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Journal of Applied Crystallography

J Filik, A W Ashton, P C Y Chang, P A Chater, S J Day, M Drakopoulos, M W Gerring, M L Hart, O V Magdysyuk, S Michalik, A Smith, C C Tang, N J Terrill, M T Wharmby, H Wilhelm
A software package for the calibration and processing of powder X-ray diffraction and small-angle X-ray scattering data is presented. It provides a multitude of data processing and visualization tools as well as a command-line scripting interface for on-the-fly processing and the incorporation of complex data treatment tasks. Customizable processing chains permit the execution of many data processing steps to convert a single image or a batch of raw two-dimensional data into meaningful data and one-dimensional diffractograms...
June 1, 2017: Journal of Applied Crystallography
A Abboud, C Kirchlechner, J Keckes, T Conka Nurdan, S Send, J S Micha, O Ulrich, R Hartmann, L Strüder, U Pietsch
The full strain and stress tensor determination in a triaxially stressed single crystal using X-ray diffraction requires a series of lattice spacing measurements at different crystal orientations. This can be achieved using a tunable X-ray source. This article reports on a novel experimental procedure for single-shot full strain tensor determination using polychromatic synchrotron radiation with an energy range from 5 to 23 keV. Microbeam X-ray Laue diffraction patterns were collected from a copper micro-bending beam along the central axis (centroid of the cross section)...
June 1, 2017: Journal of Applied Crystallography
Philipp Jacobs, Andreas Houben, Werner Schweika, Andrei L Tchougréeff, Richard Dronskowski
The method of angular- and wavelength-dispersive (e.g. two-dimensional) Rietveld refinement is a new and emerging tool for the analysis of neutron diffraction data measured at time-of-flight instruments with large area detectors. Following the approach for one-dimensional refinements (using either scattering angle or time of flight), the first step at each beam time cycle is the calibration of the instrument including the determination of instrumental contributions to the peak shape variation to be expected for diffraction patterns measured by the users...
June 1, 2017: Journal of Applied Crystallography
Jiangkun Fan, Jinshan Li, Yudong Zhang, Hongchao Kou, Jaafar Ghanbaja, Weimin Gan, Lionel Germain, Claude Esling
For the β phase of Ti-5553-type metastable β-Ti alloys, striations in transmission electron microscopy (TEM) bright- and dark-field images have been frequently observed but their origin has not been sufficiently investigated. In the present work, this phenomenon is studied in depth from the macroscopic scale by neutron diffraction to the atomic scale by high-resolution TEM. The results reveal that the β phase contains homogeneously distributed modulated structures, intermediate between that of the β phase (cubic) and that of the α phase or the ω phase (hexagonal), giving rise to the appearance of additional diffraction spots at 1/2, 1/3 and 2/3 β diffraction positions...
June 1, 2017: Journal of Applied Crystallography
Ross N Andrews, Joseph Serio, Govindarajan Muralidharan, Jan Ilavsky
Intermetallic γ' precipitates typically strengthen nickel-based superalloys. The shape, size and spatial distribution of strengthening precipitates critically influence alloy strength, while their temporal evolution characteristics determine the high-temperature alloy stability. Combined ultra-small-, small- and wide-angle X-ray scattering (USAXS-SAXS-WAXS) analysis can be used to evaluate the temporal evolution of an alloy's precipitate size distribution (PSD) and phase structure during in situ heat treatment...
June 1, 2017: Journal of Applied Crystallography
Zbigniew Swiatek, Igor Fodchuk, Ruslan Zaplitnyy
New capabilities of the Berg-Barrett topographic method are demonstrated using a skew-asymmetric X-ray diffraction scheme for investigating structural changes near the surface of semiconductor materials. Specifying the X-ray extinction depth, the details of defects and strains are revealed with high resolution. Consequently, analysis of structural distortion of layers near the surface after various types of surface processing becomes more complete.
June 1, 2017: Journal of Applied Crystallography
Mariana Borcha, Igor Fodchuk, Mykola Solodkyi, Marina Baidakova
This article presents the results of research on multi-layered heterostructures by a modified calculation technique of multiple X-ray diffraction. The Al x In1-x Sb heterostructure and a Zn(Mn)Se/GaAs(001) multi-layered system were used as models to specify conditions for cases of coincidental coplanar three-beam or coincidental noncoplanar four-beam X-ray diffraction. These conditions provide the means for a high-precision determination of lattice parameters and strain anisotropy in layers.
June 1, 2017: Journal of Applied Crystallography
Jinxing Jiang, Keiichi Hirano, Kenji Sakurai
Recently, the authors have succeeded in realizing X-ray reflectivity imaging of heterogeneous ultrathin films at specific wavevector transfers by applying a wide parallel beam and an area detector. By combining in-plane angle and grazing-incidence angle scans, it is possible to reconstruct a series of interface-sensitive X-ray reflectivity images at different grazing-incidence angles (proportional to wavevector transfers). The physical meaning of a reconstructed X-ray reflectivity image at a specific wavevector transfer is the two-dimensional reflectivity distribution of the sample...
June 1, 2017: Journal of Applied Crystallography
Qi Zhong, Lars Melchior, Jichang Peng, Qiushi Huang, Zhanshan Wang, Tim Salditt
Iterative phase retrieval has been used to reconstruct the near-field distribution behind tailored X-ray waveguide arrays, by inversion of the measured far-field pattern recorded under fully coherent conditions. It is thereby shown that multi-waveguide interference can be exploited to control the near-field distribution behind the waveguide exit. This can, for example, serve to create a secondary quasi-focal spot outside the waveguide structure. For this proof of concept, an array of seven planar Ni/C waveguides are used, with precisely varied guiding layer thickness and cladding layer thickness, as fabricated by high-precision magnetron sputtering systems...
June 1, 2017: Journal of Applied Crystallography
Sérgio L Morelhão, Cláudio M R Remédios, Guilherme A Calligaris, Gareth Nisbet
In this work, experimental and data analysis procedures were developed and applied for studying amino acid crystals by means of X-ray phase measurements. The results clearly demonstrated the sensitivity of invariant triplet phases to electronic charge distribution in d-alanine crystals, providing useful information for molecular dynamics studies of intermolecular forces. The feasibility of using phase measurements to investigate radiation damage mechanisms is also discussed on experimental and theoretical grounds...
June 1, 2017: Journal of Applied Crystallography
Ihar Lobach, Andrei Benediktovitch, Alexander Ulyanenkov
Diffraction in multilayers in the presence of interfacial roughness is studied theoretically, the roughness being considered as a transition layer. Exact (within the framework of the two-beam dynamical diffraction theory) differential equations for field amplitudes in a crystalline structure with varying properties along its surface normal are obtained. An iterative scheme for approximate solution of the equations is developed. The presented approach to interfacial roughness is incorporated into the recursion matrix formalism in a way that obviates possible numerical problems...
June 1, 2017: Journal of Applied Crystallography
Arman Davtyan, Thilo Krause, Dominik Kriegner, Ali Al-Hassan, Danial Bahrami, Seyed Mohammad Mostafavi Kashani, Ryan B Lewis, Hanno Küpers, Abbes Tahraoui, Lutz Geelhaar, Michael Hanke, Steven John Leake, Otmar Loffeld, Ullrich Pietsch
Coherent X-ray diffraction imaging at symmetric hhh Bragg reflections was used to resolve the structure of GaAs/In0.15Ga0.85As/GaAs core-shell-shell nanowires grown on a silicon (111) substrate. Diffraction amplitudes in the vicinity of GaAs 111 and GaAs 333 reflections were used to reconstruct the lost phase information. It is demonstrated that the structure of the core-shell-shell nanowire can be identified by means of phase contrast. Interestingly, it is found that both scattered intensity in the (111) plane and the reconstructed scattering phase show an additional threefold symmetry superimposed with the shape function of the investigated hexagonal nanowires...
June 1, 2017: Journal of Applied Crystallography
Virginie Chamard, Václav Holý
The latest virtual special issue of Journal of Applied Crystallography features some highlights of the 13th Biennial Conference on High-Resolution X-ray Diffraction and Imaging (XTOP 2016), held in Brno, Czech Republic, in September 2016.
June 1, 2017: Journal of Applied Crystallography
Ai Woon Yee, Matthew P Blakeley, Martine Moulin, Michael Haertlein, Edward Mitchell, V Trevor Forsyth
The application of IR spectroscopy to the characterization and quality control of samples used in neutron crystallography is described. While neutron crystallography is a growing field, the limited availability of neutron beamtime means that there may be a delay between crystallogenesis and data collection. Since essentially all neutron crystallographic work is carried out using D2O-based solvent buffers, a particular concern for these experiments is the possibility of H2O back-exchange across reservoir or capillary sealants...
April 1, 2017: Journal of Applied Crystallography
Michael G Bowler, David R Bowler, Matthew W Bowler
The humidity surrounding a sample is an important variable in scientific experiments. Biological samples in particular require not just a humid atmosphere but often a relative humidity (RH) that is in equilibrium with a stabilizing solution required to maintain the sample in the same state during measurements. The controlled dehydration of macromolecular crystals can lead to significant increases in crystal order, leading to higher diffraction quality. Devices that can accurately control the humidity surrounding crystals while monitoring diffraction have led to this technique being increasingly adopted, as the experiments become easier and more reproducible...
April 1, 2017: Journal of Applied Crystallography
Steffen M Sedlak, Linda K Bruetzel, Jan Lipfert
A new model is proposed for the measurement errors incurred in typical small-angle X-ray scattering (SAXS) experiments, which takes into account the setup geometry and physics of the measurement process. The model accurately captures the experimentally determined errors from a large range of synchrotron and in-house anode-based measurements. Its most general formulation gives for the variance of the buffer-subtracted SAXS intensity σ(2)(q) = [I(q) + const.]/(kq), where I(q) is the scattering intensity as a function of the momentum transfer q; k and const...
April 1, 2017: Journal of Applied Crystallography
Thu Nhi Tran Thi, J Morse, D Caliste, B Fernandez, D Eon, J Härtwig, C Barbay, C Mer-Calfati, N Tranchant, J C Arnault, T A Lafford, J Baruchel
Bragg diffraction imaging enables the quality of synthetic single-crystal diamond substrates and their overgrown, mostly doped, diamond layers to be characterized. This is very important for improving diamond-based devices produced for X-ray optics and power electronics applications. The usual first step for this characterization is white-beam X-ray diffraction topography, which is a simple and fast method to identify the extended defects (dislocations, growth sectors, boundaries, stacking faults, overall curvature etc...
April 1, 2017: Journal of Applied Crystallography
Mykhailo Barchuk, Mykhaylo Motylenko, Gleb Lukin, Olf Pätzold, David Rafaja
The microstructure of polar GaN layers, grown by upgraded high-temperature vapour phase epitaxy on [001]-oriented sapphire substrates, was studied by means of high-resolution X-ray diffraction and transmission electron microscopy. Systematic differences between reciprocal-space maps measured by X-ray diffraction and those which were simulated for different densities of threading dislocations revealed that threading dislocations are not the only microstructure defect in these GaN layers. Conventional dark-field transmission electron microscopy and convergent-beam electron diffraction detected vertical inversion domains as an additional microstructure feature...
April 1, 2017: Journal of Applied Crystallography
B K Tanner, A N Danilewsky, R K Vijayaraghavan, A Cowley, P J McNally
Transmission X-ray diffraction imaging in both monochromatic and white beam section mode has been used to measure quantitatively the displacement and warpage stress in encapsulated silicon devices. The displacement dependence with position on the die was found to agree well with that predicted from a simple model of warpage stress. For uQFN microcontrollers, glued only at the corners, the measured misorientation contours are consistent with those predicted using finite element analysis. The absolute displacement, measured along a line through the die centre, was comparable to that reported independently by high-resolution X-ray diffraction and optical interferometry of similar samples...
April 1, 2017: Journal of Applied Crystallography
Andrey Lomov, Kirill Shcherbachev, Yurii Chesnokov, Dmitry Kiselev
The structural changes in the surface layer of p-type Cz-Si(001) samples after high-dose low-energy (2 keV) He(+) plasma-immersion ion implantation and subsequent thermal annealing were studied using a set of complementary methods: high-resolution X-ray reflectometry, high-resolution X-ray diffraction, transmission electron microscopy and atomic force microscopy. The formation of a three-layer structure was observed (an amorphous a-SiO x layer at the surface, an amorphous a-Si layer and a heavily damaged tensile-strained crystalline c-Si layer), which remained after annealing...
April 1, 2017: Journal of Applied Crystallography
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