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

A review is presented of Synchrotron White Beam X-ray Topography (SWBXT) studies of stacking faults observed in PVT-Grown 4H-SiC crystals. A detailed analysis of various interesting phenomena were performed and one such observation is the deflection of threading dislocations with Burgers vector c/c+a onto the basal plane and associated stacking faults. Based on the model involving macrostep overgrowth of surface outcrops of threading dislocations, SWBXT image contrast studies of these stacking faults on different reflections and comparison with calculated phase shits for postulated fault vectors, has revealed faults to be of basically four types: (a) Frank faults; (b) Shockley faults; (c) Combined Shockley + Frank faults with fault vector s+c/2; (d) Combined Shockley + Frank faults with fault vector s+c/4.

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.897.209 ◽

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.

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Microstructure and Physical Properties of Clay-Polymer Composites

MRS Proceedings ◽

10.1557/proc-628-cc11.14 ◽

2000 ◽

Vol 628 ◽

Author(s):

T.N. Blanton ◽

D. Majumdar ◽

S.M. Melpolder

Keyword(s):

Composite Materials ◽

Physical Properties ◽

Polymer Composites ◽

Basal Plane ◽

X Ray Diffraction ◽

X Ray ◽

Layered Clay

ABSTRACTClay-polymer nanoparticulate composite materials are evaluated by the X-ray diffraction technique. The basal plane spacing provided information about the degree of intercalation and exfoliation of the 2: 1 layered clay structure. Both intercalation and exfoliation are controlled by the identity of the polymer and the clay:polymer ratio.

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Synchrotron X-Ray Topography Study on the Relationship between Local Basal Plane Bending and Basal Plane Dislocations in PVT-Grown 4H-SiC Substrate Wafers

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1004.393 ◽

2020 ◽

Vol 1004 ◽

pp. 393-400

Author(s):

Tuerxun Ailihumaer ◽

Hongyu Peng ◽

Balaji Raghothamachar ◽

Michael Dudley ◽

Gilyong Chung ◽

...

Keyword(s):

Basal Plane ◽

Local Strain ◽

Grazing Incidence ◽

Peak Shift ◽

Linear Mapping ◽

Incidence Geometry ◽

Convex Shape ◽

X Ray ◽

Black And White ◽

Plane Bending

Synchrotron monochromatic beam X-ray topography (SMBXT) in grazing incidence geometry shows black and white contrast for basal plane dislocations (BPDs) with Burgers vectors of opposite signs as demonstrated using ray tracing simulations. The inhomogeneous distribution of these dislocations is associated with the concave/convex shape of the basal plane. Therefore, the distribution of these two BPD types were examined for several 6-inch diameter 4H-SiC substrates and the net BPD density distribution was used for evaluating the nature and magnitude of basal plane bending in these wafers. Results show different bending behaviors along the two radial directions - [110] and [100] directions, indicating the existence of non-isotropic bending. Linear mapping of the peak shift of the 0008 reflection along the two directions was carried out using HRXRD to correlate with the results from the SMBXT measurements. Basal-plane-tilt angle calculated using the net BPD density derived from SMBXT shows a good correlation with those obtained from HRXRD measurements, which further confirmed that bending in basal plane is caused by the non-uniform distribution of BPDs. Regions of severe bending were found to be associated with both large tilt angles (95% black contrast BPDs to 5% white contrast BPDs) and abrupt changes in a and c lattice parameters i.e. local strain.

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

RSC Advances ◽

10.1039/c4ra14140g ◽

2014 ◽

Vol 4 (110) ◽

pp. 64608-64616 ◽

Cited By ~ 5

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.

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X‐ray study of Kr and Xe adsorbed on the basal plane of nickel chloride

The Journal of Chemical Physics ◽

10.1063/1.454623 ◽

1988 ◽

Vol 88 (1) ◽

pp. 451-456 ◽

Cited By ~ 5

Author(s):

K. Morishige ◽

M. Hanayama ◽

S. Kittaka

Keyword(s):

Basal Plane ◽

Nickel Chloride ◽

X Ray

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

Japanese Journal of Applied Physics ◽

10.1143/jjap.40.l884 ◽

2001 ◽

Vol 40 (Part 2, No. 8B) ◽

pp. L884-L887 ◽

Cited By ~ 5

Author(s):

Riichirou Negishi ◽

Masami Yoshizawa ◽

Shengming Zhou ◽

Isao Matsumoto ◽

Tomoe Fukamachi ◽

...

Keyword(s):

Resonant Scattering ◽

Image Contrast ◽

Lattice Defects ◽

X Ray

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

Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XXIII ◽

10.1117/12.2596422 ◽

2021 ◽

Author(s):

Takumi Hotta ◽

Katsuyuki Takagi ◽

Takeru Goto ◽

Akifumi Koike ◽

Yukino Imura ◽

...

Keyword(s):

Imaging System ◽

Image Contrast ◽

X Ray

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

Journal of Synchrotron Radiation ◽

10.1107/s1600577518008056 ◽

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.

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