Berg-Barrett Topography Research Articles

Contrast analysis of Shockley partial dislocations in 4H-SiC observed by synchrotron Berg–Barrett X-ray topography

Shockley partial dislocations in 4H-SiC were observed using monochromatic synchrotron X-ray topography with a grazing-incidence Bragg-case geometry, that is, Berg–Barrett topography. The contrast of partial dislocations at the edges of Shockley-type stacking faults is discussed in terms of whether they have C- or Si-core edge components, or screw components. The dissociated state of basal-plane dislocation is discussed on a basis of the stacking sequence for basal-planes in the 4H-SiC crystal structure. It is expected that the results obtained in this study will be useful for characterizing Shockley-type stacking faults in Berg–Barrett topography.

Fast and easy Bragg reflex search for Berg–Barrett topography of misoriented crystals

A fast search method for X-ray Bragg reflexes of misoriented crystals is presented. The method is also applicable to determine the accuracy of the crystal orientation. This technique is demonstrated by means of a simple setup for Berg–Barrett X-ray topography, consisting of a rotating sample holder on a two-circle diffractometer. The imaged area of the topograms is about 1 cm2, and the quality is comparable to the topograms taken by white-beam synchrotron X-ray topography.

Reconstruction of lattice structure of ion-implanted near-surface regions of Hg 1 − XCd XTe epitaxial layers

The results of X-ray, SIMS, SEM and AFM studies of near-surface regions of Hg 1 − X Cd X Te (111) and (110) structures have been presented. These structures were obtained during annealing in the vapour of main components of ISOVPE Hg 1 − X Cd X Te epitaxial layers with the surface implanted with arsenic ions. Berg-Barrett topography method and two-crystal spectrometry technique were exploited. For calculation of depth dependences of deformations and concentrations of dominating defects in the layer's near-surface regions, the Takagi-Taupin equation and generalized dynamic theory of X-ray scattering were used. From experimental SIMS analysis, the distributions of both impurity and main components of Hg 1 − X Cd X Te solid solution were determined providing more accurately the deformation profiles in near-surface regions of the structures. SIMS and SEM analyses have given evidence of abrupt gradients of content in the Hg 1 − X Cd X Te solid solution, due to small changes of thermodynamical equilibrium conditions of high-temperature annealing in the near-surface regions. These are the cause of formation of a graded-gap structure with strains in the crystal lattice. AFM studies have demonstrated that the morphology of Hg 1 − X Cd X Te structures is subjected to the influence of CdTe substrate orientation.

Gd 7T 3 (T=Rh, Pd) intermetallics crystal growth

Single crystals of intermetallic compounds Gd 7Pd 3 and Gd 7Rh 3 were grown by the Czochralski method from a levitated melt. The X-ray Berg–Barrett topography confirmed good quality of the obtained crystals. They grow in a single Th 7Fe 3-type hexagonal phase. Magnetic susceptibility measurements of Gd 7Pd 3 revealed a strong anisotropy in the examined compound.

Impact of SiC Structural Defects on the Degradation Phenomenon of Bipolar SiC Devices

In-house developed (1– 100) and (11– 20) oriented 4H-SiC wafers, and a reference wafer were used to evaluate the impact of the SiC structural defects on the degradation phenomenon of bipolar pn diodes. Evaluation of the crystal quality and the degraded devices was performed by comparing the results of etch pit densities, electroluminescence, Berg-Barrett topography, HRXRD and HRTEM analysis. Our data demonstrate that the degradation phenomenon is strongly related to the SiC structural crystal defects of the starting material. DENSO (HQ) wafers are less susceptible to the forward current degradation, which we attributed to comparatively much lower etch pit densities, specially the slip/stacking fault defects.

Surface structure of Gd 5(Si,Ge) 4 crystals

Crystal growth of Gd 5Si 4, Gd 5Si 2Ge 2 and Gd 5Ge 4 was performed using the Czochralski method from the levitated melt. Single crystalline plates were obtained for all compounds. The Berg–Barrett topography revealed the existence of stress within the plates. The surface of the plates shows a regular system of lines or channels, which is independent of the growth steps and the stress structure. The auger electron spectroscopy investigation of that structure revealed the increase of gadolinium and oxygen contents in the area of lines, which had the width of about 2 μm. We suppose this concentration of impurities may take place along dislocations, which could be formed during the structural transition at high temperature.

Crystal Growth and Characterization of RMn2(R = Gd, Tb, Dy, Er) Intermetallics

Single crystals of GdMn2, TbMn2, DyMn2 and ErMn 2 compounds were grown by the Czochralski method from a levitated melt. The quality of the obtained crystals were examined using the X-ray Berg-Barrett topography and powder diffraction method. The X-ray patterns were also calculated using the program FullProf.

Crystal Growth and Characterization of RMn2(R = Gd, Tb, Dy, Er) Intermetallics

Single crystals of GdMn 2 , TbMn 2 , DyMn 2 , and ErMn 2 compounds were grown by the Czochralski method from a levitated melt. The quality of the obtained crystals were examined using the X-ray Berg-Barrett topography and powder diffraction method. The X-ray patterns were also calculated using the program FullProf.

The π/2 Side-Reflection Laue Technique and the New Chart

For the capability of dynamic studies of structural changes of crystals under the environment of heat, electric or magnetic field, the π/2 side-reflection Laue technique is performed in which the X-ray source, the specimen and the film are aligned along an L-shaped track. A new chart has also been designed for the analysis of π/2 side-reflection Laue patterns. This new chart is applied to the analysis of crystal orientation in the π/2 side-reflection Laue technique and to indexing the planes of simultaneous multiple-reflection images in Berg–Barrett topography. Also, the equation of zonal trace has been derived for depicting the zonal curves of configurations of π/2 side-reflection spots and confirming the results which are analyzed by the new chart.

X-ray Berg–Barrett topography of the deformation substructure of stabilized zirconium oxide single crystals deformed at 1673 K

X-ray Berg–Barrett topography has been used to check the nature of the slip systems that are activated during high-temperature plastic deformation of single crystals and to follow the evolution of the microstructure with the strain. A study has been made of yttria fully stabilized zirconium oxide deformed by compression along the 〈001〉 direction at 1673 K. The {110} 〈1{\bar 1}0〉 slip system was activated.

Study of the crystalline quality of CdTe, CdZnTe and CdMnTe substrates used for liquid phase epitaxy of Cd 0.7Hg 0.3Te

The crystalline quality of epitaxial layers made of Cd 0.7Hg 0.3Te, which is a very good infrared detector at the optimal transmission wavelength (1.3 μm) in optical fibers, is strongly dependent on the crystalline quality of the substrate. Experimental observations, carried out by means of Berg-Barrett topography, cathodoluminescence, etch-pitting, and X-ray double-crystal rocking curve measurements on several CdTe, Cd 0.96Zn 0.04Te, and Cd 0.9Mn 0.1Te substrates confirm that the addition of Zn results in an improvement of the crystalline quality of the CdTe compound. The best results, in this work, were obtained on Cd 0.96Zn 0.04Te material with an etch-pit density of 5×10 4 cm -2 and an X-ray rocking curve linewidth of 25 arc sec. Mn addition, on the other hand, does not show any change in CdTe crystalline quality. Characterization of Cd 0.7Hg 0.3Te layers grown by liquid phase epitaxy (LPE) on two types of substrates (CdTe, Cd 0.96Zn 0.04Te) has demonstrated the better quality of those epitaxial layers grown on the Cd 0.96Zn 0.04Te substrate. This result constitutes an other indication of the improved crystalline quality of the Cd-rich CdZnTe material.

Dislocation structure of refractory metal single crystals after high-temperature creep—X-ray diffraction study

The dislocation structure of low molybdenum alloys doped with niobium was studied by X-ray diffraction methods, namely by Berg-Barrett topography and by the double-crystal technique. As a result, the following model of misoriented cell structure after high-temperature creep is suggested. Cell boundaries were supposed to be formed by tilt walls of equidistantly spaced dislocations, while cell dimensions were obtained from X-ray topograms and metallographic images. For this model, X-ray rocking curves were calculated in the framework of Krivoglaz's diffraction theory; the calculated diffraction profiles agreed well with the experimental profiles. It was shown that analysis of the azimuthal dependende of the rocking curve width enabled us to determine the misorientation between adjacent cells as well as the directions of the Burgers vector and of the dislocation line.

Analysis of the local excess density of dislocations in Y 2O 3-stabilized ZrO 2 by means of X-ray Berg-Barrett topography

This Letter deals with the application of X-ray Berg-Barrett topography to the Y 2O 3-Stabilized cubic zirconia. The long-scale dislocation arrangement is observed. Characteristic cusps appear in some topographs at the intersection of dislocation walls and dislocation layers. An easy way to calculate the local excess density of dislocations of one sign, associated with the cusps, is proposed. The obtained values are consistent with the results of TEM experiments.

X-ray extinction contrast in deformed single crystals

Berg–Barrett topography gives information on large-scale dislocation distribution in deformed single crystals. The Burgers vectors are determined by disappearance of the dark `extinction contrast'. This contrast cannot be extinguished by any single diffracting condition when different types of non-coplanar Burgers vectors are present simultaneously; complementary information by electron transmission microscopy agrees well with this inference. These general remarks are illustrated by some examples on deformed single crystals of α-Al2O3, (Al2O3)1.8MgO, NaCl and Cu2O.

Observations on the electrocrystallization of copper

The defects produced during epitaxial electrodeposition of copper on highly perfect copper single crystals have been studied by correlating various X-ray techniques, including Borrmann and Berg-Barrett topography, with optical microscopy and dislocation etching. In some of the deposits obtained, the measurement of the half-width of the Bragg peak and anomalously transmitted intensity revealed no significant concentration of defects. However, dislocation etching indicated the presence of small loops. Instances of formation of twin crystals were observed. Annealing of the deposits at temperatures up to 1000 °C caused the development of a small number of large strain centers and some indication of aggregation of defects.

Examination of Imperfect Muscovite Crystals by X-Ray Diffraction Methods

Single crystals of muscovite have been studied by x-ray Berg-Barrett topography. Remarkably sharp contrasting stripes exhibiting anomalous x-ray contrast were observed. From a detailed study of these as well as rocking curve experiments, it is concluded that the contrast is due to the corrugation of basal planes of mica, as a consequence of irregularity in the slip. The relation between the corrugations and the elastic properties of muscovite is discussed.