TY - JOUR A1 - Reiche, Jürgen A1 - Pietsch, Ullrich A1 - Fink, Hans-Peter A1 - Lemmetyinen, Helge T1 - A comparison fo x-ray methods for structure refinement of Langmuir-Blodgett multilayers N2 - The possibilities and limits of structure refinement of Langmuir-Blodgett films by means of symmetrical reflection of X- rays are described using the example of a stearic acid multilayer. Three different techniques for the determiantion of the electron density profile from reflectivity data are compared; a Fourier method, a Patterson method, and model calculations. The important role of the a priori information for finding the besft structure model is outlined. Y1 - 1992 ER - TY - JOUR A1 - Pietsch, Ullrich A1 - Hansen, N. K. T1 - A critical review of the valence charge density in GaAs Y1 - 1996 ER - TY - JOUR A1 - Leitenberger, Wolfram A1 - Pietsch, Ullrich T1 - A monolithic Fresnel bimirror for hard X-rays and its application for coherence measurements N2 - Experiments using a simple X-ray interferometer to measure the degree of spatial coherence of hard X-rays are reported. A monolithic Fresnel bimirror is used at small incidence angles to investigate synchrotron radiation in the energy interval 5-50 keV with monochromatic and white beam. The experimental setup was equivalent to a Young's double-slit experiment for hard X-rays with slit dimensions in the micrometre range. From the high-contrast interference pattern the degree of coherence was determined. Y1 - 2007 UR - http://journals.iucr.org/s/issues/2007/02/00/wl5137/wl5137.pdf U6 - https://doi.org/10.1107/S0909049507003846 SN - 0909-0495 ER - TY - JOUR A1 - Lichanot, Albert A1 - Azavant, P. A1 - Pietsch, Ullrich T1 - Ab-initio Hartree-Fock study of the electronic charge density of the cubic boron nitride and its comparison with the experiment Y1 - 1996 ER - TY - JOUR A1 - Stahn, Jochen A1 - Möhle, Marcus A1 - Pietsch, Ullrich T1 - Accurate structure determination for GaAs using Pendellösung oscillation Y1 - 1996 ER - TY - JOUR A1 - Herrmann, A. A1 - Kaupp, G. A1 - Geue, Thomas A1 - Pietsch, Ullrich T1 - AFM and GID investigations of the gas-solid diazotation of 4-sulfanil-acid-monohydrat single crystals Y1 - 1997 ER - TY - JOUR A1 - Send, Sebastian A1 - Abboud, Ali A1 - Leitenberger, Wolfram A1 - Weiss, Manfred S. A1 - Hartmann, Robert A1 - Strüder, Lothar A1 - Pietsch, Ullrich T1 - Analysis of polycrystallinity in hen egg-white lysozyme using a pnCCD JF - Journal of applied crystallography N2 - A crystal of hen egg-white lysozyme was analyzed by means of energy-dispersive X-ray Laue diffraction with white synchrotron radiation at 2.7 angstrom resolution using a pnCCD detector. From Laue spots measured in a single exposure of the arbitrarily oriented crystal, the lattice constants of the tetragonal unit cell could be extracted with an accuracy of about 2.5%. Scanning across the sample surface, Laue images with split reflections were recorded at various positions. The corresponding diffraction patterns were generated by two crystalline domains with a tilt of about 1 degrees relative to each other. The obtained results demonstrate the potential of the pnCCD for fast X-ray screening of crystals of macromolecules or proteins prior to conventional X-ray structure analysis. The described experiment can be automatized to quantitatively characterize imperfect single crystals or polycrystals. Y1 - 2012 U6 - https://doi.org/10.1107/S0021889812015038 SN - 0021-8898 VL - 45 IS - 6 SP - 517 EP - 522 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Pietsch, Ullrich A1 - Darowski, Nora A1 - Ulyanenkov, A. A1 - Grenzer, Jörg A1 - Wang, K. H. A1 - Forchel, Alfred T1 - Analysis of the strain distribution in lateral nanostructures for interpreting photoluminescence data Y1 - 2000 ER - TY - JOUR A1 - Leitenberger, Wolfram A1 - Hartmann, Robert A1 - Pietsch, Ullrich A1 - Andritschke, Robert A1 - Starke, Ines A1 - Strüder, Lothar T1 - Application of a pnCCD in X-ray diffraction : a three-dimensional X-ray detector N2 - The first application of a pnCCD detector for X-ray scattering experiments using white synchrotron radiation at BESSY II is presented. A Cd arachidate multilayer was investigated in reflection geometry within the energy range 7 keV < E < 35 keV. At fixed angle of incidence the two-dimensional diffraction pattern containing several multilayer Bragg peaks and respective diffuse-resonant Bragg sheets were observed. Since every pixel of the detector is able to determine the energy of every incoming photon with a resolution Delta E/E similar or equal to 10(-2). a three-dimensional dataset is finally obtained. In order to achieve this energy resolution the detector was operated in the so-called single-photon- counting mode. A full dataset was evaluated taking into account all photons recorded within 10(5) detector frames at a readout rate of 200 Hz. By representing the data in reciprocal-space coordinates, it becomes obvious that this experiment with the pnCCD detector provides the same information as that obtained by combining a large number of monochromatic scattering experiments using conventional area detectors. Y1 - 2008 UR - http://onlinelibrary.wiley.com/iucr/10.1107/S0909049508018931 U6 - https://doi.org/10.1107/S0909049508018931 ER - TY - JOUR A1 - Henneberg, Oliver A1 - Chi, Li Feng A1 - Geue, Thomas A1 - Saphiannikova, Marina A1 - Pietsch, Ullrich A1 - Rochon, Paul A1 - Natansohn, Almeria T1 - Atomic force microscopy inspection of the early state of formation of polymer surface relief grating Y1 - 2001 ER - TY - JOUR A1 - Pietsch, Ullrich A1 - Davaasambuu, Jav A1 - Pucher, Andreas A1 - Kochin, V. T1 - Atomistic origin of the inverse piezoelectric effect in alpha-SiO2 and alpha-GaPO4 Y1 - 2003 UR - http://www.edpsciences.org/articles/epl/pdf/2003/12/7666.pdf?access=ok SN - 0295-5075 ER - TY - JOUR A1 - Joshi, Siddharth A1 - Pingel, Patrick A1 - Grigorian, Souren A1 - Panzner, Tobias A1 - Pietsch, Ullrich A1 - Neher, Dieter A1 - Forster, Michael A1 - Scherf, Ullrich T1 - Bimodal temperature behavior of structure and mobility in high molecular weight p3ht thin films N2 - We report a temperature dependent crystalline structure of spin-coated thin films of high molecular weight regioregular poly(3-hexylthiophene) (P3HT) (M-n similar to 30000 g/mol) and its correlation with charge carrier mobility. These investigations show a reversible change of the crystalline structure, where the interlayer lattice spacing (100)along the alkyl side chains continuously increases up to a temperature of about 220 degrees C; in contrast, the in-plane pi-pi distance reduces with increasing temperature. These changes in structure are reversible and can be repeated several times. The temperature-induced structural properties differ for thick and thin films, pointing to a surface/interface role in stabilization of the layer morphology. In contrast to the structural changes, the carrier mobility is rather constant in the temperature range from room temperature up to 100-120 degrees C, followed by a continuous decrease. For thick layers this drop is significant and the transistor performance almost vanishes at high temperature, however, it completely recovers upon cooling back to roorn temperature. The drop of the charge carrier mobility at higher temperatures is in contrast with expectations front the structural studies, considering the increase of crystalline fraction of the polycrystalline layer. our electrical measurements Underscore that the reduction of the macroscopic mobility is mostly caused by it pronounced decrease of the intergrain transport. The thermally induced crystallization along(100) direction and the creation of numerous small crystallites at the film-substrate interface reduce the number of long polymer chain, bridging crystalline domains, which ultimately limits the macroscopic charge transport. Y1 - 2009 UR - http://pubs.acs.org/journal/mamobx U6 - https://doi.org/10.1021/Ma900021w SN - 0024-9297 ER - TY - JOUR A1 - Talalaev, V A1 - Tomm, JW A1 - Elsaesser, T A1 - Zeimer, Ute A1 - Fricke, J A1 - Knauer, A A1 - Kissel, H A1 - Weyers, Markus A1 - Tarasov, GG A1 - Grenzer, Jörg A1 - Pietsch, Ullrich T1 - Carrier dynamics in laterally strain-modulated InGaAs quantum wells N2 - We investigate the transient recombination and transfer properties of nonequilibrium carriers in an In0.16Ga0.84As/GaAs quantum well (QW) with an additional lateral confinement implemented by a patterned stressor layer. The structure thus contains QW- and quantum-wire-like areas. At low excitation densities, photoluminescence (PL) transients from both areas are well described by a rate equation model for a three-level system with a saturable interlevel carrier transfer representing the lateral drift of carriers from the QW regions into the wires. Small-signal carrier lifetimes for QW, wires, and transfer time from QW to wire are 180, 190, and 28 ps, respectively. For high excitation densities the time constants of the observed transients increase, in agreement with the model. In addition, QW and wire PL lines merge indicating a smoothening of the potential difference, i.e., the effective carrier confinement caused by the stressor structure becomes weaker with increasing excitation. (c) 2005 American Institute of Physics Y1 - 2005 ER - TY - JOUR A1 - Send, Sebastian A1 - Abboud, Ali A1 - Hartmann, Robert A1 - Huth, M. A1 - Leitenberger, Wolfram A1 - Pashniak, N. A1 - Schmidt, J. A1 - Strüder, Lothar A1 - Pietsch, Ullrich T1 - Characterization of a pnCCD for applications with synchrotron radiation JF - Nuclear instruments & methods in physics research : a journal on accelerators, instrumentation and techniques applied to research in nuclear and atomic physics, materials science and related fields in physics ; A, Accelerators, spectrometers, detectors and associated equipment N2 - In this work we study the response of a pnCCD by means of X-ray spectroscopy in the energy range between 6 key and 20 key and by Laue diffraction techniques. The analyses include measurements of characteristic detector parameters like energy resolution, count rate capability and effects of different gain settings. The limit of a single photon counting operation in white beam X-ray diffraction experiments is discussed with regard to the occurrence of pile-up events, for which the energy information about individual photons is lost. In case of monochromatic illumination the pnCCD can be used as a fast conventional CCD with a charge handling capacity (CHC) of about 300,000 electrons per pixel. If the CHC is exceeded, any surplus charge will spill to neighboring pixels perpendicular to the transfer direction due to electrostatic repulsion. The possibilities of increasing the number of storable electrons are investigated for different voltage settings by exposing a single pixel with X-rays generated by a microfocus X-ray source. The pixel binning mode is tested as an alternative approach that enables a pnCCD operation with significantly shorter readout times. KW - pnCCD KW - X-ray spectroscopy KW - X-ray imaging KW - Energy-dispersive Laue diffraction Y1 - 2013 U6 - https://doi.org/10.1016/j.nima.2013.01.044 SN - 0168-9002 VL - 711 IS - 5 SP - 132 EP - 142 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Rose, Dirk A1 - Pietsch, Ullrich A1 - Zeimer, Ute T1 - Characterization of InGaAs single quantum wells buried in GaAs[001] by grazing incidence diffraction Y1 - 1997 ER - TY - JOUR A1 - Paschke, K. A1 - Geue, Thomas A1 - Barberka, Thomas Andreas A1 - Bolm, A. A1 - Pietsch, Ullrich A1 - Rösch, M. A1 - Batke, Edwin A1 - Faller, F. A1 - Kerkel, K. A1 - Oshiniwo, J. A1 - Forchel, Alfred T1 - Characterization of lateral semiconductor nano structures by means of x-ray grazing-incidence diffraction Y1 - 1997 ER - TY - JOUR A1 - Struth, Bernd A1 - Decher, Gero A1 - Schmitt, J. A1 - Hofmeister, Wolfgang A1 - Neißendorfer, Frank A1 - Pietsch, Ullrich A1 - Brezesinski, Gerald A1 - Möhwald, Helmuth T1 - Chemical modification of Topaz surfaces Y1 - 1999 SN - 0928-4931 ER - TY - JOUR A1 - Pietsch, Ullrich A1 - Panzner, Tobias A1 - Leitenberger, Wolfram A1 - Vartanyants, Ivan A. T1 - Coherence experiments at the EDR-beamline of BESSY II Y1 - 2005 ER - TY - JOUR A1 - Pietsch, Ullrich A1 - Panzner, Tobias A1 - Leitenberger, Wolfram A1 - Grenzer, Jörg A1 - Bodenthin, Th. A1 - Geue, Thomas A1 - Möhwald, Helmuth T1 - Coherence experiments at the energy-dispersive reflectometry beamline at BESSY II Y1 - 2003 ER - TY - JOUR A1 - Panzner, Tobias A1 - Gleber, Gudrun A1 - Sant, Tushar A1 - Leitenberger, Wolfram A1 - Pietsch, Ullrich T1 - Coherence experiments at the white-beam beamline of BESSYI N2 - The third-generation X-ray source BESSYII (Berlin, Germany) provides coherent X-ray radiation which can be used for static and dynamic speckle analysis. Recently we have demonstrated that one can perform experiments with coherent white radiation provided by a bending magnet (5 < E < 20 keV). In this paper we show that the diffraction figure of the initial pinhole must be considered for the interpretation of coherent experiments. The reflectivity spectrum of a sample results from the Fresnel diffraction of the incident pinhole deformed by the static speckle features of the sample surface. For dynamical experiments all speckle like features alter with time whereas the pure Fresnel fringes remain constant. (c) 2007 Published by Elsevier B.V. Y1 - 2007 UR - http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6TW0-4N08M4P-1- F&_cdi=5548&_user=1584062&_orig=search&_coverDate=05%2F23%2F2007&_sk=994849985&view=c&wchp=dGLbVzW- zSkWA&md5=3a09375f874dccd9b382488e9d0 U6 - https://doi.org/10.1016/j.tsf.2006.12.002 ER -