Dislocation contrast on X-ray topographs under weak diffraction conditions

The contrast of dislocations in 4H-SiC crystals shows distinctive features on grazing-incidence X-ray topographs for diffraction at different positions on the operative rocking curve. Ray-tracing simulations have previously been successfully applied to describe the dislocation contrast at the peak of a rocking curve.The present work shows that the dislocation images observed under weak diffraction conditions can also be simulated using the ray-tracing method. These simulations indicate that the contrast of the dislocations is dominated by orientation contrast. Analysis of the effective misorientation reveals that the dislocation contrast in weak-beam topography is more sensitive to the local lattice distortion, consequently enabling information to be obtained on the dislocation sense which cannot be obtained from the peak.

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Dislocation Contrast of 4H-SiC in X-Ray Topography under Weak-Beam Condition

Materials Science Forum ◽

10.4028/www.scientific.net/msf.600-603.313 ◽

2008 ◽

Vol 600-603 ◽

pp. 313-316 ◽

Cited By ~ 3

Author(s):

Hirotaka Yamaguchi ◽

Hirofumi Matsuhata ◽

Ichiro Nagai

Keyword(s):

Basal Plane ◽

Dislocation Core ◽

Grazing Incidence ◽

Diffraction Peak ◽

Rocking Curve ◽

Screw Dislocations ◽

X Ray ◽

Weak Beam ◽

Diffraction Geometry ◽

Basal Plane Dislocation

We have investigated dislocation image of 4H-SiC wafers projected on synchrotron X-ray topographs taken under different positions in the rocking curve of a diffraction peak. The diffraction geometry was grazing-incidence extremely asymmetric and the diffraction vectors were g = 1 1 2 8 and 112 8. The weak-beam images were demonstrated for basal-plane dislocations and threading-screw dislocations. The basal-plane dislocation images became narrower in width at the off-Bragg conditions, and they were decomposed to separate lines under the weak-beam condition. The threading-screw dislocations showed changes in their shape and contrast as the crystal set was tilted from the rocking-curve peak, and finally the characteristic images near the dislocation core were observed under the weak-beam condition. The origin of these weak-beam images is unclear, but it will offer detailed analysis of the dislocations.

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Lattice Distortion and Phase Stability of Pd-Doped NiCoFeCr Solid-Solution Alloys

Entropy ◽

10.3390/e20120900 ◽

2018 ◽

Vol 20 (12) ◽

pp. 900 ◽

Cited By ~ 10

Author(s):

Fuxiang Zhang ◽

Yang Tong ◽

Ke Jin ◽

Hongbin Bei ◽

William Weber ◽

...

Keyword(s):

Long Range ◽

Lattice Distortion ◽

Maximum Pressure ◽

Local Lattice Distortion ◽

X Ray ◽

High Entropy ◽

Local Lattice ◽

Pd Doping ◽

Fcc Phase ◽

The Stability

In the present study, we have revealed that (NiCoFeCr)100−xPdx (x= 1, 3, 5, 20 atom%) high-entropy alloys (HEAs) have both local- and long-range lattice distortions by utilizing X-ray total scattering, X-ray diffraction, and extended X-ray absorption fine structure methods. The local lattice distortion determined by the lattice constant difference between the local and average structures was found to be proportional to the Pd content. A small amount of Pd-doping (1 atom%) yields long-range lattice distortion, which is demonstrated by a larger (200) lattice plane spacing than the expected value from an average structure, however, the degree of long-range lattice distortion is not sensitive to the Pd concentration. The structural stability of these distorted HEAs under high-pressure was also examined. The experimental results indicate that doping with a small amount of Pd significantly enhances the stability of the fcc phase by increasing the fcc-to-hcp transformation pressure from ~13.0 GPa in NiCoFeCr to 20–26 GPa in the Pd-doped HEAs and NiCoFeCrPd maintains its fcc lattice up to 74 GPa, the maximum pressure that the current experiments have reached.

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The Performance of Channel Cut Collimators for Precision X-Ray Diffraction Studies of Epitaxial Layers

MRS Proceedings ◽

10.1557/proc-208-107 ◽

1990 ◽

Vol 208 ◽

Cited By ~ 7

Author(s):

Neil Loxley ◽

D. Keith Bowen ◽

Brian K. Tanner

Keyword(s):

Grazing Incidence ◽

Curve Analysis ◽

Epitaxial Layers ◽

Angular Divergence ◽

X Ray Diffraction ◽

Rocking Curve ◽

Experimental Performance ◽

Low Background ◽

X Ray ◽

Angle Scattering

ABSTRACTReplacement of the pinhole collimator on a double axis X-ray diffractometer with a device incorporating a channel-cut crystal permits the beam to be pre-conditioned in angular divergence. We examine the merits of such devices, known as channel-cut collimators (CCC's), of different materials and reflections. The experimental performance of InP 004 and Si 022 CCC's is presented.With a reference crystal on the first axis, set in the dispersive peometry with respect to the CCC, conditioning in wavelength spread is achieved. Dispersion broadening is effectively eliminated and no resetting of the reference crystal is required when changing specimen materials or reflections. The devices have extremely low background and reduced Bragg tails. Application of the 4-reflection CCC to rocking curve analysis of thin epitaxial layers, ultra-low angle scattering from biological systems, grazing incidence reflectometry and triple axis diffraction of semi-conductors is discussed.

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Influence of surface relaxation on the contrast of threading edge dislocations in synchrotron X-ray topographs under the condition of g · b = 0 and g · b × l = 0

Journal of Applied Crystallography ◽

10.1107/s160057672100025x ◽

2021 ◽

Vol 54 (2) ◽

Author(s):

Hongyu Peng ◽

Tuerxun Ailihumaer ◽

Fumihiro Fujie ◽

Zeyu Chen ◽

Balaji Raghothamachar ◽

...

Keyword(s):

Ray Tracing ◽

Depth Profiling ◽

Simulation Method ◽

Surface Relaxation ◽

X Ray ◽

Relaxation Effects ◽

Orientation Contrast ◽

Relaxation Depth ◽

Edge Dislocations ◽

Ray Tracing Simulation

Residual contrast of threading edge dislocations is observed in synchrotron back-reflection X-ray topographs of 4H-SiC epitaxial wafers recorded using basal plane reflections where both g · b = 0 and g · b × l = 0. The ray-tracing simulation method based on the orientation contrast formation mechanism is applied to simulate images of such dislocations by applying surface relaxation effects. The simulated contrast features match the observed features on X-ray topographs, clearly demonstrating that the contrast is dominated by surface relaxation. Depth profiling indicates that the surface relaxation primarily takes place within a depth of 5 µm below the surface.

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Defect structure analysis of polycrystalline materials by computer-controlled double-crystal diffractometer with position-sensitive detector

Journal of Applied Crystallography ◽

10.1107/s0021889883009991 ◽

1983 ◽

Vol 16 (1) ◽

pp. 89-95 ◽

Cited By ~ 31

Author(s):

R. Yazici ◽

W. Mayo ◽

T. Takemoto ◽

S. Weissmann

Keyword(s):

Position Sensitive Detector ◽

Polycrystalline Materials ◽

Sensitive Detector ◽

Double Crystal ◽

Rocking Curve ◽

X Ray ◽

Local Lattice ◽

Position Sensitive ◽

The Individual ◽

Double Crystal Diffractometer

The method represents an extension of a previously developed X-ray double-crystal diffractometer method when a film was used to record the crystallite reflections, each reflecting crystallite being regarded as the second crystal of a double-crystal diffractometer. By utilizing a position-sensitive detector (PSD) with interactive computer controls, the tedious and limiting task of data acquisition and analysis is greatly simplified. The specimen is irradiated with crystal-monochromated radiation and the numerous microscopic spots emanating from the reflecting crystallites are recorded separately by the position-sensitive detector and its associated multichannel analyzer at each increment of specimen rotation. An on-line minicomputer simultaneously collects these data and applies the necessary corrections. This process is then automatically repeated through the full rocking-curve range. The computer carries out the rocking-curve analysis of the individual crystallite reflections as well as that of the entire reflecting crystallite population. The instrument is provided with a specimen translation device which permits analysis of large sections of solid specimens. Thus, sites of local lattice defects induced either mechanically, chemically or by radiation can rapidly be established and quantitatively determined in terms of rocking-curve parameters as well as imaged by X-ray topography, by inserting a film in front of the PSD. The versatility and usefulness of the method is demonstrated by examples given from studies of fracture, fatigue and stress-corrosion cracking of commercial alloys.

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Studies of c-Axis Threading Screw Dislocations in Hexagonal SiC

MRS Proceedings ◽

10.1557/proc-1069-d02-03 ◽

2008 ◽

Vol 1069 ◽

Author(s):

Yi Chen ◽

Xianrong Huang ◽

Ning Zhang ◽

Govindhan Dhanaraj ◽

Edward Sanchez ◽

...

Keyword(s):

Ray Tracing ◽

Grazing Incidence ◽

Screw Dislocations ◽

Burgers Vector ◽

X Ray ◽

Back Reflection ◽

Partial Dislocations ◽

Ray Tracing Simulation ◽

Vector Magnitude

ABSTRACTIn our study, closed-core threading screw dislocations and micropipes were studied using synchrotron x-ray topography of various geometries. The Burgers vector magnitude of TSDs can be quantitatively determined from their dimensions in back-reflection x-ray topography, based on ray-tracing simulation and this has been verified by the images of elementary TSDs. Dislocation senses of closed-core threading screw dislocations and micropipes can be revealed by grazing-incidence x-ray topography. The threading screw dislocations can be converted into Frank partial dislocations on the basal planes and this has been confirmed by transmission synchrotron x-ray topography.

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Thermal-oxidation-induced local lattice distortion at surface of 4H-SiC(0001) characterized by in-plane X-ray diffractometry

Applied Physics Express ◽

10.7567/apex.11.011201 ◽

2017 ◽

Vol 11 (1) ◽

pp. 011201 ◽

Cited By ~ 7

Author(s):

Adhi Dwi Hatmanto ◽

Koji Kita

Keyword(s):

Thermal Oxidation ◽

Lattice Distortion ◽

Local Lattice Distortion ◽

X Ray ◽

Local Lattice

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Ray tracing method for the evaluation of grazing incidence x-ray telescopes described by spatially sampled surfaces

Applied Optics ◽

10.1364/ao.57.000b74 ◽

2018 ◽

Vol 57 (7) ◽

pp. B74 ◽

Cited By ~ 8

Author(s):

Jun Yu ◽

Zhengxiang Shen ◽

Pengfeng Sheng ◽

Xiaoqiang Wang ◽

Charles J. Hailey ◽

...

Keyword(s):

Ray Tracing ◽

Grazing Incidence ◽

Ray Tracing Method ◽

X Ray ◽

Tracing Method

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Design of an online spectrometer for the diagnosis of free-electron lasers

Journal of Synchrotron Radiation ◽

10.1107/s1600577520006554 ◽

2020 ◽

Vol 27 (4) ◽

pp. 870-882

Author(s):

Ximing Zhang ◽

Zhi Guo ◽

Xiangyu Meng ◽

Jiahua Chen ◽

Zhan Ji ◽

...

Keyword(s):

Ray Tracing ◽

Free Electron ◽

Spectral Characteristics ◽

Grazing Incidence ◽

Incident Radiation ◽

Resolving Power ◽

Ray Optics ◽

X Ray ◽

Line Spacing ◽

Under Construction

A self-amplified spontaneous emission free-electron laser (FEL) is under construction at the Shanghai Soft X-ray Free-Electron Facility. Therefore, it is necessary to develop a suitable diagnostic tool capable of resolving the natural emission band of each FEL pulse. Thus, an online spectrometer with a plane mirror and plane variable-line-spacing grating at grazing incidence to monitor each single FEL pulse during the propagation of FEL radiation has been designed and is presented in this work. The method of ray tracing is used for monitoring incident radiation in order to understand spectral characteristics, and SHADOW, an X-ray optics simulation tool, and SRW, an X-ray optics wavefront tool, are applied to study the resolving power and focusing properties of the grating. The designed resolving power is ∼3 × 104 at 620 eV. Meanwhile, the effect of the actual slope error of mirrors on the ray-tracing results is also discussed. In order to provide further optimization for the choice of grating, a comparison of resolving powers between 2000 lines mm−1 and 3000 lines mm−1 gratings at different energies is analyzed in detail and radiation damage of mirrors as well as parameters such as the first-order diffraction angle β, the exit-arm length r 2, and the tilt angle θ between the focal plane and the diffraction arm are studied and optimized. This work has provided comprehensive designing methods and detailed data for the design of diagnostic spectrometers in soft X-ray FELs and will be favorable to the design of other similar instruments.

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