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Title: Direct Determination of Dislocation Sense of Closed-Core Threading Screw Dislocations using Synchrotron White Beam X-ray Topography in 4H Silicon Carbide

Abstract

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 synchrotron white beam x-ray topography.

Authors:
;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
959623
Report Number(s):
BNL-82609-2009-JA
Journal ID: ISSN 0003-6951; APPLAB; TRN: US1005767
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 91
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 43 PARTICLE ACCELERATORS; BRAGG REFLECTION; DISLOCATIONS; SCREW DISLOCATIONS; SILICON CARBIDES; SYNCHROTRONS; TOPOGRAPHY; national synchrotron light source

Citation Formats

Chen,Y., and Dudley, M. Direct Determination of Dislocation Sense of Closed-Core Threading Screw Dislocations using Synchrotron White Beam X-ray Topography in 4H Silicon Carbide. United States: N. p., 2007. Web. doi:10.1063/1.2793705.
Chen,Y., & Dudley, M. Direct Determination of Dislocation Sense of Closed-Core Threading Screw Dislocations using Synchrotron White Beam X-ray Topography in 4H Silicon Carbide. United States. doi:10.1063/1.2793705.
Chen,Y., and Dudley, M. Mon . "Direct Determination of Dislocation Sense of Closed-Core Threading Screw Dislocations using Synchrotron White Beam X-ray Topography in 4H Silicon Carbide". United States. doi:10.1063/1.2793705.
@article{osti_959623,
title = {Direct Determination of Dislocation Sense of Closed-Core Threading Screw Dislocations using Synchrotron White Beam X-ray Topography in 4H Silicon Carbide},
author = {Chen,Y. and Dudley, M.},
abstractNote = {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 synchrotron white beam x-ray topography.},
doi = {10.1063/1.2793705},
journal = {Applied Physics Letters},
number = ,
volume = 91,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • 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 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 discernedmore » 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.« less
  • Individual screw dislocations along the [0001] axis in 6H-SiC single crystals have been characterized by means of Synchrotron White Beam X-ray Topography (SWBXT). The magnitude of the Burgers vector was determined from: (1) the diameter of circular diffraction-contrast images of dislocations in back-reflection topographs, (2) the width of bi-model images associated with screw dislocations in transmission topographs, (3) the magnitude of the tilt of the lattice planes on both sides of dislocation core in projection topographs, and (4) also the magnitude of the tilt of the lattice planes in section topographs. All of the four methods showed reasonable consistency. Themore » sense of the Burgers vector can also be deduced from the above-mentioned tilt of the lattice planes. Results revealed that in 6H-SiC a variety of screw dislocations can be found with Burgers vector magnitude ranging from 1c to 7c (c is the lattice constant along [0001] axis). This work demonstrates that SWBXT can be used as a quantitative technique for detailed analyses of line defect configurations.« less
  • No abstract prepared.