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  • 1
    Electronic Resource
    Electronic Resource
    Direct evidence of micropipe-related pure superscrew dislocations in SiC (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 353-355 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A set of powerful x-ray imaging techniques using white-beam synchrotron radiation have been developed and applied to clearly reveal and map micropipes in SiC crystals at a "magnified" level. The experimental results and the corresponding simulations demonstrate explicitly that the micropipes are pure superscrew dislocations (SSDs). Moreover, these techniques provide accurate descriptions of the detailed structure of the SSDs, including the spatial distribution of the strain fields, the magnitudes of the Burgers vectors, the dislocation senses, and the surface relaxation effects. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123069
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  • 2
    Electronic Resource
    Electronic Resource
    X-ray topographic dislocation contrast visible in reflections orthogonal to the Burgers vectors of axial screw dislocations in hexagonal silicon carbide (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 34 (2001), S. 20-26 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Contrast is associated with micropipes in X-ray topographs of SiC crystals obtained with prismatic reflections, representing an apparent violation of the g·b = 0 invisibility criterion. This is explained as a population of basal-plane dislocations with Burgers vectors of the set b = {\textstyle{1 \over 3}}〈11{\bar{2}}0〉 that occur in a high density within a few micrometers of the micropipes, below the resolution of X-ray topography. These basal-plane dislocations could be observed under an electron microscope. The presence of the surfaces of the micropipes influences the dislocation images in the topographs taken with prismatic reflections, often resulting in a band of light contrast along the axes of the micropipes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889800017027
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  • 3
    Electronic Resource
    Electronic Resource
    Harmonic composition of synchrotron white-beam X-ray topographic back-reflection images of basal-cut silicon carbide single-crystal wafers (1998)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 31 (1998), S. 820-822 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Superscrew dislocations are visible in back-reflection synchrotron white-beam X-ray topographs of basal-cut SiC wafers in striking contrast as black rings surrounding white circles, even though such topographs suffer from extensive harmonic contamination. The contributions to the synchrotron white-beam topograph of each member of its series of harmonic reflections, {\bf g}=(0006n), where n=3 to 16, were calculated. Through intensity considerations and comparison with a {\bf g}=00018 topograph taken with Cu Kα1 radiation, the {\bf g}=00024 harmonic was determined to be the most important contributor. The contrast of features lying deep beneath the crystal's surface was attributed to higher harmonics with larger penetration depths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889898004683
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  • 4
    Electronic Resource
    Electronic Resource
    Superscrew dislocation contrast on synchrotron white-beam topographs: an accurate description of the direct dislocation image (1999)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 32 (1999), S. 516-524 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A kinematic (geometrical) diffraction simulation model has been developed to provide understanding of direct dislocation images on synchrotron white-beam X-ray topographs, and has been successfully applied to illustrate the contrast formation mechanisms involved in images of micropipe-related superscrew dislocations in silicon carbide crystals. The coincidence of the simulations with the contrast features of the superscrew dislocation images, recorded using a series of synchrotron topography techniques, shows that this model is capable of revealing the detailed diffraction behavior of the highly distorted region around the dislocation core and determining the quantitative characteristics of the dislocations. The simulation technique is thus demonstrated to be a simple but efficient method for interpretation of synchrotron topographs, and may be applied to explain the topographic contrast characters of general crystal defects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889899002939
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