A study of X-ray multiple diffraction by means of section topography

The results of theoretical and experimental study are presented for the question of how the X-ray multiple diffraction in a silicon single crystal influences the interference fringes of section topography for the 400 reflection in the Laue case. Two different cases of multiple diffraction are discovered for zero and very small values of the azimuthal angle for the sample in the form of a plate with the surface normal to the 001 direction. The cases are seen on the same topogram without rotation of the crystal. Accurate computer simulations of the section topogram for the case of X-ray multiple diffraction are performed for the first time. It is shown that the structure of interference fringes on the section topogram in the region of multiple diffraction becomes more complicated. It has a very sharp dependence on the azimuthal angle. The experiment is carried out using a laboratory source under conditions of low resolution over the azimuthal angle. Nevertheless, the characteristic inclination of the interference fringes on the tails of the multiple diffraction region is easily seen. This phenomenon corresponds completely to the computer simulations.

Combined Application of Section and Projection Topography to Defect Analysis in PVT-Grown 4H-SiC

ABSTRACTThe combined application of section and projection topography carried out using synchrotron white beam radiation can be a powerful tool for the determination of the three-dimensional configurations of defects in single crystals. In this paper, we present examples of the application of this combination of techniques to the analysis of defect configurations in PVT-grown 4H-SiC wafers cut perpendicular and parallel to the growth axis. Detailed correlation between section and projection topography of threading screw dislocations (TSDs) is presented with particular emphasis being laid on the determination of the signs of the dislocations. Further, information can also be determined regarding the position of the dislocations within the crystal depth. In addition, similar correlation is presented for threading edge dislocations (TEDs) and basal plane dislocations (BPDs). The section topography images of dislocations can comprise direct, intermediary and dynamical contrast and all three types are observed. The application to the study of stacking faults will be also discussed in detail.

Moiré pattern from a multiple Bragg–Laue interferometer

In X-ray section topography of Si 220 diffraction in a multiple Bragg–Laue mode, a moiré pattern is observed when the incident beam is divided into two parts by inserting a platinum wire in the middle of the beam. The moiré pattern can be explained by the summation of two interference fringes corresponding to the two incident beams. The coherency of the X-rays from the bending-magnet beamline is estimated using the moiré pattern.

Effect of Sintering Temperature on Microstructure of Porous Materials Using Iron Tailing and Shale

A type of porous material was prepared mainly using iron tailings and shale, adding foaming agent, fusing agent and flexibility agent. To determine the sintering system of porous materials basing on iron tailing and shale, the effect of sintering temperature on the microstructure of the samples was investigated by XRD and SEM as well as section topography. The results indicate that both the porosity and pore size of the samples become higher and bigger respectively as sintering temperature increases from 1100°C to 1130°C, while mineral phase anorthite decreases; when sintered at 1120°C, the size of pores is approximately the same with the mean pore size of 1.5mm; the pores are larger and some get connected to the adjacent pores when the sintering temperature increases to 1130°C.

Investigation by coherent X-ray section topography of ferroelectric domain behaviour as a function of temperature in periodically poled Rb:KTP

The behaviour of ferroelectric domains at high temperatures near the Curie temperature in a periodically poled rubidium-doped potassium titanyl phosphate crystal (Rb:KTP) has been studied by Bragg–Fresnel X-ray diffraction imagingin situusing a compact coherence-preserving furnace. The development and partial disappearance of the inverted domain structure as the temperature increases has been successfully modelled, and is explained by invoking a built-in electric field produced under heating in a low vacuum by out-diffusion of atoms from the sample.

In situinvestigation of the non-linear optical crystal rubidium titanyl arsenate, RbTiOAsO4, under applied electric field using X-ray imaging

Recent work on the non-linear optical single-crystal rubidium titanyl arsenate (RbTiOAsO4, RTA) has shown that it exhibits behaviour consistent with a ferroelectric semiconductor under large applied electric fields, with the development of a non-uniform field in the near-surface region. To confirm aspects of the proposed model, the behaviour of 001 slices of initially single-domain RTA, patterned with periodic Ag electrodes of spacing 38 µm, as for periodic poling in non-linear optics, were investigated using synchrotron X-ray section topography with the electric field appliedin situwhile under X-ray illumination at the ID19 topography beamline of the ESRF, Grenoble. The results of white-beam section topography as both a function of crystal to film distance, and under DC voltage are reported, confirming that there is a bending of the planes in the near-surface region. The strain in the near-surface region was examined directly using high-resolution monochromatic X-ray section topography. This revealed an extensive strain of 3 (±1) × 10−4at 1 kV, indicating that the electrostrictive coefficient, γ3333, in RTA is positive in sign.