Synchrotron white-beam topographic studies of 2H-SiC crystals

Synchrotron white beam X-ray topography (SWBXT) has been used to characteri ze 2H-silicon carbide crystals grown by the chemical reduction of methyltri chlorosilane at 1400 degreesC. The crystals studied had the form of tapered needles around 1 mm long with hexagonal cross-sections 0.4 mm in diameter. SWBXT images recorded from two different crystals showed their excellent q uality, as evidenced by the presence of Pendellosung fringes. Topographs re corded with various diffraction vectors revealed no evidence of the axial s crew dislocations reported in 2H-SiC by Setaka and Ejiri, based on their ob servations of spiral growth steps. Neither were there any dislocations with Burgers vectors lying in the crystals' basal planes. The absence of axial screw dislocations indicates that the growth was not screw dislocation assi sted, but occurced by diffusion-controlled growth; and some other influence such as thermodynamics, initial nucleation, and/or impurity assisted growt h, was responsible for the isolation of the 2H polytype. (C) 2001 Published by Elsevier Science B.V.