Synchrotron X-Ray Topographic Image Contrast Variation of BPDs Located at Different Depths Below the Crystal Surface in 4H-SiC

2021 ◽  
Author(s):  
Fumihiro Fujie ◽  
hongyu peng ◽  
Tuerxun Ailihumaer ◽  
Balaji Raghothamachar ◽  
Michael Dudley ◽  
...  
Keyword(s):  
Crystal Surface ◽  
Image Contrast ◽  
Topographic Image ◽  
Contrast Variation ◽  
X Ray ◽  
Different Depths

Synchrotron X-ray topographic image contrast variation of screw-type basal plane dislocations located at different depths below the crystal surface in 4H-SiC

2021 ◽  
pp. 116746
Author(s):  
Fumihiro Fujie ◽  
Hongyu Peng ◽  
Tuerxun Ailihumaer ◽  
Balaji Raghothamachar ◽  
Michael Dudley ◽  
...  
Keyword(s):  
Basal Plane ◽  
Crystal Surface ◽  
Image Contrast ◽  
Topographic Image ◽  
Contrast Variation ◽  
X Ray ◽  
Different Depths

Resolving the Discrepancy between Observed and Calculated Penetration Depths in Grazing Incidence X-Ray Topography of 4H-SiC Wafers

2017 ◽  
Vol 897 ◽  
pp. 209-213
Author(s):  
Yu Yang ◽  
Jian Qiu Guo ◽  
Balaji Raghothamachar ◽  
Michael Dudley ◽  
Gil Yong Chung ◽  
...  
Keyword(s):  
Crystal Surface ◽  
Grazing Incidence ◽  
Incidence Geometry ◽  
Formation Mechanisms ◽  
Displacement Fields ◽  
X Ray ◽  
Orientation Contrast ◽  
Different Depths ◽  
Ray Tracing Simulation ◽  
Penetration Depths

Synchrotron X-ray Topography with grazing incidence geometry is useful for discerning defects at different depths below the crystal surface, particularly for 4H-SiC epitaxial wafers. However, the penetration depths measured from X-ray topographs are much larger than the theoretical values. In order to interpret this discrepancy, we simulate topographic contrast of dislocations based on two of the most basic contrast formation mechanisms – orientation contrast and kinematical contrast. Orientation contrast considers merely the displacement fields associated with dislocations while kinematical contrast also takes the diffraction volume into account. The diffraction volume is defined by the effective misorientation around dislocations and the rocking curve width for particular diffraction vector. Ray Tracing Simulation has been carried out to visualize dislocation contrast for both models, taking into account the photoelectric absorption of X-ray beams inside the crystal. Results show that orientation contrast plays the key role in determining both the contrast and X-ray penetration depths for different types of dislocations.

scholarly journals Redox-driven atomic-scale changes in mixed catalysts: VOX/WOX/α-TiO2 (110)

RSC Advances ◽  
2014 ◽  
Vol 4 (110) ◽  
pp. 64608-64616 ◽  
Author(s):  
Z. Feng ◽  
M. E. McBriarty ◽  
A. U. Mane ◽  
J. Lu ◽  
P. C. Stair ◽  
...  
Keyword(s):  
Single Crystal ◽  
Crystal Surface ◽  
Oxide Catalysts ◽  
Atomic Scale ◽  
Redox Behavior ◽  
Single Crystal Surface ◽  
Tungsten Oxides ◽  
Mixed Monolayer ◽  
X Ray

X-ray study of vanadium–tungsten mixed-monolayer-oxide catalysts grown on the rutile α-TiO2 (110) single crystal surface shows redox behavior not observed for lone supported vanadium or tungsten oxides.

Image Contrast of Lattice Defects in X-Ray Topography by Resonant Scattering

2001 ◽  
Vol 40 (Part 2, No. 8B) ◽  
pp. L884-L887 ◽  
Author(s):  
Riichirou Negishi ◽  
Masami Yoshizawa ◽  
Shengming Zhou ◽  
Isao Matsumoto ◽  
Tomoe Fukamachi ◽  
...  
Keyword(s):  
Resonant Scattering ◽  
Image Contrast ◽  
Lattice Defects ◽  
X Ray

Simplification of imaging system for estimating changes in image contrast due to different weighting of x-ray energy

2021 ◽  
Author(s):  
Takumi Hotta ◽  
Katsuyuki Takagi ◽  
Takeru Goto ◽  
Akifumi Koike ◽  
Yukino Imura ◽  
...  
Keyword(s):  
Imaging System ◽  
Image Contrast ◽  
X Ray

Characterization and on-line adjustment of the sagittal-bent Laue crystal profile

2018 ◽  
Vol 25 (5) ◽  
pp. 1346-1353
Author(s):  
Weiwei Dong ◽  
Quan Cai ◽  
Fugui Yang ◽  
Xu Liu ◽  
Jiaowang Yang ◽  
...  
Keyword(s):  
Ray Tracing ◽  
Crystal Surface ◽  
Great Influence ◽  
High Energy ◽  
Double Crystal ◽  
X Ray ◽  
Bent Crystal ◽  
On Line ◽  
Condition Adjustment ◽  
Anticlastic Curvature

The sagittal-bent Laue monochromator can provide an ideal way to focus high-energy X-ray beams. However, the anticlastic curvature induced by sagittal bending has a great influence on the crystal performance. Thus, characterizing the bent-crystal shape is very important for predicting the performance of the bent-crystal monochromator. In this paper the crystal profile is measured by off-line optical metrology and on-line X-ray experiments. The off-line results showed that the bent-crystal surface could be well fitted to a saddle surface apart from a redundant cubic term which was related to the different couples applied on the crystal. On-line characterization of the meridional and the sagittal radius of the bent crystal includes double-crystal topography and ray-tracing measurement. In addition, the double-crystal topography experiment could be used as a quick diagnostic method for the bending condition adjustment. The sagittal radius of the bent crystal was characterized through a ray-tracing experiment by using a particularly designed tungsten mask. Moreover, rocking curves under different bending conditions were measured as well. The results were highly consistent with analytical results derived from the elastic theory. Furthermore, radii along different vertical positions under various bending conditions were measured and showed a quadratic relationship between the vertical positions and the meridional radii.

Investigation on Large-Sized Sapphire Crystalline Perfection by X-Ray Double-Crystal Diffraction Method

2007 ◽  
Vol 353-358 ◽  
pp. 1521-1524 ◽  
Author(s):  
Gui Gen Wang ◽  
Ming Fu Zhang ◽  
Hong Bo Zuo ◽  
Xiao Dong He ◽  
Jie Cai Han ◽  
...  
Keyword(s):  
Simulation Analysis ◽  
Crystal Surface ◽  
Diffraction Method ◽  
Sapphire Crystal ◽  
Crystalline Perfection ◽  
Double Crystal ◽  
X Ray ◽  
Infrared Spectral ◽  
Growth Method ◽  
Small Temperature Gradient

The large-sized sapphire (Ø225×205 mm, 27.5 kg) was grown successfully by SAPMAC method (sapphire growth technique with micro-pulling and shoulder-expanding at cooled center). The surface quality of the specimens was characterized by micro-Raman spectroscopy, and double crystal X-ray diffractometry (DCD) was utilized to investigate its crystalline perfection. The measurement of rocking curves was performed on various specimens from different region of large sapphire boule. The experimental results showed that CMP (chemo-mechanical polishing) with subsequent suitable chemically etching can develop the best-quality sapphire crystal surface and the values of FWHM obtained by conventional DCD were in the range from 27” to 58”. The infrared spectral transmission (2.0-4.5 5m) of sapphire crystal exceeded 82%. It is confirmed of SAPMAC growth method characteristics with in-situ annealing, small temperature gradient and low residual stress level by numerical simulation analysis.

Enhancement of image contrast by combination of neutron and X-ray radiography

1989 ◽  
Vol 22 (4) ◽  
pp. 246
Keyword(s):  
Image Contrast ◽  
X Ray

White matter imaging of ethanol-fixed rat brain by phase-contrast X-ray computed tomography

2021 ◽  
pp. 028418512110307
Author(s):  
Thet-Thet- Lwin ◽  
Akio Yoneyama ◽  
Shogo Kokubo ◽  
Hiroko Maruyama ◽  
Kazuyuki Hyodo ◽  
...  
Keyword(s):  
White Matter ◽  
Phase Contrast ◽  
Three Dimensional ◽  
Image Contrast ◽  
Cerebral White Matter ◽  
Tissue Fixation ◽  
X Ray ◽  
Density Values ◽  
X Ray Computed ◽  
Formalin Fixed

Background Phase-contrast X-ray computed tomography imaging (PCI) based on crystal X-ray interferometry can detect minute density differences within biological soft tissues without contrast agents. Ethanol fixation yields increased tissue-background density differences due to the dehydrating and delipidifying effects of ethanol. Purpose To obtain high image contrast of cerebral white matter structures in PCI, tissue fixation using ethanol and routinely used formalin have been examined. Material and Methods Ethanol-fixed (EF) (n = 4) and formalin-fixed (FF) (n = 4) rat brains were imaged by crystal X-ray interferometry-based PCI. Tissue staining/microscopy was also performed for histological comparison and myelin density evaluation. Three-dimensional white matter tract images were reconstructed. Results Superior image contrast was obtained in the images of EF brains (EF images) compared to those of formalin-fixed brains (FF images), particularly for white matter structures. Significant density differences between the white matter structures and hippocampus ( P < 0.01)/thalamus ( P < 0.001) were observed in the EF, but not FF, images. Ethanol fixation enhanced the image contrast of white matter tracts by approximately sixfold compared to formalin fixation, and close agreement (r2 = 0.97; P < 0.05) between the density values on the CT images and the myelin density values in histological images was observed for the EF brains. Three-dimensional reconstruction of the white matter tracts was possible from the EF images, but not FF images. Conclusion Ethanol fixation resulted in marked contrast enhancement of cerebral white matter structures in PCI. Thus, high-resolution PCI using ethanol for tissue fixation could be valuable for experimental neurological studies and postmortem neuropathology evaluation.

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