Synchrotron radiography and x-ray topography studies of hexagonal habitus SiC bulk crystals
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M.Yu. Gutkin Institute of Problems of Mechanical Engineering, Russian Academy of Sciences, St. Petersburg, Russia
Jung Ho Jea) and H.S. Kang Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, Korea
Y. Hwu and W-L. Tsai Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan, Republic of China
G. Margaritondo Institute de physique applique´e, Ecole Polytechnique Fe´de´rale de Lausanne, CH-1015 Lausanne, Switzerland (Received 16 March 2002; accepted 30 July 2002)
Phase-sensitive synchrotron radiation (SR) radiography was combined with x-ray diffraction topography to study structural defects of SiC crystals. The particular bulk SiC crystals examined had a low micropipe density and a hexagonal habitus composed of prismatic, pyramidal, and basal faces well developed. X-ray diffraction topography images of the sliced (0001) wafers, which were formed due to the complex lattice distortions associated with defective boundaries, demonstrated the existence of two-dimensional defective boundaries in the radial direction, normal to the (0001) planes. In particular, those parallel to the 〈112¯0〉 directions extended rather far from the seed. On the other hand, by phase-sensitive SR radiography the effect of micropipe collection was detected. Micropipes grouped mostly in the vicinities of the defective boundaries but rarely appeared between groups. Some general remarks about possible reasons for the development of such peculiar defect structures were made.
I. INTRODUCTION
Silicon carbide (SiC) attracts persistent research interest due to its unique electronic, thermal, mechanical, and other properties. The problem of manufacture of largesize single crystals free from structural defects, however, remains unsolved. The solution requires detailed investigations of the SiC structural quality, which is sensitive to growth conditions. For nondestructive purposes, these are typically done by x-ray methods. X-ray imaging techniques allow the visualization of lattice defects within a crystal interior. Synchrotron radiation (SR) x-ray imaging has advantages caused by very high intensities and good collimations of synchrotron beams. SR diffraction topography has already allowed to show, in SiC wafers of relatively high structural quality, the generation of a)
Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 17, No. 10, Oct 2002
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hollow core dislocations, or micropipes (MPs), and the formation of other polytype inclusions.1,2 Low divergence of the synchrotron beam at the Stony Brook Synchrotron Topography Facility made it possible to establish an accurate method to simulate the pure orientation contrast from super screw dislocations.3 High flux and high energy of the x-ray beams available at the European Synchrotron Radiation Facility (ESRF), together with the large beam size, permitted studying the whole volume of the bulky SiC ingots.2 Moreover, special properties of the third-gen
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