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Title: Sense Determination of Micropipes via Grazing-incidence Synchrotron White Beam X-ray Topography in 4H-Silicon Carbide

Abstract

Grazing-incidence synchrotron topography studies of micropipes (MPs) and closed-core threading screw dislocations (TSDs) have been carried out and the results compared with ray-tracing simulations. Simulations indicate that both MPs and TSDs appear as roughly elliptically shaped white features which are canted to one side or the other of the g-vector depending on the dislocation sense and which have asymmetric perimeters of dark contrast which are greatly enhanced on the side towards which the feature is canted (again depending on the dislocation sense). For MPs, observations are generally consistent with this although the cant of the features is more obviously discerned than the asymmetry in the perimeter contrast. Sense assignment for MPs has been validated using back-reflection reticulography. For TSDs, observation are again generally consistent with the simulations although the smaller feature size and the variability in the line direction of the TSDs make the asymmetry of perimeter contrast a more obvious and reliable way to determine the dislocation sense than the sense of cant. TSD dislocation senses so obtained were validated using back-reflection images of same-sign and opposite-sign pairs.

Authors:
; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
980447
Report Number(s):
BNL-93365-2010-JA
Journal ID: ISSN 0255-5476; MSFOEP; TRN: US1005499
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Science Forum; Journal Volume: 600-603
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ALLOCATIONS; ASYMMETRY; BEAMS; CARBIDES; DISLOCATIONS; IMAGES; SCREW DISLOCATIONS; SIZE; SYNCHROTRONS; TOPOGRAPHY; national synchrotron light source

Citation Formats

Chen, Y., Dudley, M, Sanchez, E, and MacMillan, M. Sense Determination of Micropipes via Grazing-incidence Synchrotron White Beam X-ray Topography in 4H-Silicon Carbide. United States: N. p., 2009. Web. doi:10.4028/www.scientific.net/MSF.600-603.297.
Chen, Y., Dudley, M, Sanchez, E, & MacMillan, M. Sense Determination of Micropipes via Grazing-incidence Synchrotron White Beam X-ray Topography in 4H-Silicon Carbide. United States. doi:10.4028/www.scientific.net/MSF.600-603.297.
Chen, Y., Dudley, M, Sanchez, E, and MacMillan, M. 2009. "Sense Determination of Micropipes via Grazing-incidence Synchrotron White Beam X-ray Topography in 4H-Silicon Carbide". United States. doi:10.4028/www.scientific.net/MSF.600-603.297.
@article{osti_980447,
title = {Sense Determination of Micropipes via Grazing-incidence Synchrotron White Beam X-ray Topography in 4H-Silicon Carbide},
author = {Chen, Y. and Dudley, M and Sanchez, E and MacMillan, M},
abstractNote = {Grazing-incidence synchrotron topography studies of micropipes (MPs) and closed-core threading screw dislocations (TSDs) have been carried out and the results compared with ray-tracing simulations. Simulations indicate that both MPs and TSDs appear as roughly elliptically shaped white features which are canted to one side or the other of the g-vector depending on the dislocation sense and which have asymmetric perimeters of dark contrast which are greatly enhanced on the side towards which the feature is canted (again depending on the dislocation sense). For MPs, observations are generally consistent with this although the cant of the features is more obviously discerned than the asymmetry in the perimeter contrast. Sense assignment for MPs has been validated using back-reflection reticulography. For TSDs, observation are again generally consistent with the simulations although the smaller feature size and the variability in the line direction of the TSDs make the asymmetry of perimeter contrast a more obvious and reliable way to determine the dislocation sense than the sense of cant. TSD dislocation senses so obtained were validated using back-reflection images of same-sign and opposite-sign pairs.},
doi = {10.4028/www.scientific.net/MSF.600-603.297},
journal = {Materials Science Forum},
number = ,
volume = 600-603,
place = {United States},
year = 2009,
month = 1
}
  • Computer modeling using the ray-tracing method has been used to simulate the grazing-incidence x-ray topographic images of micropipes in 4H silicon carbide recorded using the pyramidal (11-28) reflection. Simulation results indicate that the images of micropipes appear as white features of roughly elliptical shape, canted to one side or other of the g vector depending on the dislocation sense. Observed images compare well with the simulations, demonstrating that the direction of cant provides a simple, nondestructive, and reliable way to reveal the senses of micropipes. Sense assignment has been validated using back-reflection reticulography.
  • Grazing-incidence synchrotron white beam x-ray topography images of closed-core threading screw dislocations in 4H silicon carbide appear as roughly elliptically shaped white features, with an asymmetric perimeter of dark contrast which is greatly enhanced on one side or other of the g vector. Ray-tracing simulations indicate that the relative position of the enhanced dark contrast feature reveals the sense of the closed-core screw dislocation. Dislocation senses so obtained were validated using back-reflection images recorded with small Bragg angle. Therefore, the sense of the closed-core threading screw dislocations can be unambiguously revealed using either grazing-incidence or 'small Bragg angle' back-reflection synchrotronmore » white beam x-ray topography.« less
  • Detailed comparison has been drawn between synchrotron white beam X-ray topographic images of micropipes in 4H-SiC, recorded using pyramidal plane reflections in grazing-incidence geometry, and images simulated using the ray-tracing method. The simulations were carried out with and without the influence of surface relaxation effects. The images simulated in the absence of surface relaxation effects appear as white elliptical shaped features, canted to one side or other of the g-vector (depending on the dislocation sense), surrounded by a dark contrast perimeter which thickens at both ends of the major axis and which exhibits two fold symmetry axes parallel to themore » major and minor axes. On the other hand, on the images simulated taking into account the effects of surface relaxation, the features are again canted to one side or other of the g-vector (depending on the dislocation sense) but do not exhibit the same symmetry in that one of the sides of the oval shape is flattened (along the major axis) and the distribution of intensity around the perimeter no longer possesses the two fold symmetry axes parallel to the major and minor axes. While the details of the distribution of the dark perimeter contrast observed on the recorded images are not so easy to correlate with the simulated distributions, the sense of cant of the roughly elliptical white features on the observed images can be easily correlated with the simulations. Since the sense of cant has the same behavior as a function of dislocation sense for simulations carried out with and without surface relaxation, this provides a high level of confidence that the sense of cant of these features can be readily used to determine the senses of the micropipes.« less
  • Comparative studies of defect microstructure in 4H-SiC wafers have been carried out using photoluminescence (PL) imaging and grazing-incidence Synchrotron White Beam X-ray Topography. Images of low angle grain boundaries on the PL images correlate well with SWBXT observations, and similar correlation can be established for some micropipe images although the latter is complicated by the overall level of distortion and misorientation associated with the low angle grain boundaries and the fact that many of the micropipes are located in or close to the boundaries. This validation indicates that PL imaging may provide a rapid way of imaging such defect structuresmore » in large-scale SiC wafers.« less
  • Comparative studies of defect microstructure in 4H-SiC wafers have been carried out using photoluminescence (PL) imaging and grazing-incidence Synchrotron White Beam X-ray Topography. Images of low angle grain boundaries on the PL images correlate well with SWBXT observations, and similar correlation can be established for some micropipe images although the latter is complicated by the overall level of distortion and misorientation associated with the low angle grain boundaries and the fact that many of the micropipes are located in or close to the boundaries. This validation indicates that PL imaging may provide a rapid way of imaging such defect structuresmore » in large-scale SiC wafers.« less