy type defects is less resistant to creation of defect agglomeration in comparison with higher Cr alloys.
BibTeX:
	@article{Krsjak2009,
	  author = {Kršjak, Vladimir and Slugeň, Vladimir and Petriska, Martin and Sojak, Stanislav and Egger, Werner},
	  title = {Microstructural study of He-implanted Fe-Cr alloys with the use of conventional lifetime technique and pulsed low energy positron beam},
	  journal = {Physica Status Solidi (C) Current Topics in Solid State Physics},
	  year = {2009},
	  volume = {6},
	  number = {11},
	  pages = {2339-2341},
	  note = {ICPA 15},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/pssc.200982117/abstract},
	  doi = {http://doi.org/10.1002/pssc.200982117}
	}
	
Helium implanted FeCr alloys studied by positron annihilation lifetime technique
V. Kršjak, W. Egger, M. Petriska and S. Sojak; Problems of Atomic Science and Technology 4 (1) (2009) 109-115.
Abstract: The influence of chromium on the radiation damage resistance of iron based alloys has been studied using conventional positron lifetime technique and a pulsed low energy positron beam. To simulate high neutron flux, the helium implantation has been used. Different levels of helium doses ( 6.24.10(17)-3.12.10(18) cm(-2)) corresponding to a local damage of up to 90 dpa were accumulated in a thin 1 nm) and small vacancy clusters together with the initial dislocations and small point defects.
BibTeX:
	@article{Krsjak2009a,
	  author = {Kršjak, Vladimir and Egger, Werner and Petriska, Martin and Sojak, Stanislav},
	  title = {Helium implanted FeCr alloys studied by positron annihilation lifetime technique},
	  journal = {Problems of Atomic Science and Technology},
	  year = {2009},
	  volume = {4},
	  number = {1},
	  pages = {109--115},
	  note = {IAEA Technical Meeting on Accelerator Simulation and Theoretical Medeling of Radiation Effect, Kharkov Inst Phys & Technol, Natl Res Ctr, Kharkov, UKRAINE, JUN 09-13, 2008},
	  url = {http://vant.kipt.kharkov.ua/ANNOTAZII_2009/annotazii_2009_4_109.html}
	}
	
Positron annihilation studies on the nature and thermal behaviour of irradiation induced defects in tungsten
P.E. Lhuillier, M.F. Barthe, P. Desgardin, W. Egger and P. Sperr; Physica Status Solidi (C) Current Topics in Solid State Physics 6 (11) (2009) 2329-2332.
Abstract: Positron Annihilation Lifetime Spectroscopy has been performed with a pulsed positron beam to investigate the nature and evolution of implantation-induced defects created in the track region (TR) of 800 keV (3)He ions at different fluences. At high fluence - 5x10(16) cm(-2) - lifetime decomposition exhibits a predominant (98%) positron lifetime of 200 ps which is attributed to irradiation induced monovacancy. The increasing average lifetime as a function of the post-implantation annealing temperature has allowed to identify vacancy clustering due to vacancy migration (that occurs from 473 K).
BibTeX:
	@article{Lhuillier2009,
	  author = {Lhuillier, P. E. and Barthe, M. F. and Desgardin, P. and Egger, W. and Sperr, P.},
	  title = {Positron annihilation studies on the nature and thermal behaviour of irradiation induced defects in tungsten},
	  journal = {Physica Status Solidi (C) Current Topics in Solid State Physics},
	  year = {2009},
	  volume = {6},
	  number = {11},
	  pages = {2329-2332},
	  note = {ICPA 15},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/pssc.200982114/abstract},
	  doi = {http://doi.org/10.1002/pssc.200982114}
	}
	
Direct evidence by positron annihilation spectroscopy of defect distributions deeper than Rp in Ar+ implanted silica glass
P. Mazzoldi, G. Mattei, L. Ravelli, W. Egger, S. Mariazzi and R.S. Brusa; Journal of Physics D: Applied Physics 42 (11) (2009) 115418.
Abstract: Positron annihilation spectroscopy was used to depth profile the modification of intrinsic structural nanovoids in silica glass implanted with Ar+ ions at different fluences and implantation energies. Beyond an expected defect distribution below the ion projected range R-p, a second defect distribution extending more than two times deeper than R-p was revealed. This second defective layer was found to be related to recoiled oxygen atoms whose diffusion is probably increased by the stress gradient induced by the compaction of the first layer.
BibTeX:
	@article{Mazzoldi2009,
	  author = {Mazzoldi, P. and Mattei, G. and Ravelli, L. and Egger, W. and Mariazzi, S. and Brusa, R. S.},
	  title = {Direct evidence by positron annihilation spectroscopy of defect distributions deeper than Rp in Ar+ implanted silica glass},
	  journal = {Journal of Physics D: Applied Physics},
	  year = {2009},
	  volume = {42},
	  number = {11},
	  pages = {115418},
	  url = {http://iopscience.iop.org/0022-3727/42/11/115418/},
	  doi = {http://doi.org/10.1088/0022-3727/42/11/115418}
	}
	
A Time of Flight-Energy spectrometer for stopping power measurements in Heavy Ion-ERD analysis at iThemba LABS
M. Msimanga, C. Comrie, C. Pineda-Vargas, S. Murray, R. Bark and G. Dollinger; Nuclear Instruments and Methods in Physics Research Section B 267 (16) (2009) 2671-2674.
Abstract: The quantitative analysis of thin layers using Heavy Ion-Elastic Recoil Detection (HI-ERD) can be reliably performed if the stopping powers of the probing ions and recoils in a given target matrix are known accurately. Unfortunately for many projectile/target combinations experimental data is limited and where available, deviations of up to 50% between experiment and theory have been reported. This presentation describes the assembly of a Time of Flight-Energy (ToF-E) detector system developed for HI-ERD analysis and adapted for stopping power measurements at iThemba LABS. First results from energy loss measurements of 0.1-0.5 MeV/nucleon 28Si and 84Kr ions in ZrO2 are presented and compared with predictions of the widely used SRIM2003 (Stopping Range of Ions in Matter).
BibTeX:
	@article{Msimanga2009,
	  author = {Msimanga, M. and Comrie, C.M. and Pineda-Vargas, C.A. and Murray, S. and Bark, R. and Dollinger, G.},
	  title = {A Time of Flight-Energy spectrometer for stopping power measurements in Heavy Ion-ERD analysis at iThemba LABS},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2009},
	  volume = {267},
	  number = {16},
	  pages = {2671-2674},
	  note = {cited By (since 1996)4},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X09006235},
	  doi = {http://doi.org/10.1016/j.nimb.2009.05.014}
	}
	
Hydrogen Analysis by Proton-Proton Scattering
P. Reichart and G. Dollinger; In: Y. Wang and M. Nastasi (Eds.), Handbook of Modern Ion Beam Materials Analysis (2nd Ed.) , Chapter 9 , p. 187-206 , Materials Research Society , 2009.
BibTeX:
	@incollection{Reichart2009,
	  author = {Reichart, P. and Dollinger, G.},
	  title = {Hydrogen Analysis by Proton-Proton Scattering},
	  booktitle = {Handbook of Modern Ion Beam Materials Analysis (2nd Ed.)},
	  publisher = {Materials Research Society},
	  year = {2009},
	  pages = {187--206},
	  edition = {2nd},
	  editor = {Y. Wang and M. Nastasi},
	  url = {http://www.mrs.org/ibh2}
	}
	
Proton–Proton Scattering Cross Sections
P. Reichart and G. Dollinger; In: Y. Wang and M. Nastasi (Eds.), Handbook of Modern Ion Beam Materials Analysis (2nd Ed.) Appendices , Chapter 14 , p. 229-254 , Materials Research Society , 2009.
BibTeX:
	@incollection{Reichart2009a,
	  author = {Reichart, P. and Dollinger, G.},
	  title = {Proton–Proton Scattering Cross Sections},
	  booktitle = {Handbook of Modern Ion Beam Materials Analysis (2nd Ed.) Appendices},
	  publisher = {Materials Research Society},
	  year = {2009},
	  pages = {229--254},
	  edition = {2nd},
	  editor = {Y. Wang and M. Nastasi},
	  url = {http://www.mrs.org/ibh2}
	}
	
No Evidence for a Different RBE between Pulsed and Continuous 20 MeV Protons
T.E. Schmid, G. Dollinger, A. Hauptner, V. Hable, C. Greubel, S. Auer, A.A. Friedl, M. Molls and B. Röper; Radiation Research 172 (5) (2009) 567-574.
Abstract: To obtain greater insight into the future potential of tumor radiotherapy using proton beams generated from high-intensity lasers, it is important to characterize the ionization quality of the new beams by measuring the relative biological effectiveness (RBE) under conditions where the full dose at one irradiation site will be deposited by a few proton pulses less than 1 ns in duration. HeLa cells attached to a Mylar foil were irradiated with 70 kV X rays to obtain a reference dose–response curve or with 3 Gy of 20 MeV protons at the Munich tandem accelerator (Garching), either using a continuous mode where a cell sample was irradiated within a 100-ms time span or using a pulsed mode where radiation was given in a single proton pulse of about 1 ns. After irradiation cytochalasin B was added; 24 h later cells were fixed and stained with acridine orange and micronuclei were counted. The X-ray dose–response curve for the production of micronuclei in HeLa cells followed a linear-quadratic model. The corresponding RBE values for 20 MeV protons in pulsed and continuous irradiation modes were 1.07 ± 0.08 and 1.06 ± 0.10 in the first proton experiment and 1.09 ± 0.08 and 1.05 ± 0.11 in the second, respectively. There was no evidence for a difference in the RBE for pulsed and continuous irradiation of HeLa cells with 20 MeV protons.
BibTeX:
	@article{Schmid2009,
	  author = {Schmid, T. E. and Dollinger, G. and Hauptner, A. and Hable, V. and Greubel, C. and Auer, S. and Friedl, A. A. and Molls, M. and Röper, B.},
	  title = {No Evidence for a Different RBE between Pulsed and Continuous 20 MeV Protons},
	  booktitle = {Radiation Research},
	  journal = {Radiation Research},
	  year = {2009},
	  volume = {172},
	  number = {5},
	  pages = {567--574},
	  note = {cited By (since 1996)18},
	  url = {http://www.bioone.org/doi/10.1667/RR1539.1},
	  doi = {http://doi.org/10.1667/RR1539.1}
	}
	
Advanced Fe-Cr alloys studied by pulsed low energy positron system before and after helium ions implantation
S. Sojak, V. Kršjak and W. Egger; American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP 5 (2009) 469-472.
Abstract: Positron annihilation spectroscopy (PAS) is a non-destructive technique which provides information about microstructural damage of structural materials. In this paper, the Pulsed Low Energy Positron System (PLEPS) at the research reactor FRM-II at TU Munich was used to study depth profiling of binary Fe-Cr alloys. Fe-Cr model alloys with different chromium content were investigated in the as-received state as well as after helium ion implantation (dose up to 6.24x1017 ions/cm-2). Measured results show changes in the size of defects after implantation and also in non-implanted specimens depending on the Cr content.
BibTeX:
	@article{Sojak2009,
	  author = {Sojak, S. and Kršjak, V. and Egger, W.},
	  title = {Advanced Fe-Cr alloys studied by pulsed low energy positron system before and after helium ions implantation},
	  journal = {American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP},
	  year = {2009},
	  volume = {5},
	  pages = {469--472},
	  url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1635396},
	  doi = {http://doi.org/10.1115/PVP2009-77537}
	}
	
IR calibrations for water determination in olivine, r-GeO2, and SiO2 polymorphs
S.-M. Thomas, M. Koch-Müller, P. Reichart, D. Rhede, R. Thomas, R. Wirth and S. Matsyuk; Physics and Chemistry of Minerals 36 (2009) 489-509.
Abstract: Mineral-specific IR absorption coefficients were calculated for natural and synthetic olivine, SiO2 polymorphs, and GeO2 with specific isolated OH point defects using quantitative data from independent techniques such as proton–proton scattering, confocal Raman spectroscopy, and secondary ion mass spectrometry. Moreover, we present a routine to detect OH traces in anisotropic minerals using Raman spectroscopy combined with the ‘‘Comparator Technique’’. In case of olivine and the SiO2 system, it turns out that the magnitude of e for one structure is independent of the type of OH point defect and therewith the peak position (quartz e = 89,000 ± 15,000 l mol^-1_H2O cm^-2), but it varies as a function of structure (coesite e = 214,000 ± 14,000 l mol-1 H2O cm-2; stishovite e = 485,000 ± 109,000 l mol-1 H2O cm-2). Evaluation of data from this study confirms that not using mineral-specific IR calibrations for the OH quantification in nominally anhydrous minerals leads to inaccurate estimations of OH concentrations, which constitute the basis for modeling the Earth’s deep water cycle.
BibTeX:
	@article{Thomas2009,
	  author = {Thomas, Sylvia-Monique and Koch-Müller, Monika and Reichart, Patrick and Rhede, Dieter and Thomas, Rainer and Wirth, Richard and Matsyuk, Stanislav},
	  title = {IR calibrations for water determination in olivine, r-GeO2, and SiO2 polymorphs},
	  journal = {Physics and Chemistry of Minerals},
	  year = {2009},
	  volume = {36},
	  pages = {489--509},
	  url = {http://link.springer.com/article/10.1007%2Fs00269-009-0295-1},
	  doi = {http://doi.org/10.1007/s00269-009-0295-1}
	}
	
Correlation of chemical composition and electrical properties of rf sputtered alumina films
M. Voigt, A. Bergmaier, G. Dollinger and M. Sokolowski; Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films 27 (2) (2009) 234-244.
Abstract: Alumina films were prepared by radio frequency magnetron sputtering from an aluminum oxide target on an indium tin oxide covered glass. The purpose of the study was to test the influence of the sputter parameters on the elemental composition, surface morphology, and electrical insulation properties (breakdown fields and leakage currents). Tested parameters were the sputter gas (Ar) pressure, the sputter rate, the sputter power, the sputter gas composition (Ar: O2), the conditioning of the target, the residual base pressure, and the substrate temperature. The surface morphology of the films was investigated by atomic force microscopy. Depth profiles of the elemental compositions were measured by elastic recoil detection using energetic heavy ions, and the insulation properties were investigated by current voltage measurements and impedance spectroscopy. The main finding is that the leakage currents increase by about five orders of magnitude, if the atomic ratio of O:Al increases from 1.35 to 2.0. In parallel the breakdown fields decrease by a factor of 100, and the character of the breakdowns changes from soft to hard. The highest breakdown fields (2.4 MVcm) and smallest leakage currents (6.5× 10-8 A cm2 at 2.0 MVcm) are obtained for slightly Al rich films with small atomic concentrations of H (
BibTeX:
	@article{Voigt2009,
	  author = {Voigt, M. and Bergmaier, A. and Dollinger, G. and Sokolowski, M.},
	  title = {Correlation of chemical composition and electrical properties of rf sputtered alumina films},
	  journal = {Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films},
	  year = {2009},
	  volume = {27},
	  number = {2},
	  pages = {234--244},
	  note = {cited By (since 1996)8},
	  url = {http://avs.scitation.org/doi/10.1116/1.3065978},
	  doi = {http://doi.org/10.1116/1.3065978}
	}
	
Differences in gamma-H2AX foci formation after irradiation with continuous and pulsed proton beams
O. Zlobinskaya, T. Schmid, G. Dollinger, V. Hable, C. Greubel, D. Michalski, J. Wilkens, G. Du, M. Molls and B. Röper; In: , O. Dössel and W.C. Schlegel (Eds.), IFMBE Proceedings 25 (2009) 142-145 , Springer International Publishing AG.
Abstract: Introduction: Classical particle accelerators offer proton pulses of some milliseconds duration. In contrast, the new technology of the high-intensity laser acceleration will produce ultimately shorter particle packages (up to one nanosecond) with substantially lower pulse frequency and higher pulse-dose achievement. Very little is known about the relative biological effectiveness (RBE) of this new beam quality, which could be a possible future application in radiation oncology. In our present study we investigate possible differences based on quantitative analysis of γ-H2AX fluorescence - a known marker of DNA double strand breaks (DSBs). Methods: HeLa cells were irradiated with 1 Gy of 20 MeV protons at the Munich tandem accelerator, either at continuous mode (100 ms), or at pulsed mode with a single pulse of 1 ns duration. A dose-effect-curve based on five doses of 75 kV x-rays served for reference. The total number of γ-H2AX foci per cell was determined using a self-developed macro (ImageJ, NIH, USA). Results: Quantitative analysis of γ-H2AX fluorescence revealed no significant difference (p=0.16) in yield of foci formation after irradiation with pulsed or continuous proton beams. γ-H2AX data for cell samples exposed to 1 Gy of 20 MeV protons at pulsed or continuous irradiation modes were 23.29 ± 2.04 and 26.54 ± 2.54 foci per cell, respectively. The corresponding RBE values for 20 MeV protons were 0.96 ± 0.18 and 1.13 ± 0.21 (p=0.21) for pulsed and continuous irradiation modes. However, the percentage of foci smaller than 5-10 pixels was slightly decreased and foci tended to cluster after irradiation with pulsed protons. Conclusions: Based on γ-H2AX foci formation no significant difference in the RBE between pulsed and continuous proton irradiation beams in HeLa cells has been detected so far. These results are well in line with our data on micronucleus induction in HeLa cells.
BibTeX:
	@inproceedings{Zlobinskaya2009,
	  author = {Zlobinskaya, O. and Schmid, T.E. and Dollinger, G. and Hable, V. and Greubel, C. and Michalski, D. and Wilkens, J. and Du, G. and Molls, M. and Röper, B.},
	  title = {Differences in gamma-H2AX foci formation after irradiation with continuous and pulsed proton beams},
	  booktitle = {IFMBE Proceedings},
	  publisher = {Springer International Publishing AG},
	  year = {2009},
	  volume = {25},
	  number = {3},
	  pages = {142--145},
	  editor = {Olaf Dössel and Wolfgang C. Schlegel},
	  note = {World Congress on Medical Physics and Biomedical Engineering: Radiation Protection and Dosimetry, Biological Effects of Radiation; Munich; Germany; 7 September 2009 through 12 September 2009;},
	  url = {http://link.springer.com/book/10.1007/978-3-642-03902-7},
	  doi = {http://doi.org/10.1007/978-3-642-03902-7}
	}
	

2008

Surface characterization of diamond-like carbon for ultracold neutron storage
F. Atchison, A. Bergmaier, M. Daum, M. Döbeli, G. Dollinger, P. Fierlinger, A. Foelske, R. Henneck, S. Heule, M. Kasprzak, K. Kirch, A. Knecht, M. Kuźniak, A. Pichlmaier, R. Schelldorfer and G. Zsigmond; Nuclear Instruments and Methods in Physics Research Section A 587 (1) (2008) 82-88.
Abstract: We report the characterization of diamond-like carbon (DLC) surfaces to be used for the storage of ultracold neutrons (UCN). The samples investigated were 100-300-nm-thick tetragonal amorphous carbon (ta-C) coatings produced by vacuum-arc technology on thin foils (0.1-0.2 mm aluminum, stainless steel, PET). The diamond sp3 fraction was determined by X-ray photoelectron spectroscopy (XPS) to be in the range 45-65%. Secondary-ion mass spectroscopy (SIMS) and elastic recoil detection analysis (ERDA) yielded consistent results for the hydrogen contribution (about 1×1016 cm-2 within the top 20 nm), strongly concentrated within a surface layer of 1 nm thickness. The boron contamination was found to be around 50 at. ppm. The fractional hole area of the coatings is on a level of about 1×10-4. Temperature cycling of mechanically pre-stressed samples between 77 and 380 K revealed no detrimental effect.
BibTeX:
	@article{Atchison2008,
	  author = {Atchison, F. and Bergmaier, A. and Daum, M. and Döbeli, M. and Dollinger, G. and Fierlinger, P. and Foelske, A. and Henneck, R. and Heule, S. and Kasprzak, M. and Kirch, K. and Knecht, A. and Kuźniak, M. and Pichlmaier, A. and Schelldorfer, R. and Zsigmond, G.},
	  title = {Surface characterization of diamond-like carbon for ultracold neutron storage},
	  journal = {Nuclear Instruments and Methods in Physics Research Section A},
	  year = {2008},
	  volume = {587},
	  number = {1},
	  pages = {82--88},
	  note = {cited By (since 1996)5},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168900207025004},
	  doi = {http://doi.org/10.1016/j.nima.2007.12.037}
	}
	
Quantitative Analyse von Proteinkinetiken nach Bestrahlung lebender Zellen mit energetischen Schwerionen am Rasterionenmikroskop SNAKE
Tino Brüning; Diplomarbeit, Universität der Bundeswehr München, 2008.
BibTeX:
	@mastersthesis{Bruening2008da,
	  author = {Brüning, Tino},
	  title = {Quantitative Analyse von Proteinkinetiken nach Bestrahlung lebender Zellen mit energetischen Schwerionen am Rasterionenmikroskop SNAKE},
	  school = {Universität der Bundeswehr München},
	  year = {2008}
	}
	
Realisierung einer Schnittstelle für die externe Steuerung der Software AxioVision 4.6.3 in Verbindung mit dem Rasterionenmikroskop SNAKE
Christian Burgdorf; Studienarbeit, Universität der Bundeswehr München, 2008.
BibTeX:
	@thesis{Burgdorf2008sa,
	  author = {Burgdorf, Christian},
	  title = {Realisierung einer Schnittstelle für die externe Steuerung der Software AxioVision 4.6.3 in Verbindung mit dem Rasterionenmikroskop SNAKE},
	  school = {Universität der Bundeswehr München},
	  year = {2008}
	}
	
Investigations of epoxy-based adhesives with PLEPS
W. Egger, P. Sperr, G. Kögel, M. Wetzel and H.-J. Gudladt; Applied Surface Science 255 (1) (2008) 209-212.
Abstract: Contamination-tolerant adhesives are of ever increasing importance in industrial applications. The possible failure mechanisms of adhesive bonds in these adhesives are however still poorly understood. Results of a series of investigations with our pulsed low energy positron beam system (PLEPS) in an epoxy-based contamination-tolerant adhesive are presented.
BibTeX:
	@article{Egger2008,
	  author = {Egger, W. and Sperr, P. and Kögel, G. and Wetzel, M. and Gudladt, H.-J.},
	  title = {Investigations of epoxy-based adhesives with PLEPS},
	  journal = {Applied Surface Science},
	  year = {2008},
	  volume = {255},
	  number = {1},
	  pages = {209--212},
	  note = {SLOPOS 11},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433208012257},
	  doi = {http://doi.org/10.1016/j.apsusc.2008.05.205}
	}
	
Characteristics of boron δ-doped diamond for electronic applications
H. El-Hajj, A. Denisenko, A. Bergmaier, G. Dollinger, M. Kubovic and E. Kohn; Diamond and Related Materials 17 (4-5) (2008) 409-414.
Abstract: Boron delta-doped profiles with peak concentrations above the full activation limit have been grown on (100)-oriented single crystal diamond substrates by microwave assisted CVD using a solid doping source technique. The growth process was optimized targeting electronic device applications. Up to now these profiles could only be analyzed by chemical/physical profiling and it had been difficult to relate these profiles to the electrical characteristics. For the first time, ERD (Electron Recoil Detection) profiles could be correlated with free carrier profiles extracted by electrochemical profiling based on electrochemical impedance analysis. The comparison shows, that it is possible to incorporate boron on acceptor site with high efficiency even for concentrations in the order of 1021 cm- 3 by the doping technique developed.
BibTeX:
	@article{El-Hajj2008,
	  author = {El-Hajj, H. and Denisenko, A. and Bergmaier, A. and Dollinger, G. and Kubovic, M. and Kohn, E.},
	  title = {Characteristics of boron δ-doped diamond for electronic applications},
	  journal = {Diamond and Related Materials},
	  year = {2008},
	  volume = {17},
	  number = {4-5},
	  pages = {409--414},
	  note = {cited By (since 1996)16},
	  url = {http://www.sciencedirect.com/science/article/pii/S092596350700502X},
	  doi = {http://doi.org/10.1016/j.diamond.2007.12.030}
	}
	
On the defect pattern evolution in sapphire irradiated by swift ions in a broad fluence range
P.M. Gordo, L. Liszkay, Z. Kajcsos, K. Havancsák, V.A. Skuratov, G. Kögel, P. Sperr, W. Egger, A.P. de Lima and M.F.F. Marques; Applied Surface Science 255 (1) (2008) 254-256.
Abstract: Sapphire samples, irradiated with swift Kr (245 MeV) ions at room temperature in a broad fluence range, were investigated using a continuous and a pulsed positron beam to study the defect structure created by the passage of the ions in depths of a few micrometers. At small doses, monovacancies were identified as dominant defects and positron trapping centres. These monovacancies are assumed to be highly concentrated inside a cylindrical volume around the ion path with an estimated radius of similar to 1.5 nm. For higher doses a second type of trapping centre emerges. This second class of structural imperfection was associated with the overlap of the individual ion tracks leading to the formation of larger vacancy clusters or voids.
BibTeX:
	@article{Gordo2008,
	  author = {Gordo, P. M. and Liszkay, L. and Kajcsos, Zs. and Havancsák, K. and Skuratov, V. A. and Kögel, G. and Sperr, P. and Egger, W. and de Lima, A. P. and Marques, M. F. Ferreira},
	  title = {On the defect pattern evolution in sapphire irradiated by swift ions in a broad fluence range},
	  journal = {Applied Surface Science},
	  year = {2008},
	  volume = {255},
	  number = {1},
	  pages = {254--256},
	  note = {SLOPOS 11},
	  url = {http://www.scientific.net/MSF.445-446.93},
	  doi = {http://doi.org/10.1016/j.apsusc.2008.05.185}
	}
	
Water in natural olivine—determined by proton-proton scattering analysis
J. Gose, P. Reichart, G. Dollinger and E. Schmädicke; American Mineralogist 93 (10) (2008) 1613-1619.
Abstract: Here we present water concentration data for olivine from different host rocks, measured with a nuclear technique using proton-proton scattering. This method, which is used here for the first time on olivine, is very powerful for determining trace amounts of water. The studied olivine specimens differ in their H2O contents, ranging from 4 to 51 wt ppm (=10–117 atom ppm H). The lowest concentrations are found in olivine from spinel peridotite xenoliths, the highest concentrations in olivine from alpine-type peridotite; the contents of an ophiolitic and a hydrothermal olivine are intermediate. Infrared spectroscopy was applied to ensure that the measured water contents stem solely from hydroxyl defects in the mineral structure. The infrared spectra differ from sample to sample. Five of six olivine specimens show absorption bands typical of hydroxyl groups associated with Ti defects. These olivines differ in their Ti contents by two orders of magnitude. However, a correlation of water and Ti content was not observed.
BibTeX:
	@article{Gose2008,
	  author = {Gose, Jürgen and Reichart, Patrick and Dollinger, Günther and Schmädicke, Esther},
	  title = {Water in natural olivine—determined by proton-proton scattering analysis},
	  journal = {American Mineralogist},
	  year = {2008},
	  volume = {93},
	  number = {10},
	  pages = {1613-1619},
	  url = {http://ammin.geoscienceworld.org/content/93/10/1613.abstract},
	  doi = {http://doi.org/10.2138/am.2008.2835}
	}
	
Quantitative analysis of DNA-damage response factors after sequential ion microirradiation
C. Greubel, V. Hable, G.A. Drexler, A. Hauptner, S. Dietzel, H. Strickfaden, I. Baur, R. Krücken, T. Cremer, A.A. Friedl and G. Dollinger; Radiation and Environmental Biophysics 47 (4) (2008) 415-422.
Abstract: Several proteins are known to form foci at DNA sites damaged by ionizing radiation. We study DNA damage response by immunofluorescence microscopy after microirradiation of cells with energetic ions. By using microirradiation, it is possible to irradiate different regions on a single dish at different time-points and to differentiate between cells irradiated earlier and later. This allows to directly compare immunofluorescence intensities in both subsets of cells with little systematic error because both subsets are cultivated and stained under identical conditions. In addition, by using irradiation patterns such as crossing lines, it is possible to irradiate individual cells twice and to differentiate between immunofluorescence signals resulting from the cellular response to the earlier and to the later irradiation event. Here, we describe the quantitative evaluation of immunofluorescence intensities after sequential irradiation.
BibTeX:
	@article{Greubel2008,
	  author = {Greubel, Christoph and Hable, Volker and Drexler, Guido A. and Hauptner, Andreas and Dietzel, Steffen and Strickfaden, Hilmar and Baur, Iris and Krücken, Reiner and Cremer, Thomas and Friedl, Anna A. and Dollinger, Günther},
	  title = {Quantitative analysis of DNA-damage response factors after sequential ion microirradiation},
	  journal = {Radiation and Environmental Biophysics},
	  year = {2008},
	  volume = {47},
	  number = {4},
	  pages = {415--422},
	  url = {http://link.springer.com/article/10.1007%2Fs00411-008-0181-0},
	  doi = {http://doi.org/10.1007/s00411-008-0181-0}
	}
	
Competition effect in DNA damage response
C. Greubel, V. Hable, G. Drexler, A. Hauptner, S. Dietzel, H. Strickfaden, I. Baur, R. Krücken, T. Cremer, G. Dollinger and A. Friedl; Radiation and Environmental Biophysics 47 (4) (2008) 423-429.
Abstract: We have built an ion-microbeam for studies of the nuclear topography and kinetics of double-strand break repair at the single cell level. Here, we show that a first and a second, delayed single ion exposure at different nuclear sites led to comparable accumulations of phospho-ATM, γ-H2AX and Mdc1 at both earlier (e) and later (l) microirradiated sites. In contrast, accumulations of 53BP1 and the recombination protein Rad51 were strongly reduced at l-sites. This apparent competition effect is accompanied by a reduced amount of 53BP1 in undamaged areas of the irradiated nuclei. We suggest that a critically limited pool size combined with strong binding at irradiated sites leads to the exhaustion of unbound factors freely roaming the nuclear space. The undersupply of these factors at l-sites requires in addition a long-lasting binding at e-sites or a weaker binding at l-sites. The observed effects suggest that DNA damage response at individual nuclear sites depends on the time course of damage load. This may have implications for therapeutic radiation treatments.
BibTeX:
	@article{Greubel2008a,
	  author = {Greubel, C. and Hable, V. and Drexler, G.A. and Hauptner, A. and Dietzel, S. and Strickfaden, H. and Baur, I. and Krücken, R. and Cremer, T. and Dollinger, G. and Friedl, A.A.},
	  title = {Competition effect in DNA damage response},
	  journal = {Radiation and Environmental Biophysics},
	  year = {2008},
	  volume = {47},
	  number = {4},
	  pages = {423--429},
	  url = {http://link.springer.com/article/10.1007%2Fs00411-008-0182-z},
	  doi = {http://doi.org/10.1007/s00411-008-0182-z}
	}
	
Surface and bulk investigations at the high intensity positron beam facility NEPOMUC
C. Hugenschmidt, G. Dollinger, W. Egger, G. Kögel, B. Löwe, J. Mayer, P. Pikart, C. Piochacz, R. Repper, K. Schreckenbach, P. Sperr and M. Stadlbauer; Applied Surface Science 255 (1) (2008) 29-32.
Abstract: The NEutron-induced POsitron source MUniCh (NEPOMUC) at the research reactor FRM II delivers a low-energy positron beam (E = 15-1000 eV) of high intensity in the range between 4 × 107 and 5 × 108 moderated positrons per second. At present four experimental facilities are in operation at NEPOMUC: a coincident Doppler-broadening spectrometer (CDBS) for defect spectroscopy and investigations of the chemical vicinity of defects, a positron annihilation-induced Auger-electron spectrometer (PAES) for surface studies and an apparatus for the production of the negatively charged positronium ion Ps-. Recently, the pulsed low-energy positron system (PLEPS) has been connected to the NEPOMUC beam line, and first positron lifetime spectra were recorded within short measurement times. A positron remoderation unit which is operated with a tungsten single crystal in back reflection geometry has been implemented in order to improve the beam brilliance. An overview of NEPOMUC's status, experimental results and recent developments at the running spectrometers are presented.
BibTeX:
	@article{Hugenschmidt2008,
	  author = {Hugenschmidt, C. and Dollinger, G. and Egger, W. and Kögel, G. and Löwe, B. and Mayer, J. and Pikart, P. and Piochacz, C. and Repper, R. and Schreckenbach, K. and Sperr, P. and Stadlbauer, M.},
	  title = {Surface and bulk investigations at the high intensity positron beam facility NEPOMUC},
	  journal = {Applied Surface Science},
	  year = {2008},
	  volume = {255},
	  number = {1},
	  pages = {29--32},
	  note = {SLOPOS 11},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433208012269},
	  doi = {http://doi.org/10.1016/j.apsusc.2008.05.304}
	}
	
A positron remoderator for the high intensity positron source NEPOMUC
C. Piochacz, G. Kögel, W. Egger, C. Hugenschmidt, J. Mayer, K. Schreckenbach, P. Sperr, M. Stadlbauer and G. Dollinger; Applied Surface Science 255 (1) (2008) 98-100.
Abstract: A remoderator for the high intensity positron source NEPOMUC was developed and installed at the beam facility. A beam of remoderated positrons could be produced with different energies and a diameter of less than 2 mm was obtained. The efficiency of the remoderation setup was determined to be 5%. Due to the brilliance of the remoderated beam, the measurements at the coincidence Doppler broadening spectrometer (CDBS) and at the positron annihilation induced Auger electron spectrometer (PAES) could be improved. The setup and functionality of the remoderation device is presented as well as the first measurements at the remoderator, CDBS and PAES.
BibTeX:
	@article{Piochacz2008,
	  author = {Piochacz, C. and Kögel, G. and Egger, W. and Hugenschmidt, C. and Mayer, J. and Schreckenbach, K. and Sperr, P. and Stadlbauer, M. and Dollinger, G.},
	  title = {A positron remoderator for the high intensity positron source NEPOMUC},
	  journal = {Applied Surface Science},
	  year = {2008},
	  volume = {255},
	  number = {1},
	  pages = {98--100},
	  note = {SLOPOS 11},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433208011975},
	  doi = {http://doi.org/10.1016/j.apsusc.2008.05.286}
	}
	
Relative biological effectiveness (RBE) of 20 MeV protons for induction of micronuclei in HeLa cells at continuous and pulsed irradiation modes
T.E. Schmid, G. Dollinger, A. Hauptner, V. Hable, C. Greubel, A.A. Friedl, M. Molls and B. Röper; In: , M. Baumann (Ed.), Proceedings des 17. Symposiums Experimentelle Strahlentherapie und Klinische Strahlenbiologie : Dresden, 28. Februar - 01. März 2008 17 (2008) 105-108 , Inst. für Biophysik u. Strahlenbiologie.
BibTeX:
	@inproceedings{Schmid2008,
	  author = {Schmid, T. E. and Dollinger, G. and Hauptner, A. and Hable, V. and Greubel, C. and Friedl, A. A. and Molls, M. and Röper, B.},
	  title = {Relative biological effectiveness (RBE) of 20 MeV protons for induction of micronuclei in HeLa cells at continuous and pulsed irradiation modes},
	  booktitle = {Proceedings des 17. Symposiums Experimentelle Strahlentherapie und Klinische Strahlenbiologie : Dresden, 28. Februar - 01. März 2008},
	  publisher = {Inst. für Biophysik u. Strahlenbiologie},
	  year = {2008},
	  volume = {17},
	  number = {17},
	  pages = {105--108},
	  editor = {Baumann, Michael}
	}
	
Status of the pulsed low energy positron beam system (PLEPS) at the Munich Research Reactor FRM-II
P. Sperr, W. Egger, G. Kögel, G. Dollinger, C. Hugenschmidt, R. Repper and C. Piochacz; Applied Surface Science 255 (1) (2008) 35-38.
Abstract: The Munich pulsed low energy positron beam system (PLEPS) is now installed at the high intensity positron source (NEPOMUC) at the Munich Research Reactor FRM-II. In order to enhance the performance of the system several improvements have been implemented: two additional collinear detector ports have been installed. Therefore in addition to the normal lifetime measurements it is now possible to simultaneously perform Doppler-broadening, coincident Doppler-broadening and age momentum correlation experiments. An additional chopper was included to periodically suppress pulses and therefore to extend the standard time window of 20 ns for precise measurements of longer lifetimes. First test-experiments have been performed in May and July 2007. With all pulsing components in operation we achieved a count-rate of 1.4 × 104 counts per second. The total time resolution (pulsing and detector) was about 240 ps (FWHM) with a peak to background ratio up to 6 × 103:1.
BibTeX:
	@article{Sperr2008,
	  author = {Sperr, P. and Egger, W. and Kögel, G. and Dollinger, G. and Hugenschmidt, C. and Repper, R. and Piochacz, C.},
	  title = {Status of the pulsed low energy positron beam system (PLEPS) at the Munich Research Reactor FRM-II},
	  journal = {Applied Surface Science},
	  year = {2008},
	  volume = {255},
	  number = {1},
	  pages = {35--38},
	  note = {SLOPOS 11},
	  url = {http://www.sciencedirect.com/science/article/pii/S016943320801218X},
	  doi = {http://doi.org/10.1016/j.apsusc.2008.05.307}
	}
	
Application of Raman spectroscopy to quantify trace water concentrations in glasses and garnets
S.-M. Thomas, R. Thomas, P. Davidson, P. Reichart, M. Koch-Müller and G. Dollinger; American Mineralogist 93 (10) (2008) 1550-1557.
Abstract: We present a new technique for the quantification of water in glasses down to the parts per million level, using confocal microRaman spectroscopy with the recently developed “Comparator Technique.” To test this method, we used a suite of glasses and gemstone-quality garnets with varying chemical compositions. Water contents were independently determined with proton-proton (pp) scattering and infrared (IR) spectroscopy. Moreover, water concentrations obtained for the garnets were compared to data from a study by Maldener et al. (2003) using nuclear reaction analysis (NRA). For each sample, we recorded Raman spectra in the frequency range from 3100 to 3750 cm−1 and standardized them using an independently well-characterized glass. In this paper, we demonstrate the usefulness of this technique for quantifying water concentrations in natural and synthetic glass samples and garnets, and verify its adaptability for concentrations from 40 wt ppm up to 40 wt% H2O. However, in the case of absorbing material (e.g., Fe-bearing samples), the suggested method needs to be modified to overcome problems due to heating and melting of those phases. Furthermore, we propose an integrated molar absorption coefficient for water in quartz glass, εitot = 72 000 ± 12 000 Lmol−1H2Ocm−2, for quantitative IR spectroscopy that is higher than a previously reported value of Paterson (1982) or that predicted by the general calibration trend determined by Libowitzky and Rossman (1997).
BibTeX:
	@article{Thomas2008,
	  author = {Thomas, Sylvia-Monique and Thomas, Rainer and Davidson, Paul and Reichart, Patrick and Koch-Müller, Monika and Dollinger, Günther},
	  title = {Application of Raman spectroscopy to quantify trace water concentrations in glasses and garnets},
	  journal = {American Mineralogist},
	  year = {2008},
	  volume = {93},
	  number = {10},
	  pages = {1550-1557},
	  url = {http://ammin.geoscienceworld.org/content/93/10/1550.abstract},
	  doi = {http://doi.org/10.2138/am.2008.2834}
	}
	

2007

Doping density depth profiling analysis with high resolution elastic recoil detection
A. Bergmaier and G. Dollinger; ECS Transactions 11 (3) (2007) 243-255.
Abstract: The quantitative analysis of light elements in ultra thin films thinner than 10 nm is still a nontrivial task. This paper summarizes the prospects of high-resolution Elastic Recoil Detection (ERD) using a Q3D magnetic spectrograph. It is shown that sub-nanometer resolution can be achieved in ultra thin films and even monolayer resolution is possible close to the surface. ERD has the best quantification possibilities compared to any other method. Sensitivity is sufficient to analyze main elements and impurities as e,g, necessary for the characterization of microelectronic materials, In addition, high-resolution channeling ERD can be performed in order to obtain information on lattice location of light elements in crystalline ultra thin layers. The potential of high-resolution ERD is demonstrated by several applications where it is the most valuable tool for elemental profiling.
BibTeX:
	@article{Bergmaier2007,
	  author = {Bergmaier, A. and Dollinger, G.},
	  title = {Doping density depth profiling analysis with high resolution elastic recoil detection},
	  booktitle = {212th ECS Meeting},
	  journal = {ECS Transactions},
	  year = {2007},
	  volume = {11},
	  number = {3},
	  pages = {243--255},
	  url = {http://ecst.ecsdl.org/content/11/3/243},
	  doi = {http://doi.org/10.1149/1.2778668}
	}
	
Entwicklung von Auswertemethoden zur Bestimmung von Proteinkinetiken nach Zellbestrahlungen am Rasterionenmikroskop SNAKE
Tino Brüning; Studienarbeit, Universität der Bundeswehr München, 2007.
BibTeX:
	@thesis{Bruening2007sa,
	  author = {Brüning, Tino},
	  title = {Entwicklung von Auswertemethoden zur Bestimmung von Proteinkinetiken nach Zellbestrahlungen am Rasterionenmikroskop SNAKE},
	  school = {Universität der Bundeswehr München},
	  year = {2007}
	}
	
Pulsed low energy positron system (PLEPS) at the Munich research reactor FRMII
W. Egger, P. Sperr, G. Kögel and G. Dollinger; Physica Status Solidi (C) Current Topics in Solid State Physics 4 (10) (2007) 3969-3972.
Abstract: Currently, the Munich pulsed low energy positron beam-system (PLEPS) is transferred to the high-intensity positron source (NEPOMUC) at the Munich research Reactor FRM II. We expect count-rates up to 106 cps. Several improvements to enhance the performance of the system have been implemented. Until now, PLEPS was employed exclusively for lifetime measurements. To enable also Doppler-broadening, coincident Doppler-broadening and AMOC experiments, two additional detector ports have been installed. An additional chopper allows to suppress pulses and, therefore, to extend the standard time window of 20 ns for precise measurements of longer lifetimes. The high event-rate supports the use of smaller scintillators. Consequently an improvement in time resolution is expected. Also envisaged is the use of new detector materials. Various measures to further reduce background from back-scattered positrons and a reduction of the beam diameter down to 1 mm will improve the overall performance of the system.
BibTeX:
	@article{Egger2007,
	  author = {Egger, W. and Sperr, P. and Kögel, G. and Dollinger, G.},
	  title = {Pulsed low energy positron system (PLEPS) at the Munich research reactor FRMII},
	  journal = {Physica Status Solidi (C) Current Topics in Solid State Physics},
	  year = {2007},
	  volume = {4},
	  number = {10},
	  pages = {3969--3972},
	  note = {ICPA 14},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/pssc.200675812/abstract},
	  doi = {http://doi.org/10.1002/pssc.200675812}
	}
	
Near surface stress determination in Kr-implanted polycrystalline titanium by the X-ray sin2Ψ-method
M. Härting, S. Nsengiyumva, A. Raji, G. Dollinger, P. Sperr, S. Naidoo, T. Derry, C. Comrie and D. Britton; Surface and Coatings Technology 201 (19-20 SPEC. ISS.) (2007) 8237-8241.
Abstract: Ion implantation has been performed on polycrystalline titanium samples with 180 keV Kr+ ions at various doses from 1 × 1015 to 5 × 1016 ions cm- 2 at room temperature. The samples where characterised by Rutherford backscattering spectrometry, positron annihilation lifetime spectroscopy and X-ray diffraction. By means of the sin2Ψ technique the near surface stress has been determined for both unimplanted and implanted samples. The initial stress state has been shown to be strongly tensile in the first 75 nm below the surface, and weakly compressive deeper inside. The main effect of the implantation process was to relax the pre-existing tensile stress in the track region. An additional compressive stress was introduced deeper in the sample and could be attributed to the presence of larger defect clusters.
BibTeX:
	@article{Haerting2007,
	  author = {Härting, M. and Nsengiyumva, S. and Raji, A.T. and Dollinger, G. and Sperr, P. and Naidoo, S.R. and Derry, T.E. and Comrie, C.M. and Britton, D.T.},
	  title = {Near surface stress determination in Kr-implanted polycrystalline titanium by the X-ray sin2Ψ-method},
	  journal = {Surface and Coatings Technology},
	  year = {2007},
	  volume = {201},
	  number = {19-20 SPEC. ISS.},
	  pages = {8237--8241},
	  note = {14th International Conference on Surface Modification by Ion Beams (SMMIB 05), Kusadasi, TURKEY, SEP 04-09, 2005},
	  url = {http://www.sciencedirect.com/science/article/pii/S0257897207002587},
	  doi = {http://doi.org/10.1016/j.surfcoat.2006.02.072}
	}
	
Implementation of the Munich scanning positron microscope at the positron source NEPOMUC
C. Piochacz, W. Egger, C. Hugenschmidt, G. Kögel, K. Schreckenbach, P. Sperr and G. Dollinger; Physica Status Solidi (C) Current Topics in Solid State Physics 4 (10) (2007) 4028-4031.
Abstract: The Munich scanning positron microscope (SPM) permits positron lifetime measurements with a lateral resolution down to 2 um within an energy range of 1-20 keV. One practical limitation of the SPM is set by the long measurement times of several days per a 2D-scan due to the low intensity positron beam produced by standard 22Na sources. This disadvantage will be overcome by installing the SPM at the high intense positron beam facility NEPOMUC at the research reactor FRM II in Garching. Thus the time for one measurement will be shortened by a factor of 60. In addition it is expected to reduce the lateral resolution to about 100 nm. Due to the beam characteristics of the NEPOMUC facility an interface is needed, which enhances the phase space density of the beam. The requirements, which have to be fulfilled by the interface, will be described and an overview of the different components such as bunching units, remoderation stages and rf-elevator will be given.
BibTeX:
	@article{Piochacz2007,
	  author = {Piochacz, C. and Egger, W. and Hugenschmidt, C. and Kögel, G. and Schreckenbach, K. and Sperr, P. and Dollinger, G.},
	  title = {Implementation of the Munich scanning positron microscope at the positron source NEPOMUC},
	  journal = {Physica Status Solidi (C) Current Topics in Solid State Physics},
	  year = {2007},
	  volume = {4},
	  number = {10},
	  pages = {4028--4031},
	  note = {ICPA 14},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/pssc.200675824/abstract},
	  doi = {http://doi.org/10.1002/pssc.200675824}
	}
	

2006

Ferromagnetic Ge(Mn) nanostructures
S. Ahlers, D. Bougeard, H. Riedl, G. Abstreiter, A. Trampert, W. Kipferl, M. Sperl, A. Bergmaier and G. Dollinger; Physica E: Low-Dimensional Systems and Nanostructures 32 (1-2 SPEC. ISS.) (2006) 422-425.
Abstract: We present structural, magnetic and transport properties of Mn-doped Ge layers grown by molecular beam epitaxy (MBE) at low substrate temperatures TS. Atomic force microscopy (AFM), reflection high energy electron diffraction (RHEED) and transmission electron microscopy (TEM) analysis of structures grown at TS = 70 ring operator C and 120 ring operator C reveal defect-free epitaxy of Ge(Mn) on Ge(0 0 1) substrates. Despite the low TS we observe the formation of round shaped clusters with a diameter of 15-20 nm which are incoherent with the Ge matrix in TEM analysis for a Mn concentration x of 3.4%. SQUID measurements reveal ferromagnetism and a TC of around 300 ring operator C for the layers, reminiscent of the intermetallic compound Mn5 Ge3. Transport measurements, however, indicate that Mn is incorporated into the Ge matrix between the Mn5 Ge3 clusters as well.
BibTeX:
	@article{Ahlers2006,
	  author = {Ahlers, S. and Bougeard, D. and Riedl, H. and Abstreiter, G. and Trampert, A. and Kipferl, W. and Sperl, M. and Bergmaier, A. and Dollinger, G.},
	  title = {Ferromagnetic Ge(Mn) nanostructures},
	  journal = {Physica E: Low-Dimensional Systems and Nanostructures},
	  year = {2006},
	  volume = {32},
	  number = {1-2 SPEC. ISS.},
	  pages = {422--425},
	  note = {cited By (since 1996)9},
	  url = {http://www.sciencedirect.com/science/article/pii/S1386947705005540},
	  doi = {http://doi.org/10.1016/j.physe.2005.12.129}
	}
	
The analysis of a thin SiO2/Si3N4/SiO2 stack: A comparative study of low-energy heavy ion elastic recoil detection, high-resolution Rutherford backscattering and secondary ion mass spectrometry
B. Brijs, T. Sajavaara, S. Giangrandi, T. Janssens, T. Conard, K. Arstila, K. Nakajima, K. Kimura, A. Bergmaier, G. Dollinger, A. Vantomme and W. Vandervorst; Nuclear Instruments and Methods in Physics Research Section B 249 (1-2 SPEC. ISS.) (2006) 847-850.
Abstract: The analysis of thin films in the range of 10 nm and less has become very important in microelectronics. The goal of this article is an evaluation of low-energy TOF-ERDA (time-of-flight elastic recoil detection analysis) in comparison with low-energy SIMS (secondary ion mass spectrometry) and HRBS (high-resolution Rutherford backscattering spectrometry), using a thin SiO2/Si3N4/SiO2 stack as a test vehicle. Comparisons are made on the depth resolution, its loss as a function of depth and the quantification accuracy.
BibTeX:
	@article{Brijs2006,
	  author = {Brijs, B. and Sajavaara, T. and Giangrandi, S. and Janssens, T. and Conard, T. and Arstila, K. and Nakajima, K. and Kimura, K. and Bergmaier, A. and Dollinger, G. and Vantomme, A. and Vandervorst, W.},
	  title = {The analysis of a thin SiO2/Si3N4/SiO2 stack: A comparative study of low-energy heavy ion elastic recoil detection, high-resolution Rutherford backscattering and secondary ion mass spectrometry},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2006},
	  volume = {249},
	  number = {1-2 SPEC. ISS.},
	  pages = {847--850},
	  note = {cited By (since 1996)3},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X06004204},
	  doi = {http://doi.org/10.1016/j.nimb.2006.03.191}
	}
	
Microstructural defect characterisation of a-Si:H deposited by low temperature HW-CVD on paper substrates
D.T. Britton, M. Härting, D. Knoesen, Z. Sigcau, F.P. Nemalili, T.P. Ntsoane, P. Sperr, W. Egger and M. Nippus; Thin Solid Films 501 (1-2) (2006) 79-83.
Abstract: Hydrogenated amorphous silicon has been deposited on 80 g m(-2) wood-free paper, with and without an intermediate metallic interlayer, using low temperature hot wire chemical vapor deposition (HW-CVD). Electrical measurements show these layers to be of good quality. In this paper we cornpare the differences in microstructural properties of the two types of layer, concentrating on the influence of the substrates, including their effect on the deposition rate of the material and substrate temperature. During the deposition process, the metallized substrates reach a higher temperature than plain paper. Both X-diffiraction and positron annihilation lifetime studies indicate that the growth rate on the uncoated substrate is slightly higher than with prior metallization. There is no evidence of a crystalline phase or voids in the a-Si:H layers, and the internal defect structure is similar, with a dominant dangling-bond complex of similar size.
BibTeX:
	@article{Britton2006,
	  author = {Britton, D. T. and Härting, M. and Knoesen, D. and Sigcau, Z. and Nemalili, F. P. and Ntsoane, T. P. and Sperr, P. and Egger, W. and Nippus, M.},
	  title = {Microstructural defect characterisation of a-Si:H deposited by low temperature HW-CVD on paper substrates},
	  journal = {Thin Solid Films},
	  year = {2006},
	  volume = {501},
	  number = {1-2},
	  pages = {79--83},
	  note = {3rd International Conference on Hot-Wire CVD Process, Utrecht Univ, Utrecht, NETHERLANDS, AUG 23-27, 2004},
	  url = {http://www.sciencedirect.com/science/article/pii/S0040609005009764},
	  doi = {http://doi.org/10.1016/j.tsf.2005.07.111}
	}
	
Decoration of buried surfaces in Si detected by positron annihilation spectroscopy
R. Brusa, C. Macchi, S. Mariazzi, G. Karwasz, W. Egger, P. Sperr and G. Kögel; Applied Physics Letters 88 (1) (2006) 011920.
Abstract: The terminations of buried surfaces of two different cavity types (nano- and microcavities) produced in the same He+-H+ co-implanted p-type Si (100) sample annealed at 900 degrees C, are studied and characterized by positron annihilation spectroscopy. The characterization was carried out by means of three complementary positron techniques: Doppler broadening and coincidence-Doppler broadening spectroscopy with a continuous slow positron beam, and lifetime spectroscopy with a pulsed slow positron beam. It was found that the nanocavities have a pristine surface of Si, while the surfaces of the microcavities, formed below protruding blisters, are oxygen decorated. This case study opens the interesting use of the positron spectroscopy tool in the topical subject of empty space for microelectronics applications.
BibTeX:
	@article{Brusa2006,
	  author = {Brusa, R.S. and Macchi, C. and Mariazzi, S. and Karwasz, G.P. and Egger, W. and Sperr, P. and Kögel, G.},
	  title = {Decoration of buried surfaces in Si detected by positron annihilation spectroscopy},
	  journal = {Applied Physics Letters},
	  year = {2006},
	  volume = {88},
	  number = {1},
	  pages = {011920},
	  url = {http://scitation.aip.org/content/aip/journal/apl/88/1/10.1063/1.2162691},
	  doi = {http://doi.org/10.1063/1.2162691}
	}
	
Hydrogen microscopy and analysis of DNA repair using focused high energy ion beams
G. Dollinger, A. Bergmaier, A. Hauptner, S. Dietzel, G. Drexler, C. Greubel, V. Hable, P. Reichart, R. Krücken, T. Cremer and A. Friedl; Nuclear Instruments and Methods in Physics Research Section B 249 (1-2) (2006) 270-277.
Abstract: The ion microprobe SNAKE (Supraleitendes Nanoskop für Angewandte Kernphysikalische Experimente) at the Munich 14 MV tandem accelerator achieves beam focussing by a superconducting quadrupole doublet and can make use of a broad range of ions and ion energies, i.e. 4-28 MeV protons or up to 250 MeV gold ions. Due to these ion beams, SNAKE is particularly attractive for ion beam analyses in various fields. Here we describe two main applications of SNAKE. One is the unique possibility to perform three-dimensional hydrogen microscopy by elastic proton-proton scattering utilizing high energy proton beams. The high proton energies allow the analysis of samples with a thickness in the 100 μm range with micrometer resolution and a sensitivity better than 1 ppm. In a second application, SNAKE is used to analyse protein dynamics in cells by irradiating live cells with single focussed ions. Fluorescence from immunostained protein 53BP1 is used as biological track detector after irradiation of HeLa cells. It is used to examine the irradiated region in comparison with the targeted region. Observed patterns of fluorescence foci agree reasonably well with irradiation patterns, indicating an overall targeting accuracy of about 2 μm while the beam spot size is less than 0.5 μm in diameter. This performance shows successful adaptation of SNAKE for biological experiments where cells are targeted on a sub-cellular level by energetic ions.
BibTeX:
	@article{Dollinger2006,
	  author = {Dollinger, G. and Bergmaier, A. and Hauptner, A. and Dietzel, S. and Drexler, G.A. and Greubel, C. and Hable, V. and Reichart, P. and Krücken, R. and Cremer, T. and Friedl, A.A.},
	  title = {Hydrogen microscopy and analysis of DNA repair using focused high energy ion beams},
	  booktitle = {Proceedings of the Seventeenth International Conference on Ion Beam Analysis},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2006},
	  volume = {249},
	  number = {1-2},
	  pages = {270--277},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X06004587},
	  doi = {http://doi.org/10.1016/j.nimb.2006.04.012}
	}
	
Analysis of defect configurations with positron lifetime measurements by pulsed low energy beams
W. Egger, G. Kögel, P. Sperr and H.-J. Gudladt; International Journal of Materials Research 97 (12) (2006) 1633-1641.
Abstract: To understand the damage behavior of mechanically deformed metallic materials in more detail, the kind of defect and its concentration have to be known. In addition, the kinetics of decomposition and of precipitation hardening are influenced by the presence of defects and the corresponding concentration. Consequently, an analysis of dominating defects would be helpful. Compared with well known techniques, positron annihilation spectroscopy offers the opportunity for lifetime measurements that are characteristic for special kinds of defects, e. g. dislocations, small vacancy clusters and micro-voids. To detect the spatial distribution and to determine the concentration of defects, the low energy pulsed positron beam technique can be used. This technique, in combination with the scanning positron microscope, opens a broad field of applications for defect analysis in metallic and ceramic materials.
BibTeX:
	@article{Egger2006,
	  author = {Egger, W. and Kögel, G. and Sperr, P. and Gudladt, H.-J.},
	  title = {Analysis of defect configurations with positron lifetime measurements by pulsed low energy beams},
	  journal = {International Journal of Materials Research},
	  year = {2006},
	  volume = {97},
	  number = {12},
	  pages = {1633-1641},
	  url = {http://www.hanser-elibrary.com/doi/abs/10.3139/146.101394},
	  doi = {http://doi.org/10.3139/146.101394}
	}
	
Radiobiological Experiments at the Munich Microprobe SNAKE
A.A. Friedl, G.A. Drexler, M. Deutsch, H. Strickfaden, S. Dietzel, T. Cremer, A. Hauptner, R. Krücken, C. Greubel, V. Hable and G. Dollinger; In: Proceedings of the 7th International Workshop: Microbeam Probes of Cellular Radiation Response , Radiation Research 166 (2006) 668 , Radiation Research Society.
BibTeX:
	@inproceedings{Friedl2006,
	  author = {Friedl, A. A. and Drexler, G. A. and Deutsch, M. and Strickfaden, H. and Dietzel, S. and Cremer, T. and Hauptner, A. and Krücken, R. and Greubel, C. and Hable, V. and Dollinger, G.},
	  title = {Radiobiological Experiments at the Munich Microprobe SNAKE},
	  booktitle = {Proceedings of the 7th International Workshop: Microbeam Probes of Cellular Radiation Response},
	  journal = {Radiation Research},
	  publisher = {Radiation Research Society},
	  year = {2006},
	  volume = {166},
	  number = {4},
	  pages = {668},
	  url = {http://www.bioone.org/doi/abs/10.1667/RR0683.1},
	  doi = {http://doi.org/10.1667/RR0683.1}
	}
	
The Munich Microprobe SNAKE, a Single-Ion Cell Irradiation Facility
C. Greubel, V. Hable, G. Dollinger, A. Hauptner, R. Krücken, H. Strickfaden, S. Dietzel, T. Cremer, G.A. Drexler, M. Deutsch and A.A. Friedl; In: Proceedings of the 7th International Workshop: Microbeam Probes of Cellular Radiation Response , Radiation Research 166 (2006) 654 , Radiation Research Society.
BibTeX:
	@inproceedings{Greubel2006,
	  author = {Greubel, C. and Hable, V. and Dollinger, G. and Hauptner, A. and Krücken, R. and Strickfaden, H. and Dietzel, S. and Cremer, T. and Drexler, G. A. and Deutsch, M. and Friedl, A. A.},
	  title = {The Munich Microprobe SNAKE, a Single-Ion Cell Irradiation Facility},
	  booktitle = {Proceedings of the 7th International Workshop: Microbeam Probes of Cellular Radiation Response},
	  journal = {Radiation Research},
	  publisher = {Radiation Research Society},
	  year = {2006},
	  volume = {166},
	  number = {4},
	  pages = {654},
	  url = {http://www.bioone.org/doi/abs/10.1667/RR0683.1},
	  doi = {http://doi.org/10.1667/RR0683.1}
	}
	
Dynamics of DNA Repair Proteins after Directed Heavy-Ion Cell Irradiation.
V. Hable, G. Dollinger, C. Greubel, A. Hauptner, R. Krücken, S. Dietzel, T. Cremer, G.A. Drexler and A.A. Fried; In: Proceedings of the 7th International Workshop: Microbeam Probes of Cellular Radiation Response , Radiation Research 166 (2006) 676 , Radiation Research Society.
BibTeX:
	@inproceedings{Hable2006,
	  author = {Hable, V. and Dollinger, G. and Greubel, C. and Hauptner, A. and Krücken, R. and Dietzel, S. and Cremer, T. and Drexler, G. A. and Fried, A. A.},
	  title = {Dynamics of DNA Repair Proteins after Directed Heavy-Ion Cell Irradiation.},
	  booktitle = {Proceedings of the 7th International Workshop: Microbeam Probes of Cellular Radiation Response},
	  journal = {Radiation Research},
	  publisher = {Radiation Research Society},
	  year = {2006},
	  volume = {166},
	  number = {4},
	  pages = {676},
	  url = {http://www.bioone.org/doi/abs/10.1667/RR0683.1},
	  doi = {http://doi.org/10.1667/RR0683.1}
	}
	
Methods for quantitative evaluation of dynamics of repair proteins within irradiated cells
V. Hable, G. Dollinger, C. Greubel, A. Hauptner, R. Krücken, S. Dietzel, T. Cremer, G. Drexler, A. Friedl and R. Löwe; Nuclear Instruments and Methods in Physics Research Section B 245 (1) (2006) 298-301.
Abstract: Living HeLa cells are irradiated well directed with single 100 MeV oxygen ions by the superconducting ion microprobe SNAKE, the Superconducting Nanoscope for Applied Nuclear (=Kern-) Physics Experiments, at the Munich 14 MV tandem accelerator. Various proteins, which are involved directly or indirectly in repair processes, accumulate as clusters (so called foci) at DNA-double strand breaks (DSBs) induced by the ions. The spatiotemporal dynamics of these foci built by the phosphorylated histone γ-H2AX are studied. For this purpose cells are irradiated in line patterns. The γ-H2AX is made visible under the fluorescence microscope using immunofluorescence techniques. Quantitative analysis methods are developed to evaluate the data of the microscopic images in order to analyze movement of the foci and their changing size.
BibTeX:
	@article{Hable2006a,
	  author = {Hable, V. and Dollinger, G. and Greubel, C. and Hauptner, A. and Krücken, R. and Dietzel, S. and Cremer, T. and Drexler, G.A. and Friedl, A.A. and Löwe, R.},
	  title = {Methods for quantitative evaluation of dynamics of repair proteins within irradiated cells},
	  booktitle = {Proceedings of the Sixth International Symposium on Swift Heavy Ions in Matter (SHIM 2005)},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2006},
	  volume = {245},
	  number = {1},
	  pages = {298--301},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X05020628},
	  doi = {http://doi.org/10.1016/j.nimb.2005.11.118}
	}
	
Positron lifetime and microstructural characterisation of a-Si:H deposited by low temperature HW-CVD on paper substrates
M. Härting, D. Britton, D. Knoesen and W. Egger; Applied Surface Science 252 (9) (2006) 3188-3193.
Abstract: In thin film electronic applications, the limiting factor, in terms of cost and usability, is generally the substrate material. As a consequence, different materials are being investigated as potential lightweight, inexpensive and flexible substrates. In this respect, we have been the first research collaboration to produce silicon-based electronics on paper substrates. Here we present structural characterisation of hydrogenated amorphous silicon (a-Si:H) layers deposited on 80 g m-2 wood-free paper, with and without an intermediate metallic interlayer, using low temperature hot wire chemical vapour deposition (HW-CVD). Both pulsed positron beam profiling and X-ray diffraction studies indicate that the growth rate on the uncoated substrate is slightly higher than with prior metallization. There is no evidence of a crystalline phase or voids in the a-Si:H layers. The internal defect structure is similar, with a dominant dangling bond complex of similar size, which has a slightly longer lifetime than in layers grown at higher temperatures on conventional substrates.
BibTeX:
	@article{Haerting2006,
	  author = {Härting, M. and Britton, D.T. and Knoesen, D. and Egger, W.},
	  title = {Positron lifetime and microstructural characterisation of a-Si:H deposited by low temperature HW-CVD on paper substrates},
	  journal = {Applied Surface Science},
	  year = {2006},
	  volume = {252},
	  number = {9},
	  pages = {3188-3193},
	  note = {SLOPOS 10},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433205012018},
	  doi = {http://doi.org/10.1016/j.apsusc.2005.08.068}
	}
	
Czochralski-grown nitrogen-doped silicon: Electrical properties of MOS structures; A positron annihilation study
L. Harmatha, M. Ťapajna, V. Slugeň, P. Ballo, P. Písečný, J. Šik and G. Kögel; Microelectronics Journal 37 (4) (2006) 283-289.
Abstract: Czochralski-grown nitrogen-doped (NCZ) silicon was studied using different methods. Measurements of interface traps density, effective generation lifetime and effective surface generation velocity were performed on selected Metal-Oxide-Semiconductor (MOS) structures. Application of the positron annihilation technique (PAS) - pulsed low energy positron system (PLEPS) - was focused on the detection of nitrogen-related defects in NCZ silicon in the near surface region. PAS - PLEPS technique gave relevant results on p-type NCZ silicon. Low sensitivity in the application to n-type NCZ silicon discriminates the PAS - PLEPS technique and should be alternated by other experimental technique. On the other hand, more pertinent measurement of generation lifetime was performed on MOS structures with n-type Si. Although the generation lifetime decreases in NCZ silicon, considerable lateral homogenization of the relaxation time was observed on the wafer.
BibTeX:
	@article{Harmatha2006,
	  author = {Harmatha, L. and Ťapajna, M. and Slugeň, V. and Ballo, P. and Písečný, P. and Šik, J. and Kögel, G.},
	  title = {Czochralski-grown nitrogen-doped silicon: Electrical properties of MOS structures; A positron annihilation study},
	  journal = {Microelectronics Journal},
	  year = {2006},
	  volume = {37},
	  number = {4},
	  pages = {283--289},
	  url = {http://www.sciencedirect.com/science/article/pii/S0026269205002387},
	  doi = {http://doi.org/10.1016/j.mejo.2005.04.059}
	}
	
Spatial Distribution of DNA Double-Strand Breaks from Ion Tracks
A. Hauptner, W. Friedland, S. Dietzel, G.A. Drexler, C. Greubel, V. Hable, H. Strickfaden, T. Cremer, A.A. Friedl, R. Krücken, H.G. Paretzke and G. Dollinger; In: P. Sigmund (Ed.), Ion Beam Science: Solved and Unsolved Problems , Vol. 52 , p. 59-85 , Royal Danish Academy of Sciences and Letter , 2006.
Abstract: Theoretical and experimental approaches are developed to investigate the spatial distribution of DNA damage induced by energetic ions in cell nuclei, with a special emphasis on DNA double-strand breaks (DSB). Using a phenomenological description for the relationship between energy dose and DSB induction, the total number of DSBs and their average number per unit pathlength can be calculated analytically for single ion tracks in cell nuclei. A simple approach to microscopic DNA damage description is offered by analytical representations which give the average energy dose in dependence of the radial distance from the ion track. However, the extreme fluctuations in the DNA damage per volume, which is due to the inhomogeneous ionisation events of the individual secondary electron paths and the structure of chromatin in the nucleus, make a true follow-up of the ionisation and excitation events desirable, e.g. by using Monte Carlo methods. The visualisation of DSBs by staining proteins which accumulate in large amounts at DSB repair sites, thus forming so-called foci, allows to analyse the spatial distribution of DSB sites under the fluorescence microscope. With this method, generally a much lower number of DSB sites along an ion track is observed than expected on basis of calculations. This observation hints at insufficient consideration of gross structures in the organisation of nuclear DNA or at a fast clustering of DSBs, possibly to form repair factories.
BibTeX:
	@incollection{Hauptner2006,
	  author = {Hauptner, A. and Friedland, W. and Dietzel, S. and Drexler, G. A. and Greubel, C. and Hable, V. and Strickfaden, H. and Cremer, T. and Friedl, A. A. and Krücken, R. and Paretzke, H. G. and Dollinger, G.},
	  title = {Spatial Distribution of DNA Double-Strand Breaks from Ion Tracks},
	  booktitle = {Ion Beam Science: Solved and Unsolved Problems},
	  publisher = {Royal Danish Academy of Sciences and Letter},
	  year = {2006},
	  volume = {52},
	  pages = {59--85},
	  editor = {P. Sigmund},
	  url = {http://www.sdu.dk/Bibliotek/matfys}
	}
	
DNA-repair protein distribution along the tracks of energetic ions
A. Hauptner, R. Krücken, C. Greubel, V. Hable, G. Dollinger, G. Drexler, M. Deutsch, R. Löwe, A. Friedl, S. Dietzel, H. Strickfaden and T. Cremer; Radiation Protection Dosimetry 122 (1-4) (2006) 147-149.
Abstract: A simple model of homogenous chromatin distribution in HeLa-cell nuclei suggests that the track of an energetic ion hits 30 nm chromatin fibers with a mean distance of 0.55 μm. To test this assumption, living HeLa-cells were irradiated at the irradiation setup of the ion microprobe SNAKE using the ion beams provided by the Munich 14 MV tandem accelerator. After irradiation, the distribution of 53BP1 protein foci was studied by immunofluorescence. The observed 53BP1 distribution along the tracks of 29 MeV 7Li ions and 24 MeV 12C ions differed significantly from the expectations resulting from the simple chromatin model, suggesting that the biological track structure is determined by cell nuclear architecture with higher order organisation of chromatin.
BibTeX:
	@article{Hauptner2006a,
	  author = {Hauptner, A. and Krücken, R. and Greubel, C. and Hable, V. and Dollinger, G. and Drexler, G.A. and Deutsch, M. and Löwe, R. and Friedl, A.A. and Dietzel, S. and Strickfaden, H. and Cremer, T.},
	  title = {DNA-repair protein distribution along the tracks of energetic ions},
	  journal = {Radiation Protection Dosimetry},
	  year = {2006},
	  volume = {122},
	  number = {1-4},
	  pages = {147--149},
	  url = {http://rpd.oxfordjournals.org/content/122/1-4/147.abstract},
	  doi = {http://doi.org/10.1093/rpd/ncl420}
	}
	
Irradiation of living cells with single ions at the ion microprobe SNAKE
A. Hauptner, T. Cremer, M. Deutsch, S. Dietzel, G. Drexler, C. Greubel, V. Hable, R. Krücken, R. Löwe, H. Strickfaden, G. Dollinger and A. Friedl; Acta Physica Polonica A 109 (3) (2006) 273-278.
Abstract: The irradiation setup at the ion microprobe SNAKE is used to irradiate living cells with single energetic ions. The irradiation accuracy of 0.55 µm and respectively 0.40 µm allows to irradiate substructures of the cell nucleus. By the choice of ion atomic number and energy the irradiation can be performed with a damage density adjustable over more than three orders of magnitude. Immunofluorescence detection techniques show the distribution of proteins involved in the repair of DNA double-strand breaks. In one of the first experiments the kinetics of appearance of irradiation-induced foci in living HeLa cells was examined. In other experiments a new effect was detected which concerned the interaction between irradiation events performed at different time points within the same cell nucleus.
BibTeX:
	@article{Hauptner2006b,
	  author = {Hauptner, A. and Cremer, T. and Deutsch, M. and Dietzel, S. and Drexler, G.A. and Greubel, C. and Hable, V. and Krücken, R. and Löwe, R. and Strickfaden, H. and Dollinger, G. and Friedl, A.A.},
	  title = {Irradiation of living cells with single ions at the ion microprobe SNAKE},
	  journal = {Acta Physica Polonica A},
	  year = {2006},
	  volume = {109},
	  number = {3},
	  pages = {273--278},
	  note = {Proceedings of the XL Zakopane School of Physics, Zakopane 2005},
	  url = {http://przyrbwn.icm.edu.pl/APP/SPIS/a109-3.html},
	  doi = {0.12693/APhysPolA.109.273}
	}
	
Mikroskopisch genaue Zellbestrahlung mit hochenergetischen Ionen.
Andreas Hauptner; Dissertation, Technische Universität München, 2006.
Abstract: Im Rahmen der Arbeit wurde die physikalisch-biologische Schädigungswirkung von hochenergetischer Ionenstrahlung in Modell-Zellkernen auf mikroskopischer Ebene abgeschätzt. Zur Durchführung von Bestrahlungsexperimenten wurde am Rasterionenmikroskop SNAKE des Münchener 14 MV Tandembeschleunigers ein Einzel-Ionen-Bestrahlungsaufbau für lebende Zellen realisiert. An HeLa-Zellen konnten damit Bestrahlungen mit einer räumlichen Auflösung von 0,5 µm durchgeführt und mittels Immunofluoreszenz-Methoden Proteine nachgewiesen werden, die an der Reparatur von DNA-Doppelstrangbrüchen beteiligt sind. Dies ermöglichte das Studium der Chromatin-Dynamik an geschädigten Zellkernbereichen sowie die Charakterisierung eines neu entdeckten "Konkurrenzeffekts" der DNA-Reparatur nach fraktionierter Bestrahlung. Durch Änderung der Bestrahlungsgeometrie konnten Schädigungsereignisse in Form sogenannter Foci entlang von Ionenspuren mit hoher Auflösung untersucht und mit Modellrechnungen verglichen werden.
BibTeX:
	@phdthesis{Hauptner2006diss,
	  author = {Hauptner, Andreas},
	  title = {Mikroskopisch genaue Zellbestrahlung mit hochenergetischen Ionen.},
	  school = {Technische Universität München},
	  year = {2006},
	  url = {http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:91-diss20060915-1726116123}
	}
	
Depth-Resolved Analysis of the Aging Behavior of Epoxy Thin Films by Positron Spectroscopy
J. Kanzow, F. Faupel, W. Egger, P. Sperr, G. Kögel, C. Wehlack, A. Meiser and W. Possart; In: W. Possart (Ed.), Adhesion: Current Research and Applications , Chapter 29 , p. 465-477 , Wiley-VCH , 2006.
Abstract: During recent decades positron annihilation spectroscopy has become a very powerful tool for the investigation of polymers. In particular, positron annihilation lifetime spectroscopy (PALS) yields valuable information about free volume and related properties. Moreover, special chemical information can be obtained. Now advances in positron beam technology also allow investigations of thin polymer films and surface regions. In this paper, we report the use, for the first time, of PALS to elucidate aging mechanisms in thin epoxy films, based on depth-resolved investigations of the epoxy films exposed to two different aging conditions. We also consider the results of IR external reflection absorption spectroscopy (IR-ERAS) and X-ray photoelectron spectroscopy (XPS) depth-profiling of the elemental composition. This additional information enables us to clarify structural modifications due to aging. Nitrogen depletion and a decrease in free volume were observed, especially in the near-surface region of the thin epoxy films.
BibTeX:
	@incollection{Kanzow2006,
	  author = {Kanzow, J. and Faupel, F. and Egger, W. and Sperr, P. and Kögel, G. and Wehlack, C. and Meiser, A. and Possart, W.},
	  title = {Depth-Resolved Analysis of the Aging Behavior of Epoxy Thin Films by Positron Spectroscopy},
	  booktitle = {Adhesion: Current Research and Applications},
	  publisher = {Wiley-VCH},
	  year = {2006},
	  pages = {465--477},
	  editor = {Wulff Possart},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/3527607307.ch29/summary},
	  doi = {http://doi.org/10.1002/3527607307.ch29}
	}
	
Planned positron experiments at FRM-II
G. Kögel and G. Dollinger; Applied Surface Science 252 (9) (2006) 3111-3120.
Abstract: The new research reactor FRM-II near Munich has a strong positron source, which delivers an intense, nearly monoenergetic positron beam. Our positron systems, the pulsed low energy positron source (PLEPS) and the scanning positron microscope (SPM) will be operated at this beam. Some aspects of matching these systems to the new positron source will be discussed. Considerable improvements are expected, e.g. more than 105 s-1 recorded events at PLEPS and sub-micrometre resolution at SPM. They will enable investigations in so far inaccessible problems like the evaluation of annihilation characteristics and trapping constants of individual defects or studies of fast dynamical processes. In applied materials science complex defect structures will be studied which demand a resolution into many differing lifetimes, e.g. fractured specimens, wear, corrosion, etc. Also large series of measurements at small systematic modifications are planned. There is also the opportunity to analyse in addition the chemical microstructure of the specimens by means of a hydrogen microprobe and other ion beam techniques available close to FRM-II at the Technical University of Munich.
BibTeX:
	@article{Koegel2006,
	  author = {Kögel, G. and Dollinger, G.},
	  title = {Planned positron experiments at FRM-II},
	  journal = {Applied Surface Science},
	  year = {2006},
	  volume = {252},
	  number = {9},
	  pages = {3111-3120},
	  editor = {Al-Qaradawi I.Y., Coleman P.G.},
	  note = {SLOPOS 10},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433205012158},
	  doi = {http://doi.org/10.1016/j.apsusc.2005.08.048}
	}
	
Design and advanced preparation of multilayer converters for ultracold-neutron detectors
P. Maier-Komor, I. Altarev, A. Bergmaier, P. Böni, G. Dollinger, R. Krücken, S. Paul and W. Schott; Nuclear Instruments and Methods in Physics Research Section A 561 (1) (2006) 45-51.
Abstract: For experiments at the planned ultracold neutron (UCN) source of the new Munich research reactor (FRM II) highly efficient UCN detectors must be developed. The principle of this type of detector is the conversion of UCN in 6Li layers into 2.06 MeV α-particles and 2.73 MeV t-particles created in the reaction 6Li(n,α)t. Since the α- and t-particles are emitted in opposite direction, each reaction of a neutron with a 6Li atom could be identified, e.g. in a silicon PIN diode. The design of an UCN converter must take in account the high reflectance of UCN at 6Li with its positive optical potential. This must be compensated by a material with negative optical potential. Candidates for this are either 62Ni or 48Ti and as cheap compromise natTi. Since Ti and 6Li-metal can only be processed in an UHV plant without introducing disturbing oxygen impurities, the new multilayer stacks have been prepared all with 62Ni and 6LiF. One UCN converter with a stack of 125 double layers of 6LiF/62Ni was deposited on a 450 μg/cm2 rolled natTi backing foil. This was investigated by means of ERD analysis for its atomic concentration. These results are presented. A proposal is discussed where the backing foil is made from the neutron reflector material 58Ni. The required self-supporting 58Ni foil of 200-400 μg/cm2 thickness and a square area of 6.2 cm2 can be prepared by rolling. A UHV vacuum system for electron beam evaporation of Ti and 6Li is being assembled. Some annealing tests at another UHV system led to a modification of the planned pumping system. One of the three refrigerator cryopumps foreseen in the design has been replaced for a turbomolecular pump. Its gate valve is closed when annealing to 470 K is finished.
BibTeX:
	@article{Maier-Komor2006,
	  author = {Maier-Komor, P. and Altarev, I. and Bergmaier, A. and Böni, P. and Dollinger, G. and Krücken, R. and Paul, S. and Schott, W.},
	  title = {Design and advanced preparation of multilayer converters for ultracold-neutron detectors},
	  journal = {Nuclear Instruments and Methods in Physics Research Section A},
	  year = {2006},
	  volume = {561},
	  number = {1},
	  pages = {45--51},
	  note = {cited By (since 1996)0},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168900205026197},
	  doi = {http://doi.org/10.1016/j.nima.2005.12.226}
	}
	
Preparation and investigation of thick carbon foils prepared by laser plasma ablation deposition
P. Maier-Komor, G. Dollinger and R. Krücken; Nuclear Instruments and Methods in Physics Research Section A 561 (1) (2006) 4-10.
Abstract: Carbon foils prepared by laser plasma ablation deposition using a power density of > 1 GW / cm2 are so far the only ones which have been shown to have a total random orientation of the nanocrystallites and thus the theoretically best resistance against irradiation damage caused by ion bombardment. Need for longer lifetimes of carbon stripper foils was observed firstly in tandem accelerator experiments with heavy ions. There the required thickness is 3 to 10 μ g / cm2 and the plant was developed to meet these needs. Thicker carbon stripper foils are required as dead-section strippers and post-strippers. For the stripping of H- beams in the GeV range thick ( > 100 μ g / cm2) carbon stripper foils are required. The new plant which should facilitate the ablation deposition for this type of foils of unlimited thickness has been constructed. First results are presented about the preparation of thick ( > 50 μ g / cm2) carbon stripper foils of this kind and the applicability of the results to the preparation of carbon stripper foils of several hundred μ g / cm2 is discussed. For the application as gas detector windows very good chemical resistance is required if the carbon foil becomes hot due to the energy loss of the ion beam. Investigations for a 4 μ g / cm2 laser plasma carbon foil window transmitting 10 p μ A of 3 MeV multiscripts(C, mml:none(), 2 +, prescripts(), mml:none(), 12) are reported. If very uniform electronic energy loss is required the corrugated structure, caused by the betaine parting agent on laser plasma carbon foils, is not suited. Therefore, it was tried to utilize release agents of different types of evaporated salt layers which were covered by 100μg/cm2 copper in the same vacuum process. The floating success rates for those release agent combinations are reported.
BibTeX:
	@article{Maier-Komor2006a,
	  author = {Maier-Komor, P. and Dollinger, G. and Krücken, R.},
	  title = {Preparation and investigation of thick carbon foils prepared by laser plasma ablation deposition},
	  journal = {Nuclear Instruments and Methods in Physics Research Section A},
	  year = {2006},
	  volume = {561},
	  number = {1},
	  pages = {4--10},
	  note = {cited By (since 1996)6},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168900205026197},
	  doi = {http://doi.org/10.1016/j.nima.2005.12.184}
	}
	
3D-Hydrogen analysis of ferromagnetic microstructures in proton irradiated graphite
P. Reichart, D. Spemann, A. Hauptner, A. Bergmaier, V. Hable, R. Hertenberger, C. Greubel, A. Setzer, G. Dollinger, D. Jamieson, T. Butz and P. Esquinazi; Nuclear Instruments and Methods in Physics Research Section B 249 (1-2) (2006) 286-291.
Abstract: Recently, magnetic order in highly oriented pyrolytic graphite (HOPG) induced by proton broad- and microbeam irradiation was discovered. Theoretical models propose that hydrogen could play a major role in the magnetism mechanism. We analysed the hydrogen distribution of pristine as well as irradiated HOPG samples, which were implanted to μm-sized spots as well as extended areas with various doses of 2.25 MeV protons at the Leipzig microprobe LIPSION. For this we used the sensitive 3D hydrogen microscopy system at the Munich microprobe SNAKE. The background hydrogen level in pristine HOPG is determined to be less than 0.3 at-ppm. About 4.8 × 1015 H-atoms/cm2 are observed in the near-surface region (4 μm depth resolution). The depth profiles of the implants show hydrogen located within a confined peak at the end of range, in agreement with SRIM Monte Carlo simulations, and no evidence of diffusion broadening along the c-axis. At the sample with microspots, up to 40 at.% of the implanted hydrogen is not detected, providing support for lateral hydrogen diffusion.
BibTeX:
	@article{Reichart2006,
	  author = {Reichart, P. and Spemann, D. and Hauptner, A. and Bergmaier, A. and Hable, V. and Hertenberger, R. and Greubel, C. and Setzer, A. and Dollinger, G. and Jamieson, D.N. and Butz, T. and Esquinazi, P.},
	  title = {3D-Hydrogen analysis of ferromagnetic microstructures in proton irradiated graphite},
	  booktitle = {Proceedings of the Seventeenth International Conference on Ion Beam Analysis},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2006},
	  volume = {249},
	  number = {1-2},
	  pages = {286--291},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X06004605},
	  doi = {http://doi.org/10.1016/j.nimb.2006.04.014}
	}
	
An experiment for the measurement of the bound- β-decay of the free neutron
W. Schott, G. Dollinger, T. Faestermann, J. Friedrich, F. Hartmann, R. Hertenberger, N. Kaiser, A. Müller, S. Paul and A. Ulrich; European Physical Journal A 30 (3) (2006) 603-611.
Abstract: The hyperfine-state population of hydrogen after the bound-β-decay of the neutron directly yields the neutrino left-handedness or a possible right-handed admixture and possible small scalar and tensor contributions to the weak force. Using the through-going beam tube of a high-flux reactor, a background free hydrogen rate of ca. 3s-1 can be obtained. The detection of the neutral hydrogen atoms and the analysis of the hyperfine states is accomplished by Lamb shift source type quenching and subsequent ionization. The constraints on the neutrino helicity and the scalar and tensor coupling constants of the weak interaction can be improved by a factor of ten.
BibTeX:
	@article{Schott2006,
	  author = {Schott, W. and Dollinger, G. and Faestermann, T. and Friedrich, J. and Hartmann, F.J. and Hertenberger, R. and Kaiser, N. and Müller, A.R. and Paul, S. and Ulrich, A.},
	  title = {An experiment for the measurement of the bound- β-decay of the free neutron},
	  journal = {European Physical Journal A},
	  year = {2006},
	  volume = {30},
	  number = {3},
	  pages = {603--611},
	  note = {cited By (since 1996)10},
	  url = {http://link.springer.com/article/10.1140%2Fepja%2Fi2006-10136-3},
	  doi = {http://doi.org/10.1140/epja/i2006-10136-3}
	}
	
Electrical properties of MOS structures on nitrogen-doped Czochralski-grown silicon: A positron annihilation study
V. Slugeň, L. Harmatha, M. Ťapajna, P. Ballo, P. Písečný, J. Šik, G. Kögel and V. Kršjak; Applied Surface Science 252 (9) (2006) 3201-3208.
Abstract: Measurements of interface trap density, effective generation lifetime (GL) and effective surface generation velocity have been performed using differen: methods on selected MOS structures prepared on nitrogen-doped Czochralski-grown (NCz) silicon. The application of the positron annihilation technique using a pulsed low energy positron system (PLEPS) focused on the detection of nitrogen-related defects in NCz silicon in the near surface region. In the case of p-type Cz silicon, all the results could be used for the testing of homogeneity. In n-type Cz silicon, positron annihilation was found insensitive to nitrogen doping.
BibTeX:
	@article{Slugen2006,
	  author = {Slugeň, V. and Harmatha, L. and Ťapajna, M. and Ballo, P. and Písečný, P. and Šik, J. and Kögel, G. and Kršjak, V.},
	  title = {Electrical properties of MOS structures on nitrogen-doped Czochralski-grown silicon: A positron annihilation study},
	  journal = {Applied Surface Science},
	  year = {2006},
	  volume = {252},
	  number = {9},
	  pages = {3201-3208},
	  note = {SLOPOS 10},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433205012031},
	  doi = {http://doi.org/10.1016/j.apsusc.2005.08.071}
	}
	
Heavy ion irradiation of U-Mo/Al dispersion fuel
N. Wieschalla, A. Bergmaier, P. Böni, K. Böning, G. Dollinger, R. Großmann, W. Petry, A. Röhrmoser and J. Schneider; Journal of Nuclear Materials 357 (1-3) (2006) 191-197.
Abstract: The usage of high-density U-Mo/Al dispersion fuel for high burn up in research and test reactors seems to be limited by the unfavourable interdiffusion layer between the fuel and the Al-matrix, which develops during irradiation. This interdiffusion layer was observed up to now only after costly and time consuming in-pile irradiation and could not be created in out-of-pile experiments. This paper presents a new approach of creating such an interdiffusion layer out-of-pile by irradiation with heavy ions. An appropriate choice of heavy-ion irradiation simulates irradiation damage and deposition of fission fragments as it happens during in-pile irradiation and induces a diffusion process between the fuel and the Al matrix. An irradiation experiment and post-irradiation examinations are presented.
BibTeX:
	@article{Wieschalla2006,
	  author = {Wieschalla, N. and Bergmaier, A. and Böni, P. and Böning, K. and Dollinger, G. and Großmann, R. and Petry, W. and Röhrmoser, A. and Schneider, J.},
	  title = {Heavy ion irradiation of U-Mo/Al dispersion fuel},
	  journal = {Journal of Nuclear Materials},
	  year = {2006},
	  volume = {357},
	  number = {1-3},
	  pages = {191--197},
	  note = {cited By (since 1996)12},
	  url = {http://www.sciencedirect.com/science/article/pii/S0022311506003679},
	  doi = {http://doi.org/10.1016/j.jnucmat.2006.06.006}
	}
	

2005

Absence of positronium formation in clean buried nanocavities in p-type silicon
R.S. Brusa, C. Macchi, S. Mariazzi, G.P. Karwasz, W. Egger, P. Sperr and G. Kögel; Physical Review B - Condensed Matter and Materials Physics 71 (24) (2005) 245320.
Abstract: Buried nanocavities at about 350 nm depth in Si were produced by thermal treatment of He implanted p-type (100) Si. The internal surfaces of the nanocavities were found free of impurity decorations by examining the high-momentum part of the Doppler-broadened positron annihilation spectra. Positron lifetime measurements with a pulsed slow positron beam show neither a short lifetime (125-150 ps) ascribable to parapositronium nor a longer lifetime (2-4 ns) ascribable to pick-off annihilation of orthopositronium. The lifetime of positrons trapped into nanocavities was found to be about 500 ps. The absence of positronium formation could be explained by an insufficient electron density and a lack of electron states in the band gap at the nanocavities internal surfaces produced in the p-type silicon.
BibTeX:
	@article{Brusa2005,
	  author = {Brusa, R. S. and Macchi, C. and Mariazzi, S. and Karwasz, G. P. and Egger, W. and Sperr, P. and Kögel, G.},
	  title = {Absence of positronium formation in clean buried nanocavities in p-type silicon},
	  journal = {Physical Review B - Condensed Matter and Materials Physics},
	  year = {2005},
	  volume = {71},
	  number = {24},
	  pages = {245320},
	  url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.71.245320},
	  doi = {http://doi.org/10.1103/PhysRevB.71.245320}
	}
	
Microirradiation of cells with energetic heavy ions
G. Dollinger, V. Hable, A. Hauptner, R. Krücken, P. Reichart, A. Friedl, G. Drexler, T. Cremer and S. Dietzel; Nuclear Instruments and Methods in Physics Research Section B 231 (1-4) (2005) 195-201.
Abstract: The ion microprobe SNAKE (superconducting nanoscope for applied nuclear (Kern) physics experiments) at the Munich 14 MV tandem accelerator achieves beam focusing by a superconducting quadrupole doublet and can make use of a broad range of ions and ion energies, from 20 MeV protons to 200 MeV gold ions. This allows to adjust the number of DNA single strand breaks (SSBs) and double strand breaks (DSBs) per ion and per cell nucleus from about 0.1 DSBs per ion to several 100 DSBs per ion. When irradiating with single 100 MeV 16O ions, the adapted setup permits a fwhm irradiation accuracy of 0.55 μm in x-direction and 0.4 μm in y-direction, as demonstrated by retrospective track etching of polycarbonate foils. The experiments point to investigate protein dynamics after targeted irradiation. As an example for such experiments we show a kind of three dimensional representation of foci of γ-H2AX which are visible 0.5 h after the irradiation with 100 MeV 16O ions took place. It shows the gross correlation with the irradiation pattern but also distinct deviations which are attributed to protein dynamics in the cell.
BibTeX:
	@article{Dollinger2005,
	  author = {Dollinger, G. and Hable, V. and Hauptner, A. and Krücken, R. and Reichart, P. and Friedl, A.A. and Drexler, G. and Cremer, T. and Dietzel, S.},
	  title = {Microirradiation of cells with energetic heavy ions},
	  booktitle = {Proceedings of the 9th International Conference on Nuclear Microprobe Technology and Applications},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2005},
	  volume = {231},
	  number = {1-4},
	  pages = {195--201},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X05000765},
	  doi = {http://doi.org/10.1016/j.nimb.2005.01.056}
	}
	
Three dimensional hydrogen microscopy in diamond
G. Dollinger, P. Reichart, A. Bergmaier, A. Hauptner and C. Wild; In: , S. Ashok, J. Chevallier, B.L. Sopori, M. Tabe and P. Kiesel (Ed.), Materials Research Society Symposium Proceedings 864 (2005) 541-547 , MRS, Warrendale, PA, United States.
Abstract: We introduce proton-proton scattering at a microprobe of 17 MeV protons to quantitatively image three dimensional hydrogen distributions in polycrystalline diamond at a lateral resolution better than 1 μm and high sensitivity. The images show that most of the hydrogen of a 〈110〉-textured undoped polycrystalline diamond film is located at grain boundaries. The average amount of hydrogen is (8.1±1.5)·10 14 atoms/cm 2 along the grain boundaries which corresponds to about a third of a monolayer. The content within the grain is below the detection limit of 1.4-10 16 atoms/cm 2 (0.08 at-ppm).
BibTeX:
	@inproceedings{Dollinger2005a,
	  author = {Dollinger, G. and Reichart, P. and Bergmaier, A. and Hauptner, A. and Wild, C.},
	  title = {Three dimensional hydrogen microscopy in diamond},
	  booktitle = {Materials Research Society Symposium Proceedings},
	  publisher = {MRS, Warrendale, PA, United States},
	  year = {2005},
	  volume = {864},
	  pages = {541--547},
	  editor = {Ashok S., Chevallier J., Sopori B.L., Tabe M., Kiesel P.},
	  note = {cited By (since 1996)0},
	  url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-30544438196&partnerID=40&md5=4d513ce20703288ffbfba125377daf31}
	}
	
Dynamik der Verteilung von DNA-Reparaturfaktoren in lebenden Zellen nach fraktionierter Bestrahlung am Rasterionenmikroskop SNAKE
Christoph Greubel; Diplomarbeit, Technische Universität München, 2005.
BibTeX:
	@mastersthesis{Greubel2005da,
	  author = {Greubel, Christoph},
	  title = {Dynamik der Verteilung von DNA-Reparaturfaktoren in lebenden Zellen nach fraktionierter Bestrahlung am Rasterionenmikroskop SNAKE},
	  school = {Technische Universität München},
	  year = {2005}
	}
	
Specific defects and thermomechanical properties of electrodeposited Cu foils
V. Gröger, G. Khatabi, A. Kotas-Betzwar, P. Zimprich, B. Mikulowski, G. Boczkal, W. Egger, H.D. Merchant and B. Weiss; Archives of Metallurgy and Materials 50 (1) (2005) 167-174.
Abstract: Electrodeposition of copper foils is a commercially widely used technique whose potential for producing functionally graded materials by deliberate time variation of the deposition parameters has been shown. Due to the presence of superabundant vacancies (stabilized by hydrogen) structural instabilities are strongly enhanced. More detailed knowledge of microstructural details (especially defect changes during annealing and stability at elevated temperatures) is needed for a basic understanding. Electrical residual resistivity isochrones, positron annihilation, Young's modulus and linear thermal expansion of copper foils of 35 μm thickness of different grain size electrodeposited at commercially usual rates are investigated. For all samples structural changes have been observed during the measurements, the strongest influence seems to be due to the annealing out of single vacancies (presumably by releasing hydrogen) and to grain coarsening.
BibTeX:
	@article{Groeger2005,
	  author = {Gröger, V. and Khatabi, G. and Kotas-Betzwar, A. and Zimprich, P. and Mikulowski, B. and Boczkal, G. and Egger, W. and Merchant, H. D. and Weiss, B.},
	  title = {Specific defects and thermomechanical properties of electrodeposited Cu foils},
	  journal = {Archives of Metallurgy and Materials},
	  year = {2005},
	  volume = {50},
	  number = {1},
	  pages = {167--174},
	  note = {Symposium on Texture and Microstructure Analysis of Functionally Graded Materials, Cracow, POLAND, OCT 03-07, 2004},
	  url = {http://www.imim.pl/archives/volume-50-issue-1-2005}
	}
	
The nucleation centers formed during bias-enhanced nucleation of diamond on iridium: Structure and stability
S. Gsell, M. Schreck, T. Bauer, H. Karl, G. Thorwarth, A. Bergmaier, G. Dollinger and B. Stritzker; Diamond and Related Materials 14 (3-7) (2005) 328-334.
Abstract: During bias-enhanced nucleation (BEN) of diamond on iridium, an ultrathin carbon nucleation layer is deposited. The nature of the nucleation centers or nuclei which gather in discrete islands is investigated in the present work by subjecting the as-biased samples to different treatments. In high vacuum annealing experiments, the structures proved completely stable up to 1000°C. Above this temperature, the nuclei were destroyed and the iridium was etched within the domain areas. Low energy oxygen and xenon ion beams were then used to etch very shallow craters of varying depth. The induced modifications of the surface and the influence on the nucleation density can be understood on the basis of calculations which simulate the damage caused by the ion bombardment. Finally, the stability of the nucleation structures under hot chromo sulfuric acid treatment was compared with the corresponding behavior of a thick amorphous carbon layer. In all the experiments, the nucleation structures formed during BEN behaved similar to diamond situated at the surface of the iridium buffer layer possibly covered by a thin stable amorphous carbon layer.
BibTeX:
	@article{Gsell2005,
	  author = {Gsell, S. and Schreck, M. and Bauer, T. and Karl, H. and Thorwarth, G. and Bergmaier, A. and Dollinger, G. and Stritzker, B.},
	  title = {The nucleation centers formed during bias-enhanced nucleation of diamond on iridium: Structure and stability},
	  journal = {Diamond and Related Materials},
	  year = {2005},
	  volume = {14},
	  number = {3-7},
	  pages = {328--334},
	  note = {cited By (since 1996)5},
	  url = {http://www.sciencedirect.com/science/article/pii/S0925963504003954},
	  doi = {http://doi.org/10.1016/j.diamond.2004.10.027}
	}
	
Highly Si-doped AlN grown by plasma-assisted molecular-beam epitaxy
M. Hermann, F. Furtmayr, A. Bergmaier, G. Dollinger, M. Stutzmann and M. Eickhoff; Applied Physics Letters 86 (19) (2005) 1-3.
Abstract: We have studied the influence of the growth conditions on the Si incorporation in AlN films grown by plasma-assisted molecular-beam epitaxy. Nitrogen-rich growth conditions allow controlled incorporation of Si up to a concentration of 5.2× 1021 cm-3, determined by elastic recoil detection analysis, whereas Si incorporation is supressed under Al-rich growth conditions. The structural and morphological properties determined by x-ray diffraction and atomic force microscopy were not affected up to Si concentrations of 1.2× 1021 cm-3. The electrical conductivity for the N-rich growth regime first increases with Si concentration followed by a decrease due to an increase of the activation energy up to 570 meV for a Si content of 1.2× 1021 cm-3. For higher silicon concentrations, we have observed a sharp decrease in activation energy and an increase in conductivity by four orders of magnitude, attributed to the onset of impurity band conduction.
BibTeX:
	@article{Hermann2005,
	  author = {Hermann, M. and Furtmayr, F. and Bergmaier, A. and Dollinger, G. and Stutzmann, M. and Eickhoff, M.},
	  title = {Highly Si-doped AlN grown by plasma-assisted molecular-beam epitaxy},
	  journal = {Applied Physics Letters},
	  year = {2005},
	  volume = {86},
	  number = {19},
	  pages = {1--3},
	  note = {cited By (since 1996)23},
	  url = {http://aip.scitation.org/doi/10.1063/1.1923180},
	  doi = {http://doi.org/10.1063/1.1923180}
	}
	
Optimization of thin, nitrogen-rich silicon oxynitrides grown by rapid thermal nitridation
A. Ludsteck, J. Schulze, I. Eisele, W. Dietl, H. Chung, Z. Nenyei, A. Bergmaier and G. Dollinger; Journal of the Electrochemical Society 152 (5) (2005) G334-G338.
Abstract: We have systematically examined nitrogen-rich silicon oxynitrides with a thickness of about 2 nm grown by rapid thermal nitridation in ammonia. In this paper the nitrogen incorporation as well as the electrical properties of the oxynitrides are discussed in detail. With the help of elastic recoil detection measurements it could be shown that the incorporated nitrogen concentration can be controlled precisely in a range between 20 and 60%, which means that even pure silicon nitride can be thermally grown in ammonia. Depending on the process flow it is also possible to adjust the nitrogen and oxygen profiles across the dielectrics depth. Regarding the electrical properties of the grown oxynitrides, we examined the impact of the variation of the process parameters and the impact of postnitridation anneals. It was found that the dilution of the process gas ammonia by the inert gas argon has a big impact on the quality of the dielectric. The optimized oxynitrides show leakage current densities which are significantly reduced compared to that of SiO2, but their interface quality is not sufficient for metal oxide semiconductor (MOS) applications. In order to reduce the interface state density Dit, a short reoxidation in steam atmosphere combined with an anneal in forming gas results in oxynitrides with Dit values of 1011 eV-1 cm-2. It is shown that for an equivalent oxide thickness of 1.3-1.5 nm, the leakage current densities are four orders of magnitude below that of SiO2 with the same thickness. Promising measurements of the effective electron mobility show that the presented oxynitrides are suitable as gate dielectrics in MOS applications in spite of the high nitrogen concentration of more than 25%.
BibTeX:
	@article{Ludsteck2005,
	  author = {Ludsteck, A. and Schulze, J. and Eisele, I. and Dietl, W. and Chung, H. and Nenyei, Z. and Bergmaier, A. and Dollinger, G.},
	  title = {Optimization of thin, nitrogen-rich silicon oxynitrides grown by rapid thermal nitridation},
	  journal = {Journal of the Electrochemical Society},
	  year = {2005},
	  volume = {152},
	  number = {5},
	  pages = {G334-G338},
	  note = {cited By (since 1996)3},
	  url = {http://jes.ecsdl.org/content/152/5/G334},
	  doi = {http://doi.org/10.1149/1.1872652}
	}
	
Nitrogen profile and electrical properties of reoxidized thermally grown silicon nitrides
A. Ludsteck, J. Schulze, I. Eisele, W. Dietl, H. Chung, Z. Nényei, A. Bergmaier and G. Dollinger; In: , R.E. Sah, M.J. Deen, J. Zhang, J. Yota and Y. Kamakura (Eds.), ECS Meeting Abstracts 207 (2005) 232-241 , ECS - The Electrochemical Society.
Abstract: Starting from thermally grown Si3N4 we have examined the effects of dry and wet reoxidation in 100% O2 and H2O, respectively, in order to improve the electrical properties interface state density and tunneling current density of nitrogen-rich oxynitrides. It was found that only wet reoxidation can sufficiently improve them without too much increasing the equivalent oxide thickness. This result could be explained with the help of Elastic Recoil Detection measurements. We determined the exact oxygen and nitrogen profiles across the sample depth with a sub-nm resolution after nitridation as well as after different reoxidation steps. It was found that in the case of reoxidations in O2 both, longer times and higher temperatures are necessary in order to get oxygen at the SiOxN y/Si interface compared to the reoxidation in H2O.
BibTeX:
	@inproceedings{Ludsteck2005a,
	  author = {Ludsteck, A. and Schulze, J. and Eisele, I. and Dietl, W. and Chung, H. and Nényei, Z. and Bergmaier, A. and Dollinger, G.},
	  title = {Nitrogen profile and electrical properties of reoxidized thermally grown silicon nitrides},
	  booktitle = {ECS Meeting Abstracts},
	  publisher = {ECS - The Electrochemical Society},
	  year = {2005},
	  volume = {207},
	  number = {412},
	  pages = {232--241},
	  editor = {Sah, R. E. and Deen, M. J. and Zhang, J. and Yota, J. and Kamakura, Y.},
	  note = {Film Preparation, Characterization, and Applications II - Abstract 412},
	  url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-31944437706&partnerID=40&md5=bec0de09644cecd68e6fe635a2e8b46d}
	}
	

2004

Free volume determination of azobenzene-PMMA copolymer by a pulsed low-energy positron lifetime beam with in-situ UV illumination
J. Algers, P. Sperr, W. Egger, L. Liszkay, G. Kögel, J. de Baerdemaeker and F.H.J. Maurer; Macromolecules 37 (21) (2004) 8035-8042.
Abstract: The free volume properties of a poly(methyl methacrylate)-azobenzene copolymer were for the first time directly probed by use of a low-energy positron lifetime beam with in-situ excitation capabilities, showing that the free volume cavity size was not appreciably influenced by photoisomerization and thermal isomerization in the temperature range 34-180°C. Isomerization is therefore suggested to occur without any molecular rearrangement of the glassy polymer matrix, which would also account for the lack of any shift to shorter wavelengths for the photoisomerization occurring in a glassy polymer in comparison to a chloroform solution. A decrease in the thermal isomerization rate at room temperature caused by the glassy polymer is explained in terms of a model in which only a fraction of the azobenzene is free to isomerize. The cis-azobenzene was found to be an efficient inhibitor of positronium formation, which enabled measurements of thermal isomerization rates and changes in the steady-state concentration of cis-azobenzene for an illuminated sample as a function of temperature.
BibTeX:
	@article{Algers2004,
	  author = {Algers, J. and Sperr, P. and Egger, W. and Liszkay, L. and Kögel, G. and de Baerdemaeker, J. and Maurer, F. H. J.},
	  title = {Free volume determination of azobenzene-PMMA copolymer by a pulsed low-energy positron lifetime beam with in-situ UV illumination},
	  journal = {Macromolecules},
	  year = {2004},
	  volume = {37},
	  number = {21},
	  pages = {8035-8042},
	  url = {http://pubs.acs.org/doi/abs/10.1021/ma0486086},
	  doi = {http://doi.org/10.1021/ma0486086}
	}
	
Thermal Isomerization of Azo-Benzene in PMMA Probed by a Pulsed Low-Energy Positron Beam
J. Algers, V. Skeppstedt, P. Sperr, W. Egger and F.H.J. Maurer; Materials Science Forum 445-446 (2004) 262-264.
Abstract: Polymers containing the Azo-benzene group have attracted attention due to anticipated uses such as materials for data storage, membranes with controllable permeability and materials with changeable solubility [1,2]. These expectations are due to the change in shape and dipole moment of the Azo-compound when excited by photo isomerization from the trans-state to the cis-state by UV light of ca 360 nm. Films of copolymers of poly-methyl methacrylate (PMMA) containing 8 wt-% Azo-benzene were photo isomerized with a UV lamp and then measured as a function of time in a low-energy positron beam. The observed changes in the lifetime parameters as a function of time were in agreement with the thermal isomerization (decay) of the cis-isomer as measured by conventional UV spectroscopy, The results show that positron lifetime spectra at low energy are sensitive for the cis-trans isomerization of the Azo-compound, suggesting trapping and annihilation of positrons at free volume sites around the Azo-benzene groups.
BibTeX:
	@article{Algers2004a,
	  author = {Algers, J. and Skeppstedt, V. and Sperr, P. and Egger, W. and Maurer, F. H. J.},
	  title = {Thermal Isomerization of Azo-Benzene in PMMA Probed by a Pulsed Low-Energy Positron Beam},
	  journal = {Materials Science Forum},
	  year = {2004},
	  volume = {445-446},
	  pages = {262--264},
	  note = {ICPA 13},
	  url = {https://www.scientific.net/MSF.445-446.262},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.445-446.262}
	}
	
Physical characterization of mixed HfAlOx layers by complementary analysis techniques
H. Bender, T. Conard, O. Richard, B. Brijs, J. Pétry, W. Vandervorst, C. Defranoux, P. Boher, N. Rochat, C. Wyon, P. Mack, J. Wolstenholme, R. Vitchev, L. Houssiau, J.-J. Pireaux, A. Bergmaier and G. Dollinger; Materials Science and Engineering B: Solid-State Materials for Advanced Technology 109 (1-3) (2004) 60-63.
Abstract: The combined information of complementary physical analysis techniques is applied to obtain a full characterisation of the important material parameters of new high-k layers, i.e. the layer thickness, density, composition and interlayer thickness and nature, and to optimise the measurement methodologies of the different techniques.
BibTeX:
	@article{Bender2004,
	  author = {Bender, H. and Conard, Th. and Richard, O. and Brijs, B. and Pétry, J. and Vandervorst, W. and Defranoux, C. and Boher, P. and Rochat, N. and Wyon, C. and Mack, P. and Wolstenholme, J. and Vitchev, R. and Houssiau, L. and Pireaux, J.-J. and Bergmaier, A. and Dollinger, G.},
	  title = {Physical characterization of mixed HfAlOx layers by complementary analysis techniques},
	  journal = {Materials Science and Engineering B: Solid-State Materials for Advanced Technology},
	  year = {2004},
	  volume = {109},
	  number = {1-3},
	  pages = {60--63},
	  editor = {Dimoulas A., Fompeyrine J., Fanciulli M., Alexe M., Os H.J.},
	  note = {cited By (since 1996)6},
	  url = {http://www.sciencedirect.com/science/article/pii/S092151070300518X},
	  doi = {http://doi.org/10.1016/j.mseb.2003.10.118}
	}
	
Defect Characterization of the Structure-Growth Zone-Model for Sputter Deposited Cu Films
J. De Baerdemaeker, C. Dauwe, D. Segers, C. Detavernier, D. Deduytsche, W. Egger and P. Sperr; Materials Science Forum 445-446 (2004) 69-71.
Abstract: The 'zone-model' for sputter deposited Cu films was analyzed by positron annihilation spectroscopy to give a valuable insight in the nature of the defects present in the different zones of the model. Both depth selective Doppler broadening and positron lifetime spectroscopy were applied using slow positron beams. Room temperature grain growth for films sputtered in the zoneT regime was also analyzed for the first time with positron annihilation spectroscopy.
BibTeX:
	@article{DeBaerdemaeker2004,
	  author = {De Baerdemaeker, J. and Dauwe, C. and Segers, D. and Detavernier, C. and Deduytsche, D. and Egger, W. and Sperr, P.},
	  title = {Defect Characterization of the Structure-Growth Zone-Model for Sputter Deposited Cu Films},
	  journal = {Materials Science Forum},
	  year = {2004},
	  volume = {445-446},
	  pages = {69--71},
	  note = {ICPA 13},
	  url = {http://www.scientific.net/MSF.445-446.69},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.445-446.69}
	}
	
High resolution elastic recoil detection
G. Dollinger, A. Bergmaier, L. Goergens, P. Neumaier, W. Vandervorst and S. Jakschik; Nuclear Instruments and Methods in Physics Research Section B 219-220 (1-4) (2004) 333-343.
Abstract: The quantitative analysis of light elements in ultra thin films being thinner than 10 nm is still a nontrivial task. This paper will summarise the prospects of high resolution elastic recoil detection (ERD) using a Q3D magnetic spectrograph. It has been shown that subnanometer resolution can be achieved in ultra thin films and even monolayer resolution is possible close to the surface. ERD has best quantification possibilities compared to any other method. Sensitivity is sufficient to analyse main elements and impurities as e.g. being necessary for the characterisation of microelectronic materials. In addition, high resolution channeling ERD can be performed in order to get information on lattice location of light elements in crystalline ultra thin layers. The potential of high resolution ERD will be demonstrated by several applications where it is the most valuable tool for elemental profiling.
BibTeX:
	@article{Dollinger2004,
	  author = {Dollinger, G. and Bergmaier, A. and Goergens, L. and Neumaier, P. and Vandervorst, W. and Jakschik, S.},
	  title = {High resolution elastic recoil detection},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2004},
	  volume = {219-220},
	  number = {1-4},
	  pages = {333--343},
	  editor = {Vizkelethy G., McDaniel F.D., Thevuthasan S., Tesmer J.R.},
	  note = {cited By (since 1996)16},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X04001077},
	  doi = {http://doi.org/10.1016/j.nimb.2004.01.079}
	}
	
Membrane, transparent for particle beams, with improved emissity of electromagnetic radiation
J. Wieser, A. Ulrich and G. Dollinger; Patent Application, Tuilaser Ag, WO 2004097882 A1, 2004.
BibTeX:
	@patent{Dollinger2004a,
	  author = {Wieser, Jochen and Ulrich, Andreas and Dollinger, Günther},
	  title = {Membrane, transparent for particle beams, with improved emissity of electromagnetic radiation},
	  type = {Patent Application},
	  holder = {Tuilaser Ag},
	  year = {2004},
	  volume = {WO 2004097882 A1},
	  url = {https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2004097882&recNum=1&maxRec=&office=&prevFilter=&sortOption=&queryString=&tab=PCT+Biblio}
	}
	
Studies of light alloys by positron annihilation techniques
A. Dupasquier, G. Kögel and A. Somoza; Acta Materialia 52 (16) (2004) 4707-4726.
Abstract: The potential of positron annihilation spectroscopy (PAS) in the study of light alloys is illustrated with special regards to age-hardening, severe plastic deformation, fatigue and fracture in aluminium- and magnesium-based alloys. First, the physical grounds of PAS sensitivity to open-volume defects are explained. Then the main conventional variants of PAS, lifetime spectroscopy and Doppler-broadening spectroscopy, are introduced. State-of-the-art equipment, based on intense positron sources and energy-controlled beams, is also described, in view of applications where microscopic spatial resolution and sub-nanosecond time resolution are combined. Various examples of PAS studies in the field of light alloys, mainly based on the latest experience of the authors, are presented. It is shown how PAS detects structural changes in age-hardenable alloys, helps to describe the solute aggregation kinetics and gives information on vacancy-solute interactions. PAS characterisation of internal surfaces (misfit interfaces and grain boundaries) in terms of local structure (degree of disorder, chemistry) is also discussed. Lastly, recent advances in the study of fatigue by positron microscopy are reported.
BibTeX:
	@article{Dupasquier2004,
	  author = {Dupasquier, A and Kögel, G and Somoza, A},
	  title = {Studies of light alloys by positron annihilation techniques},
	  journal = {Acta Materialia},
	  year = {2004},
	  volume = {52},
	  number = {16},
	  pages = {4707-4726},
	  url = {http://www.sciencedirect.com/science/article/pii/S1359645404004033},
	  doi = {http://doi.org/10.1016/j.actamat.2004.07.004}
	}
	
Measurements of defect structures of a cyclically deformed Al-Mg-Si alloy by positron annihilation techniques
W. Egger, G. Kögel, P. Sperr, W. Triftshäuser, J. Bär, S. Rödling and H.-J. Gudladt; Materials Science and Engineering A 387-389 (1-2 SPEC. ISS.) (2004) 317-320.
Abstract: Defect distributions close to cracks created by monotonic and fatigue tests in the Al-Mg-Si alloy Al 6013 have been investigated by positron lifetime studies. The defect structure close to the crack surface was studied at sub-mum resolution with a pulsed positron beam, whereas the lateral defect distribution in the crack-tip near region was determined using a scanning positron microscope with a few mum resolution. A high concentration of large vacancy clusters of up to 30 vacancies and voids close to the fatigue crack, as well as a high dislocation density in a region with an extension of similar to100 mum around the crack tip, were detected in the fatigued samples. Moreover, the generation of vacancy clusters found in the fatigued samples seems to be independent of the loading history. In monotonically fractured samples, no vacancy clusters have been found. If this difference holds as a general rule, positron lifetime spectroscopy would be suitable to distinguish quantitatively monotonic front fatigue fracture without any further fractographic studies.
BibTeX:
	@article{Egger2004,
	  author = {Egger, W. and Kögel, G. and Sperr, P. and Triftshäuser, W. and Bär, J. and Rödling, S. and Gudladt, H.-J.},
	  title = {Measurements of defect structures of a cyclically deformed Al-Mg-Si alloy by positron annihilation techniques},
	  journal = {Materials Science and Engineering A},
	  year = {2004},
	  volume = {387-389},
	  number = {1-2 SPEC. ISS.},
	  pages = {317--320},
	  note = {13th International Conference on Strength of Materials (ICSMA 13), Budapest, HUNGARY, AUG, 2003},
	  url = {http://www.sciencedirect.com/science/article/pii/S0921509304004563},
	  doi = {http://doi.org/10.1016/j.msea.2004.02.070}
	}
	
Positron Annihilation Spectroscopy in Polymers
F. Faupel, J. Kanzow, K. Gunther-Schade, C. Nagel, P. Sperr and G. Kögel; Materials Science Forum 445-446 (2004) 219-223.
Abstract: During the last decades positron annihilation has become a very powerful tool for the investigation of polymers. In particular, positron annihilation lifetime spectroscopy (PALS) yields valuable information on free volume and other properties. The present invited paper gives examples from recent research of the Kiel group. Generally, the so-called standard model, developed by Tao and Eldrup, is used to determine the size of free volume holes from the ortho-positronium (o-Ps) lifetime tau(oPs). Despite its success, the model resorts to several assumptions, including a spherical hole shape. Although the deviations from spherical shape are significant for holes above the size of positronium, average hole sizes V(h), determined by the standard model from T,p, show a good correlation with diffusivities D of inert gas molecules when plotted as 1/V(h) vs logD, as predicted by the free volume approach. The correlation can further be improved by taking into account the cohesive energy density of the polymers. The o-Ps intensity I(o-Ps) is often taken as a measure of the hole density. However, I(o-Ps) is also affected by the Ps formation probability and drops during mechanical milling of polymers due to formation of free radicals by chain scission, for instance. I(o-Ps), is also seen to change during phase separation in polymer blends. This can be explored to detect both, the binodal and the spinodal decomposition, already at the initial stage which is not easily accessible by other techniques. PALS was also used to study thermosets. Here we show in-situ results on the cross-linking of an epoxy resin. Finally, we demonstrate the benefits of the positron beam technique which allows investigations of polymer thin films and surfaces. For example, very recent results, obtained at the positron beam in Munich, on the structure and dynamics of epoxy films as function of film thickness will be presented.
BibTeX:
	@article{Faupel2004,
	  author = {Faupel, F. and Kanzow, J. and Gunther-Schade, K. and Nagel, C. and Sperr, P. and Kögel, G.},
	  title = {Positron Annihilation Spectroscopy in Polymers},
	  journal = {Materials Science Forum},
	  year = {2004},
	  volume = {445-446},
	  pages = {219--223},
	  note = {ICPA 13},
	  url = {http://www.scientific.net/MSF.445-446.219},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.445-446.219}
	}
	
Comparison of Vacancy Creation by Nuclear and Electronic Processes in Silicon Irradiated with Swift Kr and Bi Ions
P.M. Gordo, L. Liszkay, K. Havancsák, V.A. Skuratov, P. Sperr, W. Egger, C. Lopes Gil, A.P. de Lima and Z. Kajcsos; Materials Science Forum 445-446 (2004) 93-95.
Abstract: Silicon samples, irradiated with swift Kr (245 MeV) and Bi (710 MeV) ions at room temperature, were investigated using a continuous and a pulsed positron beam and conventional Doppler broadening and lifetime spectroscopy. In the fluence and depth ranges studied, creation of large voids and amorphization was not observed. The dominant defects were found to be divacancies, present from the near surface region all along the ion tracks. We found that the formation of divacancies from ion-induced vacancies as predicted by Monte-Carlo-calculations is higher in the case of the heavier Bi ion.
BibTeX:
	@article{Gordo2004,
	  author = {Gordo, P. M. and Liszkay, L. and Havancsák, K. and Skuratov, V. A. and Sperr, P. and Egger, W. and Lopes Gil, C. and de Lima, A. P. and Kajcsos, Z.},
	  title = {Comparison of Vacancy Creation by Nuclear and Electronic Processes in Silicon Irradiated with Swift Kr and Bi Ions},
	  journal = {Materials Science Forum},
	  year = {2004},
	  volume = {445-446},
	  pages = {93--95},
	  note = {ICPA 13},
	  url = {http://www.scientific.net/MSF.445-446.93},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.445-446.93}
	}
	
Untersuchung der Dynamik von DNA-Reparaturproteinen nach Bestrahlung lebender Zellen am Rasterionenmikroskop SNAKE.
Volker Hable; Diplomarbeit, Technische Universität München, 2004.
Abstract: In dieser Arbeit wurde die Dynamik der Reparaturvorgänge von DNA-Schäden in biologischen Zellen nach Schwerionenbestrahlung untersucht. Dazu wurden lebende HeLa-Zellen am Rasterionenmikroskop SNAKE mit 100MeV Sauerstoff-Ionen des Münchner 14MV Tandembeschleuniger bestrahlt. Die dort installierte Bestrahlungseinrichtung ermöglicht es, Zellkernen eine definierte Anzahl von Ionen und somit eine definierte Dosis mikroskopisch genau zu applizieren. Die erreichbare Strahlauflösung konnte im Rahmen dieser Arbeit mittels einer 50 Hz-Pulsung in x auf 0.55μm fwhm und in y auf 0.40μm verbessert werden. Durch die Entwicklung mikrostrukturierter Zellträgerfolien wurde das Auffinden der bestrahlten Zellen deutlich erleichtert und somit erstmals Experimente zur gezielten Bestrahlung einzelner Zellkerne ermöglicht.
Die schwersten Schäden, die hochenergetische Ionen in Zellkernen bewirken, sind Doppelstrangbrüche der DNA. Zu deren Reparatur stehen der Zelle verschiedene Mechanismen zur Verfügung. An der Reparatur direkt oder indirekt beteiligte Proteine
wie gH2AX, 53BP1, Rad51 und Mdc1 werden an Doppelstrangbrüchen angehängt und bilden sogenannte Foci aus. Ihre Funktion und Dynamik wurde in dieser Arbeit untersucht. Mittels biochemischer Prozesse wurden diese Proteine nach der Bestrahlung
angefärbt und unter dem Fluoreszenzmikroskop in einer Fokusserie abgebildet. So gewonnene und rechnergestützt entfaltete, dreidimensionale Bilder lieferten die Grundlage für eine quantitative Auswertung der Proteinverteilungen, um so die Dynamik der
Reparaturproteine zu studieren.
In Zeitreihenstudien wurde in der Zellkernmitte innerhalb der ersten 2 – 4 Stunden nach Bestrahlung ein Anwachsen der Focigröße (fwhm) von 1.2μm auf 1.5μm bei gH2AX und von 0.8μm auf 1.1μm bei 53BP1 beobachtet. In den folgenden zwei Stunden
fällt sie wieder in etwa auf den Anfangswert ab, und bleibt über 24 Stunden nahezu konstant. Am Zellkernrand wächst die Größe der gH2AX-Foci von ebenfalls 1.2μm innerhalb der ersten Stunde um knapp 0.1μm an und fällt daraufhin auf ca. 0.8μm
ab.
Des weiteren wurde die Bewegung der geschädigten DNA im Zellkern untersucht. Die hierbei gewonnenen Ergebnisse sind mit dem Modell einer Diffusion verträglich. Die Diffusionskonstante ließ sich zu (7 · 10^(−7) ± 4 · 10^(−7))μm^2/s bestimmen. Dabei waren keine signifikanten Unterschiede zwischen Zellkernmitte und -rand erkennbar.
Darüber hinaus wurde durch markiertes Bestrahlen zu zwei verschiedenen Zeitpunkten festgestellt, dass in Zellkernen, die gerade Doppelstrangbrüche reparieren, neu hinzukommende Strahlenschäden eine Unterversorgung von Protein 53BP1 erleiden.
Dieser Effekt tritt auf, wenn die Zeitdauer zwischen den beiden Bestrahlungen unter einer Stunde liegt.
BibTeX:
	@mastersthesis{Hable2004da,
	  author = {Hable, Volker},
	  title = {Untersuchung der Dynamik von DNA-Reparaturproteinen nach Bestrahlung lebender Zellen am Rasterionenmikroskop SNAKE.},
	  school = {Technische Universität München},
	  year = {2004}
	}
	
Microirradiation of cells with energetic heavy ions
A. Hauptner, S. Dietzel, G.A. Drexler, P. Reichart, R. Krücken, T. Cremer, A.A. Friedl and G. Dollinger; Radiation and Environmental Biophysics 42 (4) (2004) 237-245.
Abstract: The ion microprobe SNAKE at the Munich 14 MV tandem accelerator achieves beam focussing by a superconducting quadrupole doublet and can make use of a broad range of ions and ion energies, from 20 MeV protons to 200 MeV gold ions. Because of these properties, SNAKE is particularly attractive for biological microbeam experiments. Here we describe the adaptation of SNAKE for microirradiation of cell samples. This includes enlarging of the focal distance in order to adjust the focal plane to the specimen stage of a microscope, construction of a beam exit window in a flexible nozzle and of a suitable cell containment, as well as development of procedures for on-line focussing of the beam, preparation of single ions and scanning by electrostatic deflection of the beam. When irradiating with single 100 MeV 16O ions, the adapted set-up permits an irradiation accuracy of 0.91 µm (full width at half maximum) in the x-direction and 1.60 µm in the y-direction, as demonstrated by retrospective track etching of polycarbonate foils. Accumulation of the repair protein Rad51, as detected by immunofluorescence, was used as a biological track detector after irradiation of HeLa cells with geometric patterns of counted ions. Observed patterns of fluorescence foci agreed reasonably well with irradiation patterns, indicating successful adaptation of SNAKE. In spite of single ion irradiation, we frequently observed split fluorescence foci which might be explained by small-scale chromatin movements.
BibTeX:
	@article{Hauptner2004,
	  author = {Hauptner, A. and Dietzel, S. and Drexler, G. A. and Reichart, P. and Krücken, R. and Cremer, T. and Friedl, A. A. and Dollinger, G.},
	  title = {Microirradiation of cells with energetic heavy ions},
	  journal = {Radiation and Environmental Biophysics},
	  year = {2004},
	  volume = {42},
	  number = {4},
	  pages = {237--245},
	  url = {http://link.springer.com/article/10.1007%2Fs00411-003-0222-7},
	  doi = {http://doi.org/10.1007/s00411-003-0222-7}
	}
	
The Munich Microprobe Setup for Single-Ion Irradiation of Cells
A. Hauptner, G. Dollinger, G. Datzmann, H.-J. Körner, R. Krücken and P. Reichart; In: Proceedings of the 6th International Workshop/12th L. H. Gray Workshop: Microbeam Probes of Cellular Radiation ResponseMarch 29–31, 2003 , Radiation Research 161 (2004) 98 , Radiation Research Society.
BibTeX:
	@inproceedings{Hauptner2004a,
	  author = {Hauptner, A. and Dollinger, G. and Datzmann, G. and Körner, H.-J. and Krücken, R. and Reichart, P.},
	  title = {The Munich Microprobe Setup for Single-Ion Irradiation of Cells},
	  booktitle = {Proceedings of the 6th International Workshop/12th L. H. Gray Workshop: Microbeam Probes of Cellular Radiation ResponseMarch 29–31, 2003},
	  journal = {Radiation Research},
	  publisher = {Radiation Research Society},
	  year = {2004},
	  volume = {161},
	  number = {1},
	  pages = {98},
	  url = {http://www.rrjournal.org/toc/rare/161/1},
	  doi = {http://doi.org/10.1667/RR3091}
	}
	
NEPOMUC - the New Positron Beam Facility at FRM II
C. Hugenschmidt, G. Kögel, R. Repper, K. Schreckenbach, P. Sperr, B. Straßer and W. Triftshäuser; Materials Science Forum 445-446 (2004) 480-482.
Abstract: An in-pile positron source is installed in the vicinity of the reactor core of the new research reactor FRM-II. This neutron induced positron source at Munich NEPOMUC is based on absorption of high-energy prompt gamma-rays from thermal neutron capture in (113)Cd. For this purpose, a cadmium cap is placed inside the tip of the inclined beam tube SR 11 in the heavy water moderator tank. Inside the cadmium cap a structure of platinum foils is placed in order to convert the high-energy gamma-radiation into positron-electron pairs. Due to the negative positron work function, moderation in annealed platinum leads to emission of monoenergetic positrons. After acceleration to several keV by electrical lenses the positron beam is magnetically guided in a solenoid field of 7.5 mT. The beam profile is determined with a micro-channel plate (MCP) detector at the end of the beam line. In addition, a NaI-scintillator detects the 511 keV gamma-radiation of the positrons which annihilate at the front side of the MCP in order to perform intensity measurements as a function of acceleration energy and magnetic guide field.
BibTeX:
	@article{Hugenschmidt2004,
	  author = {Hugenschmidt, C. and Kögel, G. and Repper, R. and Schreckenbach, K. and Sperr, P. and Straßer, B. and Triftshäuser, W.},
	  title = {NEPOMUC - the New Positron Beam Facility at FRM II},
	  journal = {Materials Science Forum},
	  year = {2004},
	  volume = {445-446},
	  pages = {480--482},
	  note = {ICPA 13},
	  url = {http://www.scientific.net/MSF.445-446.480},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.445-446.480}
	}
	
The neutron induced positron source at Munich - NEPOMUC
C. Hugenschmidt, G. Kögel, R. Repper, K. Schreckenbach, P. Sperr, B. Straßer and W. Triftshäuser; Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 221 (1-4) (2004) 160-164.
Abstract: Monoenergetic positron beams of high intensity are of major interest in atomic and particle physics as well as in material science. The intensity of conventional positron beams using beta(+) sources amounts typically to 10(6) positrons per second. Therefore, great efforts are undertaken to generate positrons by pair production using bright gamma-sources, i.e. bremsstrahlung in a target at linear accelerators, gamma-radiation from the nuclear fission or high-energy prompt gamma-rays after thermal neutron capture. The NEutron induced POsitron source at MUniCh, NEPOMUC, is installed at the new research reactor FRM II. The world's highest positron intensity of up to 10(10) positrons per second is expected at this novel user dedicated positron beam facility. Since the final license for reactor operation was granted in May 2003 positrons will presently be available at FRM II. In this work, a brief overview of positron beams is given and the status of the positron project NEPOMUC as well as the linked experiments is reported.
BibTeX:
	@article{Hugenschmidt2004a,
	  author = {Hugenschmidt, C. and Kögel, G. and Repper, R. and Schreckenbach, K. and Sperr, P. and Straßer, B. and Triftshäuser, W.},
	  title = {The neutron induced positron source at Munich - NEPOMUC},
	  journal = {Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms},
	  year = {2004},
	  volume = {221},
	  number = {1-4},
	  pages = {160--164},
	  note = {12th International Workshop on Positron and Positronium Physics (POSITRON03), Aarhus Univ, Inst Phys & Astron, Sandbjerg, DENMARK, JUL 19-21, 2003},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X04003842},
	  doi = {http://doi.org/10.1016/j.nimb.2004.03.048}
	}
	
Physical properties of ALD-Al2O3 in a DRAM-capacitor equivalent structure comparing interfaces and oxygen precursors
S. Jakschik, U. Schroeder, T. Hecht, G. Dollinger, A. Bergmaier and J. Bartha; Materials Science and Engineering B: Solid-State Materials for Advanced Technology 107 (3) (2004) 251-254.
Abstract: Aluminum oxide was deposited on arsenic doped silicon, using atomic layer deposition (ALD) with either a silicon oxide or a silicon nitride interface. The physical properties of these films were investigated by elastic-recoil-detection, X-ray-photoelectron-spectroscopy and transmission electron microscopy. Special focus was given to contamination of the film and the interface, crystallization and temperature effect on diffusion. The films remained stoichiometric and did not have Al-Al clusters, even post annealing steps. Evidence of diffusion of silicon and arsenic into the dielectric and of aluminum from the film was found. Carbon and hydrogen were seen in the film and at the interface as well, whereas hydrogen diffused out of the film to some extent due to anneal. Carbon content in the layer was reduced by using O 3 as oxidant. Grain size of crystalline Al2O3 films was in the order of film thickness.
BibTeX:
	@article{Jakschik2004,
	  author = {Jakschik, S. and Schroeder, U. and Hecht, T. and Dollinger, G. and Bergmaier, A. and Bartha, J.W.},
	  title = {Physical properties of ALD-Al2O3 in a DRAM-capacitor equivalent structure comparing interfaces and oxygen precursors},
	  journal = {Materials Science and Engineering B: Solid-State Materials for Advanced Technology},
	  year = {2004},
	  volume = {107},
	  number = {3},
	  pages = {251--254},
	  note = {cited By (since 1996)11},
	  url = {http://www.sciencedirect.com/science/article/pii/S0921510703004835},
	  doi = {http://doi.org/10.1016/j.mseb.2003.09.044}
	}
	
Doping and its efficiency in a-SiOx:H
A. Janotta, R. Janssen, M. Schmidt, T. Graf, M. Stutzmann, L. Görgens, A. Bergmaier, G. Dollinger, C. Hammerl, S. Schreiber and B. Stritzker; Physical Review B - Condensed Matter and Materials Physics 69 (11) (2004) 1152061-11520616.
Abstract: Amorphous hydrogenated silicon suboxides (a-SiOx:H) deposited by plasma enhanced chemical vapor deposition have a band gap which can be tuned from 1.9 to 3.0 eV by varying the oxygen content [O] from 0 to 50 at. %. n- and p-type doping is realized by adding PH3 and B2H 6, respectively, to the source gases SiH4, H2, and CO2. Alloying with increasing amounts of oxygen reduces the average coordination number 〈r〉 from a value close to 4 (a-Si:H) to ≈2.7, which gradually approaches the ideal value of 〈r〉=2.4 for network glasses. This goes along with a softening of the amorphous SiO x network, i.e., a reduction of the mechanical hardness of the material, which is also predicted by rigidity percolation theory. Also the incorporation of dopant atoms into electrically active, fourfold coordinated sites becomes more unlikely with increasing [O]. As a consequence, n- and p-type doped SiOx shows increasingly intrinsic character for higher oxygen concentrations. Doping fails for values of 〈r〉<3 and the doping efficiency tends towards zero. Thus, an overall fourfold coordination was found to be a crucial requirement for efficient doping in amorphous semiconductors.
BibTeX:
	@article{Janotta2004,
	  author = {Janotta, A. and Janssen, R. and Schmidt, M. and Graf, T. and Stutzmann, M. and Görgens, L. and Bergmaier, A. and Dollinger, G. and Hammerl, C. and Schreiber, S. and Stritzker, B.},
	  title = {Doping and its efficiency in a-SiOx:H},
	  journal = {Physical Review B - Condensed Matter and Materials Physics},
	  year = {2004},
	  volume = {69},
	  number = {11},
	  pages = {1152061-11520616},
	  note = {cited By (since 1996)20},
	  url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.69.115206},
	  doi = {http://doi.org/10.1103/PhysRevB.69.115206}
	}
	
Investigation of Fatigue Cracks in an Al-Based Alloy by Means of Pulsed Positron (Micro-)Beams
G. Kögel, W. Egger, S. Rödling and H.-J. Gudladt; Materials Science Forum 445-446 (2004) 126-128.
Abstract: Positron lifetime studies have been undertaken with the Munich pulsed beam and the scanning positron microscope to investigate areas close to fatigue cracks of a precipitation-hardened AlMgSi (6013) alloy. These cracks were initiated by cyclic loading under full automatic stress and crack length control. Close to the surface of fatigue cracks, always three lifetimes of about 245 ps, 300 - 500 ps and 1200 - 2500 ps are observed which are attributed to annihilations at dislocations, vacancy clusters and voids. These defects are believed to indicate remnants of dislocation interactions within the cyclic plastic zone in front of the fatigue crack tip.
BibTeX:
	@article{Koegel2004,
	  author = {Kögel, G. and Egger, W. and Rödling, S. and Gudladt, H.-J.},
	  title = {Investigation of Fatigue Cracks in an Al-Based Alloy by Means of Pulsed Positron (Micro-)Beams},
	  journal = {Materials Science Forum},
	  year = {2004},
	  volume = {445-446},
	  pages = {126--128},
	  note = {ICPA 13},
	  url = {http://www.scientific.net/MSF.445-446.126},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.445-446.126}
	}
	
Vacancy defects in epitaxial InN: Identification and electrical properties
A. Laakso, J. Oila, A. Kemppinen, K. Saarinen, W. Egger, L. Liszkay, P. Sperr, H. Lu and W.J. Schaff; Journal of Crystal Growth 269 (1) (2004) 41-49.
Abstract: We have used a low-energy positron beam to identify and quantify the dominant vacancy defects in InN layers grown on Al2O3 by molecular beam epitaxy. By applying both continuous and pulsed positron beams, we can show that In vacancies are formed during the crystal growth. Their concentration decreases from similar to 5 x 10(18); to below loll cm(-3) with increasing layer thickness (120-800 nm). The In vacancy concentration correlates with the free electron concentration and decreases with increasing electron Hall mobility. These results suggest that In vacancies act as both compensating defects and electron scattering centers in InN films.
BibTeX:
	@article{Laakso2004,
	  author = {Laakso, A. and Oila, J. and Kemppinen, A. and Saarinen, K. and Egger, W. and Liszkay, L. and Sperr, P. and Lu, H. and Schaff, W. J.},
	  title = {Vacancy defects in epitaxial InN: Identification and electrical properties},
	  journal = {Journal of Crystal Growth},
	  year = {2004},
	  volume = {269},
	  number = {1},
	  pages = {41--49},
	  note = {1st International Workshop on Indium Nitride, Fremantle, AUSTRALIA, NOV 16-20, 2003},
	  url = {http://www.sciencedirect.com/science/article/pii/S0022024804001800},
	  doi = {http://doi.org/10.1016/j.jcrysgro.2004.02.032}
	}
	
Positron Beam Splitter at the High Intensity Positron Beam in Munich
L. Liszkay, G. Kögel, P. Sperr, W. Egger, C. Hugenschmidt and W. Triftshäuser; Materials Science Forum 445-446 (2004) 492-494.
Abstract: The high intensity positron source at the new research reactor FRM-II in Munich will be used to serve three instruments simultaneously: a scanning positron microscope, a pulsed positron beam and a system for positron induced Auger electron spectroscopy. In order to split the continuous beam into three parts with variable intensity, a beam splitter is being built. The device consists of an electrostatic optical system embedded in the constant magnetic guiding field of the beam line. In the first stage an electrostatic quadrupole is used to change the cross section of the beam into an ellipse. The resulting beam is then split into three parts by two pairs of deflection plates. The central part is transported to the microscope without deflection. The beam intensities can be varied by mechanical movement of the plates. At the exit port of the beam splitter the guiding magnetic field is split into three beamlines with the help of a magnetic shield made of mumetal.
BibTeX:
	@article{Liszkay2004,
	  author = {Liszkay, L. and Kögel, G. and Sperr, P. and Egger, W. and Hugenschmidt, C. and Triftshäuser, W.},
	  title = {Positron Beam Splitter at the High Intensity Positron Beam in Munich},
	  journal = {Materials Science Forum},
	  year = {2004},
	  volume = {445-446},
	  pages = {492--494},
	  note = {ICPA 13},
	  url = {http://www.scientific.net/MSF.445-446.492},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.445-446.492}
	}
	
Antireflection foils with multi-layer converter for ultracold neutron detectors
P. Maier-Komor, I. Altarev, A. Bergmaier, P. Böni, G. Dollinger, R. Krücken, S. Paul and W. Schott; Nuclear Instruments and Methods in Physics Research Section A 521 (1) (2004) 242-246.
Abstract: For experiments at the ultracold neutron (UCN) source of the new high-luminosity neutron source, Forschungsreaktor München II (FRM II), highly efficient detectors are needed. The desired type of detectors utilizes 6Li as the neutron converter based on the huge cross-section reaction 6Li(n,α)t and detection of the 2.06MeV α-particles or the 2.73MeV t-particles. The high reflectance of UCN from 6Li with its positive optical potential must be compensated by a material with negative optical potential. Instead of the expensive 62Ni material, natural Ti can be chosen. It was demonstrated that neither 6Li metal nor Ti metal can be deposited in a high-vacuum evaporation apparatus without creating a positive optical potential and thus increasing the reflectivity for the UCN due to oxygen impurities coming from the H2O partial pressure in the high-vacuum system. To overcome these problems, a new UHV evaporation apparatus was developed and built which is capable of reaching a vacuum in the 10-10 Pa range. Such a good vacuum can be obtained only when annealing the vacuum system up to 470K. At such a high annealing temperature the silicon detectors for the α- and t particles might suffer degradation of their energy resolution. Therefore, the multi-layer system of 6Li and natTi is not deposited directly on the silicon detector but a thin rolled Ti foil is applied as backing. A test deposition of 200 double layers of 6LiF/ 62Ni on a thin Ti foil is described and a report is given about the setup of the new UHV evaporation apparatus.
BibTeX:
	@article{Maier-Komor2004,
	  author = {Maier-Komor, P. and Altarev, I. and Bergmaier, A. and Böni, P. and Dollinger, G. and Krücken, R. and Paul, S. and Schott, W.},
	  title = {Antireflection foils with multi-layer converter for ultracold neutron detectors},
	  journal = {Nuclear Instruments and Methods in Physics Research Section A},
	  year = {2004},
	  volume = {521},
	  number = {1},
	  pages = {242--246},
	  editor = {Green J.P., Maier-Komor P.},
	  note = {cited By (since 1996)1},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168900203030936},
	  doi = {http://doi.org/10.1016/j.nima.2003.11.179}
	}
	
A new UHV system for the preparation of carbon stripper foils by laser plasma ablation deposition
P. Maier-Komor, G. Dollinger and R. Krücken; Nuclear Instruments and Methods in Physics Research Section A 521 (1) (2004) 176-182.
Abstract: Laser plasma ablation of spectroscopically pure graphite under UHV conditions is a well established method for the preparation of thin carbon stripper foils. Such foils with their structure of randomly oriented nanocrystallites can best withstand ion irradiation damage. Accelerator users around the world are interested in this type of carbon stripper foils due to a guaranteed reproducibility, quality, thickness and uniformity given by the procedure. In addition a high reproducible yield with a low effort for floating, mounting and slackening is desired. Users of high-energy accelerators want to profit from this development, but need stripper foils of up to 500 μg/cm 2 for the relevant charge state equilibrium whereas carbon foils of this type could only be prepared with an upper limit of 10 μg/cm2 in the existing set up. The new design was aimed to overcome all thickness limitations. The crucial component of the laser plasma ablation technique is the laser entrance window which becomes opaque during carbon ablation. A new plant which overcomes this problem is being assembled. Due to a higher source-to-window distance and a better laser light transmission, caused by slightly changed laser plasma conditions, the life of the laser entrance window before exchange could be prolonged by a factor of five. Presumably, there are no thickness limitations anymore due to a vacuum interlock that permits the exchange of the entrance window without breaking the vacuum in the ablation-deposition chamber.
BibTeX:
	@article{Maier-Komor2004a,
	  author = {Maier-Komor, P. and Dollinger, G. and Krücken, R.},
	  title = {A new UHV system for the preparation of carbon stripper foils by laser plasma ablation deposition},
	  journal = {Nuclear Instruments and Methods in Physics Research Section A},
	  year = {2004},
	  volume = {521},
	  number = {1},
	  pages = {176--182},
	  editor = {Green J.P., Maier-Komor P.},
	  note = {cited By (since 1996)4},
	  url = {http://www.sciencedirect.com/science/article/pii/S016890020303081X},
	  doi = {http://doi.org/10.1016/j.nima.2003.11.148}
	}
	
Influence of layer thickness on the formation of in vacancies in InN grown by molecular beam epitaxy
J. Oila, A. Kemppinen, A. Laakso, K. Saarinen, W. Egger, L. Liszkay, P. Sperr, H. Lu and W.J. Schaff; Applied Physics Letters 84 (9) (2004) 1486-1488.
Abstract: We have used a low-energy positron beam to identify In vacancies in InN layers grown on Al2O3 by molecular beam epitaxy. Their concentration decreases from similar to5x10(18) to below 10(16) cm(-3) with increasing layer thickness (120-800 nm). The decrease in the vacancy concentration coincides with the increase in the electron Hall mobility, suggesting that In vacancies act as electron scattering centers.
BibTeX:
	@article{Oila2004,
	  author = {Oila, J. and Kemppinen, A. and Laakso, A. and Saarinen, K. and Egger, W. and Liszkay, L. and Sperr, P. and Lu, H. and Schaff, W. J.},
	  title = {Influence of layer thickness on the formation of in vacancies in InN grown by molecular beam epitaxy},
	  journal = {Applied Physics Letters},
	  year = {2004},
	  volume = {84},
	  number = {9},
	  pages = {1486-1488},
	  url = {http://scitation.aip.org/content/aip/journal/apl/84/9/10.1063/1.1651327},
	  doi = {http://doi.org/10.1063/1.1651327}
	}
	
Defect structural characterization of organic polymer layers
O. Osiele, D. Britton, M. Härting, P. Sperr, M. Topic, S. Shaheen and H. Branz; Journal of Non-Crystalline Solids 338-340 (1 SPEC. ISS.) (2004) 612-616.
Abstract: In this paper, we study the effect of blending the conducting polymers, P3HT with the fullerene complex PCBM on its structural and defect characteristics. The films were deposited on glass substrates by spin casting, and were characterized with positron annihilation, microscopy and other techniques with regard to thickness, and structural homogeneity. The unblended polymers have positron annihilation characteristics similar to most non-polar polymers, exhibiting a relatively broad electron momentum distribution, a long-lived ( > 1 ns) positron state corresponding to the formation of orthopositronium, and strong-localization of the positron. Blending with PCBM causes the sample electron momentum distribution to narrow, and results in a single state with a lifetime of around 370 ps in both polymer mixtures. We postulate that this state corresponds to annihilation with low-momentum electrons in the fullerene cage.
BibTeX:
	@article{Osiele2004,
	  author = {Osiele, O.M. and Britton, D.T. and Härting, M. and Sperr, P. and Topic, M. and Shaheen, S.E. and Branz, H.M.},
	  title = {Defect structural characterization of organic polymer layers},
	  journal = {Journal of Non-Crystalline Solids},
	  year = {2004},
	  volume = {338-340},
	  number = {1 SPEC. ISS.},
	  pages = {612--616},
	  note = {20th International Conference on Amorphous and Microcrystalline Semiconductors, Campos do Jordao, BRAZIL, AUG 25-29, 2003},
	  url = {http://www.sciencedirect.com/science/article/pii/S0022309304002224},
	  doi = {http://doi.org/10.1016/j.jnoncrysol.2004.03.053}
	}
	
Positron Annihilation Characteristics of Polymer Films for Photovoltaic Applications
O. Osiele, D. Britton, M. Härting, P. Sperr, M. Topic, S. Shaheen and H. Branz; Materials Science Forum 445-446 (2004) 337-339.
Abstract: In this paper we study the effect of combining the conducting polymers, P3HT and OC(1)C(10)-PPV with the fullerene complex PCBM, on its positron annihilation characteristics. The films were deposited on glass substrates by spin casting, and were also characterised with scanning electron microscopy with regard to thickness, and structural homogeneity. Both pure polymers have positron annihilation characteristics similar to most non-polar polymers, exhibiting a relatively broad electron momentum distribution, a long-lived (>1 ns) positron state corresponding to the formation of ortho-positronium, and strong-localisation of the positron. Mixing with PCBM causes the sampled electron momentum distribution to narrow, and results in a single annihilation state with a lifetime of around 370 ps in both polymer mixtures. We postulate that this state corresponds to annihilation with the low-momentum electrons in the fullerene cage.
BibTeX:
	@article{Osiele2004a,
	  author = {Osiele, O.M. and Britton, D.T. and Härting, M. and Sperr, P. and Topic, M. and Shaheen, S.E. and Branz, H.M.},
	  title = {Positron Annihilation Characteristics of Polymer Films for Photovoltaic Applications},
	  journal = {Materials Science Forum},
	  year = {2004},
	  volume = {445-446},
	  pages = {337--339},
	  note = {ICPA 13},
	  url = {http://www.scientific.net/MSF.445-446.337},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.445-446.337}
	}
	
Three-Dimensional Hydrogen Microscopy in Diamond
P. Reichart, G. Datzmann, A. Hauptner, R. Hertenberger, C. Wild and G. Dollinger; Science 306 (5701) (2004) 1537-1540.
Abstract: A microprobe of protons with an energy of 17 million electron volts is used to quantitatively image three-dimensional hydrogen distributions at a lateral resolution better than 1 micrometer with high sensitivity. Hydrogen images of a -textured undoped polycrystalline diamond film show that most of the hydrogen is located at grain boundaries. The average amount of hydrogen atoms along the grain boundaries is (8.1 ± 1.5) × 1014 per square centimeter, corresponding to about a third of a monolayer. The hydrogen content within the grain is below the experimental sensitivity of 1.4 × 1016 atoms per cubic centimeter (0.08 atomic parts per million). The data prove a low hydrogen content within chemical vapor deposition–grown diamond and the importance of hydrogen at grain boundaries, for example, with respect to electronic properties of polycrystalline diamond.
BibTeX:
	@article{Reichart2004,
	  author = {Reichart, P. and Datzmann, G. and Hauptner, A. and Hertenberger, R. and Wild, C. and Dollinger, G.},
	  title = {Three-Dimensional Hydrogen Microscopy in Diamond},
	  journal = {Science},
	  year = {2004},
	  volume = {306},
	  number = {5701},
	  pages = {1537-1540},
	  url = {http://www.sciencemag.org/content/306/5701/1537.abstract},
	  doi = {http://doi.org/10.1126/science.1102910}
	}
	
3D hydrogen microscopy with sub-ppm detection limit
P. Reichart, G. Dollinger, A. Bergmaier, G. Datzmann, A. Hauptner, H.-J. Körner and R. Krücken; Nuclear Instruments and Methods in Physics Research Section B 219-220 (1-4) (2004) 980-987.
Abstract: Coincident elastic proton-proton scattering at a 17 MeV microprobe is used to investigate hydrogen distributions on microscopic scale inside freestanding samples up to some 100 μm thickness. Hydrogen imaging at atomic ppm level needs a total count rate of about 100 kHz of scattered protons in order to get sufficient statistics from the small fraction of coincident hydrogen signals. It is obtained using a highly segmented silicon strip detector of 2.3 sr for proton currents of less than 100 pA impinging on films thicker 10 μm. A five level filter almost completely suppresses accidental coincidences. The sensitivity of this kind of 3D hydrogen microscopy is demonstrated by the analysis of a 55 μm thick synthetic diamond layer showing a detection limit of 0.08 at-ppm hydrogen. In addition, the proposed depth resolution of 3-6 μm is experimentally confirmed and a lateral resolution of 0.6 μm full width half maximum is obtained at a significant hydrogen enhancement inside the layer.
BibTeX:
	@article{Reichart2004a,
	  author = {Reichart, P. and Dollinger, G. and Bergmaier, A. and Datzmann, G. and Hauptner, A. and Körner, H.-J. and Krücken, R.},
	  title = {3D hydrogen microscopy with sub-ppm detection limit},
	  booktitle = {Proceedings of the Sixteenth International Conference on Ion Beam Analysis},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2004},
	  volume = {219-220},
	  number = {1-4},
	  pages = {980--987},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X04002502},
	  doi = {http://doi.org/10.1016/j.nimb.2004.01.200}
	}
	
Dreidimensionale Wasserstoffmikroskopie mittels Proton-Proton-Streuung
Patrick Reichart; Dissertation, Technische Universität München, 2004.
Abstract: Mit der Methode der Proton-Proton-Streuung zum Wasserstoffnachweis wurde ein Verfahren entwickelt, um unter Einsatz eines fokussierten 17 MeV Protonenstrahls Wasserstoffverteilungen auf mikroskopischer Skala quantitativ mit einer sub-ppm Nachweisgrenze dreidimensional abzubilden. Die Realisierung am Rasterionenmikroskop SNAKE am Münchener 14 MV Tandembeschleuniger mit einem großen ringförmigen, segmentierten Detektor und einem komplexen Analysesystem ermöglicht eine Nachweisgrenze von 0.08 at-ppm bei einer lateralen Auflösung von 0.6 μm und einer Tiefenauflösung besser als 5 μm. Mit den hohen Protonenenergien können Proben bis einige 100 μm untersucht werden. Damit konnte erstmals nachgewiesen werden, dass in künstlich hergestellten polykristallinen Diamantschichten der Wasserstoff hauptsächlich an den Korngrenzen lokalisiert ist. In weiteren Experimenten wird das Potential für zukünftige Anwendungen zur Untersuchung organischer Materialien oder innerer Grenzflächen demonstriert.
BibTeX:
	@phdthesis{Reichart2004diss,
	  author = {Reichart, Patrick},
	  title = {Dreidimensionale Wasserstoffmikroskopie mittels Proton-Proton-Streuung},
	  school = {Technische Universität München},
	  year = {2004},
	  url = {http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:91-diss2004030314833}
	}
	
Positron annihilation Investigations of defects in copper alloys selected for nuclear fusion technology
V. Slugeň, J. Kuriplach, P. Ballo, P. Domonkos, G. Kögel, P. Sperr, W. Egger, W. Triftshäuser, V.M. Domankova, P. Kovac, I. Vavra, S. Stancek, M. Petriska and A. Zeman; Fusion Engineering and Design 70 (2) (2004) 141-153.
Abstract: A positron annihilation spectroscopy (PAS) based on positron lifetime measurements, using the pulsed low energy positron system (PLEPS), is used to investigate defects create by hydrogen implantation and thermal treat of copper alloys. These alloys are designated for the use in the international thermonuclear experimental reactor (ITER). The results show that the changes in the microstructure of selected copper alloys (CuCrZr, CuAl25) depend strongly on the preparing technology of alloys as well as on the implantation dose experimentally simulating the neutron treatment. The full recovering of the structure after isochronal annealing in vacuum is observed in all implanted specimens at the temperature of 450 °C. Using the PLEPS technique, for the first time, depth profiling of the positron lifetime spectra in the near-surface region (20-500 nm) of hydrogen implanted copper alloys was performed and compared with the TRIM calculations and transmission electron microscopy (TEM) studies. Possible annihilation channels in CuCrZr and CuAl25 materials are discussed in details together with corresponding annihilation characteristics determined theoretically and using computer simulations. We discuss the results of positron lifetime measurements of the irradiated and non-irradiated CuZrCr and CuAl25 specimens. We identified the most probable types of positron trapping sites. Finally, the results are discussed in terms of microstructural changes of the studied materials upon irradiation and subsequent heat treatment.
BibTeX:
	@article{Slugen2004,
	  author = {Slugeň, V. and Kuriplach, J. and Ballo, P. and Domonkos, P. and Kögel, G. and Sperr, P. and Egger, W. and Triftshäuser, W. and Domankova, V. M. and Kovac, P. and Vavra, I. and Stancek, S. and Petriska, M. and Zeman, A.},
	  title = {Positron annihilation Investigations of defects in copper alloys selected for nuclear fusion technology},
	  journal = {Fusion Engineering and Design},
	  year = {2004},
	  volume = {70},
	  number = {2},
	  pages = {141--153},
	  url = {http://www.sciencedirect.com/science/article/pii/S0920379603004691},
	  doi = {http://doi.org/10.1016/j.fusengdes.2003.10.002}
	}
	
Investigation of Defects in Copper Alloys Selected for Nuclear Fusion Technology
V. Slugeň, G. Kögel, J. Kuriplach, P. Ballo, P. Sperr, W. Egger, W. Triftshäuser, P. Domonkos, M. Petriska and A. Zeman; Materials Science Forum 445-446 (2004) 183-185.
Abstract: Positron lifetime measurements using a Pulsed Low Energy Positron System (PLEPS) were applied to the investigation of defects in hydrogen implanted and subsequently thermally treated copper alloys which are designated for the use in the International Thermonuclear Experimental Reactor (ITER). PLEPS results showed that the changes in the microstructure of selected copper-alloys (CuCrZr, CuAl25) depend strongly on the preparing technology of alloys and on the implantation dose. The full recovery of the structure after isochronal annealing in vacuum in a region of 100-600 °C was observed in all implanted specimens at a level of about 450 °C. With the PLEPS technique, for the first time, depth profiling of the near-surface region (20-500 nm) of hydrogen implanted copper alloys was performed and compared with the transmission electron microscopy (TEM) studies.
BibTeX:
	@article{Slugen2004a,
	  author = {Slugeň, V. and Kögel, G. and Kuriplach, J. and Ballo, P. and Sperr, P. and Egger, W. and Triftshäuser, W. and Domonkos, P. and Petriska, M. and Zeman, A.},
	  title = {Investigation of Defects in Copper Alloys Selected for Nuclear Fusion Technology},
	  journal = {Materials Science Forum},
	  year = {2004},
	  volume = {445-446},
	  pages = {183--185},
	  note = {ICPA 13},
	  url = {https://www.scientific.net/MSF.445-446.183},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.445-446.183}
	}
	
Positron Microprobes
W. Triftshäuser; Materials Science Forum 445-446 (2004) 452-456.
Abstract: The history of the concept and the attempts for the realisation of a positron microprobe as well as the present state of development will be reviewed and evaluated. The principle and the design of a scanning positron microscope (SPM), built and operated at our university in Munich, will be presented. A pulsed positron beam, with a variable energy from 0.5 to 20 keV and a final spot diameter of currently 2 mum, can be electronically scanned over an area of 0.6 mm x 0.6 mm. In this way, microscopic regions of 2 mum x 2 mum x 0.1 mum can be evaluated. This beam is formed after a double-stage moderation of positrons emitted from a radioactive isotope acting as primary positron source. In the first stage, the beam spot of about 3 nun is reduced to a diameter of less than 20 mum. After the second moderation stage, this diameter is then further reduced to 2 mum. This is possible, due to the special properties of the magnetic lenses used in the design. In order to enable positron lifetime measurements, the positron beam is pulsed (time interval 20 ns). This feature makes this SPM the first and up to now only system worldwide. Included in the system is a conventional scanning electron microprobe for surface analysis and for the selection of interesting regions. Three-dimensional positron lifetime spectra of mechanically damaged and fatigued specimens will be presented. The real potential power of the SPM will be achieved when the intense reactor-based positron source at the new Munich research reactor FRM-II can be used, which will be possible now in the very near future.
BibTeX:
	@article{Triftshaeuser2004,
	  author = {Triftshäuser, W.},
	  title = {Positron Microprobes},
	  journal = {Materials Science Forum},
	  year = {2004},
	  volume = {445-446},
	  pages = {452--456},
	  note = {ICPA 13},
	  url = {http://www.scientific.net/MSF.445-446.452},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.445-446.452}
	}
	
Errors in near-surface and interfacial profiling of boron and arsenic
W. Vandervorst, T. Janssens, B. Brijs, T. Conard, C. Huyghebaert, J. Frühauf, A. Bergmaier, G. Dollinger, T. Buyuklimanli, J. VandenBerg and K. Kimura; Applied Surface Science 231-232 (2004) 618-631.
Abstract: To get an insight in the diffusion behavior of dopants such as arsenic and boron after annealing and in particular their segregation characteristics towards the interface in oxide structures on silicon, it is necessary to probe the dopant profile with very high accuracy and depth resolution. Sputter depth profiling as employed in secondary ion mass spectrometry (SIMS) is frequently used as the most suited tool for dopant profiling in view of its sensitivity and depth resolution. However in order to determine the segregated arsenic/boron peak, sub-nanometer depth resolution is required and artifacts such as beam induced broadening effects, potential ionization yield changes at interfaces, transient sputter yields need to be considered in detail. When reducing the primary beam energy the depth resolution can be improved and sub-nanometer depth sensitivity can be demonstrated. However comparisons with high resolution elastic recoil detection analysis demonstrate that it is at present impossible to obtain a reliable depth profile in the first nanometer near the surface nor even in the oxide part of the profile, where no ionization nor sputter yield transients are expected. Enhanced beam induced migration of boron during the initial phase of the bombardment needs to be invoked to explain the results. The latter appears to be enhanced under conditions (∼normal incidence) where full oxidation occurs.
BibTeX:
	@article{Vandervorst2004,
	  author = {Vandervorst, W. and Janssens, T. and Brijs, B. and Conard, T. and Huyghebaert, C. and Frühauf, J. and Bergmaier, A. and Dollinger, G. and Buyuklimanli, T. and VandenBerg, J.A. and Kimura, K.},
	  title = {Errors in near-surface and interfacial profiling of boron and arsenic},
	  journal = {Applied Surface Science},
	  year = {2004},
	  volume = {231-232},
	  pages = {618--631},
	  note = {cited By (since 1996)36},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433204003630},
	  doi = {http://doi.org/10.1016/j.apsusc.2004.03.125}
	}
	
Basic aspects of deep lithography with particles for the fabrication of micro-optical and micro-mechanical structures
B. Volckaerts, P. Vynck, M. Vervaeke, L. Cosentino, P. Finocchiaro, P. Reichart, G. Datzmann, A. Hauptner, G. Dollinger, A. Hermanne and H. Thienpont; In: , P. Daele and J. Mohr (Ed.), Proc. SPIE 5454, Micro-Optics: Fabrication, Packaging, and Integration 5454 (2004) 52-63 , SPIE.
Abstract: The strength of today's deep lithographic micro-machining technologies is their ability to fabricate monolithic building-blocks including optical and mechanical functionalities that can be precisely integrated in more complex photonic systems. In this contribution we present the physical aspects of Deep Lithography with ion Particles (DLP). We investigate the impact of the ion mass, energy and fluence on the developed surface profile to find the optimized irradiation conditions for different types of high aspect ratio micro-optical structures. To this aim, we develop a software program that combines the atomic interaction effects with the macroscopic beam specifications. We illustrate the correctness of our simulations with experimental data that we obtained in a collaboration established between the accelerator facilities at TUM, LNS and VUB. Finally, we review our findings and discuss the strengths and weaknesses of DLP with respect to Deep Lithography with X-rays (LIGA).
BibTeX:
	@inproceedings{Volckaerts2004,
	  author = {Volckaerts, B. and Vynck, P. and Vervaeke, M. and Cosentino, L. and Finocchiaro, P. and Reichart, P. and Datzmann, G. and Hauptner, A. and Dollinger, G. and Hermanne, A. and Thienpont, H.},
	  title = {Basic aspects of deep lithography with particles for the fabrication of micro-optical and micro-mechanical structures},
	  booktitle = {Proc. SPIE 5454, Micro-Optics: Fabrication, Packaging, and Integration},
	  publisher = {SPIE},
	  year = {2004},
	  volume = {5454},
	  number = {52},
	  pages = {52--63},
	  editor = {Daele P., Mohr J.},
	  note = {cited By (since 1996)0},
	  url = {http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=845728},
	  doi = {http://doi.org/10.1117/12.547718}
	}
	

2003

Diamond diodes and transistors
A. Aleksov, A. Denisenko, M. Kunze, A. Vescan, A. Bergmaier, G. Dollinger, W. Ebert and E. Kohn; Semiconductor Science and Technology 18 (3) (2003) 59-S66.
Abstract: Over the past few years a variety of diamond electron devices have been fabricated, analysed and simulated. This includes Schottky diodes on boron-doped p+ diamond substrates, boron/nitrogen pn-junction diodes, bipolar transistors based on this pn-junction and field effect transistors (FETs) with boron delta-doped channels and hydrogen-related surface conductive layers. Many of the fabricated devices considered here represent the current state-of-the-art in this field. This includes the operation of diamond Schottky diodes at temperatures of up to 1000 °C, as well as diamond FET devices with a cut-off frequency of 30 GHz and channel current densities of 300 mA mm-1. Simulations show that diamond boron delta-doped FETs might yield an RF-output power density of up to 30 W mm-1.
BibTeX:
	@article{Aleksov2003,
	  author = {Aleksov, A. and Denisenko, A. and Kunze, M. and Vescan, A. and Bergmaier, A. and Dollinger, G. and Ebert, W. and Kohn, E.},
	  title = {Diamond diodes and transistors},
	  journal = {Semiconductor Science and Technology},
	  year = {2003},
	  volume = {18},
	  number = {3},
	  pages = {59-S66},
	  note = {cited By (since 1996)40},
	  url = {http://iopscience.iop.org/article/10.1088/0268-1242/18/3/308/meta},
	  doi = {http://doi.org/10.1088/0268-1242/18/3/308}
	}
	
Diamond field effect transistors - Concepts and challenges
A. Aleksov, M. Kubovic, N. Kaeb, U. Spitzberg, A. Bergmaier, G. Dollinger, T. Bauer, M. Schreck, B. Stritzker and E. Kohn; Diamond and Related Materials 12 (3-7) (2003) 391-398.
Abstract: Field effect transistors (FETs) in diamond should outperform FET structures on other wide bandgap materials like SiC and GaN in high power/high temperature applications due to the ideal diamond materials properties. However, the technology of these structures proved difficult leaving two device concepts to investigate: (1) the boron δ-doped p-channel FET and (2) the hydrogen induced p-type surface-channel-FET. The δ-channel-FET approach follows a traditional design path of power FET structures. Here, simulation results have enabled the extrapolation of a maximum RF output power to 27 W/mm, a value which is indeed higher than for any FET based on III-Nitrides or SiC. However, due to the narrow technological parameter window, fabricated δ-channel-FETs are still well behind expectations. In contrast, concerning the surface-channel-FET the physical/chemical nature of its channel remains still under discussion. Nevertheless, results obtained with this FET concept yielded a VDmax > 200 V (LG = 1 μm) and a IDmax > 360 mA/mm a fT = 11.5 GHz and fmaxU > 40 GHz (LG = 0.2 μm) and a recently obtained RF power measurement at 1 GHz. Furthermore, the 1 GHz power measurement result has been obtained on a diamond quasi-substrate grown on a Ir/SrTiO3 substrate. This result may therefore open up the perspective for wafer scale diamond electronics.
BibTeX:
	@article{Aleksov2003a,
	  author = {Aleksov, A. and Kubovic, M. and Kaeb, N. and Spitzberg, U. and Bergmaier, A. and Dollinger, G. and Bauer, Th. and Schreck, M. and Stritzker, B. and Kohn, E.},
	  title = {Diamond field effect transistors - Concepts and challenges},
	  journal = {Diamond and Related Materials},
	  year = {2003},
	  volume = {12},
	  number = {3-7},
	  pages = {391--398},
	  note = {cited By (since 1996)62},
	  url = {http://www.sciencedirect.com/science/article/pii/S0925963502004016},
	  doi = {http://doi.org/10.1016/S0925-9635(02)00401-6}
	}
	
Median implantation depth and implantation profile of 3-18 keV positrons in amorphous polymers
J. Algers, P. Sperr, W. Egger, G. Kögel and F. Maurer; Physical Review B - Condensed Matter and Materials Physics 67 (12) (2003) 1254041-1254047.
Abstract: Most applications of positron beams require knowledge of the implantation characteristics for an appropriate interpretation of the experimental data. In this work, the median implantation depth as a function of implantation energy, z1/2(E), of 3-18 keV positrons and their implantation profile P(z, E) in a total of 13 thin films of atactic polystyrene, poly(styrene-co-acrylonitrile), and polymethylmethacrylate spin coated onto a silicon substrate were determined from positron lifetime measurements using a pulsed, low-energy positron beam. z1/2(E) and P(z,E) were determined from the measurement of the ortho-positronium yield obtained from the intensity I3 of the long lifetime, z1/2(E) was parametrized with the commonly used power-law fit z1/2(E) = (A/ρ)En, with ρ and E in units of g cm-3 and keV, respectively, yielding A = 2.81(± 0.2) μg cm-2 and n = 1.71(± 0.05). Excellent agreement between amorphous polymer and literature data on A1 and Cu suggests that the median implantation depth of positrons for low- to medium-Z materials in the studied energy range is independent of structure and only a function of mass density. Fitting of the Makhovian implantation profile to the experimental data suggested that the value of the parameter m varies between 1.7 and 2.3, systematically increasing with z at constant implantation energy, but is independent of the implantation energy. Using an equation proposed by Baker et al., the experimental data of 12 of the 13 studied polymer films could be described with a slightly better agreement than the Makhovian equation.
BibTeX:
	@article{Algers2003,
	  author = {Algers, J. and Sperr, P. and Egger, W. and Kögel, G. and Maurer, F.H.J.},
	  title = {Median implantation depth and implantation profile of 3-18 keV positrons in amorphous polymers},
	  journal = {Physical Review B - Condensed Matter and Materials Physics},
	  year = {2003},
	  volume = {67},
	  number = {12},
	  pages = {1254041--1254047},
	  url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.67.125404},
	  doi = {http://doi.org/10.1103/PhysRevB.67.125404}
	}
	
Physical characterization of thin HfO2 layers by the combined analysis with complementary techniques
H. Bender, T. Conard, O. Richard, B. Brijs, J. Pétry, W. Vandervorst, C. Defranoux, P. Boher, N. Rochat, C. Wyon, P. Mack, J. Wolstenholme, R. Vitchev, L. Houssiau, J.-J. Pireaux, A. Bergmaier and G. Dollinger; In: , B.O. Kolbesen, C. Claeys, P. Stallhofer, F. Tardif, D.K. Schroder, T.J. Shaffner, M. Tajima and P. Rai Choudhury (Eds.), Proceedings of SPIE - The International Society for Optical Engineering 5133 (2003) 223-232 , SPIE.
Abstract: The physical properties of HfO2 layers prepared by atomic layer and metal organic chemical vapor deposition (MOCVD) were analyzed. A combination of different complementary analysis techniques was used during the analysis. A similar deposition time dependence was found for the MOCVD layers deposited at 300 and 485° C. It was shown that the density increases with the number of deposition cycles for the atomic layer deposition (ALD) layers.
BibTeX:
	@inproceedings{Bender2003,
	  author = {Bender, H. and Conard, Th. and Richard, O. and Brijs, B. and Pétry, J. and Vandervorst, W. and Defranoux, Chr. and Boher, P. and Rochat, N. and Wyon, C. and Mack, P. and Wolstenholme, J. and Vitchev, R. and Houssiau, L. and Pireaux, J.-J. and Bergmaier, A. and Dollinger, G.},
	  title = {Physical characterization of thin HfO2 layers by the combined analysis with complementary techniques},
	  booktitle = {Proceedings of SPIE - The International Society for Optical Engineering},
	  publisher = {SPIE},
	  year = {2003},
	  volume = {5133},
	  pages = {223--232},
	  editor = {Kolbesen, B. O. and Claeys, C. and Stallhofer, P. and Tardif, F. and Schroder, D. K. and Shaffner, T. J. and Tajima, M. and Rai - Choudhury, P.},
	  note = {cited By (since 1996)1},
	  url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-0242468973&partnerID=40&md5=1c49e313f7666ce84bbd5ef30b1e189d}
	}
	
Recent developments in nuclear methods in support of semiconductor characterization
B. Brijs, H. Bender, C. Huyghebaert, T. Janssens, W. Vandervorst, K. Nakajima, K. Kimura, A. Bergmaier, G. Dollinger and J. Van den Berg; In: , B.O. Kolbesen, C. Claeys, P. Stallhofer, F. Tardif, D.K. Schroder, T.J. Shaffner, M. Tajima and P. Rai Choudhury (Eds.), Proceedings of SPIE - The International Society for Optical Engineering 5133 (2003) 50-62 , SPIE.
Abstract: The analysis of thin materials related to semiconductors using nuclear techniques was presented. Decreasing the beam energy from the conventional energy of 2 MeV to lower than 0.5 MeV or lower transforms rutherford backscattering (RBS) to a near surface analysis technique. It was concluded that problems of material characterization could be solved using secondary ion mass spectrometry (SIMS) and dedicated nuclear techniques that provide good insight in the material behavior in shallow layers.
BibTeX:
	@inproceedings{Brijs2003,
	  author = {Brijs, B. and Bender, H. and Huyghebaert, C. and Janssens, T. and Vandervorst, W. and Nakajima, K. and Kimura, K. and Bergmaier, A. and Dollinger, G. and Van den Berg, J.A.},
	  title = {Recent developments in nuclear methods in support of semiconductor characterization},
	  booktitle = {Proceedings of SPIE - The International Society for Optical Engineering},
	  publisher = {SPIE},
	  year = {2003},
	  volume = {5133},
	  pages = {50--62},
	  editor = {Kolbesen, B. O. and Claeys, C. and Stallhofer, P. and Tardif, F. and Schroder, D. K. and Shaffner, T. J. and Tajima, M. and Rai - Choudhury, P.},
	  note = {cited By (since 1996)0},
	  url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-0242497089&partnerID=40&md5=20345bca5db47484b0f8807dfe96affa}
	}
	
The Munich ion microprobe: Characteristics and prospect
G. Dollinger, G. Datzmann, A. Hauptner, R. Hertenberger, H.-J. Körner, P. Reichart and B. Volckaerts; Nuclear Instruments and Methods in Physics Research Section B 210 (2003) 6-13.
Abstract: The newly developed ion microprobe SNAKE (superconducting nanoscope for applied nuclear (Kern-) physics experiments) has gone into routine operation at the Munich 14 MV tandem accelerator. It focuses ion beams, from protons to uranium, with energies that are about 10 times larger than they are available at standard nuclear microprobes. Lateral resolutions of Δx=1.6 μm and Δy=1.2 μm for x- and y-direction at full aperture and as low as Δx=600 nm and Δy=150 nm for a pencil beam have been achieved so far. The latter values are limited by positional drifts and 50 Hz oscillating fields which have become obvious in time resolved measurements.
SNAKE opens new possibilities for analysis of microstructured materials as well as materials modifications. The highlights are three dimensional hydrogen analysis using proton proton scattering, high resolution transmission energy loss measurements utilizing a magnetic spectrograph and materials modification with available high energy proton and heavy ion beams. Standard techniques like particle induced X-ray emission, elastic and inelastic scattering are also used for imaging. The paper summarizes some of the prospects using the enlarged range of available ion beams and ion energies.
BibTeX:
	@article{Dollinger2003,
	  author = {Dollinger, Günther and Datzmann, Gerd and Hauptner, Andreas and Hertenberger, Ralf and Körner, Hans-Joachim and Reichart, Patrick and Volckaerts, Bart},
	  title = {The Munich ion microprobe: Characteristics and prospect},
	  booktitle = {8th International Conference of Nuclear Microprobe Technology and Applications},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2003},
	  volume = {210},
	  pages = {6--13},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X03010012},
	  doi = {http://doi.org/10.1016/S0168-583X(03)01001-2}
	}
	
Three-dimensional hydrogen microscopy using a high-energy proton probe
G. Dollinger, P. Reichart, G. Datzmann, A. Hauptner and H.-J. Körner; Applied Physics Letters 82 (1) (2003) 148-150.
Abstract: It is a challenge to measure two-dimensional or three-dimensional (3D) hydrogen profiles on a micrometer scale. Quantitative hydrogen analyses of micrometer resolution are demonstrated utilizing proton–proton scattering at a high-energy proton microprobe. It has more than an-order-of-magnitude better position resolution and in addition higher sensitivity than any other technique for 3D hydrogen analyses. This type of hydrogen imaging opens plenty room to characterize microstructured materials, and semiconductor devices or objects in microbiology. The first hydrogen image obtained with a 10 MeV proton microprobe shows the hydrogen distribution of the microcapillary system being present in the wing of a mayfly and demonstrates the potential of the method.
BibTeX:
	@article{Dollinger2003a,
	  author = {Dollinger, G. and Reichart, P. and Datzmann, G. and Hauptner, A. and Körner, H.-J},
	  title = {Three-dimensional hydrogen microscopy using a high-energy proton probe},
	  journal = {Applied Physics Letters},
	  year = {2003},
	  volume = {82},
	  number = {1},
	  pages = {148--150},
	  url = {http://apl.aip.org/resource/1/applab/v82/i1/p148_s1},
	  doi = {http://doi.org/10.1063/1.1533111}
	}
	
Fatigue and fracture-induced defect structures of metals investigated by positron microscopy
W. Egger, G. Kögel, P. Sperr, W. Triftshäuser, J. Bär, S. Rödling and H.-J. Gudladt; Zeitschrift fuer Metallkunde/Materials Research and Advanced Techniques 94 (6) (2003) 687-693.
Abstract: Defect distributions close to cracks from monotonic and fatigue fractures have been investigated for the first time by positron lifetime studies. The positron beams probe either the depth profile of defects at sub-μm resolution or the lateral distribution of defects at a few μm spatial resolution. Both in pure Cu and in the precipitation-hardened alloy Al 6013, in addition to dislocations, large clusters of up to 30 vacancies were detected close to a fatigue crack exclusively, whereas at monotonic fractures only the annihilation characteristics of dislocations were observed. If this characteristic difference holds as a general rule, then positron lifetime microscopy will provide a simple, quantitative method to distinguish a posteriori monotonic fractures from fatigue fractures without any further fractographic studies.
BibTeX:
	@article{Egger2003,
	  author = {Egger, W. and Kögel, G. and Sperr, P. and Triftshäuser, W. and Bär, J. and Rödling, S. and Gudladt, H.-J.},
	  title = {Fatigue and fracture-induced defect structures of metals investigated by positron microscopy},
	  journal = {Zeitschrift fuer Metallkunde/Materials Research and Advanced Techniques},
	  year = {2003},
	  volume = {94},
	  number = {6},
	  pages = {687--693},
	  url = {http://www.hanser-elibrary.com/doi/abs/10.3139/146.030687},
	  doi = {http://doi.org/10.3139/146.030687}
	}
	
Characterization of the b and as pile-up at the si-sio2 interface
J. Frühauf, R. Lindsay, A. Bergmaier, G. Dollinger, W. Vandervorst, K. Maex and F. Koch; In: Ultra Shallow Junctions. 7th Int. Worksh. Fabrication, Characterization and Modeling of Ultra Shallow Doping Profiles in Semic. (2003) .
BibTeX:
	@inproceedings{Fruehauf2003,
	  author = {Frühauf, J. and Lindsay, R. and Bergmaier, A. and Dollinger, G. and Vandervorst, W. and Maex, K. and Koch, Frederick},
	  title = {Characterization of the b and as pile-up at the si-sio2 interface},
	  booktitle = {Ultra Shallow Junctions. 7th Int. Worksh. Fabrication, Characterization and Modeling of Ultra Shallow Doping Profiles in Semic.},
	  year = {2003}
	}
	
Transverse cooling and heating in ion channeling
F. Grüner, W. Assmann, F. Bell, M. Schubert, J. Andersen, S. Karamian, A. Bergmaier, G. Dollinger, L. Görgens, W. Günther and M. Toulemonde; Physical Review B - Condensed Matter and Materials Physics 68 (17) (2003) 1741041-17410412.
Abstract: In contrast to predictions from the standard theory of ion channeling we have observed strong redistributions of initially isotropic ion beams after transmission of thin crystal foils. Depending on the experimental parameters, there can be strong enhancements, corresponding to "transverse cooling," or strong reductions, "transverse heating," of the ion flux along a crystal axis or plane. For most ions there is a transition from cooling to heating when the ion energy is decreased, which depends on the crystal direction and on the atomic numbers of the ion and of the crystal atoms. In this paper we present an overview of this newly discovered phenomenon. Redistribution of an initially isotropic flux violates basic symmetries in the theory of channeling. We have argued earlier that the observed transverse cooling or heating can be understood as a consequence of fluctuations in the charge state of the channeled ions, but a detailed explanation of the transition from cooling to heating has yet to be established. A theoretical description is the most difficult for ions with many electrons. A different type of simulation has been developed based on n-body classical trajectory Monte-Carlo procedures and the first results are discussed.
BibTeX:
	@article{Gruener2003,
	  author = {Grüner, F. and Assmann, W. and Bell, F. and Schubert, M. and Andersen, J.U. and Karamian, S. and Bergmaier, A. and Dollinger, G. and Görgens, L. and Günther, W. and Toulemonde, M.},
	  title = {Transverse cooling and heating in ion channeling},
	  journal = {Physical Review B - Condensed Matter and Materials Physics},
	  year = {2003},
	  volume = {68},
	  number = {17},
	  pages = {1741041-17410412},
	  note = {cited By (since 1996)15},
	  url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.68.174104},
	  doi = {http://doi.org/10.1103/PhysRevB.68.174104}
	}
	
Positron source based on neutron capture
C. Hugenschmidt, G. Kögel, R. Repper, K. Schreckenbach, P. Sperr and W. Triftshäuser; Radiation Physics and Chemistry 68 (3-4) (2003) 669-671.
Abstract: A positron beam based on absorption of high-energy prompt γ-rays from thermal neutron capture in 113Cd was installed at a neutron guide of the High Flux Reactor at the ILL in Grenoble. The positron source consists of platinum foils acting as γ-e+e --converter and positron moderator. After acceleration to 3keV by electrical lenses the positrons were magnetically guided through the beamline. Measurements were performed for various source geometries. The beam diameter and moderation characteristics such as positron work function, moderation efficiency and degradation were determined as well. The results lead to an optimised design of the in-pile positron source which will be implemented at the Munich research reactor FRM-II. © 2003 Elsevier Science Ltd. All rights reserved.
BibTeX:
	@article{Hugenschmidt2003,
	  author = {Hugenschmidt, C. and Kögel, G. and Repper, R. and Schreckenbach, K. and Sperr, P. and Triftshäuser, W.},
	  title = {Positron source based on neutron capture},
	  journal = {Radiation Physics and Chemistry},
	  year = {2003},
	  volume = {68},
	  number = {3-4},
	  pages = {669--671},
	  url = {http://www.sciencedirect.com/science/article/pii/S0969806X0300197X},
	  doi = {http://doi.org/10.1016/S0969-806X(03)00197-X}
	}
	
Physical characterization of thin ALD-Al2O3 films
S. Jakschik, U. Schroeder, T. Hecht, D. Krueger, G. Dollinger, A. Bergmaier, C. Luhmann and J. Bartha; Applied Surface Science 211 (1-4) (2003) 352-359.
Abstract: Aluminum oxide was deposited using atomic layer deposition on either a silicon oxide or a silicon nitride interface. Water vapor or ozone were used as oxidation precursors. The structural properties of these films were investigated by time-of-flight secondary-ion-mass-spectroscopy (ToF-SIMS), X-ray photoelectron spectroscopy (XPS) and elastic recoil detection (ERD). Special attention was given to contamination issues of the film and the interface, bonding conditions and temperature influence on diffusion. The results suggest that the silicon most likely diffused along grain boundaries of polycrystalline Al2O3. Carbon and hydrogen were located at the interface and furthermore hydrogen diffused out of the film to some extent due to anneal. Carbon content in the layer was reduced when using O3 as an oxidant. The formation of metallic aluminum clusters was not observed for any of the investigated process conditions.
BibTeX:
	@article{Jakschik2003,
	  author = {Jakschik, S. and Schroeder, U. and Hecht, T. and Krueger, D. and Dollinger, G. and Bergmaier, A. and Luhmann, C. and Bartha, J.W.},
	  title = {Physical characterization of thin ALD-Al2O3 films},
	  journal = {Applied Surface Science},
	  year = {2003},
	  volume = {211},
	  number = {1-4},
	  pages = {352--359},
	  note = {cited By (since 1996)36},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433203002642},
	  doi = {http://doi.org/10.1016/S0169-4332(03)00264-2}
	}
	
Study of radiation defects in semiconductors by means of positron annihilation
R. Krause-Rehberg, V. Bondarenko, F. Redmann, F. Borner, H. Feick, E. Weber, C. Da Via, W. Egger, G. Kögel, P. Sperr and W. Triftshäuser; In: Proceedings of the 3rd international Symposium on Material Chemistry in Nuclear Environment (Materials Chemistry MC’02) 36 (2003) 114-117 .
Abstract: In a nuclear environment, a strong degradation of important properties is observed for many materials which are otherwise very reliable. This is especially valid for silicon, the most important semiconductor. In the presented paper, two examples for the study of lattice defects in silicon by means of positron annihilation will be given. Firstly, the degradation of silicon detectors used for the particle detection in high-luminosity collider experiments starts to limit the lifetime of the whole experiment. An annealing experiment on n-irradiated Si will be presented. Beside the destructive effect of high-radiation conditions, such radiation-induced defects can have a beneficial result. This will be demonstrated for the creation of new gettering zones by high-energy self-implantation of silicon.
BibTeX:
	@inproceedings{Krause-Rehberg2003,
	  author = {Krause-Rehberg, R. and Bondarenko, V. and Redmann, F. and Borner, F. and Feick, H. and Weber, E. and Da Via, C. and Egger, W. and Kögel, G. and Sperr, P. and Triftshäuser, W.},
	  title = {Study of radiation defects in semiconductors by means of positron annihilation},
	  booktitle = {Proceedings of the 3rd international Symposium on Material Chemistry in Nuclear Environment (Materials Chemistry MC’02)},
	  year = {2003},
	  volume = {36},
	  number = {50},
	  pages = {114--117},
	  url = {https://inis.iaea.org/search/search.aspx?orig_q=RN:36116010}
	}
	
Diffusion in diamond-like carbon
H. Kröger, C. Ronning, H. Hofsäss, P. Neumaier, A. Bergmaier, L. Görgens and G. Dollinger; Diamond and Related Materials 12 (10-11) (2003) 2042-2050.
Abstract: The diffusion of carbon and five other elements in amorphous carbon (a-C) films was studied. One set of samples were sp2 dominated a-C and the other set of samples were sp3 dominated tetrahedral amorphous carbon (ta-C). The films were deposited using mass separated ion beam deposition under UHV conditions. The diffusion of 13C as well as that of hydrogen and deuterium was studied using high resolution elastic recoil detection analysis. No apparent self-diffusion could be detected using this technique. The diffusion of hydrogen was found to start at temperatures between 600 and 800 °C. For deuterium, activation energies of 3.34(5) and 3.39(5) eV were found for diffusion in ta-C and a-C, respectively. Tungsten, copper and silver were used to study the diffusion of metals in ta-C. Up to annealing temperatures of 1000 °C no diffusion took place in the samples. During annealing at 1200 °C the ta-C is converted into graphite, making diffusion into the carbon matrix possible. The fact that there is no diffusion of copper in ta-C at temperatures below 1200 °C shows that ta-C is a possible diffusion barrier between copper and silicon.
BibTeX:
	@article{Kroeger2003,
	  author = {Kröger, H. and Ronning, C. and Hofsäss, H. and Neumaier, P. and Bergmaier, A. and Görgens, L. and Dollinger, G.},
	  title = {Diffusion in diamond-like carbon},
	  journal = {Diamond and Related Materials},
	  year = {2003},
	  volume = {12},
	  number = {10-11},
	  pages = {2042-2050},
	  note = {cited By (since 1996)12},
	  url = {http://www.sciencedirect.com/science/article/pii/S0925963503002188},
	  doi = {http://doi.org/10.1016/S0925-9635(03)00218-8}
	}
	
Sensitive 3D hydrogen microscopy using high energy protons at SNAKE
P. Reichart, G. Dollinger, G. Datzmann, A. Hauptner, R. Hertenberger and H.J. Körner; Nuclear Instruments and Methods in Physics Research Section B 210 (2003) 135-141.
Abstract: The new ion microprobe SNAKE (Superconducting Nanoscope for Applied nuclear (Kern-) physics Experiments) is a tool to focus, beside heavy ions, 4-28 MeV protons to submicron beam spot size. This facility establishes a sensitive 3D microscopy of hydrogen distributions by elastic proton proton scattering. The high proton energy enables analysis at a target thickness up to some 100 μm without significant reduction of the micrometer lateral resolution. The scattered projectile and recoiled target protons are detected in coincidence using an annular silicon strip detector. It covers scattering angles from 29° to 61° and a 2.3 sr solid angle of detection. The readout electronics with a 50 ns coincidence window allows an efficient reduction of accidental coincidence events even at some 10 kHz count rates. 3D hydrogen microscopy using 17 MeV proton proton scattering is tested successfully providing a ppm detection limit in a 55 μm thick diamond plate. First measurements on CVD grown diamond show the possibility to investigate such low hydrogen content of the bulk region with micrometer lateral resolution.
BibTeX:
	@article{Reichart2003,
	  author = {Reichart, P. and Dollinger, G. and Datzmann, G. and Hauptner, A. and Hertenberger, R. and Körner, H. - J.},
	  title = {Sensitive 3D hydrogen microscopy using high energy protons at SNAKE},
	  booktitle = {8th International Conference of Nuclear Microprobe Technology and Applications},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2003},
	  volume = {210},
	  pages = {135--141},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X0301084X},
	  doi = {http://doi.org/10.1016/S0168-583X(03)01084-X}
	}
	
Cooling and heating of channeled ions and corresponding charge state distributions
M. Schubert, F. Grüner, W. Assmann, F. Bell, A. Bergmaier, L. Goergens, O. Schmelmer, G. Dollinger and S. Karamian; Nuclear Instruments and Methods in Physics Research Section B 209 (2003) 224-232.
Abstract: Our group has recently [Phys. Rev. Lett., 83 (1999) 1759] reported experimental evidence for the redistribution of an isotropic ion flux after transmission through thin crystals. For not fully stripped ions we have observed either an enhancement (cooling) or a reduction (heating) of the angular flux along crystal directions. For a possible explanation of this unpredicted effect an additional mechanism was introduced: cooling or heating of the transverse motion by spatially correlated charge exchange processes. One consequence of this mechanism could be a different charge state distribution of well-channeled versus non-channeled ions: for cooling channeled ions should exit the crystal with a higher charge state than in random directions and heating should yield the opposite result. We report here measurements that show indeed shifts of the mean charge state of channeled ions in comparison to the one of random ions. These shifts depend on the ion velocity, but there seems to be no general correlation between the shifts and the appearance of cooling or heating. © 2003 Elsevier B.V. All rights reserved.
BibTeX:
	@article{Schubert2003,
	  author = {Schubert, M. and Grüner, F. and Assmann, W. and Bell, F. and Bergmaier, A. and Goergens, L. and Schmelmer, O. and Dollinger, G. and Karamian, S.},
	  title = {Cooling and heating of channeled ions and corresponding charge state distributions},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2003},
	  volume = {209},
	  pages = {224--232},
	  editor = {Marletta G., Bouffard S., Neumann R.},
	  note = {cited By (since 1996)7},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X02020384},
	  doi = {http://doi.org/10.1016/S0168-583X(02)02038-4}
	}
	
Growth and properties of CVD diamond films grown under H2S addition
H. Sternschulte, M. Schreck, B. Stritzker, A. Bergmaier and G. Dollinger; Diamond and Related Materials 12 (3-7) (2003) 318-323.
Abstract: The influence of H2S on the CVD diamond growth, the sulfur incorporation and the electronic properties of sulfur containing homoepitaxial diamond films were studied. Laser reflection interferometry (LRI) in combination with mass spectroscopy (MS) showed that H2S modifies the gas phase chemistry by reducing the concentration of CHx species. As a consequence thereof, at high deposition temperatures the growth rate decreased. At lower substrate temperatures, the observed increase in the growth rate after sulfur addition indicates that these gas phase effects are overcompensated by processes at the growing diamond surface. The incorporation coefficient of sulfur into the definitely boron free diamond films was very low (less than 10-6). Incorporation seems to be enhanced by a reduction of the substrate temperature, by the presence of Si and, most effectively, by addition of CO2. For 0.5% CO2 in the gas mixture a maximum S concentration of 480 ppm (9 × 1019/cm3) corresponding to an incorporation coefficient of 6 × 10-4 was attained. Even for the highest H2S concentrations (nearly 1%) the deposited diamond films preserve their excellent quality as judged from μ-Raman measurements. The electrical properties were not changed by the S incorporation. The electrical conductivity is thermally activated with typically 1.4-1.5 eV independent from the S concentration in the films. No values below 1.0 eV have been measured which argues against doping. © 2002 Elsevier Science B.V. All rights reserved.
BibTeX:
	@article{Sternschulte2003,
	  author = {Sternschulte, H. and Schreck, M. and Stritzker, B. and Bergmaier, A. and Dollinger, G.},
	  title = {Growth and properties of CVD diamond films grown under H2S addition},
	  journal = {Diamond and Related Materials},
	  year = {2003},
	  volume = {12},
	  number = {3-7},
	  pages = {318--323},
	  note = {cited By (since 1996)15},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433202006785},
	  doi = {http://doi.org/10.1016/S0925-9635(02)00312-6}
	}
	
An (un)solvable problem in SIMS: B-interfacial profiling
W. Vandervorst, T. Janssens, R. Loo, M. Caymax, I. Peytier, R. Lindsay, J. Frühauf, A. Bergmaier and G. Dollinger; Applied Surface Science 203-204 (2003) 371-376.
Abstract: To get an insight in the diffusion behavior of boron after annealing and in particular its segregation characteristics towards the interface in oxide structures on silicon, it is necessary to probe the boron profile with very high accuracy and depth resolution. Sputter depth profiling as employed in secondary ion mass spectrometry (SIMS) is frequently used as the most suited tool for dopant profiling in view of its sensitivity and depth resolution. However, in order to determine the segregated boron peak, sub-nm depth resolution is required and artifacts such as beam induced broadening effects, potential ionization yield changes at interfaces, transient sputter yields need to be considered in detail. When reducing the primary beam energy the depth resolution can be improved and sub-nm depth sensitivity can be demonstrated. However, comparisons with high-resolution elastic recoil detection analysis demonstrate that even under those conditions no reliable depth profile can be obtained in the first nm near the surface nor even in the oxide part of the profile, where no ionization nor sputter yield transients are expected. Enhanced beam induced migration of boron during the initial phase of the bombardment needs to be invoked to explain the results.
BibTeX:
	@article{Vandervorst2003,
	  author = {Vandervorst, W. and Janssens, T. and Loo, R. and Caymax, M. and Peytier, I. and Lindsay, R. and Frühauf, J. and Bergmaier, A. and Dollinger, G.},
	  title = {An (un)solvable problem in SIMS: B-interfacial profiling},
	  journal = {Applied Surface Science},
	  year = {2003},
	  volume = {203-204},
	  pages = {371--376},
	  note = {cited By (since 1996)21},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433202006785},
	  doi = {http://doi.org/10.1016/S0169-4332(02)00678-5}
	}
	

2002

Vacancy defects in as-polished and in high-fluence H+-implanted 6H-SiC detected by slow positron annihilation spectroscopy
M.-F. Barthe, P. Desgardin, L. Henry, C. Corbel, D. Britton, G. Kögel, P. Sperr, W. Triftshäuser, P. Vicente and L. Dicioccio; Materials Science Forum 389-393 (1) (2002) 493-496.
Abstract: The vacancy defects in near surface region are investigated in n-type 6H-SiC after polishing or low-energy-proton implantation using slow-positron-beam-based positron annihilation spectroscopy. Measuring the momentum distribution of annihilating electron-positron pairs by Doppler broadening spectroscopy we detect an about 100 nm thick vacancy-defects layer under the surface of mechanically polished wafers. No damaged layer is detected after mechano-chemical finishing. Measuring positron lifetime as a function of temperature, we show that neutral and negatively-charged vacancy clusters exist in the track region of low-energy proton-implanted 6H-SiC(H). Depending on annealing, they give rise to positron lifetimes of 257 ± 2 ps, 281 ± 4 ps and 345 ± 2 ps, respectively. By comparison with theory, the 257 ps and 280 ps are attributed to (VC-VSi) 2 and (VC-VSi)3 clusters, respectively. The (VC-VSi)3 cluster has likely an ionization level near the middle of the bandgap. © 2002 Trans Tech Publications.
BibTeX:
	@article{Barthe2002,
	  author = {Barthe, M.-F. and Desgardin, P. and Henry, L. and Corbel, C. and Britton, D.T. and Kögel, G. and Sperr, P. and Triftshäuser, W. and Vicente, P. and Dicioccio, L.},
	  title = {Vacancy defects in as-polished and in high-fluence H+-implanted 6H-SiC detected by slow positron annihilation spectroscopy},
	  journal = {Materials Science Forum},
	  year = {2002},
	  volume = {389-393},
	  number = {1},
	  pages = {493--496},
	  url = {https://www.scientific.net/MSF.389-393.493},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.389-393.493}
	}
	
Analysis of the total carbon deposition during the bias enhanced nucleation of diamond on Ir/SrTiO3 (001) using 13C-methane
T. Bauer, M. Schreck, F. Hörmann, A. Bergmaier, G. Dollinger and B. Stritzker; Diamond and Related Materials 11 (3-6) (2002) 493-498.
Abstract: Carbon deposition during bias enhanced nucleation (BEN) of diamond on Ir/SrTiO3 (001) was measured by elastic recoil detection (ERD) analysis using 13C-methane in the process gas. High resolution optical emission spectra (OES) of CH emission lines from the gas phase as well as Raman spectra of deposited diamond films showed the high isotopic purity of the reaction gas. During the biasing step a carbon coverage of approximately 1 × 1016 cm-2 equivalent to a 0.6-nm-thick diamond layer was deposited at the surface after 45 min. Its thickness only increased slowly for longer biasing. A similar carbon enrichment was also found at the iridium/SrTiO3 interface. After the nucleation step, nanometer-size particles of very uniform height were found at the iridium surface. Their integral volume was more than an order of magnitude lower than the total volume of the carbon layer present at the surface after BEN. Our experiments indicate that most of the carbon is continuously distributed over the surface which allows to sketch a rough image of the processes occurring during BEN on iridium.
BibTeX:
	@article{Bauer2002,
	  author = {Bauer, Th. and Schreck, M. and Hörmann, F. and Bergmaier, A. and Dollinger, G. and Stritzker, B.},
	  title = {Analysis of the total carbon deposition during the bias enhanced nucleation of diamond on Ir/SrTiO3 (001) using 13C-methane},
	  journal = {Diamond and Related Materials},
	  year = {2002},
	  volume = {11},
	  number = {3-6},
	  pages = {493--498},
	  note = {cited By (since 1996)17},
	  url = {http://www.sciencedirect.com/science/article/pii/S0925963501006264},
	  doi = {http://doi.org/10.1016/S0925-9635(01)00626-4}
	}
	
Advanced characterization of high-k materials: A nuclear approach
B. Brijs, C. Huyghebaert, S. Nauwelaerts, M. Caymax, W. Vandervorst, K. Nakajima, K. Kimura, A. Bergmaier, G. Dollinger G.llinger, W. Lennard, G. Terwagne and A. Vantomme; Nuclear Instruments and Methods in Physics Research Section B 190 (1-4) (2002) 505-509.
Abstract: The determination of the composition of thin (1.5-3 nm) high-k layers ZrO2/Al2O3 becomes more and more important in microelectronics. High resolution Rutherford backscattering spectrometry and high resolution elastic recoil detection can achieve depth resolutions down to 1 nm while Rutherford backscattering spectrometry and nuclear reaction analysis are perfectly suited to quantify the zirconium, the oxygen and the aluminum content. The goal of this paper is to investigate the use of nuclear techniques for the characterization of thin high-k materials.
BibTeX:
	@article{Brijs2002,
	  author = {Brijs, B. and Huyghebaert, C. and Nauwelaerts, S. and Caymax, M. and Vandervorst, W. and Nakajima, K. and Kimura, K. and Bergmaier, A. and Dollinger, G.llinger, G. and Lennard, W.N. and Terwagne, G. and Vantomme, A.},
	  title = {Advanced characterization of high-k materials: A nuclear approach},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2002},
	  volume = {190},
	  number = {1-4},
	  pages = {505--509},
	  note = {cited By (since 1996)6},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X02004688},
	  doi = {http://doi.org/10.1016/S0168-583X(02)00468-8}
	}
	
Shallow traps and positron dynamics in epitaxial silicon carbide
D. Britton, M.-F. Barthe, C. Corbel, P. Desgardin, W. Egger, P. Sperr, G. Kögel and W. Triftshäuser; Applied Surface Science 194 (1-4) (2002) 122-126.
Abstract: We have used slow positron beam-based positron lifetime spectroscopy to study positron diffusion in thick epitaxial n-type 6H-SiC layers. The layers are considerably thicker than the maximum positron penetration depth, and can therefore, be treated as homogeneous semi-infinite bulk material in an analysis including the time-dependent diffusion of a single group of probe particles. Temperature-dependent measurements show a reduction in positron diffusion at low temperatures, which has been interpreted by an increase in trapping to negatively charged defect states. © 2002 Published by Elsevier Science B.V.
BibTeX:
	@article{Britton2002,
	  author = {Britton, D.T. and Barthe, M.-F. and Corbel, C. and Desgardin, P. and Egger, W. and Sperr, P. and Kögel, G. and Triftshäuser, W.},
	  title = {Shallow traps and positron dynamics in epitaxial silicon carbide},
	  journal = {Applied Surface Science},
	  year = {2002},
	  volume = {194},
	  number = {1-4},
	  pages = {122--126},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433202001101},
	  doi = {http://doi.org/10.1016/S0169-4332(02)00110-1}
	}
	
Positron states in hydrogenated amorphous silicon
D. Britton, M. Härting, A. Hempel, G. Kögel, P. Sperr, W. Triftshäuser, M. Hempel and D. Knoesen; Journal of Non-Crystalline Solids 299-302 (Part 1) (2002) 249-253.
Abstract: Low-hydrogen-concentration a-Si:H grown by HW-CVD forms a continuous random network with no detectable free volume in the form of microvoids, and no evidence of a microcrystalline phase. Over a wide temperature range we observe a single positron state in the amorphous network with a temperature-independent lifetime of 322 ps. From the temperature dependence of the positron diffusion we show that this is a localized state and present direct observation of hopping diffusion of positrons. On annealing up to 400 °C the amorphous network is seen to relax and the first stages of crystallization occur. There is also evidence of vacancy clustering to form a low concentration of microvoids. The structural relaxation has a very low-activation energy, around 0.1 eV, and is interpreted in terms of a reconfiguration of the fundamental defect identifed by positron annihilation. © 2002 Published by Elsevier Science B.V.
BibTeX:
	@article{Britton2002a,
	  author = {Britton, D.T. and Härting, M. and Hempel, A. and Kögel, G. and Sperr, P. and Triftshäuser, W. and Hempel, M. and Knoesen, D.},
	  title = {Positron states in hydrogenated amorphous silicon},
	  journal = {Journal of Non-Crystalline Solids},
	  year = {2002},
	  volume = {299-302},
	  number = {Part 1},
	  pages = {249--253},
	  url = {http://www.sciencedirect.com/science/article/pii/S0022309301011656},
	  doi = {http://doi.org/10.1016/S0022-3093(01)01165-6}
	}
	
Aufbau und Charakterisierung des Hochenergie Rasterionenmikroskops SNAKE
Gerd Datzmann; Dissertation, Technische Universität München, 2002.
Abstract: Im Rahmen der Arbeit wurde am Münchner Tandembeschleuniger das Hochenergie Rasterionenmikroskop SNAKE (Supraleitendes Nanoskop für Angewandte Kernphysikalische Experimente) aufgebaut und charakterisiert. Die speziell dafür entwickelte supraleitende Multipollinse kann Protonen- und Schwerionenstrahlen mit einem Masse-Energieprodukt bis 160 MeV×u auf Mikrometergröße und kleiner fokussieren. SNAKE ist ein vielseitiges Werkzeug für Materialanalyse und -modifikation. Einen Schwerpunkt bildet dabei eine quantitative dreidimensionale Wasserstoffanalytik
BibTeX:
	@phdthesis{Datzmann2002diss,
	  author = {Datzmann, Gerd},
	  title = {Aufbau und Charakterisierung des Hochenergie Rasterionenmikroskops SNAKE},
	  school = {Technische Universität München},
	  year = {2002},
	  url = {http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:91-diss2002050313488}
	}
	
Vacancy clusters close to a fatigue crack observed with the München scanning positron microscope
W. Egger, G. Kögel, P. Sperr, W. Triftshäuser, S. Rödling, J. Bär and H.-J. Gudladt; Applied Surface Science 194 (1-4) (2002) 214-217.
Abstract: The accumulation of plastic strain by low cycle fatigue has been expected for a long time to induce vacancy clusters, particularly in the most damaged region, i.e. close to a fatigue crack. For the first time, the München scanning positron microscope (SPM) enables the detection of the expected vacancy clusters by positron lifetime studies of a fatigue crack with micrometer resolution. A fatigue crack with a length of about 8 mm was created in a single edge-notched specimen of cold-rolled technical copper. The fatigue crack propagation test was performed under K-controlled conditions with a constant stress intensity factor of 9 MPa m1/2. Lifetime images from a region of about 200 × 400 μm2 around the crack tip were obtained at about 5 μm spatial resolution for 5, 8 and 16 keV positron implantation energies. Independent of position, a positron lifetime of about 190 ps is observed, indicating annihilation of positrons at dislocations. Within about 40 μm from the crack path, however, a second lifetime in the range of 360-420 ps is observed at all positron implantation energies and with an intensity up to 25%. Therefore in this region there must be large vacancy clusters with a trapping rate comparable to one of the dislocations. © 2002 Elsevier Science B.V. All rights reserved.
BibTeX:
	@article{Egger2002,
	  author = {Egger, W. and Kögel, G. and Sperr, P. and Triftshäuser, W. and Rödling, S. and Bär, J. and Gudladt, H.-J.},
	  title = {Vacancy clusters close to a fatigue crack observed with the München scanning positron microscope},
	  journal = {Applied Surface Science},
	  year = {2002},
	  volume = {194},
	  number = {1-4},
	  pages = {214--217},
	  url = {http://www.sciencedirect.com/science/article/pii/S016943320200106X},
	  doi = {http://doi.org/10.1016/S0169-4332(02)00106-X}
	}
	
Electrical activity of B and As segregated at the Si-SiO2 interface
J. Frühauf, R. Lindsay, A. Bergmaier, W. Vandervorst, G. Tempel, K. Maex, G. Dollinger and F. Koch; In: , D.F. Downey, M.E. Law, A. Claverie and M.J. Rendon (Eds.), Silicon Front-End Junction Formation Technologies; San Francisco, CA; United States; 2 -4 April 2002 717 (2002) 115-120 , Materials Research Society.
Abstract: During spike annealing of ultra-shallow junctions, large fractions of the dopants form a partially active pile-up at the interface between silicon and the screening oxide layer. In this paper, we show results of sheet resistance, SIMS and high resolution Elastic Recoil Detection measurements to investigate the physical and electrical behaviour of B and As dopant atoms at the interface. Our results show that the fraction of dopants segregated at the interface is as high as 30-50% for B, but is dependent on dose and the type of screening oxide. Concentrations of up to 3e20 cm-3 and more of active dopants are found on the Si side of the interface. The presence of nitrogen in the oxide at the interface causes a higher and sharper pile-up. Results indicate that a similar peak is expected for As, with active concentrations above 6e20 cm-3. In an HF dip, the pile-up is removed together with the oxide or deactivated during native oxide regrowth. Further experiments show that immediately after removing the screening oxide in an HF dip the sheet resistance for B decreases sharply due to carrier accumulation, then raises to about 6-9% above the initial level depending on the oxide and dopant species. The sharp decrease in resistance is not observed for As.
BibTeX:
	@inproceedings{Fruehauf2002,
	  author = {Frühauf, J. and Lindsay, R. and Bergmaier, A. and Vandervorst, W. and Tempel, G. and Maex, K. and Dollinger, G. and Koch, F.},
	  title = {Electrical activity of B and As segregated at the Si-SiO2 interface},
	  booktitle = {Silicon Front-End Junction Formation Technologies; San Francisco, CA; United States; 2 -4 April 2002},
	  publisher = {Materials Research Society},
	  year = {2002},
	  volume = {717},
	  pages = {115--120},
	  editor = {Downey, D. F. and Law, M. E. and Claverie, A. and Rendon, M. J.},
	  note = {cited By (since 1996)1},
	  url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-0036447886&partnerID=40&md5=543aa7a20112572d57821363721ec1fe},
	  doi = {http://doi.org/10.1557/PROC-717-C3.4}
	}
	
Electron-stimulated hydrogen desorption from diamond surfaces and its influence on the low-pressure synthesis of diamond
C. Goeden and G. Dollinger; Applied Physics Letters 81 (26) (2002) 5027-5029.
Abstract: A total cross section σD = (5±2.6)×10e−18 cm2 is measured for electron-stimulated desorption (ESD) of deuterium from a boron-doped, deuterated diamond(100) surface at 5 eV incident electron energy. This large ESD cross section means a significant contribution of ESD to hydrogen abstraction reactions in microwave-driven chemical vapor deposition of diamond. The ESD cross section decreases when changing to a nitrogen-doped diamond. This change is suggested to be the reason for the reported influence of small concentrations of nitrogen or boron added to the process gas on diamond growth.
BibTeX:
	@article{Goeden2002,
	  author = {Goeden, C. and Dollinger, G.},
	  title = {Electron-stimulated hydrogen desorption from diamond surfaces and its influence on the low-pressure synthesis of diamond},
	  journal = {Applied Physics Letters},
	  year = {2002},
	  volume = {81},
	  number = {26},
	  pages = {5027-5029},
	  url = {http://link.aip.org/link/?APL/81/5027/1},
	  doi = {http://doi.org/10.1063/1.1526460}
	}
	
Electron stimulated desorption of negative ions: A time-of-flight experiment
C. Goeden and G. Dollinger; Review of Scientific Instruments 73 (8) (2002) 3058-3064.
Abstract: We present a setup for stimulated desorption experiments of negative ions using low energy incident electrons and time-of-flight identification of the desorbed ions. It consists of a pulsed electron gun, an electrostatic focusing system, and a channel plate detector setup. Electron beams down to sub-eV energies can be used due to electrostatic shielding and the compensation of the earth’s magnetic field by a set of Helmholtz coils. The main advantage is the large acceptance for ions of all masses, energies, and desorption angles at the same time, which keeps measuring time reasonably short and allows us to gain information before degeneration of the irradiated sample occurs, even if weak desorption channels are investigated. We demonstrate the power of our setup with first results from a boron doped, (100)-oriented diamond sample, which is partly oxidized and partly hydrogenated with some water contaminations on it. Different binding states of oxygen are disclosed clearly by different desorption thresholds. The C–O binding on oxidized diamond forms a carbonyl group. The 1b_2 orbital of water can be seen in a O desorption threshold. The yield of negative hydrogen desorption shows a linear increase for incident electron energies higher than 13 eV. It results from a dipolar dissociation as has been published previously.
BibTeX:
	@article{Goeden2002a,
	  author = {Goeden, C. and Dollinger, G.},
	  title = {Electron stimulated desorption of negative ions: A time-of-flight experiment},
	  journal = {Review of Scientific Instruments},
	  year = {2002},
	  volume = {73},
	  number = {8},
	  pages = {3058-3064},
	  url = {http://link.aip.org/link/?RSI/73/3058/1},
	  doi = {http://doi.org/10.1063/1.1491030}
	}
	
Elektronisch stimulierte Wasserstoffdesorption von Diamantoberflächen
Christian Goeden; Dissertation, Technische Universität München, 2002.
Abstract: Im Rahmen dieser Arbeit wurden zwei Instrumente zur stimulierten Desorption (ESD) negativer und positiver Ionen von Festkörperoberflächen unter Elektronenbeschuß (Anregungsenergie 0.5 - 300 eV) aufgebaut und betrieben. Damit wurde die stimulierte Wasserstoffdesorption von Diamantoberflächen untersucht. Die Ergebnisse werden in Bezug auf die technische Verwendbarkeit des Prozesses zum Bau einer brillanten Ionenquelle dargestellt. Darüberhinaus zeigen die Ergebnisse einen signifikanten Einfluß von ESD-Prozessen auf die Diamant-Niederdrucksynthese. Der lange bekannte Einfluß der Dotierung auf das Wachstum wird damit erklärbar.
BibTeX:
	@phdthesis{Goeden2002diss,
	  author = {Goeden, Christian},
	  title = {Elektronisch stimulierte Wasserstoffdesorption von Diamantoberflächen},
	  school = {Technische Universität München},
	  year = {2002},
	  url = {http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:91-diss2002072313551}
	}
	
Design of the munich microprobe facility for single-ion irradiation of cells
A. Hauptner, G. Datzmann, G. Dollinger, H.-J. Körner, P. Reichart and O. Schmelmer; In: Proceedings of the 5th International Workshop: Microbeam Probes of Cellular Radiation Response , Radiation Research 158 (2002) 367 , Radiation Research Society.
BibTeX:
	@inproceedings{Hauptner2002,
	  author = {Hauptner, A. and Datzmann, G. and Dollinger, G. and Körner, H.-J. and Reichart, P. and Schmelmer, O.},
	  title = {Design of the munich microprobe facility for single-ion irradiation of cells},
	  booktitle = {Proceedings of the 5th International Workshop: Microbeam Probes of Cellular Radiation Response},
	  journal = {Radiation Research},
	  publisher = {Radiation Research Society},
	  year = {2002},
	  volume = {158},
	  number = {3},
	  pages = {367},
	  note = {Stresa, Lago Maggiore, Italy,May 26–27, 2001},
	  url = {http://www.rrjournal.org/toc/rare/158/3},
	  doi = {http://doi.org/10.1667/0033-7587(2002)158%5B0365:POTIWM%5D2.0.CO;2}
	}
	
Ion beam analysis of aluminium in thin layers
M. Healy, A. Pidduck, G. Dollinger, L. Görgens and A. Bergmaier; Nuclear Instruments and Methods in Physics Research Section B 190 (1-4) (2002) 630-635.
Abstract: This work quantifies aluminium in thin surface and near surface layers. In one example, the layer overlies a thin gallium nitride layer on an aluminium oxide substrate and in a second example the aluminium exists just below the surface of an indium arsenide substrate. The technique of non-Rutherford elastic backscattering of protons was used for the samples where aluminum in the layer of interest needed to be resolved from aluminium in the sapphire substrate and the results were corroborated at the Technische Universität München using heavy ion elastic recoil detection analysis. In the second example, where it was unnecessary to isolate the signal of aluminium in the layer of interest (as the substrate contained no aluminium), then the 27Al(d,p01)28 Al nuclear reaction was used. The elastic proton scattering cross section of aluminum was found to vary very rapidly over the energy range of interest.
BibTeX:
	@article{Healy2002,
	  author = {Healy, M.J.F. and Pidduck, A.J. and Dollinger, G. and Görgens, L. and Bergmaier, A.},
	  title = {Ion beam analysis of aluminium in thin layers},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2002},
	  volume = {190},
	  number = {1-4},
	  pages = {630--635},
	  note = {cited By (since 1996)3},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X01012861},
	  doi = {http://doi.org/10.1016/S0168-583X(01)01286-1}
	}
	
The In-Pile Positron Source at the Munich Research Reactor FRM-II
C. Hugenschmidt, K. Schreckenbach, R. Repper and G. Kögel; In: Annual Meeting on Nuclear Technology 2002 Proceedings (2002) 519-522 .
BibTeX:
	@inproceedings{Hugenschmidt:1062,
	  author = {Hugenschmidt, C. and Schreckenbach, K. and Repper, R. and Kögel, G.},
	  title = {The In-Pile Positron Source at the Munich Research Reactor FRM-II},
	  booktitle = {Annual Meeting on Nuclear Technology 2002 Proceedings},
	  year = {2002},
	  pages = {519--522}
	}
	
Intense positron source at the Munich research reactor FRM-II
C. Hugenschmidt, G. Kögel, R. Repper, K. Schreckenbach, P. Sperr, B. Straßer and W. Triftshäuser; Applied Physics A: Materials Science and Processing 74 (SUPPL.I) (2002) S295-S297.
Abstract: The principle and the design of the in-pile positron source at the new Munich research reactor FRM-II are presented. Absorption of high-energy prompt γ-rays from thermal neutron capture in 113Cd generates positrons by pair production. For this purpose, a cadmium cap is placed inside the tip of the inclined beam tube SR11 in the neutron field of the reactor, where an undisturbed thermal neutron flux up to 2 × 1014 n cm-2 s-1 is expected. At this position the flux ratio of thermal to fast neutrons will be better than 104. Monte Carlo calculations showed that a mean capture rate in cadmium between 4.5 and 6.0 × 1013 n cm-2 s-1 can be expected. Inside the cadmium cap a structure of platinum foils is placed for converting γ-radiation into positron-electron pairs. The heated foils also act as positron moderators to generate monoenergetic positrons. After acceleration to 5 keV a positron beam is formed by electric lenses and guided by magnetic fields. In the primary positron beam an intensity up to 1010 slow positrons per second is expected.
BibTeX:
	@article{Hugenschmidt2002,
	  author = {Hugenschmidt, C. and Kögel, G. and Repper, R. and Schreckenbach, K. and Sperr, P. and Straßer, B. and Triftshäuser, W.},
	  title = {Intense positron source at the Munich research reactor FRM-II},
	  journal = {Applied Physics A: Materials Science and Processing},
	  year = {2002},
	  volume = {74},
	  number = {SUPPL.I},
	  pages = {S295-S297},
	  url = {http://link.springer.com/article/10.1007%2Fs003390201398},
	  doi = {http://doi.org/10.1007/s003390201398}
	}
	
First platinum moderated positron beam based on neutron capture
C. Hugenschmidt, G. Kögel, R. Repper, K. Schreckenbach, P. Sperr and W. Triftshäuser; Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 198 (3-4) (2002) 220-229.
Abstract: A positron beam based on absorption of high energy prompt γ-rays from thermal neutron capture in 113Cd was installed at a neutron guide of the high flux reactor at the ILL in Grenoble. Measurements were performed for various source geometries, dependent on converter mass, moderator surface and extraction voltages. The results lead to an optimised design of the in-pile positron source which will be implemented at the Munich research reactor FRM-II. The positron source consists of platinum foils acting as γ-e+e--converter and positron moderator. Due to the negative positron work function moderation in heated platinum leads to emission of monoenergetic positrons. The positron work function of polycrystalline platinum was determined to 1.95(5) eV. After acceleration to several keV by four electrical lenses the beam was magnetically guided in a solenoid field of 7.5 mT leading to a NaI-detector in order to detect the 511 keV γ-radiation of the annihilating positrons. The positron beam with a diameter of less than 20 mm yielded an intensity of 3.1 × 104 moderated positrons per second. The total moderation efficiency of the positron source was about ε = 1.06(16) × 10-4. Within the first 20 h of operation a degradation of the moderation efficiency of 30% was observed. An annealing procedure at 873 K in air recovers the platinum moderator. © 2002 Elsevier Science B.V. All rights reserved.
BibTeX:
	@article{Hugenschmidt2002a,
	  author = {Hugenschmidt, C. and Kögel, G. and Repper, R. and Schreckenbach, K. and Sperr, P. and Triftshäuser, W.},
	  title = {First platinum moderated positron beam based on neutron capture},
	  journal = {Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms},
	  year = {2002},
	  volume = {198},
	  number = {3-4},
	  pages = {220--229},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X02015276},
	  doi = {http://doi.org/10.1016/S0168-583X(02)01527-6}
	}
	
Monoenergetic positron beam at the reactor based positron source at FRM-II
C. Hugenschmidt, G. Kögel, R. Repper, K. Schreckenbach, P. Sperr, B. Straßer and W. Triftshäuser; Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 192 (1-2) (2002) 97-101.
Abstract: The principle of the in-pile positron source at the Munich research reactor FRM-II is based on absorption of high energy prompt γ-rays from thermal neutron capture in 113Cd. For this purpose, a cadmium cap is placed inside the tip of the inclined beam tube SR-11 in the moderator tank of the reactor, where an undisturbed thermal neutron flux up to 2 × 1014 n cm-2s-1 is expected. Inside the cadmium cap a structure of platinum foils is placed for converting high energy γ-radiation into positron-electron pairs. Due to the negative positron work function, moderation in annealed platinum leads to emission of monoenergetic positrons. Therefore, platinum will also be used as moderator, since its moderation property seems to yield long-term stability under reactor conditions and it is much easier to handle than tungsten. Model calculations were performed with SIMION-7.0w to optimise geometry and potential of Pt-foils and electrical lenses. It could be shown that the potentials between the Pt-foils must be chosen in the range of 1-10 V to extract moderated positrons. After successive acceleration to 5 keV by four electrical lenses the beam is magnetically guided in a solenoid field of 7.5 mT resulting in a beam diameter of about 25 mm. An intensity of about 1010 slow positrons per second is expected in the primary positron beam. Outside of the reactor shield a W(1 0 0) single crystal remoderation stage will lead to an improvement of the positron beam brilliance before the positrons are guided to the experimental facilities. © 2002 Elsevier Science B.V. All rights reserved.
BibTeX:
	@article{Hugenschmidt2002b,
	  author = {Hugenschmidt, C. and Kögel, G. and Repper, R. and Schreckenbach, K. and Sperr, P. and Straßer, B. and Triftshäuser, W.},
	  title = {Monoenergetic positron beam at the reactor based positron source at FRM-II},
	  journal = {Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms},
	  year = {2002},
	  volume = {192},
	  number = {1-2},
	  pages = {97--101},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X02007887},
	  doi = {http://doi.org/10.1016/S0168-583X(02)00788-7}
	}
	
Dependence of the doping efficiency on material composition in n-type a-SiOx:H
A. Janotta, R. Janssen, M. Schmidt, T. Graf, L. Görgens, C. Hammerl, S. Schreiber, G. Dollinger, A. Bergmaier, B. Stritzker and M. Stutzmann; Journal of Non-Crystalline Solids 299-302 (PART 1) (2002) 579-584.
Abstract: Amorphous hydrogenated silicon suboxides (a-SiOx:H) deposited by plasma enhanced chemical vapour deposition (PECVD) have a band gap which can be tuned from 1.9 to 3.0 eV by varying the oxygen content from 0 to 50 at.%. n- and p-type doping is realised by adding PH3 and B2H6, respectively, to the source gases SiH4, H2 and CO2. Alloying with increasing amounts of oxygen reduces the mean co-ordination number 〈r〉 from a value close to 4 (a-Si:H) to approximately 2.7, which gradually approaches the ideal value of 〈r〉=2.4 for network glasses. Thus the incorporation of dopant atoms into electrically active, fourfold co-ordinated sites becomes more unlikely with increasing [O]. As a consequence the conductivity, defect density and doping efficiency in phosphorus doped n-type SiOx undergo drastic changes and show increasingly intrinsic character for higher oxygen concentrations. The dependence of the doping efficiency on average co-ordination 〈r〉 is examined in a quantitative manner.
BibTeX:
	@article{Janotta2002,
	  author = {Janotta, A. and Janssen, R. and Schmidt, M. and Graf, T. and Görgens, L. and Hammerl, C. and Schreiber, S. and Dollinger, G. and Bergmaier, A. and Stritzker, B. and Stutzmann, M.},
	  title = {Dependence of the doping efficiency on material composition in n-type a-SiOx:H},
	  journal = {Journal of Non-Crystalline Solids},
	  year = {2002},
	  volume = {299-302},
	  number = {PART 1},
	  pages = {579--584},
	  note = {cited By (since 1996)4},
	  url = {http://www.sciencedirect.com/science/article/pii/S0022309301009632},
	  doi = {http://doi.org/10.1016/S0022-3093(01)00963-2}
	}
	
Radiation-induced defects in 4H- And 6H-SiC epilayers studied by positron annihilation and deep-level transient spectroscopy
A. Kawasuso, M. Weidner, F. Redmann, T. Frank, R. Krause-Rehberg, G. Pensl, P. Sperr, W. Triftshäuser and H. Itoh; Materials Science Forum 389-393 (1) (2002) 489-492.
Abstract: Vacancy defects in high-quality 4H and 6H SiC epilayers induced by electron irradiation have been characterized using positron annihilation and deep level transient spectroscopy (DLTS). Vacancy defects were annealed in two steps below 700°C and above 1200°C irrespective to polytype. From the correlation between positron annihilation and DLTS data using the same wafers, it was confirmed that complexes including silicon vacancies are the origin of the E1/2 levels in 6H SiC and the Z1/2 level in 4H SiC. © 2002 Trans Tech Publications.
BibTeX:
	@article{Kawasuso2002,
	  author = {Kawasuso, A. and Weidner, M. and Redmann, F. and Frank, T. and Krause-Rehberg, R. and Pensl, G. and Sperr, P. and Triftshäuser, W. and Itoh, H.},
	  title = {Radiation-induced defects in 4H- And 6H-SiC epilayers studied by positron annihilation and deep-level transient spectroscopy},
	  journal = {Materials Science Forum},
	  year = {2002},
	  volume = {389-393},
	  number = {1},
	  pages = {489--492},
	  url = {https://www.scientific.net/MSF.389-393.489},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.389-393.489}
	}
	
Microscopes/microprobes
G. Kögel; Applied Surface Science 194 (1-4) (2002) 200-209.
Abstract: Our new pulsed positron microbeam is not only a microprobe for the local analysis of defect characteristics but also a microscope providing a complete lifetime image of defect distributions at micron resolution. Both aspects are discussed with examples from recent applications to basic problems of materials research. For fundamental reasons an image of defects at nanometer resolution by the present generation of microbeams is impossible. Therefore, a more advanced dual microbeam system will be proposed, where the defects are stained with positrons. Then a scanned electron beam with nanometer spot size is sensitive to the stained defects. © 2002 Elsevier Science B.V. All rights reserved.
BibTeX:
	@article{Koegel2002,
	  author = {Kögel, G.},
	  title = {Microscopes/microprobes},
	  journal = {Applied Surface Science},
	  year = {2002},
	  volume = {194},
	  number = {1-4},
	  pages = {200--209},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433202001022},
	  doi = {http://doi.org/10.1016/S0169-4332(02)00102-2}
	}
	
Improved defect profiling with slow positrons
R. Krause-Rehberg, F. Börner, F. Redmann, W. Egger, G. Kögel, P. Sperr and W. Triftshäuser; Applied Surface Science 194 (1-4) (2002) 210-213.
Abstract: Monoenergetic positrons are widely used to study defects in near-surface regions and buried interfaces of solids. Depth information is usually obtained by varying the positron implantation energy. However, at energies larger than 10 keV the stopping profile becomes much broader than the positron diffusion length. The study shows that optimum depth resolution can be obtained by stepwise removal of the surface and measurement with the smallest possible positron implantation depth. The removal from the surface can be done by ion sputtering or chemical etching. Furthermore, excellent defect depth profiles can be obtained when a sample is wedge-shaped polished (wedge angle about 1 °). A line scan using a scanning positron microbeam along the wedge with a small positron implantation depth gives then the defect profile with optimum depth resolution. © 2002 Elsevier Science B.V. All rights reserved.
BibTeX:
	@article{Krause-Rehberg2002,
	  author = {Krause-Rehberg, R. and Börner, F. and Redmann, F. and Egger, W. and Kögel, G. and Sperr, P. and Triftshäuser, W.},
	  title = {Improved defect profiling with slow positrons},
	  journal = {Applied Surface Science},
	  year = {2002},
	  volume = {194},
	  number = {1-4},
	  pages = {210--213},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433202001046},
	  doi = {http://doi.org/10.1016/S0169-4332(02)00104-6}
	}
	
An ultracold neutron (UCN) detector with Ti/6LiF multi-layer converter and 58Ni reflector
P. Maier-Komor, I. Altarev, A. Bergmaier, G. Dollinger, S. Paul, G. Petzoldt and W. Schott; Nuclear Instruments and Methods in Physics Research Section A 480 (1) (2002) 109-113.
Abstract: High efficient detectors for ultracold neutrons (UCN) must be developed for the new high flux neutron source Forschungsreaktor München II (FRM II). On silicon PIN diodes 76 μg/cm2 58Ni was deposited as a UCN reflector. On this 100 double layers of natTi (4.7 μg/cm2) and 6LiF (1.8 μg/cm2) were deposited to function as a UCN converter. On top of this, 33 double layers of natTi (3.4 μg/cm2) and 6LiF (0.92 μg/cm2) were condensed in addition to provide sensitivity to very low-energy UCN. Finally, 6.0 μg/cm2 natV was deposited to protect the multi-layers. Vanadium has nearly zero optical potential for UCN and thus should not hinder their transmission. Since no expensive isotopes were involved, a source to substrate distance of 24 cm could be chosen, leading to excellent uniformity. The setup designed for deposition under ultrahigh vacuum conditions and the evaporation procedures are described.
BibTeX:
	@article{Maier-Komor2002,
	  author = {Maier-Komor, P. and Altarev, I. and Bergmaier, A. and Dollinger, G. and Paul, S. and Petzoldt, G. and Schott, W.},
	  title = {An ultracold neutron (UCN) detector with Ti/6LiF multi-layer converter and 58Ni reflector},
	  journal = {Nuclear Instruments and Methods in Physics Research Section A},
	  year = {2002},
	  volume = {480},
	  number = {1},
	  pages = {109--113},
	  editor = {Ingelbrecht C., Maier-Komor P.},
	  note = {cited By (since 1996)7},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168900201020770},
	  doi = {http://doi.org/10.1016/S0168-9002(01)02077-0}
	}
	
Development of antireflection coatings with a 6LiF/62Ni multilayer converter for ultracold neutron detectors
P. Maier-Komor, I. Altarev, A. Bergmaier, G. Dollinger, S. Paul and W. Schott; Nuclear Instruments and Methods in Physics Research Section A 480 (1) (2002) 104-108.
Abstract: High efficiency detectors for ultracold neutrons (UCN) are needed at the new high flux neutron source, Forschungsreaktor München II. In the development described, silicon PIN diodes were chosen to detect the α-particles or the tritons created in the reaction 6Li(n,α)t. The high reflectance of UCN on 6Li with its positive optical potential must be compensated by a material with negative optical potential. The isotope 62Ni was chosen for this. To avoid problems due to chemical reactions of Li with humidity, the compound 6LiF was chosen. One hundred and fifty double layers of 6LiF/62Ni had to be deposited by physical vapor deposition on silicon PIN diodes which had already been coated with 88 nm ≈ 77 μg/cm2 of 58Ni for reflection of the UCN. The theoretical optimal thickness of the 62Ni layers is 3 nm, and that of 6LiF is 6 nm. Since expensive isotopes were involved, a small source-to-substrate distance had to be used, but with the requirement of excellent uniformity. The complicated setup designed for deposition in the 10-6 Pa range and the evaporation procedures are described.
BibTeX:
	@article{Maier-Komor2002a,
	  author = {Maier-Komor, P. and Altarev, I. and Bergmaier, A. and Dollinger, G. and Paul, S. and Schott, W.},
	  title = {Development of antireflection coatings with a 6LiF/62Ni multilayer converter for ultracold neutron detectors},
	  journal = {Nuclear Instruments and Methods in Physics Research Section A},
	  year = {2002},
	  volume = {480},
	  number = {1},
	  pages = {104--108},
	  editor = {Ingelbrecht C., Maier-Komor P.},
	  note = {cited By (since 1996)5},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168900201020769},
	  doi = {http://doi.org/10.1016/S0168-9002(01)02076-9}
	}
	
Sensitive 3D hydrogen microscopy by proton proton scattering
P. Reichart, G. Dollinger, A. Bergmaier, G. Datzmann, A. Hauptner and H.-J. Körner; Nuclear Instruments and Methods in Physics Research Section B 197 (1-2) (2002) 134-149.
Abstract: Elastic proton proton scattering is a sensitive and fast method for hydrogen analysis. Utilising a nuclear microprobe it is actually the only technique for the absolute quantification of hydrogen distributions with micrometer or even better lateral resolution. High proton energies, e.g. 20 MeV, allow a wide field of applications since even materials, some 100 μm thick, can be analysed. Irradiation damage is reduced to a minimum compared to all other known ion beam analysis techniques, because a large solid angle of detection of some stradian can be used and the nuclear scattering cross section for protons at these energies is enhanced nearly three orders of magnitudes compared to Coulomb scattering. As a consequence, a sensitivity in the ppm range for hydrogen microscopy is possible. However, the large solid angle of detection induces geometrical effects in the energy analysis which are kept within a physical limit by an angular resolution of 10 mrad e.g. by utilising an annular silicon strip detector of 2.3 sr solid angle of detection. Therefore, the third dimension is provided with a depth resolution better 10 μm using the energy information of the scattered protons.
BibTeX:
	@article{Reichart2002,
	  author = {Reichart, P. and Dollinger, G. and Bergmaier, A. and Datzmann, G. and Hauptner, A. and Körner, H.-J.},
	  title = {Sensitive 3D hydrogen microscopy by proton proton scattering},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2002},
	  volume = {197},
	  number = {1-2},
	  pages = {134--149},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X02014799},
	  doi = {http://doi.org/10.1016/S0168-583X(02)01479-9}
	}
	
Hydrogen response mechanism of Pt-GaN Schottky diodes
J. Schalwig, G. Müller, U. Karrer, M. Eickhoff, O. Ambacher, M. Stutzmann, L. Görgens and G. Dollinger; Applied Physics Letters 80 (7) (2002) 1222-1224.
Abstract: Besides silicon carbide, group-III nitrides are also suitable large-band-gap semiconductor materials for high-temperature gas sensor devices. Exposing GaN-based Schottky diodes with catalytically active platinum electrodes to hydrogen, we observed a decrease of the rectifying characteristics which we attribute to a decrease in Schottky barrier height. Current-voltage and elastic recoil detection measurements were used to investigate the H-sensing behavior of such devices. Our results indicate an interfacial effect as the origin of the sensor response to hydrogen.
BibTeX:
	@article{Schalwig2002,
	  author = {Schalwig, J. and Müller, G. and Karrer, U. and Eickhoff, M. and Ambacher, O. and Stutzmann, M. and Görgens, L. and Dollinger, G.},
	  title = {Hydrogen response mechanism of Pt-GaN Schottky diodes},
	  journal = {Applied Physics Letters},
	  year = {2002},
	  volume = {80},
	  number = {7},
	  pages = {1222-1224},
	  note = {cited By (since 1996)140},
	  url = {http://aip.scitation.org/doi/10.1063/1.1450044},
	  doi = {http://doi.org/10.1063/1.1450044}
	}
	
Investigation of defect distributions in neutron-irradiated and thermally treated reactor steels by positron annihilation
V. Slugen, G. Kögel, P. Sperr and W. Triftshäuser; Applied Surface Science 194 (1-4) (2002) 150-154.
Abstract: Positron annihilation spectroscopy (PAS) based on positron lifetime (PL) measurements using the pulsed low-energy positron system (PLEPS) was applied for the investigation of defects of irradiated and thermally treated reactor pressure vessel (RPV) steels. PLEPS results showed that the changes in the micro structure of the RPV-steel properties caused by neutron-irradiation and post-irradiation heat treatment can be well detected. From the lifetime measurements in the near-surface region (20-550nm) the defect density in the Russian types of RPV-steels was calculated using the diffusion trapping model. The post-irradiation heat treatment studies performed on non-irradiated specimens are also presented. © 2002 Elsevier Science B.V. All rights reserved.
BibTeX:
	@article{Slugen2002,
	  author = {Slugen, V. and Kögel, G. and Sperr, P. and Triftshäuser, W.},
	  title = {Investigation of defect distributions in neutron-irradiated and thermally treated reactor steels by positron annihilation},
	  journal = {Applied Surface Science},
	  year = {2002},
	  volume = {194},
	  number = {1-4},
	  pages = {150--154},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433202001162},
	  doi = {http://doi.org/10.1016/S0169-4332(02)00116-2}
	}
	
Positron annihilation studies of neutron irradiated and thermally treated reactor pressure vessel steels
V. Slugen, G. Kögel, P. Sperr and W. Triftshäuser; Journal of Nuclear Materials 302 (2-3) (2002) 89-95.
Abstract: Positron annihilation lifetime measurements using the pulsed low energy positron system (PLEPS) were applied for the first time for the investigation of defects of irradiated and thermally treated reactor pressure vessel (RPV) steels. PLEPS results showed that the changes in the microstructure of the RPV-steel properties caused by neutron irradiation and post-irradiation thermal treatment can be detected. The samples originated from the Russian 15Kh2MFA and Sv10KhMFT steels, commercially used at WWER-440 reactors, were irradiated near the core at NPP Bohunice (Slovakia) to neutron fluences in the range from 7.8 × 1023 to 2.5 × 1024 m-2. © 2002 Elsevier Science B.V. All rights reserved.
BibTeX:
	@article{Slugen2002a,
	  author = {Slugen, V. and Kögel, G. and Sperr, P. and Triftshäuser, W.},
	  title = {Positron annihilation studies of neutron irradiated and thermally treated reactor pressure vessel steels},
	  journal = {Journal of Nuclear Materials},
	  year = {2002},
	  volume = {302},
	  number = {2-3},
	  pages = {89--95},
	  url = {http://www.sciencedirect.com/science/article/pii/S0022311502008152},
	  doi = {http://doi.org/10.1016/S0022-3115(02)00815-2}
	}
	

2001

Negatively charged vacancy defects in 6H-SiC after low-energy proton implantation and annealing
M.-F. Barthe, D. Britton, C. Corbel, A. Hempel, L. Henry, P. Desgardin, W. Bauer-Kugelmann, G. Kögel, P. Sperr and W. Triftshäuser; Physica B: Condensed Matter 308-310 (2001) 668-670.
Abstract: We have used pulsed-slow-positron-beam-based positron lifetime spectroscopy to investigate the nature of acceptors and charge states of vacancy-type defects in low-energy proton-implanted 6H-SiC(H). We can infer from the temperature dependence of the lifetime spectra that neutral and negatively charged vacancy clusters exist in the track region. Depending on annealing, they give rise to positron lifetimes of 257 ±2, 281 ±4 and 345 ±2 ps, respectively. The 281 ps cluster has likely an ionization level near the middle of the band gap. By comparison with theory, the 257 and 280 ps are identified as (VC-VSi)2 and (VC-VSi)3 clusters, respectively. In addition, other acceptors of ionic type act as strong trapping centers at low temperature (T < 150 K). Neutral monovacancy-like complexes are also detected with a lifetime of 160 ±2 after 900°C annealing. © 2001 Elsevier Science B.V. All rights reserved.
BibTeX:
	@article{Barthe2001,
	  author = {Barthe, M.-F. and Britton, D.T. and Corbel, C. and Hempel, A. and Henry, L. and Desgardin, P. and Bauer-Kugelmann, W. and Kögel, G. and Sperr, P. and Triftshäuser, W.},
	  title = {Negatively charged vacancy defects in 6H-SiC after low-energy proton implantation and annealing},
	  journal = {Physica B: Condensed Matter},
	  year = {2001},
	  volume = {308-310},
	  pages = {668--670},
	  url = {http://www.sciencedirect.com/science/article/pii/S0921452601007864},
	  doi = {http://doi.org/10.1016/S0921-4526(01)00786-4}
	}
	
Latest version of the Munich pulsed low energy positron system
W. Bauer-Kugelmann, P. Sperr, G. Kögel and W. Triftshäuser; Materials Science Forum 363-365 (2001) 529-531.
Abstract: Further improvements of the Munich pulsed low energy positron system have been performed. A new chopper, configured as a double plate deflection system with an external resonator and a new buncher working like a classical double gap buncher, are implemented. The complete rf-power electronic was redesigned and operates now at an overall master-frequency of 50 MHz for all bunching and chopping components. A new target station with an enlarged Faraday cage is installed. The sample temperature is variable between 30 K and 600 K. Up to ten samples can be stored in a magazine and transferred under vacuum conditions to the measuring position. With a primary source of 30 mCi 22Na a count rate of up to 4 kHz can be achieved with a peak-to-background ratio of 3000:1. This ratio can be further improved by the use of a Wien filter. A beam diameter of about 2 mm was determined. The total time resolution (pulsing plus detector system) is 250 ps (FWHM).
BibTeX:
	@article{Bauer-Kugelmann2001,
	  author = {Bauer-Kugelmann, W. and Sperr, P. and Kögel, G. and Triftshäuser, W.},
	  title = {Latest version of the Munich pulsed low energy positron system},
	  journal = {Materials Science Forum},
	  year = {2001},
	  volume = {363-365},
	  pages = {529--531},
	  url = {https://www.scientific.net/MSF.363-365.529},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.363-365.529}
	}
	
Deuterium depth profiles at CVD diamond surfaces
A. Bergmaier, G. Dollinger, A. Aleksov, P. Gluche and E. Kohn; Surface Science 481 (1-3) (2001) L433-L436.
Abstract: Homoepitaxial diamond films grown by chemical vapour deposition (CVD) in a methane deuterium plasma were investigated for their deuterium and hydrogen content using high resolution elastic recoil detection (ERD) with a depth resolution of about 0.5 nm. The as-grown diamond films showed large surface conductivity as it is used for diamond surface channel field effect transistors. The ERD measurements revealed an amount of (1.7±0.2) ×1015 at/cm2 of deuterium on the (100) diamond surface, which is in agreement with a deuterium terminated (2 × 1) reconstructed (100) diamond surface. The hydrogen and deuterium bulk concentration is only about 1.0 × 1019 at/cm3, even at a depth of 1.5 nm below the surface. Therefore, it can be concluded, that the highly conductive p-type layer in as-deposited CVD diamond films is not due to additionally incorporated hydrogen in the subsurface region in contrary to many conduction models.
BibTeX:
	@article{Bergmaier2001,
	  author = {Bergmaier, A. and Dollinger, G. and Aleksov, A. and Gluche, P. and Kohn, E.},
	  title = {Deuterium depth profiles at CVD diamond surfaces},
	  journal = {Surface Science},
	  year = {2001},
	  volume = {481},
	  number = {1-3},
	  pages = {L433-L436},
	  note = {cited By (since 1996)14},
	  url = {http://www.sciencedirect.com/science/article/pii/S0039602801010305},
	  doi = {http://doi.org/10.1016/S0039-6028(01)01030-5}
	}
	
Evidence for negatively charged vacancy defects in 6H-SiC after low-energy proton implantation
D. Britton, M.-F. Barthe, C. Corbel, A. Hempel, L. Henry, P. Desgardin, W. Bauer-Kugelmann, G. Kögel, P. Sperr and W. Triftshäuser; Applied Physics Letters 78 (9) (2001) 1234-1236.
Abstract: We have used pulsed-slow-positron-beam-based positron lifetime spectroscopy to investigate the nature of acceptors and charge states of vacancy-type defects in low-energy proton-implanted 6H-SiC(H). We can infer from the temperature dependence of the lifetime spectra that neutral and negatively charged vacancy clusters exist in the track region. Depending on annealing, they give rise to positron lifetimes of 257±2, 281±4, and 345±2 ps, respectively. The 281 ps cluster likely has an ionization level near the middle of the band gap. By comparison with theory, the 257 and 280 ps are identified as (VC-VSi)2 and (VC-VSi)3 clusters, respectively. In addition, other acceptors of ionic type act as strong trapping centers at low temperature (T<150 K). Neutral monovacancy-like complexes are also detected with a lifetime of 160±2 after 900 °C annealing. © 2001 American Institute of Physics.
BibTeX:
	@article{Britton2001,
	  author = {Britton, D.T. and Barthe, M.-F. and Corbel, C. and Hempel, A. and Henry, L. and Desgardin, P. and Bauer-Kugelmann, W. and Kögel, G. and Sperr, P. and Triftshäuser, W.},
	  title = {Evidence for negatively charged vacancy defects in 6H-SiC after low-energy proton implantation},
	  journal = {Applied Physics Letters},
	  year = {2001},
	  volume = {78},
	  number = {9},
	  pages = {1234--1236},
	  url = {http://aip.scitation.org/doi/10.1063/1.1350961},
	  doi = {http://doi.org/10.1063/1.1350961}
	}
	
Pulsed positron beam study of as-grown defects in epitaxial SiC
D. Britton, D. Gxawu, A. Hempel, M.-F. Barthe, L. Henry, P. Desgardin, C. Corbel, W. Bauer-Kugelmann, P. Sperr, G. Kögel and W. Triftshäuser; Materials Science Forum 363-365 (2001) 460-462.
Abstract: We have used slow positron beam based positron lifetime spectroscopy to study positron diffusion in a thick epitaxial n-type 6H-SiC. The layer is considerably thicker than the maximum positron penetration depth, and can therefore be treated as homogeneous semi-infinite bulk material in an analysis including the time-dependent diffusion of a single group of probe particles. Temperature dependent measurements show a reduction in the positron diffusivity below 100K, which can be interpreted by an increase in trapping to shallow defect states. Above this temperature, the behaviour of the diffusivity is consistent with the expected T1/2 dependence due to acoustic phonon scattering.
BibTeX:
	@article{Britton2001a,
	  author = {Britton, D.T. and Gxawu, D. and Hempel, A. and Barthe, M.-F. and Henry, L. and Desgardin, P. and Corbel, C. and Bauer-Kugelmann, W. and Sperr, P. and Kögel, G. and Triftshäuser, W.},
	  title = {Pulsed positron beam study of as-grown defects in epitaxial SiC},
	  journal = {Materials Science Forum},
	  year = {2001},
	  volume = {363-365},
	  pages = {460--462},
	  url = {https://www.scientific.net/MSF.363-365.460},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.363-365.460}
	}
	
Defect characterisation of PECVD-grown diamond
D. Britton, A. Hempel, M. Hempel, M. Härting, W. Bauer-Kugelmann and W. Triftshäuser; Materials Science Forum 363-365 (2001) 511-513.
Abstract: We present the results of a combined study of the defect structure and residual stress in a diamond layer, grown by PECVD on a polycrystalline copper substrate with a titanium interlayer. For the defect studies, both continuous and pulsed positron beam techniques were applied. X-ray diffraction techniques were used for both the stress determination in the diamond layer and for a phase analysis of the complete composite structure. The layer was found to contain a significant fraction of vacancy clusters and single vacancy type defects, situated within the individual grains. The presence of the larger defects can be correlated to a compressive stress in the layer.
BibTeX:
	@article{Britton2001b,
	  author = {Britton, D.T. and Hempel, A. and Hempel, M. and Härting, M. and Bauer-Kugelmann, W. and Triftshäuser, W.},
	  title = {Defect characterisation of PECVD-grown diamond},
	  journal = {Materials Science Forum},
	  year = {2001},
	  volume = {363-365},
	  pages = {511--513},
	  url = {https://www.scientific.net/MSF.363-365.511},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.363-365.511}
	}
	
Hopping transport of positrons in hydrogenated amorphous silicon
D. Britton, A. Hempel and W. Triftshäuser; Physical Review Letters 87 (21) (2001) 2174011-2174014.
Abstract: Positron diffusion was investigated in hydrogenated amorphous silicon using positron beam timing spectroscopy. The measurement of the rate of emission of annihilation photons as a function of the time interval between annihilation and incoming pulse of positrons, allowed the measurement of positron lifetime spectrum at different depths. The results indicated that the dominant positron state in a particular covalent random network was a localized state located at hydrogen terminated dangling bond defects. Hopping diffusion of positrons was observed and the migration enthalpy for positrons in that state was found to be 17.7(3) meV.
BibTeX:
	@article{Britton2001c,
	  author = {Britton, D.T. and Hempel, A. and Triftshäuser, W.},
	  title = {Hopping transport of positrons in hydrogenated amorphous silicon},
	  journal = {Physical Review Letters},
	  year = {2001},
	  volume = {87},
	  number = {21},
	  pages = {2174011--2174014},
	  url = {http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.87.217401},
	  doi = {http://doi.org/10.1103/PhysRevLett.87.217401}
	}
	
Annealing and recrystallization of hydrogenated amorphous silicon
D. Britton, A. Hempel, M. Härting, G. Kögel, P. Sperr, W. Triftshäuser, C. Arendse and D. Knoesen; Physical Review B 64 (7) (2001) 075403.
Abstract: Using a combination of positron annihilation and x-ray-diffraction techniques, we have shown that low hydrogen concentration hot wire chemical vapor deposition grown a-Si:H forms a continuous random network with no detectable free volume in the form of microvoids, and no evidence of a microcrystalline phase. On annealing up to 400 degreesC, the amorphous network is seen to relax and the first stages of recrystallization occur. There is also evidence of vacancy clustering to form a low concentration of microvoids. The structural relaxation has a very low activation energy, around 0.1 eV, and is probably caused by a reconfiguration of hydrogen-terminated dangling, bond defects. The formation of microvoids and therecrystallization can both be interpreted by the migration of unterminated dangling-bond defects.
BibTeX:
	@article{Britton2001d,
	  author = {Britton, D.T. and Hempel, A. and Härting, M. and Kögel, G. and Sperr, P. and Triftshäuser, W. and Arendse, C. and Knoesen, D.},
	  title = {Annealing and recrystallization of hydrogenated amorphous silicon},
	  journal = {Physical Review B},
	  year = {2001},
	  volume = {64},
	  number = {7},
	  pages = {075403},
	  url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.64.075403},
	  doi = {http://doi.org/10.1103/PhysRevB.64.075403}
	}
	
The Munich microprobe SNAKE: First results using 20 MeV protons and 90 MeV sulfur ions
G. Datzmann, G. Dollinger, C. Goeden, A. Hauptner, H.-J. Körner, P. Reichart and O. Schmelmer; Nuclear Instruments and Methods in Physics Research Section B 181 (1-4) (2001) 20-26.
Abstract: The scanning ion microprobe called Superconducting Nanoscope for Applied nuclear (Kern) physics Experiments (SNAKE) is taken into operation at the Munich 15 MV tandem accelerator. During the first experiments 16 and 20 MeV protons as well as 90 MeV 32S ions were used to test all equipments. With a reduced divergence of the beam, an overall lateral resolution of 700 nm was achieved by scanning a gold grid with a focused 90 MeV sulfur beam and detecting transmitted ions. However, some field distortions at full acceptance of the lens were detected which derive from mechanical problems at higher coil currents. In addition to the beam characterisation experiments several new detector systems were tested. Analysing the 90 MeV sulfur beam by a magnetic spectrograph behind the target chamber in transmission geometry, an overall relative energy width of 3.8×10−5 fwhm was demonstrated.
BibTeX:
	@article{Datzmann2001,
	  author = {Datzmann, Gerd and Dollinger, Günther and Goeden, Christian and Hauptner, Andreas and Körner, Hans-Joachim and Reichart, Patrick and Schmelmer, Oliver},
	  title = {The Munich microprobe SNAKE: First results using 20 MeV protons and 90 MeV sulfur ions},
	  booktitle = {7th International Conference on Nuclear Microprobe Technology and Applications},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2001},
	  volume = {181},
	  number = {1-4},
	  pages = {20--26},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X01005493},
	  doi = {http://doi.org/10.1016/S0168-583X(01)00549-3}
	}
	
Lifetime measurements with a scanning positron microscope
A. David, G. Kögel, P. Sperr and W. Triftshäuser; Physical Review Letters 87 (6) (2001) 674021-674024.
Abstract: The visible and invisible damage to the defect structure of a GaAs wafer was identified by first lifetime measurements using the scanning positron microscope. A pulsed positron beam formed by cooling positrons from a radioactive source was scanned over an area of 0.6×0.6 mm 2. A scanning electron microprobe was also included in the system for surface analysis.
BibTeX:
	@article{David2001,
	  author = {David, A. and Kögel, G. and Sperr, P. and Triftshäuser, W.},
	  title = {Lifetime measurements with a scanning positron microscope},
	  journal = {Physical Review Letters},
	  year = {2001},
	  volume = {87},
	  number = {6},
	  pages = {674021--674024},
	  url = {http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.87.067402},
	  doi = {http://doi.org/10.1103/PhysRevLett.87.067402}
	}
	
Investigation of stainless steel films sputtered on glass
J. De Baerdemaeker, T. Van Hoecke, S. Van Petegem, D. Segers, W. Bauer-Kugelmann, P. Sperr and G. Terwagne; Materials Science Forum 363-365 (2001) 496-498.
Abstract: The influence of the sputter atmosphere on glass supported magnetron sputtered stainless steel films was investigated using Positron Annihilation Lifetime Spectroscopy (PALS) and Doppler-Broadening Annihilation Radiation (DBAR) as well as Rutherford Backscattering (RBS), Integral Low Energy Electron Mössbauer Spectroscopy (ILEEMS), Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM).
BibTeX:
	@article{DeBaerdemaeker2001,
	  author = {De Baerdemaeker, J. and Van Hoecke, T. and Van Petegem, S. and Segers, D. and Bauer-Kugelmann, W. and Sperr, P. and Terwagne, G.},
	  title = {Investigation of stainless steel films sputtered on glass},
	  journal = {Materials Science Forum},
	  year = {2001},
	  volume = {363-365},
	  pages = {496--498},
	  url = {https://www.scientific.net/MSF.363-365.496},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.363-365.496}
	}
	
Identification of defect sites in FeAl by Doppler spectroscopy of core electrons
W. Egger, G. Bischof, V. Gröger and G. Krexner; Materials Science Forum 363-365 (2001) 82-84.
Abstract: Doppler spectroscopy of core electrons is used to identify defect sites in the intermetallic compound FeAl. Two-dimensional annihilation spectra were recorded both for elemental Al and Fe and for the intermetallic compound FeAl. Experimental data are compared with calculations based on density functional theory using the generalized gradient approximation (GGA) for the positron annihilation. In accordance with earlier work vacancies are found to be located on the Fe sublattice. The results show that the accuracy achieved, both experimentally and theoretically, is sufficient to distinguish clearly between vacancies on different sublattices.
BibTeX:
	@article{Egger2001,
	  author = {Egger, W. and Bischof, G. and Gröger, V. and Krexner, G.},
	  title = {Identification of defect sites in FeAl by Doppler spectroscopy of core electrons},
	  journal = {Materials Science Forum},
	  year = {2001},
	  volume = {363-365},
	  pages = {82--84},
	  url = {https://www.scientific.net/MSF.363-365.82},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.363-365.82}
	}
	
Energy distribution of thermally emitted negative particles from type Ia diamond (100)
C. Goeden and G. Dollinger; Diamond and Related Materials 10 (3-7) (2001) 496-499.
Abstract: This study explores the electron emission of natural, nitrogen-doped diamond at elevated temperatures. The diamond was resistively heated up to 870°C. Accruing negatively charged particles where accelerated by a bias voltage of 30 V and the energy distribution is measured. The electrons are analysed by an electrostatic deflection resulting in an energy resolution of 70 meV. A hydrogen-free surface at a base pressure of 2.0×10−9 mbar shows a very small emission. The energy distribution has its maximum at 2.5 eV and a FWHM of 0.52 eV. Beside the main emission peak, some smaller features are observable at higher energies. An atomic hydrogen supply at 1.9×10−5 mbar increases the emission by a factor of 30. With some delay to the hydrogen supply, a new low energy peak appears. The increase in intensity during hydrogen adsorption is explained by the occurrence of a negative electron affinity (NEA) of the hydrogen-covered diamond surface. The low-energy feature might be due to hydrogen ions, either desorbing from the surface or from charge transfer during collisions of gas phase hydrogen with the diamond surface.
BibTeX:
	@article{Goeden2001,
	  author = {Goeden, C. and Dollinger, G.},
	  title = {Energy distribution of thermally emitted negative particles from type Ia diamond (100)},
	  booktitle = {11th European Conference on Diamond, Diamond-like Materials, Carbon Nanotubes, Nitrides and Silicon Carbide},
	  journal = {Diamond and Related Materials},
	  year = {2001},
	  volume = {10},
	  number = {3-7},
	  pages = {496--499},
	  url = {http://www.sciencedirect.com/science/article/pii/S0925963500004544},
	  doi = {http://doi.org/10.1016/S0925-9635(00)00454-4}
	}
	
Annealing effects in hydrogenated amorphous silicon layers
A. Hempel, A. Dabrowski, M. Härting, M. Hempel, D. Knoesen, W. Bauer-Kugelmann, G. Kögel, W. Triftshäuser and D. Britton; Materials Science Forum 363-365 (2001) 463-465.
Abstract: The annealing behaviour of defect structures in hydrogenated amorphous silicon, produced by hot wire chemical vapour deposition (HWCVD) has been studied by pulsed and conventional positron beam techniques and X-ray diffraction. Positron lifetime measurements show a dominant component corresponding to small vacancy clusters. Doppler Broadening measurements indicate that the size and concentration of defects varies with annealing temperatures up to 400°C. This behaviour is accompanied by a change from the amorphous to a partly crystalline structure, which can be observed by X-ray diffraction studies.
BibTeX:
	@article{Hempel2001,
	  author = {Hempel, A. and Dabrowski, A. and Härting, M. and Hempel, M. and Knoesen, D. and Bauer-Kugelmann, W. and Kögel, G. and Triftshäuser, W. and Britton, D.T.},
	  title = {Annealing effects in hydrogenated amorphous silicon layers},
	  journal = {Materials Science Forum},
	  year = {2001},
	  volume = {363-365},
	  pages = {463--465},
	  url = {https://www.scientific.net/MSF.363-365.463},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.363-365.463}
	}
	
Defect studies of diamond hard coatings
A. Hempel, M. Hempel, M. Härting, D. Britton, W. Bauer-Kugelmann and W. Triftshäuser; Radiation Effects and Defects in Solids 156 (1) (2001) 215-220.
Abstract: We present the results of a combined study of the defect structure and residual stress in a diamond layer, grown by PECVD on a polycrystalline copper substrate with a titanium interlayer. For the defect studies, electron spectroscopies based on electron-positron annihilation were applied. X-ray diffraction techniques were used for both the stress determination in the diamond layer and for a phase analysis of the complete composite structure. The layer was found to contain a significant fraction of vacancy clusters and single vacancy type defects, which are probably situated within the individual grains. The presence of the larger defects may be related to a compressive stress in the layer.
BibTeX:
	@article{Hempel2001a,
	  author = {Hempel, A. and Hempel, M. and Härting, M. and Britton, D.T. and Bauer-Kugelmann, W. and Triftshäuser, W.},
	  title = {Defect studies of diamond hard coatings},
	  journal = {Radiation Effects and Defects in Solids},
	  year = {2001},
	  volume = {156},
	  number = {1},
	  pages = {215--220},
	  url = {http://www.tandfonline.com/doi/abs/10.1080/10420150108216896},
	  doi = {http://doi.org/10.1080/10420150108216896}
	}
	
Intense positron source at the Munich research reactor FRM-II
C. Hugenschmidt, G. Kögel, K. Schreckenbach, P. Sperr, B. Straßer and W. Triftshäuser; Materials Science Forum 363-365 (2001) 425-429.
Abstract: Principle and design of the intense positron source facility at the new Munich research reactor FRM-II is presented. Absorption of high energy prompt γ rays from thermal neutron capture in 113Cd generates positrons by pair production. For this purpose, a cadmium cap will be placed inside a beam tube in the neutron field of the reactor, where an undisturbed thermal neutron flux up to 2·1014 n·cm-2s-1 is expected. At this position the flux ratio of thermal to fast neutron will be better than 104. Monte Carlo calculation showed that a mean capture rate in cadmium between 4.5 and 6.0·1013 n·cm-2s-1 can be expected. Absorption of γ rays would lead to a heat impact less than 4 Wcm-2. Inside the cadmium cap a structure of platinum is placed for converting the γ radiation into positron-electron pairs. As converting material platinum is used, since the cross section for pair production is even higher than in tungsten. The heated platinum foils also act as moderators. The positron beam with a primary energy of about 5 keV is formed by electric lenses and magnetic fields. A remoderation stage leads to an improvement of the positron beam brilliance, where an intensity of about 109 slow positrons per second can be expected.
BibTeX:
	@article{Hugenschmidt2001,
	  author = {Hugenschmidt, C. and Kögel, G. and Schreckenbach, K. and Sperr, P. and Straßer, B. and Triftshäuser, W.},
	  title = {Intense positron source at the Munich research reactor FRM-II},
	  journal = {Materials Science Forum},
	  year = {2001},
	  volume = {363-365},
	  pages = {425--429},
	  url = {https://www.scientific.net/MSF.363-365.425},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.363-365.425}
	}
	
Annealing behavior of vacancies and Z1/2 levels in electron-irradiated 4H-SiC studied by positron annihilation and deep-level transient spectroscopy
A. Kawasuso, F. Redmann, R. Krause-Rehberg, M. Weidner, T. Frank, G. Pensl, P. Sperr, W. Triftshäuser and H. Itoh; Applied Physics Letters 79 (24) (2001) 3950-3952.
Abstract: Annealing behavior of vacancies and the Z1/2 levels in n-type 4H-SiC epilayers after 2 MeV electron irradiation has been studied using positron annihilation and deep-level transient spectroscopy. Isochronal annealing studies indicate that silicon vacancy-related defects are primarily responsible for positron trapping. The Z1/2 levels are the predominant deep centers after irradiation and subsequent annealing at 1200 °C. Both the positron-trapping rate at vacancies and the Z1/2 concentration decrease in a similar manner while annealing from 1200 to 1500 °C. It is thus proposed that the Z1/2 levels originate from silicon vacancy-related defects. © 2001 American Institute of Physics.
BibTeX:
	@article{Kawasuso2001,
	  author = {Kawasuso, A. and Redmann, F. and Krause-Rehberg, R. and Weidner, M. and Frank, T. and Pensl, G. and Sperr, P. and Triftshäuser, W. and Itoh, H.},
	  title = {Annealing behavior of vacancies and Z1/2 levels in electron-irradiated 4H-SiC studied by positron annihilation and deep-level transient spectroscopy},
	  journal = {Applied Physics Letters},
	  year = {2001},
	  volume = {79},
	  number = {24},
	  pages = {3950--3952},
	  url = {http://aip.scitation.org/doi/10.1063/1.1426259},
	  doi = {http://doi.org/10.1063/1.1426259}
	}
	
Vacancies and deep levels in electron-irradiated 6H SiC epilayers studied by positron annihilation and deep level transient spectroscopy
A. Kawasuso, F. Redmann, R. Krause-Rehberg, T. Frank, M. Weidner, G. Pensl, P. Sperr and H. Itoh; Journal of Applied Physics 90 (7) (2001) 3377-3382.
Abstract: The annealing behavior of defects in n-type 6H SiC epilayers irradiated with 2 MeV electrons have been studied using positron annihilation and deep level transient spectroscopy. Vacancy-type defects are annealed at 500-700°C and 1200-1400°C. From the analysis of Doppler broadening spectra (core electron momentum distribution), the latter annealing process is attributed to the disappearance of complexes related to silicon vacancies and not to nearest neighbor divacancies. Among the observed deep levels, the E1/E2 levels show similar annealing behavior to that of positron annihilation centers above 1000°C. It is thus proposed that the E1/E2 levels originate from complexes containing silicon vacancies. © 2001 American Institute of Physics.
BibTeX:
	@article{Kawasuso2001a,
	  author = {Kawasuso, A. and Redmann, F. and Krause-Rehberg, R. and Frank, T. and Weidner, M. and Pensl, G. and Sperr, P. and Itoh, H.},
	  title = {Vacancies and deep levels in electron-irradiated 6H SiC epilayers studied by positron annihilation and deep level transient spectroscopy},
	  journal = {Journal of Applied Physics},
	  year = {2001},
	  volume = {90},
	  number = {7},
	  pages = {3377--3382},
	  url = {http://aip.scitation.org/doi/10.1063/1.1402144},
	  doi = {http://doi.org/10.1063/1.1402144}
	}
	
Annealing Process of Defects in Epitaxial SiC Induced by He and Electron Irradiation: Positron Annihilation Study
A. Kawasuso, F. Redmann, R. Krause-Rehberg, P. Sperr, T. Frank, M. Weidner, G. Pensl and H. Itoh; Materials Science Forum 353-356 (2001) 537-540.
Abstract: Annealing processes of vacancy-type defects in epitaxial 6H SiC after 2 MeV electron irradiation and multiple He implantation have been investigated using positron annihilation spectroscopy. Vacancy-type defects are found to disappear in two annealing stages: at 500-800°C and 1200-1500°C. Silicon vacancies are the major positron trapping centers after electron irradiation. Two annealing stages after electron irradiation are attributed to the disappearance of isolated silicon vacancies and complexes associated with silicon vacancies, respectively. In He-irradiated SiC, divacancies are also generated in addition to silicon vacancies.
BibTeX:
	@article{Kawasuso2001b,
	  author = {Kawasuso, Atsuo and Redmann, F. and Krause-Rehberg, R. and Sperr, Peter and Frank, Thomas and Weidner, Michael and Pensl, Gerhard and Itoh, Hisayoshi},
	  title = {Annealing Process of Defects in Epitaxial SiC Induced by He and Electron Irradiation: Positron Annihilation Study},
	  journal = {Materials Science Forum},
	  year = {2001},
	  volume = {353-356},
	  pages = {537--540},
	  url = {https://www.scientific.net/MSF.353-356.537},
	  doi = {http://doi.org/10.4028/www.scientific.net/msf.353-356.537}
	}
	
Vacancies in He-implanted 4H and 6H SiC epilayers studied by positron annihilation
A. Kawasuso, M. Weidner, F. Redmann, T. Frank, P. Sperr, R. Krause-Rehberg, W. Triftshäuser and G. Pensl; Physica B: Condensed Matter 308-310 (2001) 660-663.
Abstract: Defects in epitaxially grown 4H and 6H SiC induced by He-implantation have been studied by positron annihilation and deep level transient spectroscopy. Two major annealing processes of vacancy-type defects appeared at 500-800°C and above 1000°C irrespective of polytype and conduction type. In n-type samples, the latter process is dominated by two different types of defects. In n-type 6H SiC, Z1/2 levels emerged after annealing at 800°C. The Z1/2 levels disappeared around 1100°C with an appearance of E1/2 levels. The E1/2 levels are eventually annealed at 1500-1700°C. Similar annealing behavior was observed for the corresponding levels in n-type 4H SiC, i.e., RD1/2 and Z1/2 levels. The overall annealing behavior of vacancy-type defects by positron annihilation and the deep levels are in good agreement above 800°C suggesting that the above deep levels are related to the vacancy-type defects. © 2001 Elsevier Science B.V. All rights reserved.
BibTeX:
	@article{Kawasuso2001c,
	  author = {Kawasuso, A. and Weidner, M. and Redmann, F. and Frank, T. and Sperr, P. and Krause-Rehberg, R. and Triftshäuser, W. and Pensl, G.},
	  title = {Vacancies in He-implanted 4H and 6H SiC epilayers studied by positron annihilation},
	  journal = {Physica B: Condensed Matter},
	  year = {2001},
	  volume = {308-310},
	  pages = {660--663},
	  url = {http://www.sciencedirect.com/science/article/pii/S0921452601007839},
	  doi = {http://doi.org/10.1016/S0921-4526(01)00783-9}
	}
	
Positron microscopy
G. Kögel; Materials Science Forum 363-365 (2001) 409-414.
Abstract: Positron Microscopy, particularly by means of a scanned positron microbeam, offers an universal route to control positrons before and, in principle, after the implantation into condensed matter. Besides spatial resolution also the measurements of defect concentrations and specific trapping rates are enabled. The current technique and some results will be reviewed. Instrumental requirements will be discussed for studies of various defect configurations as well as for the more advanced techniques of multi-positron pulses and of a release of positrons from surfaces and other traps.
BibTeX:
	@article{Koegel2001,
	  author = {Kögel, G.},
	  title = {Positron microscopy},
	  journal = {Materials Science Forum},
	  year = {2001},
	  volume = {363-365},
	  pages = {409--414},
	  url = {https://www.scientific.net/MSF.363-365.409},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.363-365.409}
	}
	
Identification of getter defects in high-energy self-implanted silicon at Rp/2
R. Krause-Rehberg, F. Börner, F. Redmann, J. Gebauer, R. Kögler, R. Kliemann, W. Skorupa, W. Egger, G. Kögel and W. Triftshäuser; Physica B: Condensed Matter 308-310 (2001) 442-445.
Abstract: A strong gettering effect appears after high-energy Si self-implantation and subsequent annealing in two zones at the projected range of the silicon ions (Rp) and in a region at about Rp/2. The defects responsible for the impurity gettering at Rp/2 were studied by means of positron annihilation. It was found that diffusing Cu impurities were captured by small vacancy agglomerates. Monoenergetic positron beams with improved depth resolution were used to characterize the defects. Excellent depth resolution was obtained when samples were wedge-shaped polished and studied using the Munich Scanning Positron Microscope. © 2001 Elsevier Science B.V. All rights reserved.
BibTeX:
	@article{Krause-Rehberg2001,
	  author = {Krause-Rehberg, R. and Börner, F. and Redmann, F. and Gebauer, J. and Kögler, R. and Kliemann, R. and Skorupa, W. and Egger, W. and Kögel, G. and Triftshäuser, W.},
	  title = {Identification of getter defects in high-energy self-implanted silicon at Rp/2},
	  journal = {Physica B: Condensed Matter},
	  year = {2001},
	  volume = {308-310},
	  pages = {442--445},
	  url = {http://www.sciencedirect.com/science/article/pii/S0921452601007177},
	  doi = {http://doi.org/10.1016/S0921-4526(01)00717-7}
	}
	
High-resolution elastic recoil detection utilizing Bayesian probability theory
P. Neumaier, G. Dollinger, A. Bergmaier, I. Genchev, L. Görgens, R. Fischer, C. Ronning and H. Hofsäss; Nuclear Instruments and Methods in Physics Research Section B 183 (1-2) (2001) 48-61.
Abstract: Elastic recoil detection (ERD) analysis is improved in view of depth resolution and the reliability of the measured spectra. Good statistics at even low ion fluences is obtained utilizing a large solid angle of 5 msr at the Munich Q3D magnetic spectrograph and using a 40 MeV 197Au beam. In this way the elemental depth profiles are not essentially altered during analysis even if distributions with area densities below 1×1014 atoms/cm2 are measured. As the energy spread due to the angular acceptance is fully eliminated by ion-optical and numerical corrections, an accurate and reliable apparatus function is derived. It allows to deconvolute the measured spectra using the adaptive kernel method, a maximum entropy concept in the framework of Bayesian probability theory. In addition, the uncertainty of the reconstructed spectra is quantified. The concepts are demonstrated at 13C depth profiles measured at ultra-thin films of tetrahedral amorphous carbon (ta-C). Depth scales of those profiles are given with an accuracy of 1.4×1015 atoms/cm2.
BibTeX:
	@article{Neumaier2001,
	  author = {Neumaier, P. and Dollinger, G. and Bergmaier, A. and Genchev, I. and Görgens, L. and Fischer, R. and Ronning, C. and Hofsäss, H.},
	  title = {High-resolution elastic recoil detection utilizing Bayesian probability theory},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2001},
	  volume = {183},
	  number = {1-2},
	  pages = {48--61},
	  note = {cited By (since 1996)17},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X01003470},
	  doi = {http://doi.org/10.1016/S0168-583X(01)00347-0}
	}
	
Anisotropy of the electron momentum density of graphite studied by (γ,eγ) and (e,2e) spectroscopy
T. Sattler, T. Tschentscher, J. Schneider, M. Vos, A. Kheifets, D. Lun, E. Weigold, G. Dollinger, H. Bross and F. Bell; Physical Review B - Condensed Matter and Materials Physics 63 (15) (2001) 1552041-15520417.
Abstract: The electron momentum density (EMD) of two different modifications of graphite has been measured and the results of the measurements have been compared with theoretical calculations from three different theories: a full potential linear muffin-tin orbital, a modified augmented plane wave, and a pseudopotential calculation. Experimental results have been obtained by two different methods. The complete three-dimensional EMD is determined by inelastic photon-electron scattering, i.e., by the so-called (γ,eγ) experiment, and by electron-electron scattering, the (e,2e) experiment, cuts in the spectral electron momentum density are studied. For the (γ,eγ) experiment 180 keV synchrotron radiation from the PETRA storage ring at the Deutsches Elektronen-Synchrotron has been used with coincident detection of the recoil electrons. The (e,2e) experiments were carried out at the new (e,2e) spectrometer at the Australian National University using 40 keV primary electron energy and simultaneous detection of the outgoing electrons in an equal energy sharing mode. As samples we have prepared approximately 20 nm thin self-supporting graphite foils either by thermal evaporation (TE) or by laser plasma ablation (LPA). They are thin enough to suppress in essence electron multiple scattering. Electron diffraction analysis revealed that the LPA foil contains graphitic basal planes with a random distribution of c axes, whereas the TE foil was strongly c-axis oriented in the sense that the basal planes were parallel to the foil surface. In the analysis of the results special attention was devoted to anisotropies in the EMD revealed by comparison of TE and LPA foils. The (e,2e) measurements showed furthermore a strong orientation dependence of the intensity of π and σ states (here we have for comparison additionally measured highly oriented pyrolytic graphite). The EMD's obtained by both techniques show anisotropies in the momentum distribution of graphite and are discussed in view of the theoretical results.
BibTeX:
	@article{Sattler2001,
	  author = {Sattler, T. and Tschentscher, Th. and Schneider, J.R. and Vos, M. and Kheifets, A.S. and Lun, D.R. and Weigold, E. and Dollinger, G. and Bross, H. and Bell, F.},
	  title = {Anisotropy of the electron momentum density of graphite studied by (γ,eγ) and (e,2e) spectroscopy},
	  journal = {Physical Review B - Condensed Matter and Materials Physics},
	  year = {2001},
	  volume = {63},
	  number = {15},
	  pages = {1552041-15520417},
	  note = {cited By (since 1996)9},
	  url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.63.155204},
	  doi = {http://doi.org/10.1103/PhysRevB.63.155204}
	}
	
Particle-induced X-ray emission using high energy ions with respect to microprobe application
O. Schmelmer, G. Dollinger, G. Datzmann, A. Hauptner, H.-J. Körner, P. Maier-Komor and P. Reichart; Nuclear Instruments and Methods in Physics Research Section B 179 (4) (2001) 469-479.
Abstract: Cross-sections for continuous and characteristic X-ray emission from heavy elements induced by 16 MeV protons and 70 MeV carbon ions are measured. The K- and L-line emission cross-sections are significantly increased compared to those of lower proton energies. The data are in satisfactory agreement with semi-empirical calculations for the proton beams while the experimental cross-sections for the 70 MeV carbon ions are up to one order of magnitude lower as calculated. The continuous X-ray background for protons can also be well described by theory taking into account the various sources of X-ray production by bremsstrahlung whereas again for carbon ions the background is overestimated by scaled theory. The sensitivity for particle-induced X-ray emission (PIXE) using high energy ions is within the same order of magnitude as that for the commonly used 1-3 MeV protons. However, 16 MeV proton beams may be better suited for PIXE analysis with submicron-sized beams due to the lower ion currents necessary from the increased X-ray production cross-sections and because the sample damage and lateral spread are reduced.
BibTeX:
	@article{Schmelmer2001,
	  author = {Schmelmer, O. and Dollinger, G. and Datzmann, G. and Hauptner, A. and Körner, H.-J. and Maier-Komor, P. and Reichart, P.},
	  title = {Particle-induced X-ray emission using high energy ions with respect to microprobe application},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2001},
	  volume = {179},
	  number = {4},
	  pages = {469--479},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X01006085},
	  doi = {http://doi.org/10.1016/S0168-583X(01)00608-5}
	}
	
Ein Rasterionenmikroskop für hochenergetische Ionen
Oliver Schmelmer; Dissertation, Technische Universität München, 2001.
Abstract: Im Rahmen der Arbeit wurden am Münchener Tandem Beschleuniger wesentliche Komponenten des Rasterionenmikroskops SNAKE (Supraleitendes Nanoskop für Angewandte Kernphysikalische Experimente) zur Materialanalyse und -modifikation aufgebaut. SNAKE dient zur Fokussierung von hochenergetischen Ionenstrahlen auf einen Strahldurchmesser von 100 nm. Für den sensitiven Nachweis mittelschwerer bis schwerer Elemente (Z > 26) wurde das Potential der teilcheninduzierten Röntgenfluoreszenzanalyse (PIXE, Particle Induced X-ray Emission) mit 16 MeV Protonen und 70 MeV Kohlenstoffionen untersucht.
BibTeX:
	@phdthesis{Schmelmer2001diss,
	  author = {Schmelmer, Oliver},
	  title = {Ein Rasterionenmikroskop für hochenergetische Ionen},
	  school = {Technische Universität München},
	  year = {2001},
	  url = {http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:91-diss2001072513284}
	}
	
Investigation of reactor steels
V. Slugen, J. Hascik, R. Gröne, P. Bartik, A. Zeman, G. Kögel, P. Sperr and W. Triftshäuser; Materials Science Forum 363-365 (2001) 47-51.
Abstract: Positron annihilation spectroscopy (PAS) techniques, Mössbauer spectroscopy (MS) and transmission electron microscopy (TEM) were applied in the investigation of thermally treated reactor pressure vessel steels (RPV). Results of these methods are discussed and correlated with hardness measurement. PAS and MS measurements have been performed also on the original RPV specimens which are used in frame of the "Extended surveillance specimen program" at the 3rd and 4th units of NPP Jaslovské Bohunice (Slovakia). PAS angular correlation (1D-ACAR) and lifetime spectra (PLEPS) showed that the degradation of the steel properties caused by neutron irradiation can be detected. General discussion about the contribution of PAS to micro structural study of RPV-steels is included as well.
BibTeX:
	@article{Slugen2001,
	  author = {Slugen, V. and Hascik, J. and Gröne, R. and Bartik, P. and Zeman, A. and Kögel, G. and Sperr, P. and Triftshäuser, W.},
	  title = {Investigation of reactor steels},
	  journal = {Materials Science Forum},
	  year = {2001},
	  volume = {363-365},
	  pages = {47--51},
	  url = {https://www.scientific.net/MSF.363-365.47},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.363-365.47}
	}
	
Pulsed positron beam in investigation of reactor steels
V. Slugeň, G. Kögel, P. Sperr and W. Triftshäuser; Journal of Electrical Engineering 52 (03-04) (2001) 88-91.
Abstract: The improved pulsed low-energy positron system (PLEPS) was used for positron lifetime spectroscopy in the investigation of irradiated nuclear reactor pressure vessel (RPV) steels microstructure. This system allows to study the microstructural changes in the region from 20 to 600 nm with small and very thin specimens by reducing the disturbing 60Co contribution to minimum. Such disturbance was the limiting factor for investigation of high-irradiated RPV specimens in the past. In the frame of the so-called "Extended surveillance specimens program'' started at the 3rd and 4th units of the nuclear power plant (NPP) Bohunice (Slovakia) in 1994, well-defined specimens were placed into irradiation channels and taken out after 1, 2 and 3 years in operated VVER-440 reactor, respectively. Samples from RPV base material (15Kh2MFA) and weld material (Sv10KhMFT) were measured before and after irradiation by neutron fluency in the range from 7.8x1023m-2 up to 2.3x1024m-2. Results from PLEPS measurements were correlated with those from other spectroscopic methods (Mössbauer spectroscopies and HV10) and discussed in detail.
BibTeX:
	@article{Slugen2001a,
	  author = {Slugeň, Vladimír and Kögel, Gottfried and Sperr, Peter and Triftshäuser, Werner},
	  title = {Pulsed positron beam in investigation of reactor steels},
	  journal = {Journal of Electrical Engineering},
	  year = {2001},
	  volume = {52},
	  number = {03-04},
	  pages = {88--91},
	  url = {http://iris.elf.stuba.sk/cgi-bin/jeeec?act=abs&no=03-04_101&ttl=6}
	}
	
'Smart cut' silicon by proton implantation: Lifetime studies with a pulsed positron beam
P. Sperr, G. Kögel, W. Bauer-Kugelmann, W. Triftshäuser and M. Fujinami; Materials Science Forum 363-365 (2001) 532-536.
Abstract: High dose implantation of hydrogen into silicon and subsequent annealing induce a splitting of silicon. The state of hydrogen and the implantation induced defects are of scientific and technological interest. Samples implanted with 1 · 1016 and 5 · 1016 H+/cm2 at an energy of 60 keV were investigated after different thermal annealing treatments with the pulsed positron beam as a function of the positron energy and the specimen temperature (80K to 500K). There is clear evidence of growth of defect clusters with increasing annealing temperature which correspond in depth with the mean projected range of the implanted hydrogen atoms. In addition to the large defect agglomerates, there are most likely shallow positron traps which are effective only when the specimens are measured at low temperature.
BibTeX:
	@article{Sperr2001,
	  author = {Sperr, P. and Kögel, G. and Bauer-Kugelmann, W. and Triftshäuser, W. and Fujinami, M.},
	  title = {'Smart cut' silicon by proton implantation: Lifetime studies with a pulsed positron beam},
	  journal = {Materials Science Forum},
	  year = {2001},
	  volume = {363-365},
	  pages = {532--536},
	  url = {https://www.scientific.net/MSF.363-365.532},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.363-365.532}
	}
	
Nitrogen implantations for rapid thermal oxinitride layers
A. Stadler, I. Genchev, A. Bergmaier, G. Dollinger, V. Petrova-Koch, W. Mansch, H. Baumgärtner and I. Eisele; Microelectronics and Reliability 41 (7) (2001) 977-980.
Abstract: Oxidation of nitrogen implanted substrates results in so called silicon-oxinitride layers (SixOyNz layers) which are dependent on implantation dose and energy always thinner than pure silicon-oxides (SiO2) produced under the same oxidation conditions. Elastic recoil detection profiles indicate that the implanted nitrogen diffuses out of the substrate into the silicon-oxide layer what improves the electrical quality of these insulators. The SixOyNz layers show lower Fowler-Nordheim tunnelling currents as well as lower interface state densities (Dit) than the corresponding SiO2 layers or N2O-silicon-oxinitride insulators. NH3-SixOyNz layers show the lowest Dit values because of H2-annealing effects but contain fixed charges.
BibTeX:
	@article{Stadler2001,
	  author = {Stadler, A. and Genchev, I. and Bergmaier, A. and Dollinger, G. and Petrova-Koch, V. and Mansch, W. and Baumgärtner, H. and Eisele, I.},
	  title = {Nitrogen implantations for rapid thermal oxinitride layers},
	  journal = {Microelectronics and Reliability},
	  year = {2001},
	  volume = {41},
	  number = {7},
	  pages = {977--980},
	  note = {cited By (since 1996)5},
	  url = {http://www.sciencedirect.com/science/article/pii/S0026271401000518},
	  doi = {http://doi.org/10.1016/S0026-2714(01)00051-8}
	}
	

2000

Quantitative analysis of deuterium in a-C:D layers, a Round Robin experiment
R. Behrisch, M. Mayer, W. Jacob, W. Assmann, G. Dollinger, A. Bergmaier, U. Kreissig, M. Friedrich, G. Sun, D. Hildebrandt, M. Akbi, W. Schneider, D. Schleußner, W. Knapp and C. Edelmann; Journal of Nuclear Materials 281 (1) (2000) 42-56.
Abstract: The absolute amount of deuterium in amorphous deuterated carbon (a-C:D) layers has been measured by six laboratories with different techniques, such as MeV ion beam analysis, secondary ion mass spectrometry (SIMS), and thermal desorption spectrometry (TDS). The a-C:D layers have been deposited from a CD4 glow discharge plasma onto carbon and silicon substrates. The results for the absolute numbers obtained with the different analyzing techniques show a scatter of up to about 35% around the average value. These deviations are larger than the errors stated by the experimentalists and indicate possible systematic uncertainties in some of the measurements.
BibTeX:
	@article{Behrisch2000,
	  author = {Behrisch, R. and Mayer, M. and Jacob, W. and Assmann, W. and Dollinger, G. and Bergmaier, A. and Kreissig, U. and Friedrich, M. and Sun, G.Y. and Hildebrandt, D. and Akbi, M. and Schneider, W. and Schleußner, D. and Knapp, W. and Edelmann, C.},
	  title = {Quantitative analysis of deuterium in a-C:D layers, a Round Robin experiment},
	  journal = {Journal of Nuclear Materials},
	  year = {2000},
	  volume = {281},
	  number = {1},
	  pages = {42--56},
	  note = {cited By (since 1996)15},
	  url = {http://www.sciencedirect.com/science/article/pii/S0022311500000696},
	  doi = {http://doi.org/10.1016/S0022-3115(00)00069-6}
	}
	
Characterization of ultra thin oxynitrides: a general approach
B. Brijs, J. Deleu, T. Conard, H. De Witte, W. Vandervorst, K. Nakajima, K. Kimura, I. Genchev, A. Bergmaier, L. Goergens, P. Neumaier, G. Dollinger and M. Döbeli; Nuclear Instruments and Methods in Physics Research Section B 161 (2000) 429-434.
Abstract: The determination of nitrogen depth profiles in thin oxynitride layers (1.5-3 nm) becomes more and more important in microelectronics. The goal of this paper is to investigate a methodology for the characterization of thin oxynitride layers with the aim to establish in a quantitative manner the layer thickness, N-content and detailed N-depth profile. For this study ultra thin oxynitride films of 2.5 nm on Si were grown by oxygen O2 annealing of Si followed by a NO annealing. The global film characteristics were measured using spectroscopic ellipsometry (SE) (thickness), atomic force microscopy (AFM) for roughness and X-ray photoelectron spectroscopy (XPS) for total O- and N-content. Depth profiles of oxygen, silicon and nitrogen were obtained using (low energy) secondary ion mass spectroscopy (SIMS) and time of flight (TOF)-SIMS, high resolution-Rutherford backscattering (H-RBS) (magnetic sector and TOF) and high resolution-elastic recoil detection (H-ERD). A comparison of the results obtained with the different techniques is presented and discussed.
BibTeX:
	@article{Brijs2000,
	  author = {Brijs, B. and Deleu, J. and Conard, T. and De Witte, H. and Vandervorst, W. and Nakajima, K. and Kimura, K. and Genchev, I. and Bergmaier, A. and Goergens, L. and Neumaier, P. and Dollinger, G. and Döbeli, M.},
	  title = {Characterization of ultra thin oxynitrides: a general approach},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {2000},
	  volume = {161},
	  pages = {429--434},
	  note = {cited By (since 1996)20},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X99006746},
	  doi = {http://doi.org/10.1016/S0168-583X(99)00674-6}
	}
	
Structural characterization of hydrogenated a-Si using slow positron beam techniques
D. Britton, A. Hempel, D. Knoesen, W. Bauer-Kugelmann and W. Triftshäuser; Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 164 (2000) 1010-1015.
Abstract: Hydrogenated amorphous silicon (a-Si:H) grown by hot wire chemical vapour deposition is a promising candidate for robust inexpensive solar cells. However, prolonged exposure to light is known to lead to a reduction in efficiency of a-Si:H devices. The causes for this ageing effect are still unclear, but may be related to a structural relaxation or change in hydrogen content. In this work, results are presented for positron beam studies of the defect structure, using both lifetime and Doppler-broadening spectroscopy, of a-Si:H grown under different conditions.
BibTeX:
	@article{Britton2000,
	  author = {Britton, D.T. and Hempel, A. and Knoesen, D. and Bauer-Kugelmann, W. and Triftshäuser, W.},
	  title = {Structural characterization of hydrogenated a-Si using slow positron beam techniques},
	  journal = {Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms},
	  year = {2000},
	  volume = {164},
	  pages = {1010--1015},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X99010538},
	  doi = {http://doi.org/10.1016/S0168-583X(99)01053-8}
	}
	
Nanoprobe Capabilities Using 25 MeV Protons or 200 MeV Heavy Ions
G. Datzmann, G. Dollinger, C. Goeden, H.-J. Körner and O. Schmelmer; In: Proceedings of the 4th International Workshop: Microbeam Probes of Cellular Radiation Response1Killiney Bay, Dublin, Ireland, July 17--18, 1999 153 (2000) 220-238 , Radiation Research Society.
BibTeX:
	@inproceedings{Datzmann2000,
	  author = {Datzmann, G. and Dollinger, G. and Goeden, C. and Körner, H.-J. and Schmelmer, O.},
	  title = {Nanoprobe Capabilities Using 25 MeV Protons or 200 MeV Heavy Ions},
	  booktitle = {Proceedings of the 4th International Workshop: Microbeam Probes of Cellular Radiation Response1Killiney Bay, Dublin, Ireland, July 17--18, 1999},
	  publisher = {Radiation Research Society},
	  year = {2000},
	  volume = {153},
	  number = {2},
	  pages = {220--238},
	  url = {http://www.rrjournal.org/toc/rare/153/2},
	  doi = {http://doi.org/10.1667/0033-7587(2000)153%5B0220:POTIWM%5D2.0.CO;2}
	}
	
Defect identification in GaAs grown at low temperatures by positron annihilation
J. Gebauer, F. Börner, R. Krause-Rehberg, T. Staab, W. Bauer-Kugelmann, G. Kögel, W. Triftshäuser, P. Specht, R. Lutz, E. Weber and M. Luysberg; Journal of Applied Physics 87 (12) (2000) 8368-8379.
Abstract: We use positron annihilation to study vacancy defects in GaAs grown at low temperatures (LT-GaAs). The vacancies in as-grown LT-GaAs can be identified to be Ga monovacancies, VGa, according to their positron lifetime and annihilation momentum distribution. The charge state of the vacancies is neutral. This is ascribed to the presence of positively charged As+ Ga antisite defects in vicinity to the vacancies. Theoretical calculations of the annihilation parameters show that this assignment is consistent with the data. The density of VGa is related to the growth stoichiometry in LT-GaAs, i.e., it increases with the As/Ga beam equivalent pressure (BEP) and saturates at 2×1018 cm-3 for a BEP≥20 and a low growth temperature of 200°C. Annealing at 600°C removes VGa. Instead, larger vacancy agglomerates with a size of approximately four vacancies are found. It will be shown that these vacancy clusters are associated with the As precipitates formed during annealing. © 2000 American Institute of Physics.
BibTeX:
	@article{Gebauer2000,
	  author = {Gebauer, J. and Börner, F. and Krause-Rehberg, R. and Staab, T.E.M. and Bauer-Kugelmann, W. and Kögel, G. and Triftshäuser, W. and Specht, P. and Lutz, R.C. and Weber, E.R. and Luysberg, M.},
	  title = {Defect identification in GaAs grown at low temperatures by positron annihilation},
	  journal = {Journal of Applied Physics},
	  year = {2000},
	  volume = {87},
	  number = {12},
	  pages = {8368--8379},
	  url = {http://aip.scitation.org/doi/10.1063/1.373549},
	  doi = {http://doi.org/10.1063/1.373549}
	}
	
Electron stimulated desorption of negative hydrogen ions from diamond (100)
C. Goeden, G. Dollinger and P. Feulner; Diamond and Related Materials 9 (3-6) (2000) 1164-1166.
Abstract: The electron stimulated desorption of negatively charged hydrogen ions from diamond surfaces is studied with respect to an application as a bright ion source. Desorption of macroscopic currents of negative ions from a diamond surface by stimulated desorption has been demonstrated recently. To determine the dependence of the ionization cross-section on electron affinity, an oxygen covered diamond was used as a model system for positive electron affinity diamond. On this surface, different amounts of deuterium have been adsorbed. The D− ionization cross-section has been proven to vary by one order of magnitude between 3.5×10−18 cm2 and 5×10−19 cm2 with hydrogen coverage of the surface. The energy distribution of desorbed negative ions has been measured by an electrostatic analyser. For the measured broad energy distribution, an attempt of an explanation is made.
BibTeX:
	@article{Goeden2000,
	  author = {Goeden, C. and Dollinger, G. and Feulner, P.},
	  title = {Electron stimulated desorption of negative hydrogen ions from diamond (100)},
	  journal = {Diamond and Related Materials},
	  year = {2000},
	  volume = {9},
	  number = {3-6},
	  pages = {1164--1166},
	  url = {http://www.sciencedirect.com/science/article/pii/S0925963599002915},
	  doi = {http://doi.org/10.1016/S0925-9635(99)00291-5}
	}
	
Formation of silicon(111) boron surface phases and their influence on the epitaxial growth of silicon and germanium
J. Schulze, H. Baumgärtner, C. Fink, G. Dollinger, I. Gentchev, L. Görgens, W. Hansch, H. Hoster, T. Metzger, R. Paniago, T. Stimpel, T. Sulima and I. Eisele; Thin Solid Films 369 (1) (2000) 10-15.
Abstract: We present results obtained by different analysis methods as scanning tunneling microscopy (STM), atomic force microscopy (AFM), grazing incidence small angle X-ray scattering (GISAXS), and elastic recoil detection (ERD) on two similar semiconductor structures grown by molecular beam epitaxy (1) Si(111) substrate/Si buffer layer/B layer with σ B = (2.6±δ)×10 14 cm -2/Ge cap layer and (2) Si(111) substrate/Si buffer layer/B layer with σ B = (2.6±δ)×10 14 cm -2/Si cap layer. It will be shown that the deposition of B with concentrations up to 2.6×10 14 cm -2 leads to a breakdown of the 7×7 reconstructed Si surface of the buffer layer and the formation of a Si(111)-√3×√3-R30 °B surface phase (BSP) located on T 4-sites. Furthermore it is shown that this BSP acts as a `lubricant' for additional deposited adatoms (Si and Ge) at deposition temperatures <800 °C due to the saturation of all Si dangling bonds. This leads to the formation of triangular, nearly relaxed, and well ordered Ge dots in the special case of Ge deposited at 400 °C onto a BSP. For higher deposition temperatures it is shown that this `lubricant effect' vanishes due to the B migration from the T 4-site via S 5 into the substrate.
BibTeX:
	@article{Schulze2000,
	  author = {Schulze, J. and Baumgärtner, H. and Fink, C. and Dollinger, G. and Gentchev, I. and Görgens, L. and Hansch, W. and Hoster, H.E. and Metzger, T.H. and Paniago, R. and Stimpel, T. and Sulima, T. and Eisele, I.},
	  title = {Formation of silicon(111) boron surface phases and their influence on the epitaxial growth of silicon and germanium},
	  journal = {Thin Solid Films},
	  year = {2000},
	  volume = {369},
	  number = {1},
	  pages = {10--15},
	  note = {cited By (since 1996)9},
	  url = {http://www.sciencedirect.com/science/article/pii/S0040609000008257},
	  doi = {http://doi.org/10.1016/S0040-6090(00)00825-7}
	}
	
Lithium addition during CVD diamond growth: Influence on the optical emission of the plasma and properties of the films
H. Sternschulte, M. Schreck, B. Stritzker, A. Bergmaier and G. Dollinger; Diamond and Related Materials 9 (3) (2000) 1046-1050.
Abstract: Lithium-doped homoepitaxial CVD diamond films were grown on synthetic type Ib (100) single crystal diamonds by addition of lithium-t-butoxide (LiOC4H9) to the CH4/H2 microwave plasma. Atomic lithium can easily be detected in the plasma by optical emission spectroscopy (OES). Varying the lithium precursor addition to the gas phase over a wide range, two regimes were found: in the low concentration regime the emission intensity from atomic and molecular hydrogen is independent of the Li concentration, thus facilitating the use of the Li/H emission intensity ratio as a relative measure for the concentration of atomic Li in the plasma; in the high concentration regime the Li addition feeds back on the absolute intensity of the atomic Balmer lines, on the relative intensities of atomic and molecular hydrogen lines and on the activation of different Li transitions. This indicates a modification of the electron energy distribution and also the plasma chemistry. The incorporation of lithium in the deposited homoepitaxial diamond films as studied by elastic recoil detection (ERD) measurements strongly varies with the deposition temperature. It is favoured by low substrate temperatures. A reduction from Tsub = 800 °C to Tsub = 620 °C increases the Li concentration from 8 ppm to 71 ppm. Maximum Li concentrations of 290 ppm were found. The high crystal quality of the films speaks for an incorporation in the crystal lattice and not the grain boundaries. The potential role of other impurities is discussed.
BibTeX:
	@article{Sternschulte2000,
	  author = {Sternschulte, H. and Schreck, M. and Stritzker, B. and Bergmaier, A. and Dollinger, G.},
	  title = {Lithium addition during CVD diamond growth: Influence on the optical emission of the plasma and properties of the films},
	  journal = {Diamond and Related Materials},
	  year = {2000},
	  volume = {9},
	  number = {3},
	  pages = {1046-1050},
	  note = {cited By (since 1996)20},
	  url = {http://www.sciencedirect.com/science/article/pii/S0925963599002745},
	  doi = {http://doi.org/10.1016/S0925-9635(99)00274-5}
	}
	
Positron annihilation in near-surface regions and layered structures
W. Triftshäuser; Vacuum 58 (1) (2000) 33-44.
Abstract: Positrons are very sensitive probes for vacancy-type defects of atomic dimensions, e.g. vacancies, vacancy agglomerates, dislocations or inner surfaces. It is well established that positrons can be trapped at these defects and, because of the locally reduced electron density, the lifetime of the positron localized at the defect increases. This lifetime has characteristic values for each defect type and therefore it is possible to separate out various atomic defect configurations and their relative abundance with very high sensitivity (approx. 1 ppm) and in a nondestructive way. With a pulsed positron beam (approx. 3 mm diameter) of variable energy, lifetime studies can be performed as a function of the positron energy and hence the penetrations depth. Results on silicon and silicon carbide subjected to different treatments will be discussed. For many applications in materials science a positron beam in the micrometer range is desirable. This leads to a scanning positron microscope consisting of a pulsed positron beam of micrometer dimension with a scanning facility. The design and the performance of this first system of its kind will be presented.
BibTeX:
	@article{Triftshaeuser2000,
	  author = {Triftshäuser, W.},
	  title = {Positron annihilation in near-surface regions and layered structures},
	  journal = {Vacuum},
	  year = {2000},
	  volume = {58},
	  number = {1},
	  pages = {33--44},
	  url = {http://www.sciencedirect.com/science/article/pii/S0042207X99001980},
	  doi = {http://doi.org/10.1016/S0042-207X(99)00198-0}
	}
	
Composition, nanostructure and origin of the ultrahardness in nc-TiN/a-Si3N4/a- and nc-TiSi2 nanocomposites with Hv = 80 to ≥105 GPa
S. Veprek, A. Niederhofer, K. Moto, T. Bolom, H.-D. Männling, P. Nesladek, G. Dollinger and A. Bergmaier; Surface and Coatings Technology 133-134 (2000) 152-159.
Abstract: Multiphase nanocomposite coatings (3-20 μm thick) consisting of nanocrystalline TiN, amorphous Si3N4, and amorphous and nanocrystalline TiSi2, nc-TiN/a-SiNx/a- and nc-TiSi2 were deposited on steel substrates by means of plasma CVD. The load-independent Vickers microhardness from 80 to >105 GPa was measured by the load-depth sensing technique for applied loads between 30 and 200 mN and verified by measuring the size of the remaining plastic indentation using SEM. The results of a complex analysis provide a consistent picture of the nature of the grain boundaries which determines the hardness in the whole range of silicon content between approximately 3 and 22 at.%. At a high discharge current density of ≥2.5 mA/cm2 the a-Si3N4 forms the grain boundaries and the nanocomposites are superhard (40-50 GPa) as we reported earlier. At a lower current density of ≤1 mA/cm2 a mixture of TiSi2 and Si3N4 is formed. With increasing Si-content the amount of a-TiSi2 in the grain boundaries of the TiN nanocrystals increases, and above 10 at.% of Si approximately 3 nm small TiSi2 nanocrystals precipitate. The hardness depends critically and in a complex way on the Si3N4 content and the TiSi2/Si3N4 ratio. The ultrahardness of <≥80 GPa is achieved when the surface of the TiN nanocrystals is covered with approximately one monolayer of Si3N4. Under these conditions the ultrahardness of 80-100 GPa depends on the amount of a- and nc-TiSi2.
BibTeX:
	@article{Veprek2000,
	  author = {Veprek, S. and Niederhofer, A. and Moto, K. and Bolom, T. and Männling, H.-D. and Nesladek, P. and Dollinger, G. and Bergmaier, A.},
	  title = {Composition, nanostructure and origin of the ultrahardness in nc-TiN/a-Si3N4/a- and nc-TiSi2 nanocomposites with Hv = 80 to ≥105 GPa},
	  journal = {Surface and Coatings Technology},
	  year = {2000},
	  volume = {133-134},
	  pages = {152--159},
	  note = {cited By (since 1996)277},
	  url = {http://www.sciencedirect.com/science/article/pii/S0925963599002745},
	  doi = {http://doi.org/10.1016/S0257-8972(00)00957-9}
	}
	
Epitaxial CaGe2 films on germanium
G. Vogg, M. Brandt, M. Stutzmann, I. Genchev, A. Bergmaier, L. Görgens and G. Dollinger; Journal of Crystal Growth 212 (1) (2000) 148-154.
Abstract: The epitaxial growth of thin CaGe2 films with reactive deposition epitaxy (RDE) on Ge(1 1 1) substrates is described. The films consist in general of a mixture of the known trigonal rhombohedral tr6 modification and a hexagonal h2 modification of CaGe2 containing two Ca and two buckled Ge layers per unit cell in a twofold stacking sequence whose formation appears to be favored by strain. Epitaxial layers of both polytypes show remarkably higher crystalline quality compared to epitaxial CaSi2 films grown on silicon substrates. The tr6 modification is found to be unstable in air in contrast to the h2 modification.
BibTeX:
	@article{Vogg2000,
	  author = {Vogg, G. and Brandt, M.S. and Stutzmann, M. and Genchev, I. and Bergmaier, A. and Görgens, L. and Dollinger, G.},
	  title = {Epitaxial CaGe2 films on germanium},
	  journal = {Journal of Crystal Growth},
	  year = {2000},
	  volume = {212},
	  number = {1},
	  pages = {148--154},
	  note = {cited By (since 1996)7},
	  url = {http://www.sciencedirect.com/science/article/pii/S0022024800000324},
	  doi = {http://doi.org/10.1016/S0022-0248(00)00032-4}
	}
	

1999

Diamond junction FETs based on δ-doped channels
A. Aleksov, A. Vescan, M. Kunze, P. Gluche, W. Ebert, E. Kohn, A. Bergmaier and G. Dollinger; Diamond and Related Materials 8 (2-5) (1999) 941-945.
Abstract: Diamond junction field effect transistors (FETs) utilizing δ-boron-doped diamond films were fabricated and analyzed. In order to allow full charge modulation by the gate, the total channel sheet charge must not exceed the order of 1013 cm-2. However, boron doping shows full activation only for concentrations above ca 1020 cm-3 . This yields a thickness for a fully activated channel in the range of ca 1 nm. To approach such narrow doping spikes any parasitic boron doping tails need to be eliminated. One possible way of achieving this is to compensate boron doping with nitrogen doping, an extremely deep donor. This results in the formation of a pn-junction, where the nitrogen doped part is not activated at room temperature and which therefore represents a semi-insulating (lossy) dielectric at low temperature and high frequency. At elevated temperature and low frequency the nitrogen doped layer becomes conducting acting as a series resistor to the interfacial pn-junction. Using this concept of a lossy dielectric pn-junction in the δ-doped channel FET, two gate diode configurations were investigated. In the first the nitrogen doped (Ib) synthetic diamond substrate served as a large area back gate, while in the second the nitrogen doped gate layer was grown on top of the δ-channel. The devices show high drain currents of up to 100 mA mm-1 and full channel modulation even at moderate operation temperatures of 200-250 °C. By extrapolation a current density of 1 A mm-1 is expected for a 0.25 μm gate length device.
BibTeX:
	@article{Aleksov1999,
	  author = {Aleksov, A. and Vescan, A. and Kunze, M. and Gluche, P. and Ebert, W. and Kohn, E. and Bergmaier, A. and Dollinger, G.},
	  title = {Diamond junction FETs based on δ-doped channels},
	  journal = {Diamond and Related Materials},
	  year = {1999},
	  volume = {8},
	  number = {2-5},
	  pages = {941--945},
	  note = {cited By (since 1996)45},
	  url = {http://www.sciencedirect.com/science/article/pii/S0925963598003938},
	  doi = {http://doi.org/10.1016/S0925-9635(98)00393-8}
	}
	
Oxygen at the interface of CVD diamond films on silicon
A. Bergmaier, M. Schreck, G. Dollinger, O. Schmelmer, K. Thürer and B. Stritzker; Diamond and Related Materials 8 (6) (1999) 1142-1147.
Abstract: The oxygen incorporation at the interface between the silicon substrate and chemical vapour deposited (CVD) diamond films nucleated by the bias-enhanced nucleation (BEN) procedure has been studied by heavy-ion elastic recoil detection (ERD). Using standard process conditions for the realisation of heteroepitaxial films, oxygen with a concentration equivalent to about 1nm SiO2 has been found, which was mainly incorporated during textured growth with a certain CO2 admixture to the process gas. By completely omitting CO2 during nucleation and growth, the oxygen at the interface can be reduced by nearly one order of magnitude to 6.3×1015atcm-2, corresponding to 0.14nm SiO2. Intentional addition of highly enriched C18O2 to the gas phase shows that the oxygen incorporation is strongly enhanced during BEN with hydrocarbon in the gas phase. The results indicate that roughening of the surface, the deposition of SixOyCz phases and strong lateral inhomogeneities at the silicon interface may explain the coexistence of epitaxial crystallites and amorphous phases. It is suggested that a further reduction of the oxygen concentration at the interface may have consequences for an improved heteroepitaxy of diamond on silicon.
BibTeX:
	@article{Bergmaier1999,
	  author = {Bergmaier, A. and Schreck, M. and Dollinger, G. and Schmelmer, O. and Thürer, K.H. and Stritzker, B.},
	  title = {Oxygen at the interface of CVD diamond films on silicon},
	  journal = {Diamond and Related Materials},
	  year = {1999},
	  volume = {8},
	  number = {6},
	  pages = {1142-1147},
	  note = {cited By (since 1996)6},
	  url = {http://www.sciencedirect.com/science/article/pii/S0925963599001041},
	  doi = {http://doi.org/10.1016/S0925-9635(99)00104-1}
	}
	
A superconducting multipole lens for focusing high energy ions
G. Datzmann, G. Dollinger, G. Hinderer and H.-J. Körner; Nuclear Instruments and Methods in Physics Research Section B 158 (1-4) (1999) 74-80.
Abstract: At the Munich 15 MV tandem accelerator a new two stage microprobe system Supraleitendes Nanoskop für Angewandte Kernphysikalische Experimente (SNAKE) is currently under construction. In contrast to existing facilities, it is projected to focus up to 30 MeV protons as well as heavy ions with maximum energies of 200 MeV q2/A to a submicron beam spot. In order to achieve this goal, a superconducting lens with inherent multipole corrections and special shaped edges with respect to fringe field calculations was designed. The introduction of superconductivity enables a pole tip field of 1.2 T at 10 mm bore radius and the possibility of auto correction mechanisms. An implemented electrostatic octupole for active field correction will have a maximum field strength in the same order of magnitude as the intrinsic magnetic octupole correction. For an analytical test of the novel concepts of this lens, a multipole detection device on the rotating coil principle has been built. It is capable of measuring small multipole contributions on a strong quadrupole field.
BibTeX:
	@article{Datzmann1999,
	  author = {Datzmann, G. and Dollinger, G. and Hinderer, G. and Körner, H.-J.},
	  title = {A superconducting multipole lens for focusing high energy ions},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {1999},
	  volume = {158},
	  number = {1-4},
	  pages = {74--80},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X99003080},
	  doi = {http://doi.org/10.1016/S0168-583X(99)00308-0}
	}
	
Electron stimulated desorption on diamond (100) as a negative hydrogen source
C. Goeden and G. Dollinger; Applied Surface Science 147 (1-4) (1999) 107-113.
Abstract: The electron-stimulated desorption of negatively charged hydrogen ions from diamond surfaces is studied with respect to an application as a bright ion source. Bombarding an (100)-oriented, boron-doped single crystal diamond with 40-μA electrons at energies up to 12 keV, a maximum ion current of 700 pA negative hydrogen is obtained. A supply of 1.0×10−4 mbar atomic deuterium results in a steady-state ion current of 30 pA. The ionization cross section has been proven to vary one order of magnitude between 3.5×10−18 cm2 and 5×10−19 cm2 with hydrogen coverage of the surface. This effect might be caused by the changing electron affinity of the diamond.
BibTeX:
	@article{Goeden1999,
	  author = {Goeden, C. and Dollinger, G.},
	  title = {Electron stimulated desorption on diamond (100) as a negative hydrogen source},
	  journal = {Applied Surface Science},
	  year = {1999},
	  volume = {147},
	  number = {1-4},
	  pages = {107--113},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433299000926},
	  doi = {http://doi.org/10.1016/S0169-4332(99)00092-6}
	}
	
Composition analysis using elastic recoil detection
L. Görgens, G. Dollinger, A. Bergmaier, O. Ambacher, L. Eastman, J. Smart, J. Shealy, R. Dimitrov, M. Stutzmann and A. Mitchell; Physica Status Solidi (B) Basic Research 216 (1) (1999) 679-682.
Abstract: We report quantitative ERD (Elastic Recoil Detection) measurements for the determination of the composition and distribution of the elements in nitride heterostructures. The investigated samples were MOCVD (molecular chemical vapor deposition) and PIMBE (plasma induced molecular beam epitaxy) grown HEMT (high electron mobility transistor) structures from Cornell University. We present the measured Al distribution parallel to the growth direction of Al xGa 1 xN layers of a thickness of about 10 to 30 nm and an Al concentration of x = 0.1 to 0.7. The results are compared with HRXRD (high resolution X-ray diffraction) measurements.
BibTeX:
	@article{Goergens1999,
	  author = {Görgens, L. and Dollinger, G. and Bergmaier, A. and Ambacher, O. and Eastman, L. and Smart, J.A. and Shealy, J.F. and Dimitrov, R. and Stutzmann, M. and Mitchell, A.},
	  title = {Composition analysis using elastic recoil detection},
	  journal = {Physica Status Solidi (B) Basic Research},
	  year = {1999},
	  volume = {216},
	  number = {1},
	  pages = {679--682},
	  note = {cited By (since 1996)0},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/(SICI)1521-3951(199911)216:1%3C679::AID-PSSB679%3E3.0.CO;2-L/abstract},
	  doi = {http://doi.org/10.1002/(SICI)1521-3951(199911)216:1%3C679::AID-PSSB679%3E3.0.CO;2-L}
	}
	
Der 0°-Spektrograph am Raster-Ionenmikroskop SNAKE.
Andreas Hauptner; Diplomarbeit, Technische Universität München, 1999.
Abstract: Das Ziel dieser Arbeit bestand im Aufbau und der Inbetriebnahme des 0°-Spektrographen am Raster-Ionenmikroskop SNAKE. Dieses Instrument erweitert die vielfältigen Anwendungsmöglichkeiten des Ionenmikroskops um Transmissionsmessungen mit einer Energieauflösung im Bereich von dE/E   1 x 10^(-5). Dadurch werden sowohl Dickenmessungen mit Auflösungen bis zu einatomaren Schichten als auch ganz grundlegende Experimente möglich, die sich mit der Wechselwirkung zwischen hochenergetischen Ionen und Materie beschäftigen.
Die ionenoptischen Grundlagen des Spektrographen werden ausführlich behandelt. Der vertikale 90°-Magnet als zentrales Element erlaubt dabei eine ionenoptische Abbildung in die Fokalebene mit hoher Qualität. Um die projektierte Energieauflösung
zu erreichen, ist jedoch eine weitergehende, flexible Fokussierung des Ionenstrahls notwendig.
Daher wurde der Spektrograph durch zwei Quadrupol-Linsen vervollständigt.
Um den Spektrographen betreiben zu können, wurde ein CCD (charge coupled device) Zeilensensor als Fokalebenendetektor gewählt. Dieser bietet eine Ortsauflösung von 14µm. Seine prinzipielle Eignung für die Detektion sowohl von leichten wie auch
von schweren Ionen wurde experimentell mit 20 MeV Protonen und 90 MeV Schwefelionen nachgewiesen. Bei 20 MeV Protonen konnten dabei effektive Zählraten von ca. 100kHz erreicht werden. Es zeigte sich, dass die Strahlenbeständigkeit des CCD-
Detektors ausreicht, um auf einem Pixel des Detektors zwischen 10^7 und 10^8 Protonen nachzuweisen.
In ersten Experimenten konnte die Einsetzbarkeit des Spektrographen einschließlich des Fokalebenendetektors demonstriert werden.
Mit 20 MeV Protonen wurde eine relative Energieauflösung von dE_(FWHM)/E = 1.3 x 10^(-4) erreicht und Energieverlustmessungen an Goldfolien durchgeführt. Die Auflösung war hier noch durch den Strahl beschränkt.
In einer Strahlzeit mit 90 MeV Schwefelionen wurde eine relative Energieauflösung von dE_(FWHM)/E = 3.8 x 10^(-5) erreicht. Dadurch scheint die projektierte Energieauflösung und damit auch der Einsatz des 0°-Spektrographen für die geplanten Experimente in absehbarer Zeit möglich.
BibTeX:
	@mastersthesis{Hauptner1999da,
	  author = {Hauptner, Andreas},
	  title = {Der 0°-Spektrograph am Raster-Ionenmikroskop SNAKE.},
	  school = {Technische Universität München},
	  year = {1999}
	}
	
High intense positron beam at the new Munich research reactor FRM-II
C. Hugenschmidt, G. Kögel, K. Schreckenbach, P. Sperr, M. Springer, B. Straßer and W. Triftshäuser; Applied Surface Science 149 (1) (1999) 7-10.
Abstract: The Munich Intense POsitron Source (MIPOS) facility for producing a high intense positron beam at the new Munich research reactor (Forschungs-Reaktor Muenchen II) FRM-II is presented. Positrons are generated by pair production of high energy prompt γ-rays from neutron capture in cadmium: 113Cd(n,γ)114Cd. A cadmium cap will be located inside a beamtube at an undisturbed thermal neutron flux of 2×1014 n cm-2 s-1. Model calculation showed that this would lead to a mean capture rate of 1.2×1013 n cm-2 s-1. Thermal load resulting from absorbed γ-rays is expected to be less than 4 W cm-2. Inside the cadmium cap a structure of platinum and a stack of tungsten foils is placed for converting the γ-rays into positron-electron pairs. Platinum is used as converting material, since the cross section for pair production is even higher (+11%) than in tungsten. The maximum of the energy spectrum of the positrons produced is about 800 keV. The tungsten foils also act as moderator. The positrons will be accelerated by electric lenses and guided by magnetic fields. Various arrangements are tested to improve the efficiency of the system. After remoderation of the positron beam an intensity of about 109 slow positrons per second is expected.
BibTeX:
	@article{Hugenschmidt1999,
	  author = {Hugenschmidt, C. and Kögel, G. and Schreckenbach, K. and Sperr, P. and Springer, M. and Straßer, B. and Triftshäuser, W.},
	  title = {High intense positron beam at the new Munich research reactor FRM-II},
	  journal = {Applied Surface Science},
	  year = {1999},
	  volume = {149},
	  number = {1},
	  pages = {7--10},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433299001634},
	  doi = {http://doi.org/10.1016/S0169-4332(99)00163-4}
	}
	
δ-doping in diamond
M. Kunze, A. Vescan, G. Dollinger, A. Bergmaier and E. Kohn; Carbon 37 (5) (1999) 787-791.
Abstract: δ-Boron-doped homoepitaxial diamond films grown by microwave CVD were optimized for field effect transistor application to obtain steep profiles. The critical growth steps of the δ-doped device structures were analyzed and improved using mass spectrometry gas analysis, determining growth- and etch rates, hall-effect-measurements, elastic recoil detection and conductivity measurements. Optimized growth procedures were obtained and residual doping in the gate control layer was compensated using nitrogen. This results in a novel lossy dielectric Junction FET channel with high sheet charge activation and high drain current densities at moderate operation temperatures of 200 °C.
BibTeX:
	@article{Kunze1999,
	  author = {Kunze, M. and Vescan, A. and Dollinger, G. and Bergmaier, A. and Kohn, E.},
	  title = {δ-doping in diamond},
	  journal = {Carbon},
	  year = {1999},
	  volume = {37},
	  number = {5},
	  pages = {787--791},
	  note = {cited By (since 1996)31},
	  url = {http://www.sciencedirect.com/science/article/pii/S0008622398002723},
	  doi = {http://doi.org/10.1016/S0008-6223(98)00272-3}
	}
	
Reproducibility and simplification of the preparation procedure for carbon stripper foils by laser plasma ablation deposition
P. Maier-Komor, G. Dollinger and H. Körner; Nuclear Instruments and Methods in Physics Research Section A 438 (1) (1999) 73-78.
Abstract: Carbon stripper foils prepared by laser plasma ablation deposition are so far the only ones which have a total random orientation of the nanocrystallites. This orientation is responsible for the long lifetimes under heavy ion bombardment. Accelerator users around the world are interested in this type of carbon stripper foils. Their strong interest is a guaranteed reproducibility of the foil quality, -thickness and -uniformity. In addition, a high reproducible yield with a low effort for floating, mounting and slackening is wanted. These problems are discussed and the status of their solution is described.
BibTeX:
	@article{Maier-Komor1999,
	  author = {Maier-Komor, P. and Dollinger, G. and Körner, H.J.},
	  title = {Reproducibility and simplification of the preparation procedure for carbon stripper foils by laser plasma ablation deposition},
	  journal = {Nuclear Instruments and Methods in Physics Research Section A},
	  year = {1999},
	  volume = {438},
	  number = {1},
	  pages = {73--78},
	  note = {cited By (since 1996)19},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168900299009419},
	  doi = {http://doi.org/10.1016/S0168-9002(99)00941-9}
	}
	
Characterization of RF-sputtered platinum films from industrial production plants using slow positrons
A. Osipowicz, M. Härting, M. Hempel, D. Britton, W. Bauer-Kugelmann and W. Triftshäuser; Applied Surface Science 149 (1) (1999) 198-203.
Abstract: Platinum films, used in thin film technology, produced by radiofrequency sputter deposition on alumina substrates under different conditions, have been studied by positron beam and other techniques, before and after production annealing. The defect structure in the layers has been characterized using both positron lifetime and Doppler broadening spectroscopy, and compared with X-ray studies of crystallinity and texture. The films are topographically irregular, with a grain size comparable to the thickness of the layer. All layers show pronounced crystallographic texture but this does not appear to be related to the sample processing.
BibTeX:
	@article{Osipowicz1999,
	  author = {Osipowicz, A. and Härting, M. and Hempel, M. and Britton, D.T. and Bauer-Kugelmann, W. and Triftshäuser, W.},
	  title = {Characterization of RF-sputtered platinum films from industrial production plants using slow positrons},
	  journal = {Applied Surface Science},
	  year = {1999},
	  volume = {149},
	  number = {1},
	  pages = {198--203},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433299002007},
	  doi = {http://doi.org/10.1016/S0169-4332(99)00200-7}
	}
	
Boron in mesoporous Si - where have all the carriers gone?
G. Polisski, D. Kovalev, G. Dollinger, T. Sulima and F. Koch; Physica B: Condensed Matter 273-274 (1999) 951-954.
Abstract: Highly-doped p-type Si is electrochemically etched in an HF-based electrolyte to produce mesoporous surface layers. Using both elastic-recoil detection analysis and secondary ion mass spectroscopy it is concluded that B atoms are not removed from the porous layer. Crystallite size for the most porous samples is related to the average dopant spacing. It is argued that the electrolytic erosion of Si stops when B is in the surface layer and passivated.
BibTeX:
	@article{Polisski1999,
	  author = {Polisski, G. and Kovalev, D. and Dollinger, G. and Sulima, T. and Koch, F.},
	  title = {Boron in mesoporous Si - where have all the carriers gone?},
	  journal = {Physica B: Condensed Matter},
	  year = {1999},
	  volume = {273-274},
	  pages = {951--954},
	  note = {cited By (since 1996)39},
	  url = {http://www.sciencedirect.com/science/article/pii/S0921452699005621},
	  doi = {http://doi.org/10.1016/S0921-4526(99)00562-1}
	}
	
Entwicklung eines Detektors zur 3-dimensional ortsauflösenden Wasserstoffanalytik mittels Proton-Proton-Streuung.
Patrick Reichart; Diplomarbeit, Technische Universität München, 1999.
Abstract: Mit dem neuen Raster–Ionenmikroskop SNAKE (Supraleitendes Nanoskop für Angewandte Kernphysikalische Experimente) am Münchener 15MV Tandembeschleuniger wird eine Einrichtung zur Verfügung stehen, mit der 20MeV Protonen bei einem Strahlstrom von 100 pA auf einen Strahlfleck von 100 nm Durchmesser fokussiert werden können. Dies eröffnet die Möglichkeit eines sensitiven, 3–dimensionalen Nachweises von Wasserstoffverteilungen unter Anwendung der sogenannten Proton–Proton–Streuung. Dabei ermöglicht die koinzidente Detektion der gestreuten Projektilprotonen und der rückgestreuten Wasserstoffkerne in Transmissionsrichtung hinter der Probe einen untergrundfreien Nachweis der Proton–Proton–Streuereignisse.
In dieser Arbeit werden die wesentlichen Merkmale der Proton–Proton–Streuung für dieWasserstoffanalytik diskutiert und die experimentellen Anforderungen für ein sensitives Detektorsystem zur tiefenaufgelösten Wasserstoff–Mikroskopie erarbeitet.
Der große Vorteil der Methode ist die geringst mögliche Strahlenschädigung in der Wasserstoffanalytik mit Ionenstrahlen, aufgrund eines gegenüber reiner Coulombstreuung 500–fach überhöhten Streuquerschnitts bei hohen Protonenenergien.
Zusätzlich kann fast der komplette Raumwinkel hinter der Probe für einen Nachweis genutzt werden. Daher wird das Verhältnis des Nachweisquerschnitts zum Schädigungsquerschnitt größer als in irgendeiner vergleichbaren Ionenstrahl–Analysetechnik und eine Wasserstoffanalyse bei Konzentrationen unter 100 ppm oder die Analyse von biologischen Proben jeweils mit sub–μm–Auflösung möglich.
Tiefenprofile von Wasserstoffverteilungen können durch die Analyse der Summenenergie der beiden Protonen gewonnen werden. Durch die hohe Projektilenergie ist zudem eine Untersuchung von Schichtdicken über 200 μm möglich.
In der Arbeit wurde ein Silizium–Streifendetektor mit 48 Streifen und 16 Sektoren aufgebaut, mit dem es möglich ist, einen Raumwinkel von 2.3 sr für die Proton–Proton–Streuung zu nutzen und gleichzeitig eine optimale Tiefenauflösung zu erreichen. Mit einer Winkelauflösung von unter 1° können die geometrischen Effekte so stark begrenzt werden, daß zur hohen lateralen Auflösung Tiefenauflösungen unter 10 μm erzielt werden.
Die Signalauslese wurde unter Verwendung einer speziell angepaßten Vielkanal–Elektronik mit einer Integration in das Beschleuniger–Datenaufnahmesystem realisiert. In einem ersten Experiment konnte die Funktion des Detektorsystems und die Sensitivität der Methode demonstriert werden.
BibTeX:
	@mastersthesis{Reichart1999da,
	  author = {Reichart, Patrick},
	  title = {Entwicklung eines Detektors zur 3-dimensional ortsauflösenden Wasserstoffanalytik mittels Proton-Proton-Streuung.},
	  school = {Technische Universität München},
	  year = {1999}
	}
	
A novel high precision slit system
O. Schmelmer, G. Dollinger, G. Datzmann, C. Goeden and H.-J. Körner; Nuclear Instruments and Methods in Physics Research Section B 158 (1-4) (1999) 107-112.
Abstract: A new high precision slit system has been developed for the nano beam facility SNAKE (Supraleitendes Nanoskop für Angewandte Kernphysikalische Experimente) which is under construction at the Munich tandem accelerator. Cylindrically strained germanium wafers with a bending radius of 50 mm are used as optimized slit edges. High resolution and angle resolved energy distributions of the transmitted protons were measured by means of a Q3D magnetic spectrograph at incident energies of 20 MeV. The measurements revealed the expected strong correlation between small angle scattering and energy loss processes at the slits. Within SNAKE's angular acceptance the ratio of particles suffering energy loss by interacting with the slit and particles not interacting with the slit is less than 0.6% even for aperture widths of 2 μm.
BibTeX:
	@article{Schmelmer1999,
	  author = {Schmelmer, O. and Dollinger, G. and Datzmann, G. and Goeden, C. and Körner, H.-J.},
	  title = {A novel high precision slit system},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {1999},
	  volume = {158},
	  number = {1-4},
	  pages = {107--112},
	  note = {cited By (since 1996)11},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X99003572},
	  doi = {http://doi.org/10.1016/S0168-583X(99)00357-2}
	}
	
A variable nanosecond delay for fast signals
P. Sperr and M. Maier; Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 431 (1) (1999) 234-235.
Abstract: A simple continuously variable nanosecond delay for fast signals has been devised. In this concept, the alignment of the fast channels may be performed manually or by a computer set control voltages. The performance of the design has been confirmed using conventional fast timing systems. Results from this application show that the simple delay generator is well applicable in fast timing measurements where a controllable continuous delay is needed.
BibTeX:
	@article{Sperr1999,
	  author = {Sperr, P. and Maier, M.R.},
	  title = {A variable nanosecond delay for fast signals},
	  journal = {Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment},
	  year = {1999},
	  volume = {431},
	  number = {1},
	  pages = {234--235},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168900299002405},
	  doi = {http://doi.org/10.1016/S0168-9002(99)00240-5}
	}
	
Control of lithium-t-butoxide addition during chemical vapour deposition of Li-doped diamond films by optical emission spectroscopy
H. Sternschulte, M. Schreck, B. Stritzker, A. Bergmaier and G. Dollinger; Physica Status Solidi (A) Applied Research 174 (1) (1999) 65-72.
Abstract: The potential of in situ lithium doping of diamond during microwave plasma chemical vapour deposition (MWPCVD) using a source of solid lithium-t-butoxide has been studied. It is shown that atomic lithium emission lines can be easily detected in the plasma by optical emission spectroscopy (OES). It was found that for a fixed fraction of the Li precursor in the feed gas a variation of the experimental conditions in the CVD reactor can drastically change the Li concentration in the plasma. The experimental results demonstrate that an optical control of the Li concentration in the plasma is indispensible. Elastic recoil detection (ERD) measurements clearly established that Li was incorporated into the diamond films in concentrations ranging from 40 up to 300 ppm. Etching of plasma exposed steel components in the reactor due to Li addition and the subsequent incorporation of iron, cobalt, and nickel into the films could be strongly reduced by replacing these components by graphite parts.
BibTeX:
	@article{Sternschulte1999,
	  author = {Sternschulte, H. and Schreck, M. and Stritzker, B. and Bergmaier, A. and Dollinger, G.},
	  title = {Control of lithium-t-butoxide addition during chemical vapour deposition of Li-doped diamond films by optical emission spectroscopy},
	  journal = {Physica Status Solidi (A) Applied Research},
	  year = {1999},
	  volume = {174},
	  number = {1},
	  pages = {65--72},
	  note = {cited By (since 1996)9},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/(SICI)1521-396X(199907)174:1%3C65::AID-PSSA65%3E3.0.CO;2-W/abstract},
	  doi = {http://doi.org/10.1002/(SICI)1521-396X(199907)174:1%3C65::AID-PSSA65%3E3.0.CO;2-W}
	}
	
The effect of nitrogen on low temperature growth of diamond films
J. Stiegler, A. Bergmaier, J. Michler, S. Laufer, G. Dollinger and E. Blank; Thin Solid Films 352 (1-2) (1999) 29-40.
Abstract: The intentional addition of small amounts of nitrogen to different C/H/O gas systems in microwave plasma-assisted deposition of diamond films at low substrate temperatures has been studied. The effect on growth is qualitatively different for gas mixtures with or without oxygen. Adding nitrogen to C/H mixtures results in a significant change of film morphology, growth rate, defect formation and incorporation of hydrogen. The film quality seriously deteriorates with increasing nitrogen concentration in the gas phase. The influence of nitrogen on gas phase processes has been monitored by optical emission spectroscopy. There is evidence that nitrogen affects growth primarily by surface related mechanisms. By contrast, its effect on growth from CO-rich C/H/O systems is much less pronounced. These films show a constant quality and a lower defect content. The interaction of nitrogen and oxygen in low temperature growth of diamond films has been thoroughly examined for gas mixtures containing comparatively low oxygen fractions. The presence of oxygen effectively counteracts the deleterious effect of nitrogen on the formation of defects. Elastic recoil detection has shown, however, that the incorporation of nitrogen into the film always increases when its gas phase concentration is raised, no matter which gas system is chosen.
BibTeX:
	@article{Stiegler1999,
	  author = {Stiegler, J. and Bergmaier, A. and Michler, J. and Laufer, S. and Dollinger, G. and Blank, E.},
	  title = {The effect of nitrogen on low temperature growth of diamond films},
	  journal = {Thin Solid Films},
	  year = {1999},
	  volume = {352},
	  number = {1-2},
	  pages = {29--40},
	  note = {cited By (since 1996)25},
	  url = {http://www.sciencedirect.com/science/article/pii/S0040609099002850},
	  doi = {http://doi.org/10.1016/S0040-6090(99)00285-0}
	}
	
High pressure fabrication and processing of GaN:Mg
T. Suski, J. Jun, M. Leszczynski, H. Teisseyre, I. Grzegory, S. Porowski, G. Dollinger, K. Saarinen, T. Laine, J. Nissilä, W. Burkhard, W. Kriegseis and B. Meyer; Materials Science and Engineering B: Solid-State Materials for Advanced Technology 59 (1-3) (1999) 1-5.
Abstract: Results on introduction of magnesium to GaN by three methods are presented. They consists of (i) high pressure growth of bulk, single crystals of GaN from Ga + Mg melt, (ii) diffusion of Mg to bulk GaN and to layers of GaN/Al2O3 at high temperatures and high pressures and (iii) implantation of Mg to bulk, single crystals and to layers of GaN/Al2O3 and subsequent high-pressure annealing. Applied pressure is in the range of 10-15 kbar and temperatures between 1200-1500°C. The growth of bulk, highly Mg doped crystals leads to the semi-insulating material with the characteristic blue photoluminescence band at about 3 eV. High pressure annealing of bulk crystals as well as GaN/Al2O3 layers in (N2 + Mg) atmosphere leads to the increase in the Mg incorporation with the highest diffusivity observed for GaN/Al2O3 layers. The performed experiments give an evidence of the importance of the defect (dislocations) in diffusion of Mg in the GaN semiconductor. Moreover, incorporation of Mg impurity appears to be higher on (00.1) Ga-face of the wurtzite GaN crystals than on the (00. - 1) N-face. We demonstrate also a strong enhancement of the blue-photoluminescence intensity in high pressure annealed GaN/Al2O3 layers (N2 + Mg atmosphere) and Mg-implanted and high pressure annealed GaN crystals and layers.
BibTeX:
	@article{Suski1999,
	  author = {Suski, T. and Jun, J. and Leszczynski, M. and Teisseyre, H. and Grzegory, I. and Porowski, S. and Dollinger, G. and Saarinen, K. and Laine, T. and Nissilä, J. and Burkhard, W. and Kriegseis, W. and Meyer, B.K.},
	  title = {High pressure fabrication and processing of GaN:Mg},
	  journal = {Materials Science and Engineering B: Solid-State Materials for Advanced Technology},
	  year = {1999},
	  volume = {59},
	  number = {1-3},
	  pages = {1--5},
	  note = {cited By (since 1996)7},
	  url = {http://www.sciencedirect.com/science/article/pii/S0921510798004024},
	  doi = {http://doi.org/10.1016/S0921-5107(98)00402-4}
	}
	
Optical And Electronic Structure Studies Of Gallium Nitride Single Crystals
T. Suski, H. Teisseyre, I. Grzegory, S. Porowski, O. Ambacher, L. Wittmer, T. Wethkamp and G. Dollinger; In: , D. Gershoni (Ed.), Proceedings of the 24th International Conference on the Physics of Semiconductors (1999) , World Scientific, New Jersey.
BibTeX:
	@inproceedings{Suski1999a,
	  author = {Suski, T. and Teisseyre, H. and Grzegory, I. and Porowski, S. and Ambacher, O. and Wittmer, L. and Wethkamp, T. and Dollinger, G.},
	  title = {Optical And Electronic Structure Studies Of Gallium Nitride Single Crystals},
	  booktitle = {Proceedings of the 24th International Conference on the Physics of Semiconductors},
	  publisher = {World Scientific, New Jersey},
	  year = {1999},
	  editor = {David Gershoni},
	  note = {ISBN: 978-981-02-3613-7},
	  url = {http://www.worldscientific.com/worldscibooks/10.1142/3915}
	}
	

1998

A compact ΔE-Eres detector for elastic recoil detection with high sensitivity
A. Bergmaier, G. Dollinger and C. Frey; Nuclear Instruments and Methods in Physics Research Section B 136-138 (1998) 638-643.
Abstract: A new compact ΔE-Eres detector telescope has been installed in the scattering chamber of the Munich Q3D magnetic spectrograph in order to increase the sensitivity and depth resolution in classical elastic recoil detection (ERD) measurements. It consists of a two dimensional position sensitive ionisation chamber for energy loss and a position sensitive silicon PIN diode for residual energy measurements. A large solid angle of detection of about 4.5 msr combined with good angular resolution in x and y directions enables high sensitivity ERD depth profiling with a sensitivity in the ppm range and a depth resolution of about 10 nm.
BibTeX:
	@article{Bergmaier1998,
	  author = {Bergmaier, A. and Dollinger, G. and Frey, C.M.},
	  title = {A compact ΔE-Eres detector for elastic recoil detection with high sensitivity},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {1998},
	  volume = {136-138},
	  pages = {638--643},
	  note = {cited By (since 1996)32},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X9700877X},
	  doi = {http://doi.org/10.1016/S0168-583X(97)00877-X}
	}
	
Nonequilibrium charge states of recoil ions in high resolution elastic recoil detection analysis
G. Dollinger, M. Boulouednine, A. Bergmaier and T. Faestermann; Nuclear Instruments and Methods in Physics Research Section B 136-138 (1998) 574-578.
Abstract: The measured profiles of a high resolution elastic recoil detection (ERD) analysis utilizing electrostatic or magnetic spectrographs may contain artefacts if only one charge state is measured. This effect is demonstrated by the analysis of 31.8 MeV 12Cq+ recoil ions of different charge states q+ scattered from a pure graphite sample using 60 MeV 58Ni8+ ions at a scattering angle of 15° and by the analysis of a thin BN film. The primary charge state distribution obtained from scattering events very near the surface significantly deviates from the equilibrium one which is measured for carbon ions scattered deeper than 1017 at/cm2 below the surface. Charge exchange cross sections between the main charge states are obtained analysing the depth dependent charge state distributions.
BibTeX:
	@article{Dollinger1998,
	  author = {Dollinger, G. and Boulouednine, M. and Bergmaier, A. and Faestermann, T.},
	  title = {Nonequilibrium charge states of recoil ions in high resolution elastic recoil detection analysis},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {1998},
	  volume = {136-138},
	  pages = {574--578},
	  note = {cited By (since 1996)7},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X97006629?via%3Dihub},
	  doi = {http://doi.org/10.1016/S0168-583X(97)00662-9}
	}
	
Depth profile analysis with monolayer resolution using elastic recoil detection (ERD)
G. Dollinger, C. Frey, A. Bergmaier and T. Faestermann; Europhysics Letters 42 (1) (1998) 25-30.
Abstract: The conditions for obtaining optimum depth resolution in elastic recoil detection (ERD) analysis of thin films using high-energy heavy ions are investigated. We estimate the principle limits given by energy straggling and small-angle scattering effects and show that monolayer depth resolution can be expected under optimized experimental conditions. Such a resolution is demonstrated in an ERD experiment for the first time by discrete signals of adjacent (002) graphite layers which is obtained using a 60 MeV 127I 23+ ion beam and detecting 12C 5+ recoils with a magnetic spectrograph.
BibTeX:
	@article{Dollinger1998a,
	  author = {Dollinger, G. and Frey, C.M. and Bergmaier, A. and Faestermann, T.},
	  title = {Depth profile analysis with monolayer resolution using elastic recoil detection (ERD)},
	  journal = {Europhysics Letters},
	  year = {1998},
	  volume = {42},
	  number = {1},
	  pages = {25--30},
	  note = {cited By (since 1996)23},
	  url = {http://iopscience.iop.org/article/10.1209/epl/i1998-00547-6/meta},
	  doi = {http://doi.org/10.1209/epl/i1998-00547-6}
	}
	
Elastic recoil detection with single atomic layer depth resolution
G. Dollinger, C. Frey, A. Bergmaier and T. Faestermann; Nuclear Instruments and Methods in Physics Research Section B 136-138 (1998) 603-610.
Abstract: The necessary conditions for single atomic layer depth resolution in Elastic Recoil Detection (ERD) analysis will be summarized in this paper: First there are rigorous requirements for the ion beam conditions and for the energy resolution of the recoil ion detector in order to obtain an energy resolution in the order of 5 × 10 -4. Second, the most limiting factors in depth resolution are due to the physical limits imposed by small angle scattering effects and due to the energy loss spread of the incident and recoil ions. Last but not least, the third point deals with irradiation damage which has to be carefully controlled in order to measure the original depth profile before it is altered by the ion beam. As studied by energy loss measurements in transmission geometry through thin carbon foils the energy spread of heavy ions strongly depends on the charge state of the incident ions. In order to obtain the smallest energy spread the data show that the charge state of the incident ions should be near equilibrium. Using a 60 MeV 127I 23+ ion beam the resolution of single atomic carbon layers of a highly oriented pyrolythic graphite (HOPG) sample could be demonstrated analysing the 12C 5+ recoils with the Munich Q3D magnetic spectrograph. As far as we know it is the first time that separated signals of neighbouring atomic layers could be resolved using ERD.
BibTeX:
	@article{Dollinger1998b,
	  author = {Dollinger, G. and Frey, C.M. and Bergmaier, A. and Faestermann, T.},
	  title = {Elastic recoil detection with single atomic layer depth resolution},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {1998},
	  volume = {136-138},
	  pages = {603--610},
	  note = {cited By (since 1996)27},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X97008732?via%3Dihub},
	  doi = {http://doi.org/10.1016/S0168-583X(97)00873-2}
	}
	
Monolayers of graphite resolved by elastic recoil detection
G. Dollinger, C.M. Frey, A. Bergmaier and T. Faestermann; Europhysics Letters 42 (1998) 25.
BibTeX:
	@article{Dollinger1998c,
	  author = {Dollinger, G. and Frey, C. M. and Bergmaier, A. and Faestermann, T.},
	  title = {Monolayers of graphite resolved by elastic recoil detection},
	  journal = {Europhysics Letters},
	  year = {1998},
	  volume = {42},
	  pages = {25},
	  url = {http://iopscience.iop.org/article/10.1209/epl/i1998-00547-6/meta},
	  doi = {http://doi.org/10.1209/epl/i1998-00547-6}
	}
	
High resolution depth profiling of light elements in silicon nanostructures utilizing elastic recoil detection (ERD)
G. Dollinger, V. Petrova-Koch and I. Eisele; In: Proceedings of Nano-El 98 (?) A4-1 (1998) .
BibTeX:
	@inproceedings{Dollinger1998d,
	  author = {Dollinger, G. and V. Petrova-Koch and Eisele, I.},
	  title = {High resolution depth profiling of light elements in silicon nanostructures utilizing elastic recoil detection (ERD)},
	  booktitle = {Proceedings of Nano-El 98 (?)},
	  year = {1998},
	  volume = {A4-1}
	}
	
Bias enhanced nucleation and growth of diamond films on titanium substrates
R. Fehling, M. Schreck, A. Bergmaier, G. Dollinger and B. Stritzker; Materials Science Forum 287-288 (1998) 315-318.
Abstract: Diamond films have been deposited on titanium substrates by microwave plasma chemical vapour deposition using the bias enhanced nucleation procedure. In the first minutes of exposure to the plasma there is a strong roughening of the titanium surface and a reduction of the oxide layer. Interaction with the gas phase as well as dissolution of the oxygen in the bulk contribute to this reduction. After 30 min plasma treatment the oxygen concentration in the bulk is reduced down to 0.2-0.3% and an accelerated hydrogen dissolution, hydride formation and carburization follow. Analogously to silicon the nucleation density increases with biasing time accompanied by a rise in the biasing current. Surpassing an optimum duration of the biasing process deposition of graphitic carbon is enhanced. The nucleation layer determines the bonding at the interface even after a long diamond growth process resulting in a bad adhesion of the films for long biasing procedures.
BibTeX:
	@article{Fehling1998,
	  author = {Fehling, R. and Schreck, M. and Bergmaier, A. and Dollinger, G. and Stritzker, B.},
	  title = {Bias enhanced nucleation and growth of diamond films on titanium substrates},
	  journal = {Materials Science Forum},
	  year = {1998},
	  volume = {287-288},
	  pages = {315--318},
	  note = {cited By (since 1996)0},
	  url = {https://www.scientific.net/MSF.287-288.315},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.287-288.315}
	}
	
The nucleation and growth of large area, highly oriented diamond films on silicon substrates
A. Flöter, H. Güttler, G. Schulz, D. Steinbach, C. Lutz-Elsner, R. Zachai, A. Bergmaier and G. Dollinger; Diamond and Related Materials 7 (2-5) (1998) 283-288.
Abstract: Highly oriented diamond films can play an important role in replacing single crystal diamond for their use as substrates in active electronic devices. However, for practical applications, large, homogenous films with low defect densities are required. The focus of our investigations is the nucleation of highly oriented diamond on (001) silicon via Bias Enhanced Nucleation (BEN) over large areas. A modified BEN process using repetitive pulse bias 'RP-BEN' was developed, resulting in an area of oriented nucleation of up to 30 cm2. The density of azimuthally oriented diamond seeds was measured by scanning electron microscopy (SEM) images and found to be 8 × 108 cm-2 with only 30% variation over the whole deposition area. After the nucleation, a microwave plasma assisted chemical vapor deposition (MPACVD) resulted in highly oriented and 〈100〉 textured diamond films. X-ray diffraction (XRD) measurements of the 111 diamond peak, for a 60-μm-thick film, showed azimuthally misorientations (FWHM) of 2.8° for the tilt and 5.5° for the rotation. Raman spectroscopy was used to evaluate the radial distribution of the phase purity within the films. Introducing a final growth step with a low nitrogen concentration in the gas phase yielded a significant decrease in nitrogen incorporation in the films while maintaining the morphology. Elastic recoil detection (ERD) revealed impurity concentrations in the surface layer of 1.4 ppm for the N/C ratio and 210 ppm for the H/C ratio.
BibTeX:
	@article{Floeter1998,
	  author = {Flöter, A. and Güttler, H. and Schulz, G. and Steinbach, D. and Lutz-Elsner, C. and Zachai, R. and Bergmaier, A. and Dollinger, G.},
	  title = {The nucleation and growth of large area, highly oriented diamond films on silicon substrates},
	  journal = {Diamond and Related Materials},
	  year = {1998},
	  volume = {7},
	  number = {2-5},
	  pages = {283--288},
	  note = {cited By (since 1996)36},
	  url = {http://www.sciencedirect.com/science/article/pii/S0925963597002458?via%3Dihub},
	  doi = {http://doi.org/10.1016/S0925-9635(97)00245-8}
	}
	
Gradient interface layers to improve c-BN thin film adhesion
R. Freudenstein, S. Reinke, W. Kulisch, R. Fischer, J. Zweck, A. Bergmaier and G. Dollinger; Materials Science Forum 287-288 (1998) 259-262.
Abstract: The poor adhesion commonly observed for c-BN thin films is caused by the high compressive stress of the films, and the low adhesion strength at the interface. A close examination of the special nature of the c-BN/substrate interface shows that the textured h-BN nucleation layer is mechanically the weakest link of the system and should thus be avoided. Further measures to increase the adhesion strength are a rough interface, and interfacial adhesion layers. First experiments to deposit a graded interface layer (B → BN) result in extremly rough interfaces, a reduced nucleation layer thickness, and a drastically improved adhesion.
BibTeX:
	@article{Freudenstein1998,
	  author = {Freudenstein, R. and Reinke, S. and Kulisch, W. and Fischer, R. and Zweck, J. and Bergmaier, A. and Dollinger, G.},
	  title = {Gradient interface layers to improve c-BN thin film adhesion},
	  journal = {Materials Science Forum},
	  year = {1998},
	  volume = {287-288},
	  pages = {259--262},
	  note = {cited By (since 1996)12},
	  url = {https://www.scientific.net/MSF.287-288.259},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.287-288.259}
	}
	
Aufbau einer Quelle hochbrillanter, negativer Ionen.
Christian Goeden; Diplomarbeit, Technische Universität München, 1998.
BibTeX:
	@mastersthesis{Goeden1998da,
	  author = {Goeden, Christian},
	  title = {Aufbau einer Quelle hochbrillanter, negativer Ionen.},
	  school = {Technische Universität München},
	  year = {1998}
	}
	
Diamond growth with boron addition
P. Hartmann, S. Bohr, R. Haubner, B. Lux, P. Wurzinger, M. Griesser, A. Bergmaier, G. Dollinger, H. Sternschulte and R. Sauer; International Journal of Refractory Metals and Hard Materials 16 (3) (1998) 223-232.
Abstract: Diamond coatings were produced on Si substrates by the hot-filament method, with B(C 2H 5) 3 added to the gas phase. Ratios of B(C 2H 5) 3: CH 4 up to 0.01 (10000 ppm) were used which gave boron concentrations up to 3% in the layer according to secondary ion mass spectrometry (SIMS) and elastic recoil detection (ERD) measurements. The characteristic Raman peak of diamond at 1332 cm -1 decreases with increasing boron incorporation. Studying this effect in detail shows that on (100) facets the Raman peak still can be observed while on (111) it is already severely deteriorated. TEM and localized EELS spectra show high boron incorporation in the (111) growth sectors and low boron concentration in the (100) sectors. With cathodoluminescence spectroscopy measurements electronic properties were determined. The Mott-transition from semiconductor to metal-like conduction was found to occur at 0.11% B, which is in agreement with published Hall-measurements.
BibTeX:
	@article{Hartmann1998,
	  author = {Hartmann, P. and Bohr, S. and Haubner, R. and Lux, B. and Wurzinger, P. and Griesser, M. and Bergmaier, A. and Dollinger, G. and Sternschulte, H. and Sauer, R.},
	  title = {Diamond growth with boron addition},
	  journal = {International Journal of Refractory Metals and Hard Materials},
	  year = {1998},
	  volume = {16},
	  number = {3},
	  pages = {223--232},
	  note = {cited By (since 1996)11},
	  url = {http://www.sciencedirect.com/science/article/pii/S0263436898000225?via%3Dihub},
	  doi = {http://doi.org/10.1016/S0263-4368(98)00022-5}
	}
	
Acceptor depletion in p-type porous silicon
G. Polisski, G. Dollinger, A. Bergmaier, D. Kovalev, H. Heckler and F. Koch; Physica Status Solidi (A) Applied Research 168 (1) (1998) R1-R2.
BibTeX:
	@article{Polisski1998,
	  author = {Polisski, G. and Dollinger, G. and Bergmaier, A. and Kovalev, D. and Heckler, H. and Koch, F.},
	  title = {Acceptor depletion in p-type porous silicon},
	  journal = {Physica Status Solidi (A) Applied Research},
	  year = {1998},
	  volume = {168},
	  number = {1},
	  pages = {R1-R2},
	  note = {cited By (since 1996)9},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/(SICI)1521-396X(199807)168:1%3CR1::AID-PSSA99991%3E3.0.CO;2-4/abstract},
	  doi = {http://doi.org/10.1002/(SICI)1521-396X(199807)168:1%3CR1::AID-PSSA99991%3E3.0.CO;2-4}
	}
	
Excited state population effect of 60 MeV 58Ni18+ ions penetrating thin carbon foils
O. Schmelmer, G. Dollinger, C. Frey, A. Bergmaier and S. Karsch; Nuclear Instruments and Methods in Physics Research Section B 142 (1-2) (1998) 210-213.
Abstract: Measurements of the charge fractions F(q) of 60 MeV 58Ni18+ traversing thin carbon foils in dependence on their thickness show a non-trivial behavior. Particularly, the charge fraction of the analysed charge state 18+ has a minimum for foil thickness below 1.9 μg/cm2. This behavior can be interpreted by fast electron capture into high shells and a slow depopulation and excitation of innershells.
BibTeX:
	@article{Schmelmer1998,
	  author = {Schmelmer, O. and Dollinger, G. and Frey, C.M. and Bergmaier, A. and Karsch, S.},
	  title = {Excited state population effect of 60 MeV 58Ni18+ ions penetrating thin carbon foils},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {1998},
	  volume = {142},
	  number = {1-2},
	  pages = {210--213},
	  note = {cited By (since 1996)2},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X98002730},
	  doi = {http://doi.org/10.1016/S0168-583X(98)00273-0}
	}
	
Energy straggling of 60 MeV 58Niq+ ions in thin carbon foils and gases
O. Schmelmer, G. Dollinger, C. Frey, A. Bergmaier and S. Karsch; Nuclear Instruments and Methods in Physics Research Section B 145 (3) (1998) 261-270.
Abstract: Energy straggling of 60 MeV 58Niq+ ions in thin carbon foils and gas layers has been measured with a Q3D magnetic spectrograph in dependence of the incident and analysed charge state of the ions. The straggling increases with the number of electrons per gas molecule, thus showing strong correlation effects. In solid carbon, however, energy straggling is close to the data of deuterium gas. The small straggling in carbon is interpreted as an effect of the long range interaction of the heavy ions in dense solids. Furthermore, it is observed that energy straggling depends on the charge state of the projectiles unless the equilibrium charge state is reached.
BibTeX:
	@article{Schmelmer1998a,
	  author = {Schmelmer, O. and Dollinger, G. and Frey, C.M. and Bergmaier, A. and Karsch, S.},
	  title = {Energy straggling of 60 MeV 58Niq+ ions in thin carbon foils and gases},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {1998},
	  volume = {145},
	  number = {3},
	  pages = {261--270},
	  note = {cited By (since 1996)8},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X98005266},
	  doi = {http://doi.org/10.1016/S0168-583X(98)00526-6}
	}
	
Charge dependent energy loss of 60 MeV 58Niq+ ions in argon gas
O. Schmelmer, G. Dollinger, C. Frey, A. Bergmaier and S. Karsch; Nuclear Instruments and Methods in Physics Research Section B 146 (1-4) (1998) 95-100.
Abstract: Energy loss and charge fractions of 60 MeV 58Niq+ ions in argon gas (0.1-16 μg/cm2) have been measured by means of a Q3D magnetic spectrograph in dependence of the incident and analysed charge state of the ions. The measurements show energy loss phenomena at argon gas thicknesses where the charge state distribution is not in equilibrium. For the charge state q = 8+ the stopping power at small target thickness deviates significantly from the value at larger gas thickness. The stopping power of q = 18+ is almost the same as for q = 14+ but energy loss shows a step at about 2 μg/cm2. The deviation of the stopping power at small gas thickness is a combination of two effects. The evolution of the ion's mean charge with increasing target thickness and a selection of impact parameter in collisions between projectiles and gas atoms.
BibTeX:
	@article{Schmelmer1998b,
	  author = {Schmelmer, O. and Dollinger, G. and Frey, C.M. and Bergmaier, A. and Karsch, S.},
	  title = {Charge dependent energy loss of 60 MeV 58Niq+ ions in argon gas},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {1998},
	  volume = {146},
	  number = {1-4},
	  pages = {95--100},
	  note = {cited By (since 1996)6},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X98904840},
	  doi = {http://doi.org/10.1016/S0168-583X(98)90484-0}
	}
	
Modification of diamond film growth by a negative bias voltage in microwave plasma chemical vapor deposition
M. Schreck, T. Baur, R. Fehling, M. Müller, B. Stritzker, A. Bergmaier and G. Dollinger; Diamond and Related Materials 7 (2-5) (1998) 293-298.
Abstract: Diamond growth by microwave plasma chemical vapor deposition (MPCVD) under the influence of an additional negative bias voltage has been studied. From the in-situ measurement of the growth rate and the curvature of the silicon substrate, the intrinsic film stress was monitored during the deposition for bias voltages ranging from 0 to -200 V and for different process pressures. The mass density of the films, their structural properties and the incorporation of hydrogen and nitrogen impurities from the gas phase were determined ex-situ by Rutherford backscattering, Raman spectroscopy and elastic recoil detection, respectively. For the growth under bias, two regimes have been distinguished. At 50 mbar, the intrinsic stress is tensile between Ubias=0V and -100 V, and the growth is only weakly disturbed by the biasing conditions. At -100 V the macroscopic intrinsic stress vanishes. In the second regime, compressive stress rises rapidly and saturates at -3 GPa. Furthermore, the carbon deposition rate increases by a factor of four, accompanied by an increased incorporation of hydrogen and nitrogen and a deterioration of the crystalline quality of the films. The results are discussed in terms of a modification of the film growth by the additional flux of hyperthermal gas species.
BibTeX:
	@article{Schreck1998,
	  author = {Schreck, M. and Baur, T. and Fehling, R. and Müller, M. and Stritzker, B. and Bergmaier, A. and Dollinger, G.},
	  title = {Modification of diamond film growth by a negative bias voltage in microwave plasma chemical vapor deposition},
	  journal = {Diamond and Related Materials},
	  year = {1998},
	  volume = {7},
	  number = {2-5},
	  pages = {293--298},
	  note = {cited By (since 1996)15},
	  url = {http://www.sciencedirect.com/science/article/pii/S0925963597002604?via%3Dihub},
	  doi = {http://doi.org/10.1016/S0925-9635(97)00260-4}
	}
	
Microscopic structural quality of large area highly oriented diamond on silicon substrates for active electronic applications
D. Steinbach, A.F.H.G.R. Zachai, A. Bergmaier and G. Dollinger; In: Electrochemical Society Proceedings (1998) 521 .
BibTeX:
	@inproceedings{Steinbach1998,
	  author = {Steinbach, D. and A. Flöter H. Güttler R. Zachai and Bergmaier, A. and Dollinger, G.},
	  title = {Microscopic structural quality of large area highly oriented diamond on silicon substrates for active electronic applications},
	  booktitle = {Electrochemical Society Proceedings},
	  year = {1998},
	  pages = {521}
	}
	
Impurity and defect incorporation in diamond films deposited at low substrate temperatures
J. Stiegler, A. Bergmaier, J. Michler, Y. Von Kaenel, G. Dollinger and E. Blank; Diamond and Related Materials 7 (2-5) (1998) 193-199.
Abstract: The quality of CVD diamond films degrades severely with decreasing substrate temperatures. In this report, the impurity and defect incorporation in diamond films deposited from a carbon-hydrogen-oxygen gas system at substrate temperatures between 560 and 345 °C has been investigated using elastic recoil detection (ERD), FTIR and micro-Raman spectroscopy. In approaching the low temperature limit which coincides with the formation of cauliflower morphologies, the hydrogen incorporation rises steeply. Hydrogen contents beyond 1 at.% have been measured, roughly 20 times higher than in the upper temperature range. By contrast, there was a much smaller rate of rise in the concentration of nitrogen and oxygen, despite a marked change in the microstructure of the deposited films. At the lowest substrate temperatures, the absolute hydrogen content measured by ERD increases more steeply than those measured by FTIR spectroscopy, which refers to C-H stretch vibrations only. There is evidence that hydrogen is incorporated also in the bulk rather than being concentrated at grain boundaries as at higher temperatures. This conclusion is supported by micro-Raman spectroscopy exhibiting significant peak broadening in the low temperature region.
BibTeX:
	@article{Stiegler1998,
	  author = {Stiegler, J. and Bergmaier, A. and Michler, J. and Von Kaenel, Y. and Dollinger, G. and Blank, E.},
	  title = {Impurity and defect incorporation in diamond films deposited at low substrate temperatures},
	  journal = {Diamond and Related Materials},
	  year = {1998},
	  volume = {7},
	  number = {2-5},
	  pages = {193--199},
	  note = {cited By (since 1996)18},
	  url = {http://www.sciencedirect.com/science/article/pii/S0925963597001647?via%3Dihub},
	  doi = {http://doi.org/10.1016/S0925-9635(97)00164-7}
	}
	
Phase separation in magnetron sputtered superhard BCN thin films
S. Ulrich, H. Ehrhardt, T. Theel, J. Schwan, S. Westermeyr, M. Scheib, P. Becker, H. Oechsner, G. Dollinger and A. Bergmaier; Diamond and Related Materials 7 (6) (1998) 839-844.
Abstract: The similar crystalline structure of diamond and cubix boron nitride suggests the synthesis of superhard thin films containing boron, carbon and nitrogen. BCN thin films have been prepared by reactive r.f.-magnetron sputtering of a hexagonal boron nitride target in an argon/acetylene atmosphere of a constant pressure of 2 × 10-2 mbar. A deposition temperature of 600°C leads to nearly hydrogen-free BCN films. At a flow ratio of 0.05% C2H2/Ar. the composition of the deposited BCN films is close to B5CN3 as a result of energy dispersive X-ray (EDX) and elastic recoil detection (ERD) measurements. By applying a r.f.-substrate bias, the ion energy has been varied at a constant ratio cf ions to film-forming particles of 4. The BCN films show a maximum in stress at an ion energy of 110eV due to knock-on subplantation of argon ions and a phase separation into carbon, boron and cubic boron nitride regions as a result of X-ray diffraction investigations. Auger electron- and infra-red spectroscopy.
BibTeX:
	@article{Ulrich1998,
	  author = {Ulrich, S. and Ehrhardt, H. and Theel, T. and Schwan, J. and Westermeyr, S. and Scheib, M. and Becker, P. and Oechsner, H. and Dollinger, G. and Bergmaier, A.},
	  title = {Phase separation in magnetron sputtered superhard BCN thin films},
	  journal = {Diamond and Related Materials},
	  year = {1998},
	  volume = {7},
	  number = {6},
	  pages = {839--844},
	  note = {cited By (since 1996)60},
	  url = {http://www.sciencedirect.com/science/article/pii/S0925963597003075?via%3Dihub},
	  doi = {http://doi.org/10.1016/S0925-9635(97)00307-5}
	}
	
Structural response and stress release of hexagonal and cubic boron nitride films due to the bombardment with 170-MeV iodine ions
P. Widmayer, D. Schwertberger, M. Wenig, P. Ziemann, A. Bergmaier and G. Dollinger; Diamond and Related Materials 7 (10) (1998) 1503-1508.
Abstract: To investigate the stability of the cubic (c-) and the hexagonal (h-) phase of boron nitride (BN) against radiation damage induced predominantly by electronic energy loss processes of high energy density (typical value 25 keV nm-1), thin films prepared by ion-beam-assisted sputter deposition (IBAD) were irradiated at room temperature with 170-MeV iodine ions. Though the average sample stoichiometry, as continuously monitored during the irradiation by elastic recoil detection (ERD), remains unchanged in both cases, Fourier transform infra-red (FTIR) spectra as well as reflection electron energy loss spectra (REELS) taken before and after each irradiation step clearly demonstrate that c-BN is converted to h-BN, even by small ion fluences, while h-BN remains stable. Additionally, interferometric measurements indicate a dramatic stress release for both, h-BN and c-BN starting structures. In all cases, a pronounced volume expansion of the samples perpendicular to the beam direction is observed maintaining a constant mass area density as again monitored by ERD. Atomic force microscopy (AFM) on bombarded samples reveals characteristic surface features on different length scales, which can be interpreted as being due to stress release and ion track formation. These results are consistent with h-BN being the stable high-temperature phase under relaxed pressure conditions.
To investigate the stability of the cubic (c-) and the hexagonal (h-) phase of boron nitride (BN) against radiation damage induced predominantly by electronic energy loss processes of high energy density (typical value 25 keV nm-1), thin films prepared by ion-beam-assisted sputter deposition (IBAD) were irradiated at room temperature with 170-MeV iodine ions. Though the average sample stoichiometry, as continuously monitored during the irradiation by elastic recoil detection (ERD), remains unchanged in both cases, Fourier transform infra-red (FTIR) spectra as well as reflection electron energy loss spectra (REELS) taken before and after each irradiation step clearly demonstrate that c-BN is converted to h-BN, even by small ion fluences, while h-BN remains stable. Additionally, interferometric measurements indicate a dramatic stress release for both, h-BN and c-BN starting structures. In all cases, a pronounced volume expansion of the samples perpendicular to the beam direction is observed maintaining a constant mass area density as again monitored by ERD. Atomic force microscopy (AFM) on bombarded samples reveals characteristic surface features on different length scales, which can be interpreted as being due to stress release and ion track formation. These results are consistent with h-BN being the stable high-temperature phase under relaxed pressure conditions.
BibTeX:
	@article{Widmayer1998,
	  author = {Widmayer, P. and Schwertberger, D. and Wenig, M.J. and Ziemann, P. and Bergmaier, A. and Dollinger, G.},
	  title = {Structural response and stress release of hexagonal and cubic boron nitride films due to the bombardment with 170-MeV iodine ions},
	  journal = {Diamond and Related Materials},
	  year = {1998},
	  volume = {7},
	  number = {10},
	  pages = {1503-1508},
	  note = {cited By (since 1996)10},
	  url = {http://www.sciencedirect.com/science/article/pii/S0925963598002192},
	  doi = {http://doi.org/10.1016/S0925-9635(98)00219-2}
	}
	
Thermodynamics of liquid mixtures consisting of a very polar and a non-polar aromatic: (Benzonitrile + benzene, or toluene)
E. Wilhelm, W. Egger, M. Vencour, A. Roux, M. Polednicek and J.-P. Grolier; Journal of Chemical Thermodynamics 30 (12) (1998) 1509-1532.
Abstract: For the two binary liquid systems xC6H5CN + (1 - x)C6H6 and xC6H5CN + (1 - x) C6H5CH3, excess molar volumes VEm, excess molar enthalpies HEm, and excess molar heat capacities CEp,m at constant pressure have been measured as a function of mole fraction x. Values of VEm were determined at T = (298.15, 308.15, and 318.15) K, HEm was determined at T = (293.15, 298.15, and 303.15)K, and CEp,m was determined at T = 298.15K (all at atmospheric pressure). The instruments used were, respectively, a vibrating-tube densimeter (from Sodev), an LKB differential flow microcalorimeter equipped with two computer-controlled h.p.l.c. piston pumps (from Gilson), and a Picker flow microcalorimeter (from Setaram). In addition, isobaric heat capacities divided by volume C p,m/Vm of the pure liquids, as well as several selected mixtures, were measured with a programmable differential scanning calorimeter of the Calvet type (micro-d.s.c., from Setaram) between approximately T = 280K and T = 350K. Both systems show relatively small negative excess molar volumes, which become more negative with increasing temperature. The excess molar enthalpies are highly unusual in that for both systems an M-shaped composition dependence is observed (two maxima and one minimum). The M-shape is much more prenounced for (benzonitrile + toluene) than for (benzonitrile + benzene), and appears to vanish for the latter system below T = 298.15K. The results can be understood in terms of a simple theory of complex formation (Guggenheim-McGlashan). The excess molar heat capacity at constant pressure at T = 298.15K of (benzonitrile + toluene) is positive at all compositions, while that of (benzonitrile + benzene) is positive only for 0 < x < 0.071, and negative otherwise (sigmoidal shape). Combining the heat capacities obtained with the Picker calorimeter at T = 298.15 K with our results for Cp,m/Vm obtained with the micro-d.s.c. in conjunction with our density data, excess molar heat capacities have also been derived for (benzonitrile + toluene) at T = (288.15, 308.15, 318.15, and 328.15) K. For this system, the maximum of the curve CEp,m against x becomes somewhat smaller with increasing temperature and is shifted towards larger values of x, i.e. the curves become more symmetric. © 1998 Academic Press.
BibTeX:
	@article{Wilhelm1998,
	  author = {Wilhelm, E. and Egger, W. and Vencour, M. and Roux, A.H. and Polednicek, M. and Grolier, J.-P.E.},
	  title = {Thermodynamics of liquid mixtures consisting of a very polar and a non-polar aromatic: (Benzonitrile + benzene, or toluene)},
	  journal = {Journal of Chemical Thermodynamics},
	  year = {1998},
	  volume = {30},
	  number = {12},
	  pages = {1509--1532},
	  url = {http://www.sciencedirect.com/science/article/pii/S002196149890427X},
	  doi = {http://doi.org/10.1006/jcht.1998.0427}
	}
	
Low energy positron lifetime studies on open-volume defects of epitaxial high temperature superconductor thin film YBa2Cu3O 7-x
X. Zhou and W. Triftshäuser; He Jishu/Nuclear Techniques 21 (2) (1998) .
Abstract: By using a pulsed low energy positron lifetime system, the positron lifetime spectra were measured of the high-temperature superconducting epitaxial thin film YBa2Cu3O7-x samples prepared by the pulsed laser deposition (PLD), magnetron-sputtering method and evaporation method, respectively. It is found that besides shallow positron trapping centers there are a number of deep trapping centers which the bulk material lacks. At low temperature the deep trapping centers have a tendency to enlarge. The relationship between positron lifetime and the deposition conditions (substrate temperature and partial air pressure) of the PLD films indicates that the defect type is independent of the deposition conditions and the defect concentration increases with decreasing substrate temperature or rising partial air pressure.
BibTeX:
	@article{Zhou1998,
	  author = {Zhou, X. and Triftshäuser, W.},
	  title = {Low energy positron lifetime studies on open-volume defects of epitaxial high temperature superconductor thin film YBa2Cu3O 7-x},
	  journal = {He Jishu/Nuclear Techniques},
	  year = {1998},
	  volume = {21},
	  number = {2}
	}
	
Temperature dependence of positron lifetime in a laser-ablated YBa_2Cu_3O_7 - X film
X.Y. Zhou, B.Y. Li, G. Kögel and W. Triftshäuser; Chinese Journal of Low Temperature Physics 20 (5) (1998) 348-355.
BibTeX:
	@article{Zhou1998a,
	  author = {Zhou, X. Y. and Li, B. Y. and Kögel, G. and Triftshäuser, W.},
	  title = {Temperature dependence of positron lifetime in a laser-ablated YBa_2Cu_3O_7 - X film},
	  journal = {Chinese Journal of Low Temperature Physics},
	  year = {1998},
	  volume = {20},
	  number = {5},
	  pages = {348--355}
	}
	

1997

Hydrogen in gallium nitride grown by MOCVD
O. Ambacher, H. Angerer, R. Dimitrov, W. Rieger, M. Stutzmann, G. Dollinger and A. Bergmaier; Physica Status Solidi (A) Applied Research 159 (1) (1997) 105-119.
Abstract: The role of hydrogen in gallium nitride was studied on thin films of GaN on sapphire prepared at substrate temperatures in the range of 600 to 1100°C. By using triethylgallium and ammonia as precursor and hydrogen and/or nitrogen as transport gases, we have observed a strong influence of molecular hydrogen on the deposition rate and the structural properties of epitaxial GaN. By elastic recoil detection analysis and thermal desorption measurements we were able to determine the total concentration of nitrogen, hydrogen and carbon in the bulk material. Isotope substitution of hydrogen by deuterium in the H2 carrier gas did not give rise to a noticeable deuterium incorporation, showing that the sources for hydrogen are the metalorganic precursor, ammonia or reaction products of both. Once incorporated, thermally activated hydrogen effusion from n-type GaN occurs with an activation energy of more than 3.9 eV. With the help of mass spectrometry we established hydrogen effusion from heavily magnesium-doped (2 at%) GaN at temperatures between 600 and 700°C, which is the temperature range used for acceptor activation.
BibTeX:
	@article{Ambacher1997,
	  author = {Ambacher, O. and Angerer, H. and Dimitrov, R. and Rieger, W. and Stutzmann, M. and Dollinger, G. and Bergmaier, A.},
	  title = {Hydrogen in gallium nitride grown by MOCVD},
	  journal = {Physica Status Solidi (A) Applied Research},
	  year = {1997},
	  volume = {159},
	  number = {1},
	  pages = {105--119},
	  note = {cited By (since 1996)35},
	  url = {http://onlinelibrary.wiley.com/doi/10.1002/1521-396X(199701)159:1%3C105::AID-PSSA105%3E3.0.CO;2-H/abstract},
	  doi = {http://doi.org/10.1002/1521-396X(199701)159:1%3C105::AID-PSSA105%3E3.0.CO;2-H}
	}
	
Characterization of AlxGa1-xN films prepared by plasma-induced molecular-beam epitaxy on c-plane sapphire
H. Angerer, O. Ambacher, M. Stutzmann, T. Metzger, R. Hopler, E. Born, A. Bergmaier and G. Dollinger; In: , C.R. Abernathy, H. Amano and J.C. Zolper (Ed.), Materials Research Society Symposium - Proceedings 468 (1997) 305-310 , Materials Research Society, Pittsburgh, PA, United States.
Abstract: AlxGa1-xN films were grown on c-plane sapphire by plasma induced modular beam epitaxy with 0 ≤ x ≤ 1. The composition and purity of the AlxGa1-xN layers was determined by elastic recoil deletion analysis with a relative error of 5% for the Al content. Both X-ray diffraction and atomic force microscopy indicate only a slight decrease in epitaxial quality of the AlxGa1-xN films with increasing Al content up to x = 0.65. X-ray diffraction is used to separate the effects of thermally induced biaxial compressive stress and the alloy composition on the shift of interplanar spacings by measuring both lattice constants. The deviation of the c/a ratio from that of fully relaxed films is a quantitative measure of the biaxial compressive stress leading to a distortion of the unit cell. Values up to 0.5 GPa were observed. By the method proposed, the determination of alloy composition can be corrected for this effect. The results obtained by this method are in very good agreement with the elastic recoil detection measurements substantiating the validity of Vegard's law. These results, compared with optical measurements, indicate that the bowing parameter of the optical bandgap is 1.3 eV within the experimental error.
BibTeX:
	@inproceedings{Angerer1997,
	  author = {Angerer, H. and Ambacher, O. and Stutzmann, M. and Metzger, T. and Hopler, R. and Born, E. and Bergmaier, A. and Dollinger, G.},
	  title = {Characterization of AlxGa1-xN films prepared by plasma-induced molecular-beam epitaxy on c-plane sapphire},
	  booktitle = {Materials Research Society Symposium - Proceedings},
	  publisher = {Materials Research Society, Pittsburgh, PA, United States},
	  year = {1997},
	  volume = {468},
	  pages = {305--310},
	  editor = {Abernathy C.R., Amano H., Zolper J.C.},
	  note = {cited By (since 1996)1},
	  url = {https://www.cambridge.org/core/journals/mrs-online-proceedings-library-archive/article/div-classtitlecharacterisation-of-alspan-classsubxspangaspan-classsub1-xspann-films-prepared-by-plasma-induced-molecular-beam-epitaxy-on-c-plane-sapphirediv/885D83F4B16AE5A1BC74872EA731B0C3},
	  doi = {http://doi.org/10.1557/PROC-468-305}
	}
	
Determination of the Al mole fraction and the band gap bowing of epitaxial AlxGa1-xN films
H. Angerer, D. Brunner, F. Freudenberg, O. Ambacher, M. Stutzmann, R. Höpler, T. Metzger, E. Born, G. Dollinger, A. Bergmaier, S. Karsch and H.-J. Körner; Applied Physics Letters 71 (11) (1997) 1504-1506.
Abstract: AlxGa1-xN alloys were grown on c-plane sapphire by plasma-induced molecular beam epitaxy. The Al content x was varied over the whole composition range (0≤x≤1). The molar Al fraction was deduced from x-ray diffraction and for comparison by elastic recoil detection analysis. The composition of the alloys calculated from the lattice parameter c underestimates x. This is due to a deformation of the unit cell. The exact Al mole fraction and the biaxial strain of the alloys can be calculated by an additional determination of a, using asymmetric reflections. The results obtained by x-ray diffraction and elastic recoil detection provide evidence for the validity of Vegard's law in the AlGaN system. In addition, the deviation of the band gap from a linear dependence on x was investigated. We found a downward bowing with a bowing parameter b=1.3 eV.
BibTeX:
	@article{Angerer1997a,
	  author = {Angerer, H. and Brunner, D. and Freudenberg, F. and Ambacher, O. and Stutzmann, M. and Höpler, R. and Metzger, T. and Born, E. and Dollinger, G. and Bergmaier, A. and Karsch, S. and Körner, H.-J.},
	  title = {Determination of the Al mole fraction and the band gap bowing of epitaxial AlxGa1-xN films},
	  journal = {Applied Physics Letters},
	  year = {1997},
	  volume = {71},
	  number = {11},
	  pages = {1504-1506},
	  note = {cited By (since 1996)179},
	  url = {http://aip.scitation.org/doi/10.1063/1.119949},
	  doi = {http://doi.org/10.1063/1.119949}
	}
	
Diffusivity and surface transition rate of positrons in crystalline silicon as a function of dopant concentration
W. Bauer-Kugelmann, J. Duffy, J. Störmer, G. Kögel and W. Triftshäuser; Applied Surface Science 116 (1997) 231-235.
Abstract: Positron lifetime measurements have been performed on silicon as a function of dopant concentration with the pulsed low-energy positron system (PLEPS II). The lifetime spectra were analysed with a modified version of Positronfit. Values have been obtained for the lifetimes and the corresponding intensities as a function of implantation energy for each sample. Using a new approach for the solution of the diffusion-trapping-model, the mean lifetime and the surface lifetime intensity are used to calculate the diffusion coefficient D and surface transition rate v. Both parameters vary only smoothly in n-doped and weakly p-doped material. For p-type silicon in the concentration range from 1015 to 1021 cm-3 both values first decrease by two orders of magnitude, leading to a minimum in D and v at ca= 1018 cm-3. For higher acceptor concentrations the values for D and v increase again by one order of magnitude. We believe that the accumulation of positrons in so-called Debye-Hückel clouds around negatively charged acceptors in the crystal is the most important contribution.
BibTeX:
	@article{Bauer-Kugelmann1997,
	  author = {Bauer-Kugelmann, W. and Duffy, J.A. and Störmer, J. and Kögel, G. and Triftshäuser, W.},
	  title = {Diffusivity and surface transition rate of positrons in crystalline silicon as a function of dopant concentration},
	  journal = {Applied Surface Science},
	  year = {1997},
	  volume = {116},
	  pages = {231--235},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433296010604?via%3Dihub},
	  doi = {http://doi.org/10.1016/S0169-4332(96)01060-4}
	}
	
Positron lifetimes and positron moderation of 4H-SiC subjected to various treatments
W. Bauer-Kugelmann, G. Kögel, P. Sperr and W. Triftshäuser; Materials Science Forum 255-257 (1997) 662-664.
Abstract: Epitaxial p-SiC layers on n-SiC substrates have been exposed to ion implantation, surface oxidation and post irradiation annealing prior to investigation by the Munich pulsed positron beam in order to obtain a better understanding of positron diffusion, defect trapping and positron re-emission. In the oxide layer, a fraction of up to 40% of the positrons annihilate with a very high lifetime of about 1600 ps, due to positronium formation. At intermediate energies all but the irradiated sample show a minimum in the mean lifetime which can be attributed to annihilation from the bulk. For higher positron implantation energies the mean lifetime is increasing again and the two component fit reveals a second lifetime of about 560 ps in this energy range. Therefore we conclude on defects close to the substrate surface which could be introduced in the nucleation period of epitaxy. In the Al-implanted layer we find trapping at defects with a positron lifetime of about 218 ps. After annealing these defects are almost completely removed. All the unoxidized samples show reemission of positrons at positron energies
BibTeX:
	@article{Bauer-Kugelmann1997a,
	  author = {Bauer-Kugelmann, W. and Kögel, G. and Sperr, P. and Triftshäuser, W.},
	  title = {Positron lifetimes and positron moderation of 4H-SiC subjected to various treatments},
	  journal = {Materials Science Forum},
	  year = {1997},
	  volume = {255-257},
	  pages = {662--664},
	  url = {https://www.scientific.net/MSF.255-257.662},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.255-257.662}
	}
	
Eine supraleitende Multipollinse zur Fokussierung hochenergetischer Ionen.
Gerd Datzmann; Diplomarbeit, Technische Universität München, 1997.
BibTeX:
	@mastersthesis{Datzmann1997da,
	  author = {Datzmann, Gerd},
	  title = {Eine supraleitende Multipollinse zur Fokussierung hochenergetischer Ionen.},
	  school = {Technische Universität München},
	  year = {1997}
	}
	
Progress report from the Munich Scanning Positron Microscope
A. David, G. Kögel, P. Sperr and W. Triftshäuser; Materials Science Forum 255-257 (1997) 741-743.
Abstract: A first prototype of a Scanning Positron Microscope (SPM) with a pulsed beam has been developed in Munich. Besides of the positron beam also an electron beam is provided which produces a conventional electron image of the specimen. Currently we are setting the SPM in operation. A number of problems have been encountered in this process, particularly with the beam control, with various deflection systems and with instabilities due to fluctuating magnetic fields. The technical modifications to overcome these problems and the improvements achieved in this way will be reported.
BibTeX:
	@article{David1997,
	  author = {David, A. and Kögel, G. and Sperr, P. and Triftshäuser, W.},
	  title = {Progress report from the Munich Scanning Positron Microscope},
	  journal = {Materials Science Forum},
	  year = {1997},
	  volume = {255-257},
	  pages = {741--743},
	  url = {https://www.scientific.net/MSF.255-257.741},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.255-257.741}
	}
	
Elemental analysis on group-III nitrides using heavy ion ERD
G. Dollinger, S. Karsch, O. Ambacher, H. Angerer, A. Bergmaier, O. Schmelmer and M. Stutzmann; In: , S.R. Phillpot, P.D. Bristowe, D.G. Stroud and J.R. Smith (Ed.), Proceedings of the 1997 MRS Fall Meeting; Boston, MA, USA; ; 1-4 December 1997; Code 48274 482 (1997) 745-756 , MRS, Warrendale, PA, United States.
Abstract: Elastic recoil detection (ERD) using energetic heavy ion beams is used to measure depth profiles of light and medium heavy elements in thin films. The main advantages of ERD are the possibilities of obtaining reliable and quantitative results, a sensitivity in the ppm region or a depth resolution even better than 1 nm. ERD analysis is employed to obtain quantitative information about the aluminum content of molar fraction in MBE grown AlxGa1-xN layers on Al2O3 substrates. Nitridation of heated Al2O3 substrates in NH3 atmosphere is investigated using high resolution ERD. The impurity content of group III nitrides is investigated on deposition conditions for both MBE and MOCVD grown samples.
BibTeX:
	@inproceedings{Dollinger1997,
	  author = {Dollinger, G. and Karsch, S. and Ambacher, O. and Angerer, H. and Bergmaier, A. and Schmelmer, O. and Stutzmann, M.},
	  title = {Elemental analysis on group-III nitrides using heavy ion ERD},
	  booktitle = {Proceedings of the 1997 MRS Fall Meeting; Boston, MA, USA; ; 1-4 December 1997; Code 48274},
	  publisher = {MRS, Warrendale, PA, United States},
	  year = {1997},
	  volume = {482},
	  pages = {745--756},
	  editor = {Phillpot S.R., Bristowe P.D., Stroud D.G., Smith J.R.},
	  note = {cited By (since 1996)1},
	  url = {https://www.cambridge.org/core/societies/materials-research-society}
	}
	
Investigation of band bending in silicon by slow positron lifetime measurements
J. Duffy, W. Bauer-Kugelmann, G. Kögel and W. Triftshäuser; Applied Surface Science 116 (1997) 241-246.
Abstract: A novel approach to the analysis of positron lifetime data in depth sensitive studies using a pulsed positron beam is applied to model the diffusion of positrons in silicon. By examining only the observable lifetime parameters, inhomogeneous effects can be studied without the need to solve the time dependent diffusion equation. In particular, we study the effect of band bending near the sample surface, which creates an internal electric field. We present our first results of this analysis on p- and n-type bulk silicon samples. No band-bending could be measured for samples covered with a natural oxide. After surface treatment with HF(aq), p-type samples exhibited band bending, but the results for n-type samples were not significantly affected. In only one case, a p-type Si(B) sample with acceptor concentration ca = 1020 cm-3 and with a H terminated surface, is evidence of Fermi level pinning observed.
BibTeX:
	@article{Duffy1997,
	  author = {Duffy, J.A. and Bauer-Kugelmann, W. and Kögel, G. and Triftshäuser, W.},
	  title = {Investigation of band bending in silicon by slow positron lifetime measurements},
	  journal = {Applied Surface Science},
	  year = {1997},
	  volume = {116},
	  pages = {241--246},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433296010628?via%3Dihub},
	  doi = {http://doi.org/10.1016/S0169-4332(96)01062-8}
	}
	
Vacancy defects in low-temperature-grown GaAs observed by continuous and pulsed slow positrons
J. Gebauer, R. Krause-Rehberg, S. Eichler, W. Bauer-Kugelmann, G. Kögel, W. Trifthäuser, M. Luysberg, H. Sohn and E. Weber; Materials Science Forum 255-257 (1997) 204-208.
Abstract: A systematic investigation of GaAs grown at low temperatures (LT-GaAs) was carried out. The vacancy defects in the as-grown material were identified to be mainly Ga vacancies by comparing the core-(W) and valence-(S) annihilation parameters to that of Ga vacancies in highly Si-doped GaAs. The vacancy concentration increases up to 1018 cm-3. Isochronal annealing was done at various samples. The S parameter in the samples increases with annealing, suggesting the formation of new defects. By checking the correlation between S and W we estimated that the defects seen in annealed LT-GaAs are physically different from that in the as-grown state. The annealed samples showed nearly saturated trapping with a defect related positron lifetime of 345 ps, which can be attributed to vacancy clusters or the As precipitates found by correlated TEM measurements.
BibTeX:
	@article{Gebauer1997,
	  author = {Gebauer, J. and Krause-Rehberg, R. and Eichler, S. and Bauer-Kugelmann, W. and Kögel, G. and Trifthäuser, W. and Luysberg, M. and Sohn, H. and Weber, E.R.},
	  title = {Vacancy defects in low-temperature-grown GaAs observed by continuous and pulsed slow positrons},
	  journal = {Materials Science Forum},
	  year = {1997},
	  volume = {255-257},
	  pages = {204--208},
	  url = {https://www.scientific.net/MSF.255-257.204},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.255-257.204}
	}
	
Design of the new superconducting microprobe system in Munich
G. Hinderer, G. Dollinger, G. Datzmann and H.-J. Körner; Nuclear Instruments and Methods in Physics Research Section B 130 (1-4) (1997) 51-56.
Abstract: At the Munich 15 MV tandem accelerator a new two-stage microprobe system is under construction. It will demagnify a beam spot by a factor 200 in both transversal directions for ions up to an energy of 200 MeV · q2/A. The second stage of the system is a superconducting quadrupole doublet lens, with overlayed 2n-poles, n = 4, 6 and 8. The multipole components of this lens have been determined by a ray tracing program with a special treatment of the fringing fields. As a result of these calculations, the overall geometrical aberrations at the focal point are 180 nm horizontally and 280 nm vertically at full angular acceptance (image coordinates ±9 and ±20 mrad, respectively). A main part of the superconducting lens is a central ceramic tube which defines the exact positions of the poles. Superconducting NbTi foils are used to shape the field to the desired one. Superconducting current loops automatically serve for a suppression of all odd harmonic field components.
BibTeX:
	@article{Hinderer1997,
	  author = {Hinderer, G. and Dollinger, G. and Datzmann, G. and Körner, H.-J.},
	  title = {Design of the new superconducting microprobe system in Munich},
	  booktitle = {5th International Conference of Nuclear Microprobe Technology and Applications},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {1997},
	  volume = {130},
	  number = {1-4},
	  pages = {51--56},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X9700178X},
	  doi = {http://doi.org/10.1016/S0168-583X(97)00178-X}
	}
	
Preparation of intense positron sources for beam applications
A. Kauffmann, P. Sperr, G. Kögel and W. Triftshäuser; Materials Science Forum 255-257 (1997) 680-682.
Abstract: Radioactive isotopes are most frequently used as primary positron sources for low energy positron beam systems. In order to obtain optimum positron beam conditions, small source diameters with high intensities are desirable. Two different types of sources were prepared and investigated. 58Co was produced in a nuclear reactor via the reaction 58Ni(n,p)58Co. The bulk material was chemically separated and the 58Co was electrochemically deposited on a 1 mm diameter gold surface. The other type of source was obtained from sodium-acetate, which is commercially available. The solution was deposited on various surfaces. The prepared sources were investigated regarding the influence of inactive carrier material, internal and capsule absorption as well as backing materials by direct measurements of the positron energy spectra using a PIN-diode. In order to avoid the problem of handling very high activities, which should be applicable in these preparations, inactive material was added to simulate the absorption processes in the source.
BibTeX:
	@article{Kauffmann1997,
	  author = {Kauffmann, A. and Sperr, P. and Kögel, G. and Triftshäuser, W.},
	  title = {Preparation of intense positron sources for beam applications},
	  journal = {Materials Science Forum},
	  year = {1997},
	  volume = {255-257},
	  pages = {680--682},
	  url = {https://www.scientific.net/MSF.255-257.680},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.255-257.680}
	}
	
Positron diffusion in solids and the reconstruction of inhomogeneous defect distributions from lifetime measurements
G. Kögel; Applied Physics A: Materials Science and Processing 63 (3) (1997) 227-235.
Abstract: The time dependent diffusion trapping equations for positrons implanted into inhomogeneous solids are analyzed. This problem is of central importance in the study of polycrystalline materials and for the application of pulsed positron beams to defect studies in materials research. The main problem in previous investigations was the necessity to solve the time-dependent diffusion equation. It prevented analytical treatment in all but the simplest applications. For the first time this difficulty is eliminated by invoking a new concept, the observable local annihilation characteristics for local implantation of positrons into the thermalized ensemble. It will be shown that the local annihilation characteristics are governed by field equations which reduce to the well known quantities of the standard trapping model in the case of homogeneous defect distributions. Furthermore, inhomogeneous defect distributions are uniquely determined from the field equations provided the local annihilation characteristics are known. Analytical solutions are derived and applied successfully to recent experimental results for a selection of simple, but realistic problems. The formal procedure includes internal drift fields and could be extended to cover also the epithermal period of positron thermalization, if necessary.
BibTeX:
	@article{Koegel1997,
	  author = {Kögel, G.},
	  title = {Positron diffusion in solids and the reconstruction of inhomogeneous defect distributions from lifetime measurements},
	  journal = {Applied Physics A: Materials Science and Processing},
	  year = {1997},
	  volume = {63},
	  number = {3},
	  pages = {227--235},
	  url = {http://link.springer.com/article/10.1007%2FBF01567874},
	  doi = {http://doi.org/10.1007/BF01567874}
	}
	
The München scanning positron microscope
G. Kögel, W. Triftshäuser, P. Sperr, K. Uhlmann, D. Britton, P. Willutzki, R. Steindl, W. Junker, A. Zecca, R. Brusa, M. Duarte-Naia, G. Karwasz, J. Paridaens and A. Piazza; Applied Surface Science 116 (1997) 108-113.
Abstract: For the first time a scanning positron microscope (SPM) using a pulsed positron beam for the nondestructive, three-dimensionally resolved investigation of defect distributions has been constructed. A positron beam with variable energy from 0.5 to 30 keV, with a spot diameter of 1 μm or below, can be scanned over an area of 0.6 × 0.6 mm2. Beam pulsing enables positron lifetime studies with a time resolution of 200 ps FWHM. The beam is formed by double stage stochastic cooling (moderation) of the positrons emitted from a radioactive isotope. Included in the system is a conventional scanning electron microprobe for easy alignment of the optical column and for surface analysis. The design of the entire SPM is determined by the special demands of positron physics, which are discussed briefly.
BibTeX:
	@article{Koegel1997a,
	  author = {Kögel, G. and Triftshäuser, W. and Sperr, P. and Uhlmann, K. and Britton, D.T. and Willutzki, P. and Steindl, R. and Junker, W. and Zecca, A. and Brusa, R.S. and Duarte-Naia, M.P. and Karwasz, G.P. and Paridaens, J. and Piazza, A.},
	  title = {The München scanning positron microscope},
	  journal = {Applied Surface Science},
	  year = {1997},
	  volume = {116},
	  pages = {108--113},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433296010380?via%3Dihub},
	  doi = {http://doi.org/10.1016/S0169-4332(96)01038-0}
	}
	
Recent investigations on the reconstruction of defect profiles from data obtained by pulsed positron beams
G. Kögel; Materials Science Forum 255-257 (1997) 243-247.
Abstract: A general procedure is presented for the systematic determination of the microscopic defect structure from lifetime measurements with pulsed positron beams. The proposed procedure is based on exact relations with full regard of counting statistics. Initially, a deterministic search for characteristic features of the depth profile is performed in the correlation matrix of the experimental data. On this basis the entire problem is decomposed into a set of small subproblems which can be handled by well established iterative search methods.
BibTeX:
	@article{Koegel1997b,
	  author = {Kögel, G.},
	  title = {Recent investigations on the reconstruction of defect profiles from data obtained by pulsed positron beams},
	  journal = {Materials Science Forum},
	  year = {1997},
	  volume = {255-257},
	  pages = {243--247},
	  url = {https://www.scientific.net/MSF.255-257.243},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.255-257.243}
	}
	
Improvement of the preparation procedure of carbon stripper foils from the laser plasma ablation-deposition process
P. Maier-Komor, A. Bergmaier, G. Dollinger, C. Frey and H. Körner; Nuclear Instruments and Methods in Physics Research Section A 397 (1) (1997) 131-136.
Abstract: Due to series production of the 4 μg/cm2 thick carbon stripper foils, prepared by laser plasma ablation-deposition, several improvements of the preparation procedure could be realized without impairing the crystal structure of random orientation, which leads to the insensitiveness against irradiation damage caused by swift heavy ions. Now carbon stripper foils of this kind can be floated and slackened without any plastic support. The mechanical strength of such foils was tested in dependence of ablation parameters and compared to carbon foils prepared by evaporation-condensation. So far the laser plasma ablation procedure for carbon was limited to a maximum thickness of about 10 μg/cm2. Investigations were performed to extend the thickness range to 100 μg/cm2 and more.
BibTeX:
	@article{Maier-Komor1997,
	  author = {Maier-Komor, P. and Bergmaier, A. and Dollinger, G. and Frey, C.M. and Körner, H.J.},
	  title = {Improvement of the preparation procedure of carbon stripper foils from the laser plasma ablation-deposition process},
	  journal = {Nuclear Instruments and Methods in Physics Research Section A},
	  year = {1997},
	  volume = {397},
	  number = {1},
	  pages = {131--136},
	  note = {cited By (since 1996)21},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168900297007626},
	  doi = {http://doi.org/10.1016/S0168-9002(97)00762-6}
	}
	
An UHV box coater for VUV reflective coatings on mirror substrates of up to 95 cm in diameter
P. Maier-Komor, A. Bergmaier, G. Dollinger, J. Friese, S. Karsch, P. Kienle and H. Körner; Nuclear Instruments and Methods in Physics Research Section A 397 (1) (1997) 194-199.
Abstract: Large mirrors with excellent reflectivity in the vacuum ultraviolet (VUV) range down to 140 nm are needed for large area RICH detectors with CsI photocathodes. This demand can only be fulfilled with a thin homogenous aluminium layer on a substrate with very low surface roughness. Due to the base metal properties of Al an excellent vacuum is required during the evaporation-condensation process. In addition the Al film needs suitable protective layers on both surfaces. The setup of pilot plants to investigate deposition parameters are described and the design of an appropriate box coater is presented.
BibTeX:
	@article{Maier-Komor1997a,
	  author = {Maier-Komor, P. and Bergmaier, A. and Dollinger, G. and Friese, J. and Karsch, S. and Kienle, P. and Körner, H.J.},
	  title = {An UHV box coater for VUV reflective coatings on mirror substrates of up to 95 cm in diameter},
	  journal = {Nuclear Instruments and Methods in Physics Research Section A},
	  year = {1997},
	  volume = {397},
	  number = {1},
	  pages = {194--199},
	  note = {cited By (since 1996)6},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168900297007614?via%3Dihub},
	  doi = {http://doi.org/10.1016/S0168-9002(97)00761-4}
	}
	
Defect spectroscopy in diamond, a new model for positron trapping in insulators
M. Shi, W. Waeber and W. Triftshäuser; Applied Surface Science 116 (1997) 203-210.
Abstract: The purpose of this contribution is double. The first aim is an attempt to understand the positron's behavior in diamond, i.e. the positron annihilation rate in its delocalized states and the trapping process to vacancy-type defects. The second purpose is to qualify diamond membranes which have been produced for the application of field-assisted positron moderation. The results obtained from this comprehensive study of diamond single crystals and diamond membranes by using positron annihilation techniques are presented. The proposed mechanism for the trapping of positrons to vacancy-type defects, namely through positronium formation, gives a new picture for understanding the trapping process in insulators. It can be used to interpret the discrepancies in the earlier experimental results. The obtained results for diamond membranes indicate that they have sufficient quality to be used as the main body of field-assisted moderators.
BibTeX:
	@article{Shi1997,
	  author = {Shi, M. and Waeber, W.B. and Triftshäuser, W.},
	  title = {Defect spectroscopy in diamond, a new model for positron trapping in insulators},
	  journal = {Applied Surface Science},
	  year = {1997},
	  volume = {116},
	  pages = {203--210},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433296010550?via%3Dihub},
	  doi = {http://doi.org/10.1016/S0169-4332(96)01055-0}
	}
	
Pulsing of low energy positron beams
P. Sperr, G. Kögel, P. Willutzki and W. Triftshäuser; Applied Surface Science 116 (1997) 78-81.
Abstract: In this contribution we report on the pulsing components and on the timing performance of our new positron beam facility (the first stage of the scanning positron microscope). Some details of the timing elements and the mechanical construction of the pulsing (bunching) elements are given. First experimental results of the timing measurements of the single stages of the pulsing elements are given.
BibTeX:
	@article{Sperr1997,
	  author = {Sperr, P. and Kögel, G. and Willutzki, P. and Triftshäuser, W.},
	  title = {Pulsing of low energy positron beams},
	  journal = {Applied Surface Science},
	  year = {1997},
	  volume = {116},
	  pages = {78--81},
	  url = {http://www.sciencedirect.com/science/article/pii/S016943329601032X?via%3Dihub},
	  doi = {http://doi.org/10.1016/S0169-4332(96)01032-X}
	}
	
Present performance limits of pulsed positron beams
P. Sperr and G. Kögel; Materials Science Forum 255-257 (1997) 109-113.
Abstract: Pulsed positron beams can out perform conventional positron lifetime systems by orders of magnitude in both event rate and peak to background ratio. The actual performance of low energy pulsed positron beams, however, is is still far from its limits. The technical reasons are spotted and possible improvements are discussed with respect to over ten years of technical developments performed at Munich. Improvements like reduction of the pulse period to 50 MHz, saw-tooth prebuncher, pre-chopper and redesign of the sample chamber which were performed in our currently running system (version 2) are shown. It is argued, that the third version (now under construction) will finally accumulate 104 counts/s at a peak to background ratio of 105. We also show plans of a rf-accelerator for a pulsed variable energy positron beam with source and sample on ground potential.
BibTeX:
	@article{Sperr1997a,
	  author = {Sperr, P. and Kögel, G.},
	  title = {Present performance limits of pulsed positron beams},
	  journal = {Materials Science Forum},
	  year = {1997},
	  volume = {255-257},
	  pages = {109--113},
	  url = {https://www.scientific.net/MSF.255-257.109},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.255-257.109}
	}
	
Intense positron source at the Munich research reactor
M. Springer, G. Kögel, B. Straßer, W. Triftshäuser and K. Schreckenbach; Materials Science Forum 255-257 (1997) 695-697.
Abstract: An in-pile slow positron source was recently installed at the FRM research reactor of the Technical University of Munich. Neutron capture gamma rays of 113 Cd (n,γ) 114 Cd are converted into e+ - e- pairs by absorption in tungsten foils. Moderated positrons are emitted from the foil surface, accelerated by electric lenses to a few keV and guided to a remoderator outside the reactor pool by a magnetic solenoid. In a first approach the beam at the entrance of the remoderator yielded an intensity of 2.108 slow positrons per sec. The remoderator stage is already constructed and presently tested with electrons. The source will provide an order of magnitude more intensity when it will be installed at the FRM-II high flux reactor, which is under construction.
BibTeX:
	@article{Springer1997,
	  author = {Springer, M. and Kögel, G. and Straßer, B. and Triftshäuser, W. and Schreckenbach, K.},
	  title = {Intense positron source at the Munich research reactor},
	  journal = {Materials Science Forum},
	  year = {1997},
	  volume = {255-257},
	  pages = {695--697},
	  url = {https://www.scientific.net/MSF.255-257.695},
	  doi = {http://doi.org/10.4028/www.scientific.net/MSF.255-257.695}
	}
	
A high intense reactor based positron source
G. Triftshäuser, G. Kögel, W. Triftshäuser, M. Springer, B. Straßer and K. Schreckenbach; Applied Surface Science 116 (1997) 45-48.
Abstract: An intense source of monoenergetic, low energy positrons is presented. The positrons are produced by pair production from high energy γ-rays after the capture of thermal neutrons in cadmium. The pair production itself takes place in a stack of layers, each consisting of two concentric rings made of tungsten foils. The source is placed in a beam tube at the Research Reactor Munich at Garching. From first experimental data, we can extrapolate an intensity of 2 × 108 slow positrons per second and a spot size of less than 26 mm.
BibTeX:
	@article{Triftshaeuser1997,
	  author = {Triftshäuser, G. and Kögel, G. and Triftshäuser, W. and Springer, M. and Straßer, B. and Schreckenbach, K.},
	  title = {A high intense reactor based positron source},
	  journal = {Applied Surface Science},
	  year = {1997},
	  volume = {116},
	  pages = {45--48},
	  url = {http://www.sciencedirect.com/science/article/pii/S0169433296009725?via%3Dihub},
	  doi = {http://doi.org/10.1016/S0169-4332(96)00972-5}
	}
	
A scanning positron microscope for defect analysis in materials science
W. Triftshäuser, G. Kögel, P. Sperr, D. Britton, K. Uhlmann and P. Willutzki; Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 130 (1-4) (1997) 264-269.
Abstract: The realisation of a scanning positron microscope will be presented and discussed. A positron beam with a variable energy from 0.5 to 30 keV, with a spot diameter of 1 μm or below, can be scanned over an area of 0.6 × 0.6 mm2. This beam is formed after a double stage stochastic cooling (moderation) of positrons emitted from a radioactive isotope. In addition the positron beam will be pulsed in order to have a well-defined time base for positron lifetime measurements. In the system included is a conventional scanning electron microprobe for surface analysis. The design of the scanning positron microscope is dominated by the special demands of positron physics.
BibTeX:
	@article{Triftshaeuser1997a,
	  author = {Triftshäuser, W. and Kögel, G. and Sperr, P. and Britton, D.T. and Uhlmann, K. and Willutzki, P.},
	  title = {A scanning positron microscope for defect analysis in materials science},
	  journal = {Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms},
	  year = {1997},
	  volume = {130},
	  number = {1-4},
	  pages = {264--269},
	  url = {http://www.sciencedirect.com/science/article/pii/S0168583X97001742?via%3Dihub},
	  doi = {http://doi.org/10.1016/S0168-583X(97)00174-2}
	}
	
The relationship between open volume defects and deposition conditions of superconducting thin-film YBa2Cu3O7-x
X. Zhou, X. Lu, H. Jiang, W. Bauer-Kugelmann, J. Duffy, G. Kögel and W. Triftshäuser; Journal of Physics: Condensed Matter 9 (6) (1997) L61-L66.
Abstract: The relationship between the open volume defects and the deposition conditions of superconducting thin-film YBa2Cu3O7-x was studied by the position lifetime technique. Using a low-energy pulsed positron system, positron lifetime as a function of implantation energy was measured on epitaxial superconducting thin-film YBa2Cu3O7-x deposited on yttrium stabilized cubic zirconia substrates (YSZ) with pulsed laser deposition in a partial pressure of air under different conditions. The results show that the type of open volume defect is independent of deposition conditions such as the substrate temperature, Ts, and the air pressure, pa. The defect concentration increases with decreasing Ts and increasing pa.
BibTeX:
	@article{Zhou1997,
	  author = {Zhou, X.Y. and Lu, X. and Jiang, H. and Bauer-Kugelmann, W. and Duffy, J.A. and Kögel, G. and Triftshäuser, W.},
	  title = {The relationship between open volume defects and deposition conditions of superconducting thin-film YBa2Cu3O7-x},
	  journal = {Journal of Physics: Condensed Matter},
	  year = {1997},
	  volume = {9},
	  number = {6},
	  pages = {L61-L66},
	  url = {http://iopscience.iop.org/article/10.1088/0953-8984/9/6/003/meta},
	  doi = {http://doi.org/10.1088/0953-8984/9/6/003}
	}
	
Positron trapping in a co-evaporation epitaxial superconducting thin film YBa2Cu3O7-x
X. Zhou, W. Bauer-Kugelmann, J. Störmer, G. Kögel and W. Triftshäuser; Physics Letters, Section A: General, Atomic and Solid State Physics 225 (1-3) (1997) 143-148.
Abstract: The positron lifetime as a function of implantation energy was measured on a co-evaporation epitaxial superconducting thin film YBa2Cu3O7-x by using a pulsed low energy positron beam system in Munich. Detailed analysis shows that (i) there are both shallow and deep trapping centers in the film; (ii) the defects concerning the long-lived lifetime, τ2, have an enlargement trend at lower temperature and may become one of the effective flux pinning centers. The variation of the mean lifetime with temperature indicates that almost all positrons escape from the shallow trapping centers at a temperature higher than the room temperature. At temperatures higher than 373 K, an annealing effect should be considered.
BibTeX:
	@article{Zhou1997a,
	  author = {Zhou, X.Y. and Bauer-Kugelmann, W. and Störmer, J. and Kögel, G. and Triftshäuser, W.},
	  title = {Positron trapping in a co-evaporation epitaxial superconducting thin film YBa2Cu3O7-x},
	  journal = {Physics Letters, Section A: General, Atomic and Solid State Physics},
	  year = {1997},
	  volume = {225},
	  number = {1-3},
	  pages = {143--148},
	  url = {http://www.sciencedirect.com/science/article/pii/S0375960196008560?via%3Dihub},
	  doi = {http://doi.org/10.1016/S0375-9601(96)00856-0}
	}
	

1996

Thermal stability and desorption of group III nitrides prepared by metal organic chemical vapor deposition
O. Ambacher, M. Brandt, R. Dimitrov, T. Metzger, M. Stutzmann, R. Fischer, A. Miehr, A. Bergmaier and G. Dollinger; Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures 14 (6) (1996) 3532-3542.
Abstract: We present results on the thermal stability as well as the thermally induced hydrogen, hydrocarbon, and nitrogen-hydrogen effusion from thin films of Group III nitrides prepared by low-pressure chemical vapor deposition from organometallic precursors. We have deposited amorphous, polycrystalline, and epitaxial InN, GaN, and AIN films on (0001) Al 2O 3 substrates using the chemical reaction of azido[bis(3-dimethylamino)propyl]indium, triethylgallium, and tritertiarybutylaluminium with ammonia. The substrate temperature was varied between 400 °C and 1100 °C. The elemental composition, in particular its dependence on the growth temperature, was investigated by elastic recoil detection analysis (ERDA). The influence of growth rate and crystallite size on the concentration of surface adsorbed hydrocarbons and carbon oxides is determined by a combination of ERDA and thermal desorption measurements. In addition, the stability of and the nitrogen flux from the InN, GaN, and AIN surfaces was determined by x-ray diffraction and thermal decomposition experiments.
BibTeX:
	@article{Ambacher1996,
	  author = {Ambacher, O. and Brandt, M.S. and Dimitrov, R. and Metzger, T. and Stutzmann, M. and Fischer, R.A. and Miehr, A. and Bergmaier, A. and Dollinger, G.},
	  title = {Thermal stability and desorption of group III nitrides prepared by metal organic chemical vapor deposition},
	  journal = {Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures},
	  year = {1996},
	  volume = {14},
	  number = {6},
	  pages = {3532-3542},
	  note = {cited By (since 1996)171},
	  url = {http://avs.scitation.org/doi/abs/10.1116/1.588793},
	  doi = {http://doi.org/10.1116/1.588793}
	}
	
ERDA with very heavy ion beams
W. Assmann, J. Davies, G. Dollinger, J. Forster, H. Huber, T. Reichelt and R. Siegele; Nuclear Instruments and Methods in Physics Research Section B 118 (1-4) (1996) 242-250.
Abstract: The use of very heavy ion beams such as 127I or 197Au with 1-2 MeV/u makes ERDA (elastic recoil detection analysis) a quite universal technique for thin film analysis capable of analyzing simultaneously light and heavy elements including H with almost constant sensitivity. Due to the strong increase of the recoil cross section with the projectile atomic number typically less than 10 12 ions are required to get sensitivities in the 100 ppm range. Detector systems with particle identification are advantageous for ERDA, which can be improved additionally regarding depth resolution and detection efficiency, if the kinematic energy spread is corrected. The characteristic features of heavy ion ERDA will be briefly outlined and illustrated by several examples using a position sensitive detector system. Some general problems and limitations, which are caused by heavy ion beams, will also be discussed.
BibTeX:
	@article{Assmann1996,
	  author = {Assmann, W. and Davies, J.A. and Dollinger, G. and Forster, J.S. and Huber, H. and Reichelt, Th. and Siegele, R.},
	  title = {ERDA with very heavy ion beams},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {1996},
	  volume = {118},
	  number = {1-4},
	  pages = {242--250},
	  note = {cited By (since 1996)60},
	  url = {http://www.sciencedirect.com/science/article/pii/0168583X95011838},
	  doi = {http://doi.org/10.1016/0168-583X(95)01183-8}
	}
	
Impact and characterisation of heavy ion tracks on epitaxial growth
F. Baudenbacher, G. Dollinger, F. Ohnesorge, M. Bauer, W. Assman and H. Kinder; Nuclear Instruments and Methods in Physics Research Section B 107 (1-4) (1996) 327-332.
Abstract: The possibility of influencing the epitaxial relationship by heavy ion tracks has been investigated for high temperature superconducting films YBa 2Cu 30 7-δ (YBCO) on single crystalline MgO (100) substrates. The tracks are formed by irradiation with 120 MeV 197Au ions at incidence angles of 1.5° and 1.9° from the surface plane. AFM images of irradiated surfaces reveal the presence of channels which are on average 130 nm long and 6 nm wide. The length of the surface tracks is described by cutting a 4.3 nm deep trench diagonally at an angle of 1.9° relative to the track axis. The measured apparent depth of 1 nm agrees with this assumption due to our finite tip radius of about 20 nm. YBCO films grow on non-irradiated substrates with the in-plane epitaxial relationship YBCO[100]∥MgO[100]. Heavy ion irradiation as described above with a fluence of 10 13 Au ions/cm 2 parallel to the (110) plane resulted in an almost complete change in epitaxial alignment, yielding YBCO[100]∥MgO[110]. In contrast, the in-plane orientation of YBCO did not change if the same density of tracks was created parallel to the MgO (100) plane. Although the results demonstrate the influence of heavy ion channels on the in-plane orientation, attempts to rotate the film axis by 20° on MgO substrates failed.
BibTeX:
	@article{Baudenbacher1996,
	  author = {Baudenbacher, F. and Dollinger, G. and Ohnesorge, F. and Bauer, M. and Assman, W. and Kinder, H.},
	  title = {Impact and characterisation of heavy ion tracks on epitaxial growth},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {1996},
	  volume = {107},
	  number = {1-4},
	  pages = {327--332},
	  note = {cited By (since 1996)3},
	  url = {http://www.sciencedirect.com/science/article/pii/0168583X95010424?via%3Dihub},
	  doi = {http://doi.org/10.1016/0168-583X(95)01042-4}
	}
	
Detection of nitrogen in CVD diamond
A. Bergmaier, G. Dollinger, T. Faestermann, C. Frey, M. Ferguson, H. Güttler, G. Schulz and H. Willerscheid; Diamond and Related Materials 5 (9) (1996) 995-997.
Abstract: A series of CVD diamond films was analysed for their nitrogen content by high resolution elastic recoil detection (ERD) in order to investigate the incorporation of nitrogen from the gas phase in a CVD reactor into the growing diamond film. CVD diamond films were deposited from a mixture of 1.5% CH 4 in H 2 and an admixture of nitrogen gas varying from 0.33% up to 67% [N]/[C]. The measurements revealed that the probability of nitrogen incorporation is only about 0.4% with respect to carbon. In addition, the morphology and texture of the polycrystalline films were investigated by scanning electron microscopy and X-ray texture analysis and showed a significant dependence on the nitrogen admixture.
BibTeX:
	@article{Bergmaier1996,
	  author = {Bergmaier, A. and Dollinger, G. and Faestermann, T. and Frey, C.M. and Ferguson, M. and Güttler, H. and Schulz, G. and Willerscheid, H.},
	  title = {Detection of nitrogen in CVD diamond},
	  journal = {Diamond and Related Materials},
	  year = {1996},
	  volume = {5},
	  number = {9},
	  pages = {995--997},
	  note = {cited By (since 1996)25},
	  url = {http://www.sciencedirect.com/science/article/pii/0925963595003452},
	  doi = {http://doi.org/10.1016/0925-9635(95)00345-2}
	}
	
Limits in elastic recoil detection analysis with heavy ions
G. Dollinger, M. Boulouednine, A. Bergmaier, T. Faestermann and C. Frey; Nuclear Instruments and Methods in Physics Research Section B 118 (1-4) (1996) 291-300.
Abstract: Severe alterations of the sample by the ion beam limits the detectable concentrations in elastic recoil detection analyses (ERDA). Therefore, sputtering and effusion yields were determined and an enhancement was found in comparison to collisional theory. The sputter yield ranges from 650 carbon atoms per incident 120 MeV 197Au ion to about 2500 for hydrogen of a hydrogenated polycrystalline c-BN layer for 60 MeV 58Ni ions, and up to several millions of CHx for organic materials using 60 MeV 127I ions. In addition plural scattering and secondary reactions limit sensitivity, especially when probing materials which mainly contain light elements. The actual limits in ERD with respect to depth resolution and sensitivity are discussed in terms of these principle effects and those induced by the used detection systems.
BibTeX:
	@article{Dollinger1996,
	  author = {Dollinger, G. and Boulouednine, M. and Bergmaier, A. and Faestermann, T. and Frey, C.M.},
	  title = {Limits in elastic recoil detection analysis with heavy ions},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {1996},
	  volume = {118},
	  number = {1-4},
	  pages = {291--300},
	  note = {cited By (since 1996)39},
	  url = {http://www.sciencedirect.com/science/article/pii/0168583X95014691},
	  doi = {http://doi.org/10.1016/0168-583X(95)01469-1}
	}
	
Charge state dependence of the stopping power of 1 MeV/A 58Ni ions
C. Frey, G. Dollinger, A. Bergmaier, T. Faestermann and P. Maier-Komor; Nuclear Instruments and Methods in Physics Research Section B 107 (1-4) (1996) 31-35.
Abstract: The dependence of the energy loss of 60 MeV 58Ni ions on the incident and analysed charge state was measured in thin carbon foils with a Q3D magnetic spectrograph. The surface contamination of the carbon foils was determined by elastic scattering of 12 MeV protons and included in the analysis of the energy loss data. Five incident charge states between qin = 8 + and qin = 18 + were selected. A reduction of the stopping power in the first few atomic layers is observed for low incident charge states and an enhancement for high ones with the transition occurring at qin ≈ 13.5. The results are discussed in terms of a reduction of the dynamic screening of the effective charge of the projectiles at the target surface.
BibTeX:
	@article{Frey1996,
	  author = {Frey, C.M. and Dollinger, G. and Bergmaier, A. and Faestermann, T. and Maier-Komor, P.},
	  title = {Charge state dependence of the stopping power of 1 MeV/A 58Ni ions},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {1996},
	  volume = {107},
	  number = {1-4},
	  pages = {31--35},
	  note = {cited By (since 1996)25},
	  url = {http://www.sciencedirect.com/science/article/pii/0168583X95010084?via%3Dihub},
	  doi = {http://doi.org/10.1016/0168-583X(95)01008-4}
	}
	
Positron diffusion in solids and the reconstruction of inhomogeneous defect distributions from lifetime measurements
G. Kögel; Applied Physics A 63 (3) (1996) 227-235.
Abstract: The time dependent diffusion trapping equations for positrons implanted into inhomogeneous solids are analyzed. This problem is of central importance in the study of polycrystalline materials and for the application of pulsed positron beams to defect studies in materials research. The main problem in previous investigations was the necessity to solve the time-dependent diffusion equation. It prevented analytical treatment in all but the simplest applications. For the first time this difficulty is eliminated by invoking a new concept, the observable local annihilation characteristics for local implantation of positrons into the thermalized ensemble. It will be shown that the local annihilation characteristics are governed by field equations which reduce to the well known quantities of the standard trapping model in the case of homogeneous defect distributions. Furthermore, inhomogeneous defect distributions are uniquely determined from the field equations provided the local annihilation characteristics are known. Analytical solutions are derived and applied successfully to recent experimental results for a selection of simple, but realistic problems. The formal procedure includes internal drift fields and could be extended to cover also the epithermal period of positron thermalization, if necessary.
BibTeX:
	@article{Koegel1996,
	  author = {Kögel, G.},
	  title = {Positron diffusion in solids and the reconstruction of inhomogeneous defect distributions from lifetime measurements},
	  journal = {Applied Physics A},
	  year = {1996},
	  volume = {63},
	  number = {3},
	  pages = {227--235},
	  url = {http://link.springer.com/article/10.1007%2FBF01567874},
	  doi = {http://doi.org/10.1007/BF01567874}
	}
	
Hydrogen incorporation during nucleation and growth of c-BN films
M. Kuhr, R. Freudenstein, S. Reinke, W. Kulisch, G. Dollinger and A. Bergmaier; Diamond and Related Materials 5 (9) (1996) 984-989.
Abstract: The hydrogen content of BN films deposited by the ICP plasma method from trimethyl borazine and N2 has been investigated integrally and spatially resolved by elastic recoil detection. Hydrogen contents between 15% and 25% have been found for conditions allowing the formation of c-BN compared with 4%-10% for h-BN conditions (low bias voltages). However, under c-BN conditions hydrogen is concentrated within the sp2 parts of the film, particularly within the nucleation layer. Addition of hydrogen to the gas phase prevents the formation of c-BN and leads to h-BN films with high hydrogen contents. FTIR examination shows that the films do not contain BH and NH bonds; traces of OH and CHx do not add up to the total hydrogen content. Therefore most of the hydrogen must be free, for example incorporated on interstitials.
BibTeX:
	@article{Kuhr1996,
	  author = {Kuhr, M. and Freudenstein, R. and Reinke, S. and Kulisch, W. and Dollinger, G. and Bergmaier, A.},
	  title = {Hydrogen incorporation during nucleation and growth of c-BN films},
	  journal = {Diamond and Related Materials},
	  year = {1996},
	  volume = {5},
	  number = {9},
	  pages = {984--989},
	  note = {cited By (since 1996)18},
	  url = {http://www.sciencedirect.com/science/article/pii/0925963595004726?via%3Dihub},
	  doi = {http://doi.org/10.1016/0925-9635(95)00472-6}
	}
	
The effect of hydrogen on the nucleation and growth of c-bn
M. Kuhr, R. Freudenstein, S.R.W. Kulisch, G. Dollinger and A. Bergmaier; J. Chem. Vap. Dep. (Technomic Publ. Co.) 3 (1996) 259.
BibTeX:
	@article{Kuhr1996a,
	  author = {Kuhr, M. and Freudenstein, R. and S. Reinke W. Kulisch and Dollinger, G. and Bergmaier, A.},
	  title = {The effect of hydrogen on the nucleation and growth of c-bn},
	  journal = {J. Chem. Vap. Dep. (Technomic Publ. Co.)},
	  year = {1996},
	  volume = {3},
	  pages = {259}
	}
	
Codeposition of hydrogen with beryllium, carbon and tungsten
M. Mayer, R. Behrisch, H. Plank, J. Roth, G. Dollinger and C. Frey; Journal of Nuclear Materials 230 (1) (1996) 67-73.
Abstract: The trapping of energetic deuterium codeposited with beryllium, carbon and tungsten has been measured on a silicon collector probe at room temperature. The subsequent release of the trapped deuterium at elevated temperatures was determined by thermal desorption spectroscopy. At room temperature, deuterium codeposits both with carbon and BeO with a ration of 0.41 D-atoms/C-atom and 0.38 D-atoms/BeO, respectively. No codeposition of deuterium with tungsten is observed. The thermal release of codeposited hydrogen from BeO begins at 400 K. All hydrogen is released at temperatures above 800 K.
BibTeX:
	@article{Mayer1996,
	  author = {Mayer, M. and Behrisch, R. and Plank, H. and Roth, J. and Dollinger, G. and Frey, C.M.},
	  title = {Codeposition of hydrogen with beryllium, carbon and tungsten},
	  journal = {Journal of Nuclear Materials},
	  year = {1996},
	  volume = {230},
	  number = {1},
	  pages = {67--73},
	  note = {cited By (since 1996)54},
	  url = {http://www.sciencedirect.com/science/article/pii/0022311595002391?via%3Dihub},
	  doi = {http://doi.org/10.1016/0022-3115(95)00239-1}
	}
	
Vacancy-type defects in molecular beam epitaxy low temperature grown GaAs, a positron beam lifetime study
J. Störmer, W. Triftshäuser, N. Hozhabri and K. Alavi; Applied Physics Letters 69 (13) (1996) 1867-1869.
Abstract: Positron beam lifetime spectroscopy has been utilized to study the depth distribution of vacancy-type defects in molecular beam epitaxy GaAs grown at low temperature. Lifetime spectra were measured as a function of positron energy. From the analysis of the positron lifetime in as-grown and annealed low temperature grown GaAs, the concentrations of Ga monovacancies and voids are estimated. Our results show that in an as-grown sample the Ga monovacancy concentration is >3×1018 cm-3. It is also known that vacancy-cluster concentration in an annealed sample exceeds 1018 cm-3 with a nonuniform spatial distribution. © 1996 American Institute of Physics.
BibTeX:
	@article{Stoermer1996,
	  author = {Störmer, J. and Triftshäuser, W. and Hozhabri, N. and Alavi, K.},
	  title = {Vacancy-type defects in molecular beam epitaxy low temperature grown GaAs, a positron beam lifetime study},
	  journal = {Applied Physics Letters},
	  year = {1996},
	  volume = {69},
	  number = {13},
	  pages = {1867--1869},
	  url = {http://aip.scitation.org/doi/10.1063/1.117460},
	  doi = {http://doi.org/10.1063/1.117460}
	}
	
Silicon carbide: A new positron moderator
J. Störmer, A. Goodyear, W. Anwand, G. Brauer, P. Coleman and W. Triftshäuser; Journal of Physics Condensed Matter 8 (7) (1996) L89-L94.
Abstract: Observation of copious positron re-emission from crystalline 6H-SiC, with no pretreatment and without the need for ultra-high-vacuum conditions, suggests that this material may form the basis of an important new moderator for the production of monoenergetic positrons. Its positron work function is measured to be -3.0 ± 0.2 eV. Its electrical characteristics point to SiC as a prime candidate for development as a field-assisted positron moderator, producing moderately intense slow-positron beams in laboratory-based systems and enabling a new generation of positron experimentation.
BibTeX:
	@article{Stoermer1996a,
	  author = {Störmer, J. and Goodyear, A. and Anwand, W. and Brauer, G. and Coleman, P.G. and Triftshäuser, W.},
	  title = {Silicon carbide: A new positron moderator},
	  journal = {Journal of Physics Condensed Matter},
	  year = {1996},
	  volume = {8},
	  number = {7},
	  pages = {L89-L94},
	  url = {http://iopscience.iop.org/article/10.1088/0953-8984/8/7/002/meta},
	  doi = {http://doi.org/10.1088/0953-8984/8/7/002}
	}
	
Positron annihilation in the epitaxial superconducting thin-film GdBa2Cu3O7-δ studied by using a pulsed positron beam
X. Zhou, J. Störmer, R. Wang, J. Keimel, H. Li, G. Kögel and W. Triftshäuser; Physical Review B - Condensed Matter and Materials Physics 54 (2) (1996) 1398-1403.
Abstract: The positron lifetime as a function of implantation energy was measured on the epitaxial superconducting thin film GdBa2Cu3O7-δ at different temperatures. The coexistence of both shallow and deep positron trapping centers was observed in the film. The shallow trapping centers include the screw dislocations and twin boundaries. The binding energy of the shallow trapping centers was estimated to be 56±12 meV. The deep trapping centers are assigned the cation vacancies, especially barium vacancies. On the surface of the sample there are macroscopic free volume holes in which positronium could be formed.
BibTeX:
	@article{Zhou1996,
	  author = {Zhou, X.Y. and Störmer, J. and Wang, R.L. and Keimel, J. and Li, H.C. and Kögel, G. and Triftshäuser, W.},
	  title = {Positron annihilation in the epitaxial superconducting thin-film GdBa2Cu3O7-δ studied by using a pulsed positron beam},
	  journal = {Physical Review B - Condensed Matter and Materials Physics},
	  year = {1996},
	  volume = {54},
	  number = {2},
	  pages = {1398--1403},
	  url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.54.1398},
	  doi = {http://doi.org/10.1103/PhysRevB.54.1398}
	}
	

1995

Elemental composition of thin c-BN layers
A. Bergmaier, G. Dollinger, T. Faestermann, C. Frey, W. Dworschak and H. Ehrhardt; Diamond and Related Materials 4 (4) (1995) 478-481.
Abstract: Some experiments on the growth of cubic boron nitride (c-BN) show that the content of c-BN in BN films depends on the film thickness. Non-cubic phases, such as amorphous and hexagonal BN, can be identified, particularly near the substrate. To understand these phase variations, elemental depth profiles of thin BN films were measured by high resolution elastic recoil detection (ERD). BN films have been prepared by r.f. glow discharge (r.f = 13.56 MHz) from a mixture of B2H6 (10% in argon) and N2. Layers 48 nm and 90 nm thick have been deposited on crystalline silicon with integrated portions of the cubic phase of 55% and 67% respectively. ERD measurements showed that the integrated boron-to-nitrogen ratio is close to unity for the thicker film, but significant enhancements of boron are found near the interface with the silicon substrate and at the surface. These enhancements are coupled with a decrease in the hydrogen content, which is about 9% on average. The elemental fluctuations will be correlated with the occurrence of different BN phases and improvements for c-BN deposition will be suggested.
BibTeX:
	@article{Bergmaier1995,
	  author = {Bergmaier, A. and Dollinger, G. and Faestermann, T. and Frey, C.M. and Dworschak, W. and Ehrhardt, H.},
	  title = {Elemental composition of thin c-BN layers},
	  journal = {Diamond and Related Materials},
	  year = {1995},
	  volume = {4},
	  number = {4},
	  pages = {478--481},
	  note = {cited By (since 1996)13},
	  url = {http://www.sciencedirect.com/science/article/pii/0925963594052522},
	  doi = {http://doi.org/10.1016/0925-9635(94)05252-2}
	}
	
Quantitative elastic recoil detection
A. Bergmaier, G. Dollinger and C. Frey; Nuclear Instruments and Methods in Physics Research Section B 99 (1-4) (1995) 488-490.
Abstract: Quantitative depth profiles of light and medium heavy elements can be obtained by elastic recoil detection analysis (ERDA) with heavy ions due to well known scattering cross sections and stopping powers. However, the transformation of the measured spectra (count rate versus energy) into concentration profiles is a nontrivial task in general. Therefore, based on a similar algorithm for the transformation of RBS-spectra a matrix algorithm was developed which allows to transform ERDA-spectra directly into depth profiles. This procedure can also be used to calculate depth profiles from high resolution experiments where a depth resolution better than 1 nm can be achieved. An example of ERDA-measurements demonstrates the performance of this method in determining quantitative depth profiles.
BibTeX:
	@article{Bergmaier1995a,
	  author = {Bergmaier, A. and Dollinger, G. and Frey, C.M.},
	  title = {Quantitative elastic recoil detection},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {1995},
	  volume = {99},
	  number = {1-4},
	  pages = {488--490},
	  note = {cited By (since 1996)46},
	  url = {http://www.sciencedirect.com/science/article/pii/0168583X94006660?via%3Dihub},
	  doi = {http://doi.org/10.1016/0168-583X(94)00666-0}
	}
	
Quantitative elastic recoil detection (ERD)
A. Bergmaier, G. Dollinger, C. Frey and T. Faestermann; Fresenius' Journal of Analytical Chemistry 353 (5-8) (1995) 582-584.
Abstract: Elastic recoil detection with heavy ions is a well suited method to measure depth profiles of light and medium heavy elements in thin films. Due to known Rutherford scattering cross sections and stopping powers of ions in matter, measurements can be quantified with an accuracy of about 1%. The transformation of energy spectra to quantitative elemental depth profiles, however, is generally a non trivial task and therefore a transofrmation algorithm has been developed based on a similar one for RBS analysis and realised in the program KONZERD. The transformation procedure allows a fast conversion from raw spectra to concentration profiles for classical ERD measurements as well as for high resolution measurements with a depth resolution better than 1 nm.
BibTeX:
	@article{Bergmaier1995b,
	  author = {Bergmaier, A. and Dollinger, G. and Frey, C.M. and Faestermann, T.},
	  title = {Quantitative elastic recoil detection (ERD)},
	  journal = {Fresenius' Journal of Analytical Chemistry},
	  year = {1995},
	  volume = {353},
	  number = {5-8},
	  pages = {582--584},
	  note = {cited By (since 1996)1},
	  url = {http://link.springer.com/article/10.1007%2FBF00321328},
	  doi = {http://doi.org/10.1007/BF00321328}
	}
	
Positron studies of polycrystalline TiC
G. Brauer, W. Anwand, E. Nicht, P. Coleman, A. Knights, H. Schut, G. Kögel and N. Wagner; Journal of Physics: Condensed Matter 7 (47) (1995) 9091-9099.
Abstract: The mean positron lifetime tau , positron diffusion length L, and the positron and electron work functions ( phi + and phi -) for polycrystalline TiC have been experimentally determined. The results were tau =160(2) ps, L+=138(27) nm and phi -=3.96(0.08) eV; phi + was shown to be almost certainly positive. These results strongly support the suggestion from recent first-principles electronic structure and positron state calculations that positions are trapped by and annihilate in metal vacancies in this material. XPS measurements indicate that the trapping sites may be predominantly in thin carbon-rich layers between grains, a picture which may also explain the long near-surface diffusion length.
BibTeX:
	@article{Brauer1995,
	  author = {Brauer, G. and Anwand, W. and Nicht, E. and Coleman, P.G. and Knights, A.P. and Schut, H. and Kögel, G. and Wagner, N.},
	  title = {Positron studies of polycrystalline TiC},
	  journal = {Journal of Physics: Condensed Matter},
	  year = {1995},
	  volume = {7},
	  number = {47},
	  pages = {9091--9099},
	  url = {http://iopscience.iop.org/article/10.1088/0953-8984/7/47/025/meta},
	  doi = {http://doi.org/10.1088/0953-8984/7/47/025}
	}
	
Magnetic positron optics
D. Britton, K. Uhlmann and G. Kögel; Applied Surface Science 85 (C) (1995) 158-164.
Abstract: Two different magnetic lenses, suitable for use as objective lenses in positron beams, which can be positioned outside the vacuum system, behind the target are presented. The first is a single-pole lens, optimised as a parallising objective for the reemission of slow positrons from a remoderator. The second is a side-gap lens designed as a probe-forming lens for variable incident energy up to 30 keV with no change in its optical properties. Additionally the effect of an additional solenoid field on the properties of the probe-forming lens has been investigated. © 1995.
BibTeX:
	@article{Britton1995,
	  author = {Britton, D.T. and Uhlmann, K. and Kögel, G.},
	  title = {Magnetic positron optics},
	  journal = {Applied Surface Science},
	  year = {1995},
	  volume = {85},
	  number = {C},
	  pages = {158--164},
	  url = {http://www.sciencedirect.com/science/article/pii/0169433294003262?via%3Dihub},
	  doi = {http://doi.org/10.1016/0169-4332(94)00326-2}
	}
	
High resolution depth profile analysis by elastic recoil detection with heavy ions
G. Dollinger, A. Bergmaier, T. Faestermann and C. Frey; Fresenius' Journal of Analytical Chemistry 353 (3-4) (1995) 311-315.
Abstract: Elastic recoil detection (ERD) with energetic heavy ions (e.g. 60-120 MeV127I) is a suitable method to measure depth profiles of light and medium heavy elements in thin films. The advantages of this method are reliable and quantitative results and elementally and isotopically resolved depth profiles. A relative energy resolution of 0.07% has been measured in real ERD-experiments using the Q3D magnetic spectrograph at the Munich tandem accelerator and a large solid angle of detection of 5 msr. The good energy resolution allows atomic depth resolution near to the surface which has been obtained at flat and smooth carbon samples. A large solid angle of detection is necessary to measure a depth profile with the desired accuracy before the sample is significantly altered by the ion beam. As an example carbon profiles of thin carbon layers, prepared by a laser plasma ablation deposition process, have been investigated revealing the high depth resolution and its power to resolve elemental profiles at gradiated interfaces.
BibTeX:
	@article{Dollinger1995,
	  author = {Dollinger, G. and Bergmaier, A. and Faestermann, T. and Frey, C.M.},
	  title = {High resolution depth profile analysis by elastic recoil detection with heavy ions},
	  journal = {Fresenius' Journal of Analytical Chemistry},
	  year = {1995},
	  volume = {353},
	  number = {3-4},
	  pages = {311--315},
	  note = {cited By (since 1996)23},
	  url = {http://link.springer.com/article/10.1007%2FBF00322058},
	  doi = {http://doi.org/10.1007/BF00322058}
	}
	
Impurities of light elements in CVD diamond
G. Dollinger, A. Bergmaier, C. Frey, M. Roesler and H. Verhoeven; Diamond and Related Materials 4 (5-6) (1995) 591-595.
Abstract: CVD diamond samples were investigated for their content of light elements and their influence on the physical properties by high resolution elastic recoil detection (ERD) analysis. ERD allows quantitative measurements of depth profiles for all light elements with a depth resolution better than 1 nm (near the surface) using 58Ni or 127I ions with a specific energy of about 1 MeV per nucleus and a high resolution magnetic spectrograph. The measurements were focused on the content of hydrogen in (100)-oriented CVD diamond 90 μm thick grown on (100) silicon. The hydrogen content varied from 0.07 at.% in the bulk to several atomic per cent for fine crystalline diamond near the interface to its silicon substrate. The hydrogen coverage of (100)-oriented diamond could also be determined to be near the value which is expected if the (100) surface has a (2 × 1) reconstruction. In addition to hydrogen, other light elements were simultaneously measured. Silicon and oxygen impurities were also analysed in order to get information about their physical relevance. A correlation between the Si content and the luminescence of silicon centres was attempted.
BibTeX:
	@article{Dollinger1995a,
	  author = {Dollinger, G. and Bergmaier, A. and Frey, C.M. and Roesler, M. and Verhoeven, H.},
	  title = {Impurities of light elements in CVD diamond},
	  journal = {Diamond and Related Materials},
	  year = {1995},
	  volume = {4},
	  number = {5-6},
	  pages = {591--595},
	  note = {cited By (since 1996)30},
	  url = {http://www.sciencedirect.com/science/article/pii/0925963594052743},
	  doi = {http://doi.org/10.1016/0925-9635(94)05274-3}
	}
	
Calcium targets with low hydrogen content
G. Dollinger, T. Faestermann, C. Frey and P. Maier-Komor; Nuclear Instruments and Methods in Physics Research Section A 362 (1) (1995) 60-63.
Abstract: The hydrogen content of calcium targets was determined by elastic recoil detection (ERD). Thereby a Q3D magnetic spectrograph was used to obtain best depth resolution of the hydrogen profiles. The two most promising preparation methods for calcium targets with low hydrogen content - deposition of the most stable calcium halide CaF2 and protecting metallic Ca by a diffusion barrier of Al - have been examined. A detailed description of the technique that resulted in the minimal hydrogen content of the targets will be given.
BibTeX:
	@article{Dollinger1995b,
	  author = {Dollinger, G. and Faestermann, T. and Frey, C.M. and Maier-Komor, P.},
	  title = {Calcium targets with low hydrogen content},
	  journal = {Nuclear Instruments and Methods in Physics Research Section A},
	  year = {1995},
	  volume = {362},
	  number = {1},
	  pages = {60--63},
	  note = {cited By (since 1996)1},
	  url = {http://www.sciencedirect.com/science/article/pii/0168900295003118?via%3Dihub},
	  doi = {http://doi.org/10.1016/0168-9002(95)00311-8}
	}
	
Charge state dependence of the stopping power of 1 Mev/A 58Ni-ions in thin carbon foils
C. Frey, G. Dollinger, A. Bergmaier, T. Faestermann and P. Maier-Komor; Nuclear Instruments and Methods in Physics Research Section B 99 (1-4) (1995) 205-209.
Abstract: Energy loss and energy straggling of 60 MeV 58Ni ions in ultrathin carbon foils (0.8 to 30 μg/cm2) have been measured with a Q3D magnetic spectrograph in dependence on the incident and analysed charge state of the ions. The stopping power in the first few atomic layers deviates significantly from the value in larger depths and can be scaled with the square of the incident charge state q. For larger depths the stopping power coincides with the tabulated value for all measured charge states. From this difference in the stopping power an average charge state q = 15.5 for the Ni-ions inside the bulk can be estimated in a first approximation. With the average charge state behind carbon foils being q = 17.6 the ion has to lose two electrons on average when leaving the target, e.g. by Auger processes. The energy straggling of the Ni-ions can be approximated by the known formula of Bohr. Nevertheless the systematics of the dependence on the incident and analysed charge state indicates that charge changing events contribute a significant amount to the energy straggling.
BibTeX:
	@article{Frey1995,
	  author = {Frey, C.M. and Dollinger, G. and Bergmaier, A. and Faestermann, T. and Maier-Komor, P.},
	  title = {Charge state dependence of the stopping power of 1 Mev/A 58Ni-ions in thin carbon foils},
	  journal = {Nuclear Instruments and Methods in Physics Research Section B},
	  year = {1995},
	  volume = {99},
	  number = {1-4},
	  pages = {205--209},
	  note = {cited By (since 1996)11},
	  url = {http://www.sciencedirect.com/science/article/pii/0168583X95002189?via%3Dihub},
	  doi = {http://doi.org/10.1016/0168-583X(95)00218-9}
	}
	
Defect Profiling with Pulsed e+-Beams
G. Kögel; Materials Science Forum 175-178 (1995) 107-114.
BibTeX:
	@article{Koegel1995,
	  author = {Kögel, Gottfried},
	  title = {Defect Profiling with Pulsed e+-Beams},
	  journal = {Materials Science Forum},
	  year = {1995},
	  volume = {175-178},
	  pages = {107--114},
	  url = {https://www.scientific.net/MSF.175-178.107},
	  doi = {http://doi.org/10.4028/www.scientific.net/msf.175-178.107}
	}
	
Completion of the plant for laser plasma ablation-deposition of carbon
P. Maier-Komor, G. Dollinger, C. Frey and H. Körner; Nuclear Instruments and Methods in Physics Research Section A 362 (1) (1995) 208-212.
Abstract: The strength of carbon stripper foils against heavy ion induced irradiation damage is at an optimum if the nanocrystals of the carbon foil are isotropically distributed. So far only carbon stripper foils prepared by laser plasma ablation deposition can completely fulfill this demand. This procedure is quite different from standard carbon foil preparation and needs several new developments especially for a series production. Here the realization of the previously measured ablation deposition data into a source-to-substrate configuration is demonstrated. For the total rotating substrate area of 750 cm2, an overall homogeneity of 3% could be attained with a small source-to-substrate distance of 40 cm. Problems being encountered from the high laser power density especially at the laser to vacuum entrance window have been solved. Investigations of suitable parting agents and parting agent combinations which are less sensitive on humidity were performed. Even if not all problems are solved with satisfaction, a routine preparation can be started now.
BibTeX:
	@article{Maier-Komor1995,
	  author = {Maier-Komor, P. and Dollinger, G. and Frey, C.M. and Körner, H.J.},
	  title = {Completion of the plant for laser plasma ablation-deposition of carbon},
	  journal = {Nuclear Instruments and Methods in Physics Research Section A},
	  year = {1995},
	  volume = {362},
	  number = {1},
	  pages = {208--212},
	  note = {cited By (since 1996)18},
	  url = {http://www.sciencedirect.com/science/article/pii/0168900295004130},
	  doi = {http://doi.org/10.1016/0168-9002(95)00413-0}
	}
	
A slow positron lifetime study of the annealing behaviour of an amorphous silicon layer grown by MBE
J. Störmer, P. Willutzki, D. Britton, G. Kögel, W. Triftshäuser, W. Kiunke, F. Wittmann and I. Eisele; Applied Physics A Materials Science & Processing 61 (1) (1995) 71-74.
Abstract: We have studied MBE grown amorphous silicon, which was recrystallized at different temperatures for one hour, with a pulsed positron beam. A positron lifetime of 538±10 ps in the as-grown state is attributed to microvoids containing at least 10 vacancies. An incompletely recrystallized sample annealed at 500°C shows an additional long lifetime from ortho-positronium (o-Ps) pick-off annihilation. The o-Ps component disappears for samples, recrystallized at 700°C and above, and the defect lifetime steadily decreases with higher annealing temperature until a value of 310 ps is reached for the layer annealed at 1200°C. This value is explained by positron trapping at dislocations or small vacancy defects stabilized by dislocations or impurities. © 1995 Springer-Verlag.
BibTeX:
	@article{Stoermer1995,
	  author = {Störmer, J. and Willutzki, P. and Britton, D.T. and Kögel, G. and Triftshäuser, W. and Kiunke, W. and Wittmann, F. and Eisele, I.},
	  title = {A slow positron lifetime study of the annealing behaviour of an amorphous silicon layer grown by MBE},
	  journal = {Applied Physics A Materials Science & Processing},
	  year = {1995},
	  volume = {61},
	  number = {1},
	  pages = {71--74},
	  url = {http://link.springer.com/article/10.1007%2FBF01538214},
	  doi = {http://doi.org/10.1007/BF01538214}
	}
	
A High Intense Positron Source at the Munich Research Reactor
G. Triftshäuser, G. Kögel, W. Triftshäuser, M. Springer, T. Hagner and K. Schreckenbach; Materials Science Forum 175-178 (1995) 221-224.
BibTeX:
	@article{Triftshaeuser1995,
	  author = {Triftshäuser, G. and Kögel, Gottfried and Triftshäuser, Werner and Springer, M. and Hagner, T. and Schreckenbach, K.},
	  title = {A High Intense Positron Source at the Munich Research Reactor},
	  journal = {Materials Science Forum},
	  year = {1995},
	  volume = {175-178},
	  pages = {221--224},
	  url = {https://www.scientific.net/MSF.175-178.221},
	  doi = {http://doi.org/10.4028/www.scientific.net/msf.175-178.221}
	}
	
A concept of a scanning positron microscope
K. Uhlmann, W. Triftshäuser, G. Kögel, P. Sperr, D. Britton, A. Zecca, R. Brusa and G. Karwasz; Fresenius' Journal of Analytical Chemistry 353 (5-8) (1995) 594-597.
Abstract: The concept of a scanning positron microscope which is under construction in München and Trento will be shown. A beam with a variable energy from 1 to 30 keV and a spot diameter of 1 μm, which can be scanned over an area of (0.6×0.6) mm2, is formed after a double stage stochastic cooling of the positrons emitted from a radioactive source. Additionally, the beam will be pulsed to have a well-defined time base for positron lifetime measurements. The design of the microscope is dominated by special demands of positron physics. Therefore, the microscope contains electron optical elements which are well known but rarely used. These are the through the lens reflection remoderator and the optical column with a magnetic side gap lens as probe forming lens.
BibTeX:
	@article{Uhlmann1995,
	  author = {Uhlmann, K. and Triftshäuser, W. and Kögel, G. and Sperr, P. and Britton, D.T. and Zecca, A. and Brusa, R.S. and Karwasz, G.},
	  title = {A concept of a scanning positron microscope},
	  journal = {Fresenius' Journal of Analytical Chemistry},
	  year = {1995},
	  volume = {353},
	  number = {5-8},
	  pages = {594--597},
	  url = {http://link.springer.com/article/10.1007%2FBF00321331},
	  doi = {http://doi.org/10.1007/BF00321331}
	}
	
A new optical column for a scanning positron microscope
K. Uhlmann, D. Britton and G. Kögel; Measurement Science and Technology 6 (7) (1995) 932-938.
Abstract: An optical column for a scanning positron microprobe is described. A beam of variable energy from 1 to 30 keV and a spot diameter of 1 mu m, that can be scanned over an area of 0.6*0.6 mm2 is formed using electron optical elements that are already well known but rarely used in an optical column. The idea allows the construction of a sample chamber free of material and electric fields in a hemisphere above the sample with a radius of some 100 mm or more. The absence of diaphragms and the comfortable inner diameter of the lenses used makes it possible to work with a beam of comparatively large diameter and aperture. This is necessary because of the low intensity of the positron sources available, which makes a system with a very high transmission essential. Although the idea was created for a positron microprobe, other applications, such as with a retarding field analyser introduced into the sample chamber, are conceivable.
BibTeX:
	@article{Uhlmann1995a,
	  author = {Uhlmann, K. and Britton, D.T. and Kögel, G.},
	  title = {A new optical column for a scanning positron microscope},
	  journal = {Measurement Science and Technology},
	  year = {1995},
	  volume = {6},
	  number = {7},
	  pages = {932--938},
	  url = {http://iopscience.iop.org/article/10.1088/0957-0233/6/7/012/meta},
	  doi = {http://doi.org/10.1088/0957-0233/6/7/012}
	}
	
Investigations of positron lifetimes in InP with a pulsed positron beam
P. Willutzki, J. Störmer, D. Britton and W. Triftshäuser; Applied Physics A Materials Science & Processing 61 (3) (1995) 321-324.
Abstract: Indium Phosphide layers grown by gas source Molecular Beam Epitaxy, (MBE) have been studied by positron lifetime spectroscopy using the recently modified pulsed positron beam in Munich. The as-grown samples are known to be phosphorous rich and contain a high concentration of vacancy-type defects. On annealing, phosphorous precipitates are formed and the concentration of free volume defects increases. Positron lifetime spectroscopy has identified the grown in defects to be indium vacancies at a concentration around 1018cm-3. The dominant defects after annealing exhibit a positron lifetime characteristic of divacancies and are present at concentrations in excess of 5×1019cm-3. © 1995 Springer-Verlag.
BibTeX:
	@article{Willutzki1995,
	  author = {Willutzki, P. and Störmer, J. and Britton, D.T. and Triftshäuser, W.},
	  title = {Investigations of positron lifetimes in InP with a pulsed positron beam},
	  journal = {Applied Physics A Materials Science & Processing},
	  year = {1995},
	  volume = {61},
	  number = {3},
	  pages = {321--324},
	  url = {http://link.springer.com/article/10.1007%2FBF01538197},
	  doi = {http://doi.org/10.1007/BF01538197}
	}
	
An Upgraded Version of a Pulsed Positron Beam
P. Willutzki, J. Störmer, G. Kögel, P. Sperr, D. Britton, R. Steindl and W. Triftshäuser; Materials Science Forum 175-178 (1995) 237-240.
BibTeX:
	@article{Willutzki1995a,
	  author = {Willutzki, P. and Störmer, J. and Kögel, Gottfried and Sperr, Peter and Britton, D.T. and Steindl, R. and Triftshäuser, Werner},
	  title = {An Upgraded Version of a Pulsed Positron Beam},
	  journal = {Materials Science Forum},
	  year = {1995},
	  volume = {175-178},
	  pages = {237--240},
	  url = {https://www.scientific.net/MSF.175-178.237},
	  doi = {http://doi.org/10.4028/www.scientific.net/msf.175-178.237}
	}
	
A Pulsed Positron Microbeam
A. Zecca, R.S. Brusa, M.P. Duarte-Naia, G.P. Karwasz, J. Paridaens, A. Piazza, G. Kögel, P. Sperr, D.T. Britton, K. Uhlmann, P. Willutzki and W. Triftshäuser; Europhysics Letters (EPL) 29 (8) (1995) 617-622.
Abstract: he first pulsed microbeam for positrons in the keV energy range is described. The principle of operation and the construction details are given. The performance achieved is: 20 μm (FWHM) spot diameter; 350 ps (FWHM) time resolution; 5000 e + /(s mCi) at 5 keV final energy.
BibTeX:
	@article{Zecca1995,
	  author = {Zecca, A. and Brusa, R. S. and Duarte-Naia, M. P. and Karwasz, G. P. and Paridaens, J. and Piazza, A. and Kögel, G. and Sperr, P. and Britton, D. T. and Uhlmann, K. and Willutzki, P. and Triftshäuser, W.},
	  title = {A Pulsed Positron Microbeam},
	  journal = {Europhysics Letters (EPL)},
	  year = {1995},
	  volume = {29},
	  number = {8},
	  pages = {617--622},
	  url = {http://stacks.iop.org/0295-5075/29/i=8/a=005},
	  doi = {http://doi.org/10.1209/0295-5075/29/8/005}
	}
	

1994

On the sensitivity of positrons to electric fields and defects in MBE-grown silicon structures
D. Britton, P. Willutzki, W. Triftshäuser, E. Hammerl, W. Hansch and I. Eisele; Applied Physics A Solids and Surfaces 58 (4) (1994) 389-393.
Abstract: The sensitivity of the positron to the internal electric fields in good quality thin (≈100 nm) Molecular Beam Epitaxy (MBE)-grown layers is experimentally demonstrated. Both a thin intrinsic layer grown on a p-type substrate and a highly n-doped δ profile buried in intrinsic silicon form effective barriers to positron diffusion although no defects can be detected. We also extract, from a full treatment of the positron diffusion, a quantitative estimate of the concentration, below the detection limits of other methods, of large vacancy clusters in a thick (680 nm) film. © 1994 Springer-Verlag.
BibTeX:
	@article{Britton1994,
	  author = {Britton, D.T. and Willutzki, P. and Triftshäuser, W. and Hammerl, E. and Hansch, W. and Eisele, I.},
	  title = {On the sensitivity of positrons to electric fields and defects in MBE-grown silicon structures},
	  journal = {Applied Physics A Solids and Surfaces},
	  year = {1994},
	  volume = {58},
	  number = {4},
	  pages = {389--393},
	  url = {http://link.springer.com/article/10.1007%2FBF00323615},
	  doi = {http://doi.org/10.1007/BF00323615}
	}
	
Depth microscopy at interfaces
G. Dollinger, T. Faestermann, C. Frey, A. Bergmaier, E. Schwabedissen, T. Fischer and R. Schwarz; Nuclear Instruments and Methods in Physics Research Section B 85 (1-4) (1994) 786-789.
Abstract: High resolution depth microscopy with swift heavy ions is performed at the Munich tandem accelerator and its Q3D magnetic spectrograph using the elastic recoil detection technique. The