TY - CHAP A1 - Lu, Wei A1 - Nicoul, Matthieu A1 - Shymanovich, Uladzimir A1 - Tarasevitch, A. A1 - Kammler, Martin A1 - Horn-von Hoegen, Michael A1 - von der Linde, D. A1 - Sokolowski-Tinten, Klaus T1 - Transient reversal of a Peierls-transition: Extreme phonon softening in laser-excited Bismuth T2 - International Conference on Ultrafast Phenomena, Snowmass N2 - Laser-excited coherent optical phonons in Bismuth were investigated using time-resolved X-ray diffraction. The observed extreme softening of the excited A1g-mode presents strong indication that the Peierls-distortion defining the equilibrium structure of Bismuth is transiently reversed. Y1 - 2010 U6 - https://doi.org/10.1364/UP.2010.ME41 IS - ME41 PB - Optica Publishing Group ER - TY - CHAP A1 - Gabriel, Christian A1 - Wittmann, Christoffer A1 - Hacker, B. A1 - Mauerer, Wolfgang A1 - Huntington, E. A1 - Sabuncu, M. A1 - Marquardt, Christoph A1 - Leuchs, Gerd T1 - A high-speed secure quantum random number generator based on vacuum states T2 - IEEE/OSA Conference on Lasers and Electro-Optics (CLEO), 06-11 May 2012, San Jose CA USA N2 - A high-speed continuous-variable quantum random bit generator with an expected effective bit generation rate of up to 10 GBit/s is presented. The obtained bit sequences are truly random and unique, i.e. they cannot be known by an adversary. Y1 - 2012 PB - Optical Society of America ER - TY - JOUR A1 - Portavoce, A. A1 - Kammler, Martin A1 - Hull, Robert A1 - Reuter, Mark C. A1 - Copel, M. A1 - Ross, Frances M. T1 - Growth of nanostructures by locally modified surface reactivity JF - Materials Science in Semiconductor Processing N2 - The chemical vapor deposition (CVD) of Si and Ge on Si(0 0 1) substrates covered by 1 monolayer of Ga has been studied. Ga modifies surface reactivity and surface atom mobility. We show that islanding occurs during Ga-mediated CVD even in the absence of strain, allowing for the formation of islands without a wetting layer or with a thinner wetting layer. The morphology of the grown layer is highly dependent on kinetic parameters, i.e. growth temperature and growth pressure, that control Si and Ge deposition and Ga desorption. Si Ga-mediated CVD promotes the formation of self-assembled epitaxial Si islands exhibiting {1 1 3} facets. Ge islands grown by Ga-mediated CVD present reduced lateral sizes and an increased surface density compared to non Ga-mediated CVD. The growth morphology (particularly island size and density) can be understood by considering a qualitative model in which atoms are deposited only on sites whose dangling bonds are not passivated by Ga. We suggest that modification of surface reactivity during surfactant-mediated CVD can thus provide a new degree of freedom for quantum dot fabrication. KW - UHV TEM KW - UHV CVD KW - Epitaxial growth KW - Si KW - Ge KW - Surfactant Ga Y1 - 2009 U6 - https://doi.org/10.1016/j.mssp.2009.07.001 VL - 12 IS - 1-2 SP - 25 EP - 30 PB - Elsevier ER - TY - JOUR A1 - Portavoce, A. A1 - Kammler, Martin A1 - Hull, Robert A1 - Reuter, Mark C. A1 - Ross, Frances M. T1 - Mechanism of the nanoscale localization of Ge quantum dot nucleation on focused ion beam templated Si(001) surfaces JF - Nanotechnology N2 - We investigate the fundamental mechanism by which self-assembled Ge islands can be nucleated at specific sites on Si(001) using ultra-low-dose focused ion beam (FIB) pre-patterning. Island nucleation is controlled by a nanotopography that forms after the implantation of Ga ions during subsequent thermal annealing of the substrate. This nanotopography evolves during the annealing stage, changing from a nanoscale annular depression associated with each focused ion beam spot to a nanoscale pit, and eventually disappearing (planarizing). The correspondence of Ge quantum dot nucleation sites to the focused ion beam features requires a growth surface upon which the nanotopography is preserved. A further key observation is that the Ge wetting layer thickness is reduced in patterned regions, allowing the formation of islands on the templated regions without nucleation elsewhere. These results provide routes to the greatly enhanced design and control of quantum dot distributions and dimensions. Y1 - 2006 U6 - https://doi.org/10.1088/0957-4484/17/17/028 VL - 17 IS - 17 SP - 4451 EP - 4455 PB - IOP ER - TY - JOUR A1 - Ross, Frances M. A1 - Kammler, Martin A1 - Reuter, Mark C. A1 - Hull, Robert T1 - In-situ observations of self-assembled island nucleation on patterned substrates JF - Philosophical Magazine N2 - We compare in-situ electron microscopy observations of Ge island growth on Si surfaces modulated by different techniques. Si(001) substrates were patterned either using a focused Ga ion beam or lithographically to produce similar feature sizes. In the case of the focused-ion-beam patterned substrates, chemical or strain effects caused by low Ga doses control the positions at which islands nucleate. Nucleation on topographically modulated substrates, with the pattern produced either by high-dose sputtering or lithographically, is controlled by the nature of the side walls of topographic features. The two patterning approaches have different benefits in creating arrays of islands for device applications. Y1 - 2004 U6 - https://doi.org/10.1080/14786430410001671430 VL - 84 IS - 25-26 SP - 2687 EP - 2702 PB - Taylor & Francis ER - TY - JOUR A1 - Menzel, Andreas A1 - Conrad, E. H. A1 - Tringides, Michael C. A1 - Kammler, Martin A1 - Horn- von Hoegen, Michael T1 - Finite collection time effects in autocovariance function measurements JF - Journal of Applied Physics N2 - In this paper we discuss how finite data sets influence experimental measurements of the autocovariance function. Autocovariance estimators are biased, meaning that the expectation value for any measured autocovariance function is not identical to the actual autocovariance function. In this work we show that the measured autocovariance function for a finite length time series must become negative for some lag times. We derive analytic corrections to these finite time errors for different types of correlated random sequences. Our results explain the apparent anticorrelated noise observed in experimental observations. Y1 - 2003 U6 - https://doi.org/10.1063/1.1537466 VL - 93 IS - 4 SP - 2229 EP - 2235 PB - AIP Publishing ER - TY - JOUR A1 - Kammler, Martin A1 - Hull, Robert A1 - Reuter, Mark C. A1 - Ross, Frances M. T1 - Lateral control of self-assembled island nucleation by focused-ion-beam micropatterning JF - Applied Physics Letters N2 - We demonstrate that the nucleation sites of nanoscale, self-assembled Ge islands on Si(001) can be controlled by patterning the Si surface in situ with a focused ion beam. At low doses of 6000 Ga+ ions per <100 nm spot, the selective growth is achieved without modifying the initial surface topography. At larger doses, topographic effects produced by sputtering and redeposition control the selective nucleation sites. Islands grown on irradiated spots are smaller with higher aspect ratio than islands grown on clean Si(001), suggesting a strong surfactant effect of Ga. Y1 - 2003 U6 - https://doi.org/10.1063/1.1542680 VL - 82 IS - 7 SP - 1093 EP - 1095 ER - TY - JOUR A1 - Sokolowski-Tinten, Klaus A1 - Blome, Christian A1 - Blums, Juris A1 - Shymanovich, Uladzimir A1 - Nicoul, Matthieu A1 - Cavalleri, Andrea A1 - Tarasevitch, A. A1 - Horn-von Hoegen, Michael A1 - Kammler, Martin A1 - von der Linde, D. T1 - Ultrafast X-ray diffraction JF - Ultrafast Phenomena XIV N2 - In the last few years the generation of femtosecond pulses in the X-ray regime has become possible. These ultrashort X-ray pulses have enabled femtosecond time- resolution to be extended to X-rays. Y1 - 2005 U6 - https://doi.org/10.1007/3-540-27213-5_53 VL - 79 SP - 170 EP - 174 PB - Springer ER - TY - JOUR A1 - Kammler, Martin A1 - Hull, Robert A1 - Portavoce, A. A1 - Reuter, Mark C. A1 - Ross, Frances M. T1 - In-Situ Focused Ion Beam Micropatterning of Ge Islands JF - Microscopy and Microanalysis Y1 - 2003 U6 - https://doi.org/10.1017/S1431927603441214 VL - 9 IS - S02 SP - 132 EP - 134 PB - Microscopy Society of America ER - TY - CHAP A1 - Finckh, Wolfgang A1 - Zilch, Konrad ED - Ye, Lieping ED - Feng, Peng ED - Yue, Qingrui T1 - Shear capacity of flexural strengthened reinforced concrete structures with CFRP materials T2 - Advances in FRP Composites in Civil Engineering - Proceedings of the 5th International Conference on FRP Composites in Civil Engineering (CICE 2010), Sep 27-29, 2010, Beijing, China N2 - By enlarging the flexural capacity of reinforced concrete structures with externally bonded CRFP materials the shear behavior is also affected. To evaluate this effect shear tests on flexural strengthened reinforced concrete beams were carried out. Half of the tests were done with externally bonded CFRP-strips and the other half with near surface mounted reinforcement. Based on these tests and the EC2 approach for the shear force was checked. KW - Concrete Beam KW - Shear Capacity KW - Shear Reinforcement KW - Shear Span KW - CFRP Strip Y1 - 2011 SN - 978-3-642-17486-5 SN - 978-3-642-17487-2 U6 - https://doi.org/10.1007/978-3-642-17487-2_175 PB - Springer CY - Berlin ; Heidelberg ER - TY - CHAP A1 - Altenberger, Igor A1 - Noster, Ulf A1 - Nalla, Ravi K. A1 - Ritchie, Robert O. A1 - Scholtes, Berthold T1 - Residual stress relaxation in fatigue of mechanically surface treated materials T2 - Proceedings 132nd Annual TMS Meeting, March 2–6, 2003, San Diego, California Y1 - 2003 UR - https://www.researchgate.net/publication/273462779_Residual_stress_relaxation_in_fatigue_of_mechanically_surface_treated_materials SP - 312 ER - TY - JOUR A1 - Fritz, D. M. A1 - Reis, D. A. A1 - Adams, B. A1 - Akre, R. A. A1 - Arthur, J. A1 - Blome, Christian A1 - Bucksbaum, P. H. A1 - Cavalieri, A. L. A1 - Engemann, S. A1 - Fahy, S. A1 - Falcone, R. W. A1 - Fuoss, P. H. A1 - Gaffney, K. J. A1 - George, M. J. A1 - Hajdu, J. A1 - Hertlein, M. P. A1 - Hillyard, P. B. A1 - Horn-von Hoegen, Michael A1 - Kammler, Martin A1 - Kaspar, J. A1 - Kienberger, R. A1 - Krejcik, P. A1 - Lee, S. H. A1 - Lindenberg, A. M. A1 - McFarland, B. A1 - Meyer, D. A1 - Montagne, T. A1 - Murray, E. D. A1 - Nelson, A. J. A1 - Nicoul, Matthieu A1 - Pahl, R. A1 - Rudati, J. A1 - Schlarb, H. A1 - Siddons, D. P. A1 - Sokolowski-Tinten, Klaus A1 - Tschentscher, Th A1 - von der Linde, D. A1 - Hastings, J. B. T1 - Ultrafast bond softening in bismuth: mapping a solid's interatomic potential with X-rays JF - Science N2 - Intense femtosecond laser excitation can produce transient states of matter that would otherwise be inaccessible to laboratory investigation. At high excitation densities, the interatomic forces that bind solids and determine many of their properties can be substantially altered. Here, we present the detailed mapping of the carrier density-dependent interatomic potential of bismuth approaching a solid-solid phase transition. Our experiments combine stroboscopic techniques that use a high-brightness linear electron accelerator-based x-ray source with pulse-by-pulse timing reconstruction for femtosecond resolution, allowing quantitative characterization of the interatomic potential energy surface of the highly excited solid. Y1 - 2007 U6 - https://doi.org/10.1126/science.1135009 VL - 315 IS - 5812 SP - 633 EP - 636 PB - AAAS ER - TY - JOUR A1 - Launhardt, M. A1 - Wörz, A. A1 - Loderer, A. A1 - Laumer, Tobias A1 - Drummer, Dietmar A1 - Hausotte, Tino A1 - Schmidt, Michael T1 - Detecting surface roughness on SLS parts with various measuring techniques JF - Polymer Testing N2 - Selective Laser Sintering (SLS) is an additive manufacturing technique whereby a laser melts polymer powder layer by layer to generate three-dimensional parts. It enables the fabrication of parts with high degrees of complexity, nearly no geometrical restrictions, and without the necessity of a tool or a mold. Due to the orientation in the building space, the processing parameters, and the powder properties, the resulting parts possess an increased surface roughness. In comparison to other manufacturing techniques, e.g. injection molding, the surface roughness of SLS parts results from partially melted powder particles on the surface layer. The actual surface roughness must thus be characterized with respect to the part's eventual application. At the moment, there is no knowledge regarding which measuring technique is most suitable for detecting and quantifying SLS parts' surface roughness. The scope of this paper is to compare tactile profile measurement methods, as established in industry, to optical measurement techniques such as Focus Variation, Fringe Projection Technique (FPT), and Confocal Laser Scanning Microscope (CLSM). The advantages and disadvantages of each method are presented and, additionally, the effect of tactile measurement on a part's surface is investigated. KW - Selective Laser Sintering (SLS) KW - PA12 KW - Surface roughness KW - Measuring technique Y1 - 2016 SN - 0142-9418 U6 - https://doi.org/10.1016/j.polymertesting.2016.05.022 SN - 1873-2348 VL - 53 SP - 217 EP - 226 PB - Elsevier CY - Amsterdam ER -