@article{BolmEnglischPenacoradaetal.1997, author = {Bolm, A. and Englisch, Uwe and Penacorada, Florencio and Gerstenberger, M. and Pietsch, Ullrich}, title = {Temperature and time dependent investigations of cd- and uranyl-stearate multilayers by means of neutron reflectivity measurements}, year = {1997}, language = {en} } @article{MukhopadhyayDattaSanyaletal.2001, author = {Mukhopadhyay, M. K. and Datta, A. and Sanyal, M. K. and Geue, Thomas and Pietsch, Ullrich}, title = {Synchrotron Studies of Melting of Langmuir-Blodgett Films}, year = {2001}, language = {en} } @article{PietschPanznerPfeifferetal.2005, author = {Pietsch, Ullrich and Panzner, Tobias and Pfeiffer, Franz and Robinson, Ian K.}, title = {Substrate morphology repetition in "thick" polymer films}, year = {2005}, abstract = {Using Grazing-incidence small-angle scattering (GISAXS) technique we investigated the surface morphology of polymer films spin-coated on different silicon substrates. As substrates we used either technologically smooth silicon wafers or the same silicon wafer coated with thin aluminium or gold films which show a granular structure at the surface. Although the polymer thickness exceeds 300 nm the GISAXS pattern of the film shows the same in-plane angle distribution Delta2theta as the underlying substrate. Annealing the polymer films at a temperature above its glass transition temperature Delta2theta changed from a broad to a narrow distribution as it is typically for films on pure silicon. The experiment can be interpreted by roughness replication and density fluctuation within the polymer film created while spin-coating at room temperature. Due to the low segment mobility there are density fluctuations which repeat the surface morphology of the substrate. Above the glass temperature the polymer density can be homogenized independently from the morphology of the substrate. (C) 2004 Elsevier B.V. All rights reserved}, language = {en} } @article{AbboudSendPashniaketal.2013, author = {Abboud, Ali and Send, Sebastian and Pashniak, N. and Leitenberger, Wolfram and Ihle, Sebastian and Huth, M. and Hartmann, Robert and Str{\"u}der, Lothar and Pietsch, Ullrich}, title = {Sub-pixel resolution of a pnCCD for X-ray white beam applications}, series = {Journal of instrumentation}, volume = {8}, journal = {Journal of instrumentation}, number = {3}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1748-0221}, doi = {10.1088/1748-0221/8/05/P05005}, pages = {17}, year = {2013}, abstract = {A new approach to achieve sub-pixel spatial resolution in a pnCCD detector with 75 x 75 mu m(2) pixel size is proposed for X-ray applications in single photon counting mode. The approach considers the energy dependence of the charge cloud created by a single photon and its split probabilities between neighboring pixels of the detector based on a rectangular model for the charge cloud density. For cases where the charge of this cloud becomes distributed over three or four pixels the center position of photon impact can be reconstructed with a precision better than 2 mu m. The predicted charge cloud sizes are tested at selected X-ray fluorescence lines emitting energies between 6.4 keV and 17.4 keV and forming charge clouds with size (rms) varying between 8 mu m and 10 mu m respectively. The 2 mu m enhanced spatial resolution of the pnCCD is verified by means of an x-ray transmission experiment throughout an optical grating.}, language = {en} } @article{ReicheKnochenhauerDieteletal.1997, author = {Reiche, J{\"u}rgen and Knochenhauer, Gerald and Dietel, Reinhard and Freydank, Anke-Christine and Zetzsche, Thomas and Pietsch, Ullrich and Brehmer, Ludwig and Barberka, Thomas Andreas and Geue, Thomas}, title = {Structure of thermally treated oxadiazoleamide Langmuir-Blodgett films}, year = {1997}, abstract = {The thermal treatment of Y-type Langmuir-Blodgett (LB) films formed from the amphiphilic derivative of 2,5- diphenyl-1,3,4-oxadiazole 1 results in changes of the molecular packing. These changes have been analysed by a combination of X-ray specular reflectivity data, X-ray grazing incidence diffraction data and scanning force microscopy images, On the basis of these experimental data we have simulated possible supramolecular structures, These simulations provide insight into the intermolecular interactions giving rise to the observed structural transitions. The crystalline structure induced by thermal treatment of the LB films is characterized by a uniaxial texture, which is correlated with the dipping direction during deposition of the LB film.}, language = {en} } @article{PietschBodenthinGrenzeretal.2005, author = {Pietsch, Ullrich and Bodenthin, Yves and Grenzer, J{\"o}rg and Geue, Thomas and M{\"o}hwald, Helmuth and Kurth, Dirk G.}, title = {Structure and temperature behavior of metallo-supramolecular assemblies}, year = {2005}, abstract = {A detailed structural analysis of a Langmuir-Blodgett (LB) multilayer composed of a polyelectrolyte-amphiphile complex (PAC) is presented. The PAC is self-assembled from metal ions, ditopic bis-terpyridines, and amphiphiles. The vertical structure of the LB multilayer is investigated by X-ray reflectometry. The multilayer has a periodicity of 57 A, which corresponds to an architecture of flat lying metallo-supramolecular coordination polyelectrolyte (MEPE) rods and upright-standing amphiphiles (dihexadecyl phosphate, DHP). In-plane diffraction reveals hexagonal packing of the DHP molecules. Using extended X-ray absorption fine structure (EXAFS) experiments, we prove that the central metal ion is coordinated to the terpyridine moieties in a pseudo-octahedral coordination environment. The Fe-N bond distances are 1.82 and 2.0 angstrom, respectively. Temperature resolved measurements indicate a reversible phase transition in a temperature range up to 55 degrees C. EXAFS measurements indicate a lengthening of the average Fe-N bond distance from 1.91 to 1.95 angstrom. The widening of the coordination cage upon heating is expected to lower the ligand field stabilization, thus giving rise to spin transitions in these composite materials}, language = {en} } @article{PietschGuptaPauletal.2004, author = {Pietsch, Ullrich and Gupta, Amod and Paul, A. and Meneghini, C. and Mibu, K. and Maddalena, S. and Dal Toe, S. and Principi, G.}, title = {Structural characterization of epitaxial Fe/Cr multilayers using anomalous x-ray scattering and neutron reflectivity}, year = {2004}, abstract = {The interface structure of epitaxial Fe/Cr multilayers was studied using anomalous X-ray and neutron reflectivity. The analysis of X-ray reflectivity at three different energies provided a reliable information about the interface roughnesses. It is found that the Cr-on-Fc interface is more diffused as compared to the Fe-on-Cr interface and that the roughness exhibits a significant increase with increasing depth. The magnetic roughness, as determined from neutron reflectivity, is lower than the geometrical roughness, in conformity with the behavior of a number of magnetic thin films and multilayers. (C) 2004 Elsevier B.V. All rights reserved}, language = {en} } @article{DarowskiPaschkePietschetal.1998, author = {Darowski, Nora and Paschke, K. and Pietsch, Ullrich and Wang, K. H. and Forchel, Alfred and L{\"u}bbert, Daniel and Baumbach, Tilo}, title = {Structural characterization of a GaAs surface wire structure by triple-axis X-ray grazing incidence diffraction}, year = {1998}, language = {en} } @article{ZhuangSchellingStangletal.2000, author = {Zhuang, Y. and Schelling, Christoph and Stangl, Jochen and Penn, C. and Senz, S. and Sch{\"a}ffler, Friedrich and Roche, T. and Daniel, A. and Grenzer, J{\"o}rg and Pietsch, Ullrich and Bauer, G{\"u}nther}, title = {Structural and optical properties of Si/Si{1-x}Ge{x} wires}, year = {2000}, language = {en} } @article{ZhuangHolyStangletal.1999, author = {Zhuang, Y. and Hol{\´y}, V{\´a}clav and Stangl, Jochen and Darhuber, A. and Mikulik, P. and Zerlauth, S. and Sch{\"a}ffler, F. and Bauer, G{\"u}nther and Darowski, Nora and L{\"u}bbert, Daniel and Pietsch, Ullrich}, title = {Strain relaxation in periodic arrays of Si/SiGe quantum wires determined by coplanar high-resolution x-ray diffrcation and grazing-incidence diffraction}, year = {1999}, language = {en} } @article{LuebbertBaumbachPontietal.1999, author = {L{\"u}bbert, Daniel and Baumbach, Tilo and Ponti, S. and Pietsch, Ullrich and Leprince, L. and Schneck, J. and Talneau, A.}, title = {Strain investigation of low strained buried gratings by grazing incidence X-Ray diffraction and the theory of elasticity}, year = {1999}, language = {en} } @article{PietschZeimerHofmannetal.2001, author = {Pietsch, Ullrich and Zeimer, Ute and Hofmann, L. and Grenzer, J{\"o}rg and Gramlich, S.}, title = {Strain induced compositional modulations in AlGaAs overlayers induced by lateral surface gratings}, issn = {0272-9172}, year = {2001}, language = {en} } @article{GrenzerDarowskiGeueetal.2001, author = {Grenzer, J{\"o}rg and Darowski, Nora and Geue, Thomas and Pietsch, Ullrich and Daniel, A. and Rennon, Siegfried and Reithmaier, Johann-Peter and Forchel, Alfred}, title = {Strain analysis and quantum well intermixing of a laterally modulated multiquantum well system produced by focused ion beam implantation}, year = {2001}, language = {en} } @article{HennebergPietschPanzneretal.2006, author = {Henneberg, Oliver and Pietsch, Ullrich and Panzner, Tobias and Geue, Thomas and Finkelstein, Kenneth D.}, title = {Simultaneous X-ray and visible light diffraction for the investigation of surface relief and density grating formation in azobenzene containing polymer films}, issn = {1542-1406}, doi = {10.1080/15421400500383345}, year = {2006}, abstract = {The development of surface relief and density patterns in azobenzene polymer films was studied by diffraction at two different wavelengths. We used x-ray diffraction of synchrotron radiation at 0.124 nm in combination with visible light diffraction at a wavelength of 633 nm. In contrast to visible light scattering x-ray diffraction allows the separation of a surface relief and a density grating contribution due to the different functional dependence of the scattering power. Additionally, the x-ray probe is most sensitive for the onset of the surface grating formation}, language = {en} } @article{VeldkampErkoGudatetal.1999, author = {Veldkamp, Markus and Erko, Alexei and Gudat, Wolfgang and Abrosimov, Nikolai V. and Alex, Volker and Khasanov, Salavat and Neissendorfer, Frank and Pietsch, Ullrich and Shekhtman, Veniamin}, title = {Si(1-x)Ge(x) laterally graded crystals as monochromators for X-Ray absorption spectroscopy studies}, year = {1999}, language = {en} } @article{AvilovKulyginPietschetal.1999, author = {Avilov, Anatoly S. and Kulygin, Alexander K. and Pietsch, Ullrich and Spence, John C. H. and Tsirelson, Vladimir G. and Zuo, Ming J.}, title = {Scanning system for high-energy electron diffractometry}, issn = {0021-8898}, doi = {10.1107/S0021889899006755}, year = {1999}, language = {en} } @article{PietschHazraChinietal.2004, author = {Pietsch, Ullrich and Hazra, S. and Chini, T. K. and Sanyal, M. K. and Grenzer, J{\"o}rg}, title = {Ripple structure of crystalline layers in ion beam induced Si wafers}, year = {2004}, abstract = {Ion-beam-induced ripple formation in Si wafers was studied by two complementary surface sensitive techniques, namely atomic force microscopy (AFM) and depth-resolved x-ray grazing incidence diffraction (GID). The formation of ripple structure at high doses (similar to7x10(17) ions/cm(2)), starting from initiation at low doses (similar to1x10(17) ions/cm(2)) of ion beam, is evident from AFM, while that in the buried crystalline region below a partially crystalline top layer is evident from GID study. Such ripple structure of crystalline layers in a large area formed in the subsurface region of Si wafers is probed through a nondestructive technique. The GID technique reveals that these periodically modulated wavelike buried crystalline features become highly regular and strongly correlated as one increases the Ar ion-beam energy from 60 to 100 keV. The vertical density profile obtained from the analysis of a Vineyard profile shows that the density in the upper top part of ripples is decreased to about 15\% of the crystalline density. The partially crystalline top layer at low dose transforms to a completely amorphous layer for high doses, and the top morphology was found to be conformal with the underlying crystalline ripple}, language = {en} } @article{Pietsch2002, author = {Pietsch, Ullrich}, title = {Reversible negative thermal expansion of polymer films}, year = {2002}, language = {en} } @article{TsirelsonAvilovLepeshovetal.2001, author = {Tsirelson, Vladimir G. and Avilov, Anatoly S. and Lepeshov, G. G. and Kuligin, A. K. and Stahn, Jochen and Pietsch, Ullrich and Spence, J. C. H.}, title = {Quantitative Analysis of the Inner-Crystal Electrostatic Potential of several Rock-Salt-Structure Crystals Using Accurate Electron-Diffraction Data}, issn = {1089-5647}, year = {2001}, language = {en} } @article{GeueStumpePietschetal.1995, author = {Geue, Thomas and Stumpe, Joachim and Pietsch, Ullrich and Haak, M. and Kaupp, G.}, title = {Photochemically induced changes of optical anisotropy and surface of LB-multilayers built up by an amphiphilic and liquid crystalline copolymer conating azobenzene moieties}, year = {1995}, language = {en} }