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We demonstrate the crystal quality of a 6 inch (0001) plane free-standing GaN substrate grown using a Na-flux based liquid phase epitaxy method. The 114 rocking curve profiles of every point over the substrate were recorded by synchrotron X-ray diffraction topography. The reconstructed images show that there is a huge boundary between the high crystalline area and the low crystalline area in the substrate. Anisotropic bowing of the lattice planes with respect to the [100] direction was obtained from wafer bending analysis. The mean width of the rocking curves over the wafer was 0.024°, which indicates that the newly fabricated 6 inch GaN substrate was almost a single crystal. We found that there was a competition between crystallinity and homogeneity.

The diffraction of beams of X-rays from single crystals involves very specific geometries that form the basis for the measurement of intensities used in crystal structure analysis. In terms of the incident beam itself, the two key approaches available involve either a monochromatic beam or a polychromatic `Laue' white beam. Starting from Bragg's law and the Ewald reciprocal-space construction, the methods for the collection of diffraction data, i.e. reflection intensities, using commonly available apparatus are then described. Monochromatic beam measuring methods such as rotating/oscillating crystal, stills, Weissenberg, precession and four-circle diffractometry are covered. The mathematical relationships between the reciprocal-lattice point (relp) coordinates in reciprocal space and the corresponding diffraction spot positions at the detector (flat, cylindrical or V-shaped) are given in detail. These coordinate transformations represent an idealized situation of relps (i.e. as points) and of diffracted rays as lines. Deviations from ideality arise from practical considerations such as the incident beam spectral purity, its divergence or convergence to the sample from the source via the optics, as well as the crystal perfection (`mosaicity'), and of the point-spread factor of the detector. The reflection rocking curves and diffraction spot shapes and sizes are practical manifestations of these effects.

The relationship between the angles of misorientation of macroscopic low-angle boundaries (LABs) and changes in the lattice parameter of the γ′-phase around the LABs in the root of single-crystalline (SX) turbine blades made of CMSX-4 superalloy were studied. The blades with an axial orientation of the [001] type were solidified using an industrial Bridgman furnace with a 3 mm/min withdrawal rate. X-ray diffraction topography, the EFG Ω-scan X-ray diffraction method, scanning electron microscopy, and Laue diffraction were used to study the thin lamellar samples with a thickness of 0.5 mm and orientation of the surface perpendicular to the [001] direction. It is found that in the areas with a width of a few millimetres around LABs, decreases in the lattice parameter of the γ′-phase occur. These lattice parameter changes are related to the internal stresses of the γ′-phase caused by local changes in the concentration of alloying elements and/or to the dendrite bending near the LABs. X-ray topography used on two surfaces of thin lamellar samples coupled with the lattice parameter measurements of the γ′-phase near the LAB allows separating the misorientation component of LAB diffraction contrast from the component and visualising the internal stresses of the γ′-phase.

The areas located near the cooling bores of single-crystalline cored turbine blades made of nickel-based CMSX-4 superalloy were studied. The blades were solidified by the vertical Bridgman technique in the industrial ALD furnace. Longitudinal sections of the blades were studied by Scanning Electron Microscopy, X-ray diffraction topography, X-ray diffraction measurements of the γ′-phase lattice parameter a, and the α angle of the primary crystal orientation. The local changes in α were analyzed in relation to the changes of the dendrite’s growth direction near the cooling bores. It was found that in the area approximately 3 ÷ 4 mm wide around the cooling bores, changes of α and a, both in the blade root and in the airfoil occurred. The local temperature distribution near the cooling bores formed a curved macroscopic solidification front, which caused changes in the chemical composition and, consequently, changes in the a value in a range of 0.002 Å to 0.014 Å. The mechanism of alloying elements segregation by tips of the dendrites on the bent solidification front was proposed. The multi-scale analysis that allows determining a relation between processes proceed both on a millimeter-scale and a micrometric and nanometric scale, was applied in the studies.

A successive approach to the solution of the inverse problem of diffraction X-ray topo-tomography is proposed. It is based on the semikinematic solution to the Takagi–Taupin equations for the amplitude of diffracted σ-polarized wave. An example of a point defect of Coulomb type in a Si(111) single-crystal plate under conditions of symmetric Laue diffraction and a set of oblique two-dimensional topographic projections corresponding to the rotation of plane-parallel sample crystal around the diffraction vector [ $$\bar {2}20$$ ] is considered. Iterative algorithms for simulated annealing (SA) and quasi-Newton-type algorithms are used for computer reconstruction of the three-dimensional function of the displacement field around a point defect. The results of computer simulation of the displacement field function based on the data for one 2D projection, corresponding to the point defect image in an X-ray topogram in classical X-ray diffraction topography, are presented.

In this paper, the innovative photoluminescence imaging technique is described for applications to buried defect detection in silicon devices. The validity of this emerging technique is first assessed in comparison with well-established characterization techniques (defect selective etching of silicon, X-Ray diffraction topography, cross-sectional transmission electron microscopy imaging and photoluminescence spectroscopy). This paper then describes specific applications illustrating the use of the photoluminescence imaging technique for common processes of the CMOS semiconductor industry. The benefit of this fast, high resolution and non-destructive technique is demonstrated: this includes industrial use of the technique for in-line production control on product wafers.

We have studied the lattice-plane modulation of Mg-doped GaN homoepitaxial layers by X-ray diffraction topography. X-ray rocking curve images and full-width at half maxima images of a 2 inch GaN wafer were obtained by an image stacking method. Low frequency components evaluated from Fourier transformations of the X-ray rocking curves tended to increase as the Mg-doping concentration increased, which indicates an increase of film lattice modulation. For Mg-dopant concentrations greater than 1019 cm−3, the film lattice-plane changed from a convex to concave shape and became wrinkled. We attribute this lattice-plane modulation to the relaxation of strain in the in-plane direction after the generation of dislocations by Mg doping.

This book focuses on defects in GaN based on the most up-to-date intrinsic material properties, and addresses deep levels and their analytical methods within the wide bandgap of GaN. It demonstrates nanoscale structures of extended defects in GaN using atomic-scale transmission electron microscopy. The identifi cations of their deep levels and extended defect structures are presented by comparing with reported fi rst-principles calculations. It reviews emerging technologies for defect characterizations using atom probe tomography, synchrotron x-ray diffraction topography in wafer scale, and multiphoton-excitation photoluminescence, which allows for the multidirectional characterization of structural defects. Readers will gain insight into:Electrical impacts of defects in GaN-based vertical power devicesPathways to the defect control in the fabrication process of GaN-based electric devicesUp-to-date methods for semiconductor and electronic material defect analysis Characterization of Defects and Deep Levels for GaN Power Devices is an ideal reference for industry materials scientists working in semiconductor materials and devices. It is also suitable for experts in DLTS, TEM, APT, XRDT, and multiphoton-excitation photoluminescence.

We modified a synchrotron X-ray diffraction imaging, a kind of X-ray diffraction topography (XRDT), technique to visualize a local latticeplane shape of a whole wafer and to make measurement time shorter. The technique needs monochromatic X-rays with an enough large beam size having a small angular divergence. In addition, it has two limitations related to a local d spacing as well as a local lattice-plane curvature. Our key point is that two equivalent reflections or more for different sample azimuth angles have been used. We obtained center angles of rocking curves from many positions on a sample surface with a two-dimensional detector and evaluated the local deviation angles on two respective diffraction planes. Local reciprocal-lattice vectors for respective sample surface positions were obtained using the deviation angles via the rotation matrix. Our three following studies are introduced: 1)lattice-plane orientation mapping of homoepitaxial GaN (0001) thin films grown on a 2-inch whole wafer, 2)visualization of crystal perfection and lattice-plane shape of 4-inch whole GaN(0001) wafer, and 3)visualization of lattice-plane twisting of an m-planeGaN homoepitaxial layer. The developed XRDT technology allows us to quickly visualize variation of lattice-plane orientations in a whole GaN wafer as well as the anisotropic mosaicity.

The roots of cored single-crystalline turbine blades made of a nickel-based CMSX-4 superalloy were studied. The casts were solidified by the vertical Bridgman method in an industrial ALD furnace using the spiral selector and selector continuer situated asymmetrically in the blade root transverse section. Scanning electron microscopy, the Laue diffraction and X-ray diffraction topography were used to visualize the dendrite array and the local crystal misorientation of the roots. It has been stated that heterogeneity of the dendrite array and creation of low-angle boundaries (LABs) are mostly related to the lateral dendrite branching and rapid growth of the secondary and tertiary dendrites near the surface of the continuer&ndash, root connection. These processes have an unsteady character. Additionally, the influence of the mould walls on the dendrite array heterogeneity was studied. The processes of the lateral growth of the secondary dendrites and competitive longitudinal growth of the tertiary dendrites are discussed and a method of reducing the heterogeneity of the root dendrite array is proposed.

Due to the functional limitations of SiO2 for SOI applications, alternative dielectric materials have been investigated. Alternative SOI materials in this work include, AlN and AlGaN. The dielectrics were deposited using MOCVD, and with the aid of PECVD deposited SiO2, and the SiO2 was directly bonded to a handle Si wafer. Tensile tests were performed on the samples to examine the fracture behavior and maximum tensile stresses, with results being comparable to a traditional SOI. Characterization was undertaken using TEM to understand the microstructural and interfacial properties of alternative SOI. High crystal quality Al(Ga)N was achieved on a Si(111) substrate that generally contained well defined chemical interfaces. Finally, synchrotron X-ray diffraction topography was used to understand the topographical strain profile of the device and handle wafers. Topography results showed different strain network properties between the device and handle wafer. This work has demonstrated preliminary feasibility of using alternative dielectrics for SOI applications.

In the present work, the novel high-resolution X-ray diffraction technique for imaging misorientation and mosaicity in single crystal superalloys is introduced. The technique is based on classical X-ray diffraction topography geometries combined with high-resolution diffraction and post-processing of obtained data including color coding and 3D projections of each diffraction images. For the investigations, the single crystal rods were produced from CMSX-4 superalloy at a withdrawal rate of 1, 3, 5, and 7 mm⋅min−1. The high spatial and angular resolution of the method allows to visualize the complex nature of mosaicity present in single crystal superalloys. It was observed that mosaics blocks differ in size and misorientation on the multi-scale level from the small present in dendrite arms, through single dendrites, group of dendrites, up to subgrains. Measurements of misorientation were done on cross and longitudinal sections of the castings. It was proved that increasing withdrawal rate influences the mosaicity structure and mechanisms of its evolution. Solidification at withdrawal rates from 1 to 5 mm⋅min−1 possesses higher misorientation between dendrites. With higher misorientation between dendrites, when the widening of solidification front occurs, the mosaicity spreads across the casting in the form of misoriented dendrite lines as the solidification progress by growing long secondary dendrite arms. Also, it was stated that 3–5 mm⋅min−1 rates possess a higher possibility of creation of subgrains or selector grains defects in the casting.

International audience; To control the final grain structure and the density of structural crystalline defects in silicon (Si) ingots is still a main issue for Si used in photovoltaic solar cells. It concerns both innovative and conventional fabrication processes. Due to the dynamic essence of the phenomena and to the coupling of mechanisms at different scales, the post-mortem study of the solidified ingots gives limited results. In the past years, we developed an original system named GaTSBI for Growth at high Temperature observed by Synchrotron Beam Imaging, to investigate in situ the mechanisms involved during solidification. X-ray radiography and X-ray Bragg diffraction imaging (topography) are combined and implemented together with the running of a high temperature (up to 2073 K) solidification furnace. The experiments are conducted at the European Synchrotron Radiation Facility (ESRF). Both imaging techniques provide in situ and real time information during growth on the morphology and kinetics of the solid/liquid (S/L) interface, as well as on the deformation of the crystal structure and on the dynamics of structural defects including dislocations. Essential features of twinning, grain nucleation, competition, strain building, and dislocations during Si solidification are characterized and allow a deeper understanding of the fundamental mechanisms of its growth.

The variation of the crystal orientation and the dendrite array generated in the root of the single-crystalline (SX) turbine blades made of CMSX-4 superalloy were studied. The blades with an axial orientation of the [001] type were solidified by the industrial Bridgman technique using a spiral selector at a withdrawal rate of 3 mm/min. The analysis of the crystal orientation and dendrite arrangement was carried out using scanning electron microscopy, X-ray diffraction topography, and Laue diffraction. It was found that the lateral growth of such secondary dendrite arms, which are defined as &ldquo, leading&rdquo, and grow in the root at first, is related to the rotation of their crystal lattice, which is the reason for creation of the low-angle boundary (LAB) type defects. The primary crystal orientation of the selector extension (SE) area determines the areas and directions of the lateral growth of the leading arms. Additionally, it was found that in the SE areas of the root, near the connection with the selector, the spatial distribution of the [001]&gamma, &rsquo, crystallographic direction has a complex wave-like character and may be related to the shape of the crystallization front.

International audience; Synopsis A setup for simultaneous, time-resolved X-ray radiography and diffraction topography imaging is presented. It is used to study defect generation and growth mechanisms during heating, solidification and cooling of a silicon crystal. Abstract One of the key issues to be resolved to improve the performance of silicon solar cells is to reduce crystalline defect formation and propagation during the growth process fabrication step. For this purpose, the generation of structural defects such as grain boundaries and dislocations in silicon must be understood and characterised. We combine in situ X-ray diffraction imaging, historically named topography, with radiography imaging to analyse the development of crystal defects before, during and after crystallisation. Two individual indirect detector systems are implemented to record simultaneously the crystal structure (topographs) and the solid-liquid morphology evolution (radiographs) at high temperature. This allows for a complete synchronisation of the images and for an increased image acquisition rate compared to previous studies that used X-ray sensitive films to record the topographs. The experiments are performed with X-ray synchrotron radiation at beamline ID19 at the European Synchrotron Radiation Facility (ESRF). We present in situ observations of the heating, melting, solidification and holding stages of silicon samples to demonstrate that with the upgraded setup detailed investigations of time-dependent phenomena are now possible. The motion of dislocations is recorded during the entire experiment, so that their interaction with grain boundaries and their multiplication through the activation of Frank-Read sources can be observed. Moreover, the capability to record with two camera-based detectors allows for the study of the relationship between strain distribution, twinning and nucleation events. In conclusion, the simultaneous recording of topographs and radiographs has great potential for further detailed investigations of the interaction and generation of grains and defects that influence the growth process and the final crystalline structure in silicon and other crystalline materials.

We have investigated the crystal quality of a 4-inch GaN wafer by X-ray diffraction topography. GaN (114) diffraction images at various incident angles were obtained to determine the image of maximum intensity and full-width at half-maximum (FWHM). The images reconstructed from the maximum intensity at each detector pixel position indicated that the inhomogeneous crystal quality of the wafer originated from seed crystals during wafer manufacturing. The evaluated FWHM distribution tended to increase and become broader from the center to the edge of the wafer. The q-vector components evaluated from the two rocking-curve images at different azimuthal angles combined with the rotation matrix revealed that the overall lattice planes bowed towards the diagonal direction. A histogram on the tilting angle of the wafer showed that the most frequently observed angle was about 0.03°. We expect that our findings could be applied to wafer quality estimation.

Ytterbium doped calcium gadolinium aluminate (CaGdAlO4) crystals, which is a perspective material for femto-second lasers, have been studied by means of synchrotron and conventional X-ray diffraction topography. The investigation was performed with a series of samples cut out perpendicularly and parallel to the 〈100〉 growth axis from the initial and end parts of CaGdAlO4 crystals, both undoped and doped with different concentration of Yb. The synchrotron topographic investigation was performed at the European Synchrotron (ESRF) in transmission geometry using the radiation of rather short wavelength, while the conventional topographs were obtained in the back-reflection geometry by means of the double crystal method in Cu Kα1 radiation. Some additional investigation was performed with polarization microscopy and high resolution X-ray diffraction omega scan. Apart from slightly pronounced segregation fringes and a core region the diffraction topographs revealed numerous volume defects, which most probably can be interpreted as solute trails. A characteristic feature of the presently observed volume defects were the details of the contrasts on their boundaries. These details suggested the presence of strong stress and the generation of the dislocations. The increase of the defect concentration with the increase in ytterbium concentration was observed.

The as-cast single-crystalline turbine blades made of CMSX-4 superalloy were studied. The blades were obtained by the Bridgman technique at a withdrawal rate of 5mm/min. The as-cast samples were prepared by cutting the blade root with a fragment of selector. The dendritic structure of obtained samples was studied by Scanning Electron Microscopy. The crystal orientation and lattice parameters were analyzed by Ω-scan mapping method. Additionally, the X-ray diffraction topography was applied. It was found that the most structural defects are created in the areas where a change in the shape and dimensions of the blades occur. Even minor changes in their geometry and the unevenness of mold walls may also affect the formation of defects.

New possibilities are presented for the characterization ofAIIIBVmixed superlattice compounds by the complementary use of synchrotron diffraction topography and rocking curves. In particular, using a synchrotron white beam and the section diffraction pattern of a 5 µm slit taken at a 10 cm film-to-crystal distance, it was possible to reproduce a set of stripes corresponding to interference fringes. These are analogous to the interference maxima revealed in high-resolution rocking curves, but are created by the changes in orientation of the planes inclined to the surface which are induced by unrelaxed strain. The section diffraction topographic method enabled examination of the sample homogeneity along the narrow intersecting beam. This was important in the case of the present sample containing a twin lamella in the InP substrate wafer. Both the section and projection Bragg case topographic methods enabled the crystallographic identification of the twin lamella. Another characteristic feature indicated in the section topography was the bending of the stripes corresponding to the superlattice peaks close to the boundaries of the twin lamella. The most probable interpretation of this phenomenon is an increase in the thickness of the deposited layers close to the lamella, together with possible changes in the chemical composition, leading to a decrease in the mean lattice parameter in the superlattice.

The structure and optical diffraction properties of monolayers of monodisperse spheres crystallized on transparent dielectric substrates are studied. Two types of diffraction phenomena are considered: surface light diffraction on the lattice of spheres and waveguide resonances in the monolayer plane. For experimental study of these phenomena, optical retroreflection and transmission spectra are measured as functions of the light incidence angle and azimuthal orientation of the incidence plane. The monolayer structures determined by scanning electron microscopy and light diffraction methods are in quantitative agreement. It is concluded that one-dimensional Fraunhofer diffraction is applicable to describe surface diffraction in the hexagonal lattice of spheres. In the case of oblique light incidence, anisotropy of diffraction and transmission spectra depending on the light incidence plane orientation with respect to the sphere lattice and linear polarization of incident light is detected. Waveguide resonances of the planar two-dimensional photonic crystal are approximated within the light diffraction model in the “empty” hexagonal lattice. The best approximation of the waveguide resonance dispersion is achieved using the effective refractive index, depending on the wavelength. Surface diffraction suppression by waveguide resonances of the photonic crystal is demonstrated. Surface diffraction orders are identified as diffraction at singular points of the Brillouin zone of the planar twodimensional photonic crystal.

Commercial detector-grade cadmium zinc telluride (CZT) crystals still suffer from various types of extended defects, e.g., dislocations, micro-grains, grain boundaries, and Te-rich secondary phases. Most of these defects cannot readily be identified and characterized using conventional techniques, though they are believed to be the dominant factor causing non-uniformity in the detector response. In this work, we revealed and characterized these secondary-phase defects in CZT crystals by employing multiple advanced techniques, e.g. X-ray diffraction topography, micro-scale X-ray response mapping, chemical etching and infrared microscopy. We then evaluate the detector performance of the crystals by recording high spatial-resolution raster scans of the charge collection and spectral response. We directly correlated the influence of the secondary-phase defects on the performance of the detector responses. The experimental results exhibit clear evidence of the undesirable effects of extended defects on the performance of commercial CZT radiation detectors.

Triple Bragg diffraction in a paratellurite crystal has been considered for the case when the plane of diffraction is oblique to the optical axis of the crystal. It has been shown that effective photoelastic constants for isotropic and anisotropic diffraction depend on the inclination of the plane of diffraction insignificantly. Triple Bragg diffraction of 0.63-μm coherent radiation in paratellurite at a 47.3-MHz slow acoustic wave has been experimentally demonstrated. For an optical power of 0.69 W delivered to a piezoconverter, the relative intensities of diffraction orders equal ~0.4, 0.4, 0.1, and 0.1, respectively.

Strontium titanate (SrTiO3), a well-established traditional perovskite substrate as well as a promising substrate crystal for the epitaxy of new advanced perovskite-type thin films, suffers from the unavailability in adequate quality for the latter. To improve the situation attempts have been made to grow SrTiO3 at moderate temperatures (

X-ray Bragg diffraction in sagittal geometry on a Y-cut langasite crystal (La3Ga5SiO14) modulated by Λ = 3 µm Rayleigh surface acoustic waves was studied at the BESSY II synchrotron radiation facility. The surface acoustic waves create a dynamical diffraction grating on the crystal surface, which can be used for space–time modulation of an X-ray beam., X-ray Bragg diffraction in sagittal geometry on a Y-cut langasite crystal (La3Ga5SiO14) modulated by Λ = 3 µm Rayleigh surface acoustic waves was studied at the BESSY II synchrotron radiation facility. Owing to the crystal lattice modulation by the surface acoustic wave diffraction, satellites appear. Their intensity and angular separation depend on the amplitude and wavelength of the ultrasonic superlattice. Experimental results are compared with the corresponding theoretical model that exploits the kinematical diffraction theory. This experiment shows that the propagation of the surface acoustic waves creates a dynamical diffraction grating on the crystal surface, and this can be used for space–time modulation of an X-ray beam.

Investigations of the spatial resolution of a setup for verification of the equivalence of inertial and gravitational masses of a neutron by the method of diffraction in a perfect crystal have been performed. Tests were conducted at Bragg angles of 74°–82°. A decrease in spatial resolution at Bragg angles >78° is detected.

A design method based on one-dimensional photonic crystal theory (1-D PC theory) is presented to design Bragg concave diffraction grating (Bragg-CDG) for the demultiplexer. With this design method, the reflection condition calculated by the 1-D PC theory can be matched perfectly with the diffraction condition. As a result, the shift of central wavelength of diffraction spectra can be improved, while keeping high diffraction efficiency. Performances of Bragg-CDG for TE and TM-mode are investigated, and the simulation results are consistent with the 1-D PC theory. This design method is expected to be applied to improve the accuracy and efficiency of Bragg-CDG after further research.

Using the method of Green functions in the symmetric Laue geometry the rocking curves of plane X-ray wave were theoretically investigated depending on the departure of a beam from exact Bragg condition in the diffraction plane and in the direction perpendicular to the diffraction plane. The Si(220) reflection of MoKα radiation was considered by way of illustration.

Energy dispersive X-ray fluorescence mapping (μ-EDXRF) is a fast and non-destructive method for chemical quantification and therefore used in many scientific fields. The combination of spatial and chemical information is highly valuable for understanding geological processes. Problems occur with crystalline samples due to diffraction, which appears according to Bragg's law, depending on the energy of the X-ray beam, the incident angle and the crystal parameters. In the spectra these peaks can overlap with element peaks suggesting higher element concentrations. The aim of this study is to investigate the effect of diffraction, the possibility of diffraction removal and potential geoscientific applications for X-ray mapping. In this work the μ-EDXRF M4 Tornado from Bruker was operated with a Rh-tube and polychromatic beam with two SDD detectors mounted each at ± 90° to the tube. Due to the polychromatic beam the Bragg condition fits for several mineral lattice planes. Since diffraction depends on the angle, it is shown that a novel correction approach can be applied by measuring from two different angles and calculating the minimum spectrum of both detectors gaining a better limit of quantification for this method. Furthermore, it is possible to use the diffraction information for separation of differently oriented crystallites within a monomineralic aggregate and obtain parameters like particle size distribution for the sample, as it is done by thin section image analysis in cross-polarized light. Only with μ-EDXRF this can be made on larger samples without preparation of thin sections.

The possibility of formation of the edge of a 2D optical image in two diffraction orders by means of Fourier processing with the use of triple Bragg diffraction is proposed and confirmed experimentally. A new model of 3D acousto-optic interaction in a gyrotropic crystal is developed, and transfer functions are calculated. The theoretical results of image processing are confirmed experimentally using triple Bragg diffraction in a TeO2 crystal.

We investigated the surface morphology changes in a 2 inch-diameter, c-plane, free-standing GaN wafer using X-ray diffraction topography in a grazing-incidence geometry. We observed a decrease in the peak intensity and increase in the full width at half maximum of the GaN 114 Bragg peak after the deposition of a homoepitaxial layer on the same GaN wafer. However, the lattice plane bending angles did not change after homoepitaxial layer deposition. Distorted-wave Born approximation calculations near the total external reflection condition revealed a decrease in the X-ray incidence angle of the 114 Bragg peak after the homoepitaxial layer deposition. The decrease in both X-ray penetration and incidence angle induced broader and weaker diffraction peaks from the surface instead of the bulk GaN.

An analysis of the defects in the vicinity of the selector&ndash, root connection plane occurring during the creation of single-crystalline turbine blades made of CMSX-6 Ni-based superalloy was performed. X-ray diffraction topography, scanning electron microscopy, and positron annihilation lifetime spectroscopy were used. Comparing the area of undisturbed axial growth of dendrites to the area of lateral growth concluded that the low-angle boundaries-like (LAB-like) defects were created in the root as a result of unsteady-state lateral growth of some secondary dendrite arms in layers of the root located directly at the selector&ndash, root connection plane. Additional macroscopic low-angle boundaries (LABs) with higher misorientation angles were created as a result of concave curvatures of liquidus isotherm in platform-like regions near selector&ndash, root connections. Two kinds of vacancy-type defects, mono-vacancies and vacancy clusters, were determined in relation to the LABs and LAB-like defects. Only mono-vacancies appeared in the areas of undisturbed axial growth. Reasons for the creation of macroscopic LABs and LAB-like defects, and their relationships with vacancy-type defects were discussed.

In industrial semiconductor fabrication, it is important to determine the quality of an entire wafer, not just a small area. Energy-resolved x-ray diffraction topography is important for visualizing the tilting distribution of a crystal lattice over a large area, yet in spite of technical progress it has been difficult to analyze a whole wafer qualitatively. By analyzing diffracted-angle positions of a two-dimensional detector under one-dimensional polychromatic (white) x-ray illumination, the authors visualize the periodic lattice-tilting structure over a large area on a substrate. This approach will have an impact on improving manufacturing processes for single-crystal wafers.

Specific features of the acousto-optic diffraction of Bessel light beams propagating in the vicinity of the optical axis of a uniaxial gyrotropic crystal have been investigated. The dependences of the diffraction efficiency on the acousto-optic interaction length, ultrasound power, and polarization state of the incident Bessel light beam have been analyzed using the coupled-wave equations and the overlap-integral method. It is shown that polarization-independent diffraction of Bessel light beams is observed in paratellurite crystals, when the Bragg diffraction efficiency is independent of the polarization state of the incident beam. The physical reason for this diffraction has been established (both theoretically and experimentally) to be simultaneous implementation of two processes of anisotropic scattering, at which the Bragg synchronism conditions are satisfied for orthogonal polarized Bessel beams with elliptical polarization.

Acousto-optic Bragg diffraction in paratellurite is investigated within the two first diffraction orders for the case of diffraction by the sidelobes of the spatial radiation spectrum of an acoustic transducer. One of the diffraction orders is due to anisotropic diffraction, and the other, to isotropic diffraction. Such a diffraction regime is achieved when the diffraction plane is inclined toward the optical axis of the crystal. For light with a wavelength of 0.63 × 10–4 cm diffracted by a “slow” sound wave with a frequency of 26 MHz, the effect manifests itself when the angle between the acousto-optic diffraction plane and the optical axis of paratellurite is ~3°. The effect is experimentally verified. The diffraction efficiency is 20% for each of the diffraction orders for a microwave signal of 8 V at the transducer.

Single crystals of mercurous halide were grown by physical vapor transport method (PVT). The orientation and the crystalline quality of the grown crystals were determined using high resolution x-ray diffraction (HRXRD) technique. The full width at half maximum (FWHM) of the grown mercurous bromide crystals was measured to be 0.13 degrees for (004) reflection, which is the best that has been achieved so far for PVT grown mercurous halide single crystals. The extended defects of the crystals were also analyzed using high resolution x-ray diffraction topography. Preliminary studies were carried out to evaluate the performance of the crystals on acousto-optic modulator (AOM) and gamma-ray detector applications. The results indicate the grown mercurous halide crystals are excellent materials for acousto-optic modulator device fabrication. The diffraction efficiencies of the fabricated AOM device with 1152 and 1523 nm wavelength lasers polarizing parallel to the acoustic wave were found to be 35% and 28%, respectively. The results also indicate the grown crystals are a promising material for gamma-ray detector application with a very high energy resolution of 1.86% FWHM.

The background of an electron backscattered diffraction pattern contains quantitative surface topography data. We propose a new approach to extract this topography from the location of the maximum background intensity in each diffraction pattern. Using specular reflection as a zero-th order approximation, we employ Monte Carlo simulations to determine corrections to the scattering angles, which then allow us to accurately determine the local surface normal. We derive the theoretical model and illustrate the approach experimentally using a β-Sn sphere, for which we determine the local surface normal orientation from the background intensity shifts in electron backscatter diffraction patterns.

Two-dimensional photonic crystals with square symmetry C 4v were obtained using the laser lithography method. The structure of these samples was studied by scanning electron microscopy. Optical Laue diffraction for monochromatic light was studied experimentally depending on the incidence angle of laser beam and lattice constant. Interpretation of the observed diffraction patterns is given in the framework of the Laue diffraction mechanism for an one-dimensional chain of scattering elements. Red thresholds for different diffraction orders were determined experimentally and theoretically. The results of calculations are in an excellent agreement with experiment.

High-speed (submicrosecond) translation and rotation of crystals are tracked in real time via simultaneous synchrotron X-ray imaging and Laue diffraction., Dynamic compression experiments are performed on single-crystal Si under split Hopkinson pressure bar loading, together with simultaneous high-speed (250–350 ns resolution) synchrotron X-ray Laue diffraction and phase-contrast imaging. A methodology is presented which determines crystal rotation parameters, i.e. instantaneous rotation axes and angles, from two unindexed Laue diffraction spots. Two-dimensional translation is obtained from dynamic imaging by a single camera. High-speed motion of crystals, including translation and rotation, can be tracked in real time via simultaneous imaging and diffraction.

A new mechanism of neutron acceleration is studied experimentally in detail for cold neutrons passing through the accelerated perfect crystal with the energies close to the Bragg one. The effect arises due to the following reason. The crystal refraction index (neutron–crystal interaction potential) for neutron in the vicinity of the Bragg resonance sharply depends on the parameter of deviation from the exact Bragg condition, i.e. on the crystal–neutron relative velocity. Therefore the neutrons enter into the accelerated crystal with one neutron–crystal interaction potential and exit with the other. Neutron kinetic energy cannot vary inside the crystal due to its homogeneity. So, after passage through such a crystal, neutrons will be accelerated or decelerated because of the different energy change at the entrance and exit crystal boundaries.

A program for calculating characteristics of acousto-optic interaction in biaxial crystals is developed and used to analyze light diffraction by ultrasound in an iodic acid crystal. Crystal cuts with maximum acousto-optic figures of merits are found. It is shown that in the region of the optical axes the frequency dependences of the Bragg angles under anisotropic diffraction are substantially different from those in uniaxial crystals.

The dynamic diffraction of an X-ray wave in a crystal with a third-order nonlinear response to external field strength has been theoretically investigated. General equations for the wave propagation in crystal and nonlinear Takagi equations for both ideal and deformed crystals are derived. Integrals of motion are determined for the nonlinear problem of dynamic diffraction. The results of the numerical calculations of reflectivity in the symmetric Laue geometry for an incident plane wave and the intensity distributions on the output crystal surface for a point source are reported as an example.

Simultaneous Bragg diffraction and coherent small-angle scattering of a single solar cell nanowire is demonstrated, using a nanofocused hard X-ray beam and two detectors., Simultaneous scanning Bragg contrast and small-angle ptychographic imaging of a single solar cell nanowire are demonstrated, using a nanofocused hard X-ray beam and two detectors. The 2.5 µm-long nanowire consists of a single-crystal InP core of 190 nm diameter, coated with amorphous SiO2 and polycrystalline indium tin oxide. The nanowire was selected and aligned in real space using the small-angle scattering of the 140 × 210 nm X-ray beam. The orientation of the nanowire, as observed in small-angle scattering, was used to find the correct rotation for the Bragg condition. After alignment in real space and rotation, high-resolution (50 nm step) raster scans were performed to simultaneously measure the distribution of small-angle scattering and Bragg diffraction in the nanowire. Ptychographic reconstruction of the coherent small-angle scattering was used to achieve sub-beam spatial resolution. The small-angle scattering images, which are sensitive to the shape and the electron density of all parts of the nanowire, showed a homogeneous profile along the nanowire axis except at the thicker head region. In contrast, the scanning Bragg diffraction microscopy, which probes only the single-crystal InP core, revealed bending and crystalline inhomogeneity. Both systematic and non-systematic real-space movement of the nanowire were observed as it was rotated, which would have been difficult to reveal only from the Bragg scattering. These results demonstrate the advantages of simultaneously collecting and analyzing the small-angle scattering in Bragg diffraction experiments.

Single crystals of trans -stilbene, C 14 H 12, with properties suitable for high-energy neutron detection were grown from solution in anisole and toluene by the temperature reduction method with growth rates up to 6 mm/day. From these crystals, slices of appropriate orientation and thickness of 2–4 mm were cut and studied by X-ray diffraction topography applying the Lang method using CuKα radiation. The topographs exhibit growth defects such as liquid inclusions, dislocations, striations, and faulty growth-sector boundaries. These defects occur in the same typical arrangements and geometries as is observed in all kinds of crystals grown on habit faces from solution. Besides growth dislocations originating from inclusions and propagating with the growth front, many plastic glide dislocations in the shape of loops or half-loops emitted from inclusions by stress relaxation are observed. The glide system underlying this plasticity is discussed.

A Bragg diffraction variant consisting in the diffraction of three-color radiation with wavelengths of 488, 514, and 633 nm by an acoustic wave propagating in a paratellurite crystal is investigated. The radiation with a wavelength of 633 nm is in strict Bragg synchronism with the acoustic wave, while other beams are diffracted with slight violations of the synchronism condition. The diffraction efficiency in the first diffraction order is experimentally determined to be no less than 70% for all the aforementioned wavelengths of optical radiation.

International audience; We report on indirect X-ray detector systems for various full-field, ultra high-speed X-ray imaging methodologies, such as X-ray phase-contrast radiography, diffraction topography, grating interferometry and speckle-based imaging performed at the hard X-ray imaging beamline ID19 of the European Synchrotron—ESRF. Our work highlights the versatility of indirect X-ray detectors to multiple goals such as single synchrotron pulse isolation, multiple-frame recording up to millions frames per second, high efficiency, and high spatial resolution. Besides the technical advancements, potential applications are briefly introduced and discussed.

The effect of two-crystal focusing of neutrons at Laue diffraction from large perfect silicon crystals has been studied. It has been shown that the focusing effect makes it possible to reach an angular resolution better than 0.03″, which is about 0.01 of the width of a Bragg reflection. This circumstance allows a new ultraprecision neutron-spectrometry method based on the method of spin-echo small-angle neutron scattering in combination with Laue diffraction.