The subsurface damage generated by the polishing of silicon carbide crystals was investigated by measuring dislocation densities in sublimation grown SiC layers and through the use of high-resolution X-ray diffraction. Physical vapor transport growth on silicon carbide seeds, with a typical polishing finish using 1 m diamond paste, leads to the nucleation of threading edge dislocations of density on the order of 10 7 cm Ϫ2 and threading screw dislocations of density on the order of 10 6 cm Ϫ2 . Chemical mechanical polishing lowered the dislocation density by four orders of magnitude for threading screw dislocations and two orders of magnitude for threading edge dislocations. Controlled high temperature hydrogen etching was used to determine the depth of damage produced by mechanical polishing and it was found to be 700 Ϯ 300 Å. Diffuse scattering from mechanically polished, chemical mechanically polished, and hydrogen etched SiC crystals were quantified by triple axis high-resolution X-ray diffraction. A consistent trend of decreasing diffuse scattering intensity was observed in mechanically polished, chemical mechanically polished, and hydrogen etched surfaces. Root mean squared ͑rms͒ roughness measurements of the surface finishes, obtained with atomic force microscopy, were in agreement with the high-resolution X-ray diffraction results. The mechanically polished surfaces had an rms roughness that was two to three times larger than the chemical mechanically polished surfaces.

The recently appeared distorted wave Born approximation formalism is used for quantitative determination of interface roughness replication and lateral correlation length in periodical multilayered structures. The results obtained from x-ray diffraction are in very good agreement with analysis of cross-section transmission electron micrographs. We interpret transparently the obtained parameters and demonstrate the ability of the low-angle x-ray diffraction methodology for nondestructive and quantitative studying of interface roughness in magnetic multilayers.

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The subsurface damage generated by mechanical polishing of silicon carbide wafers was investigated and quantified by plan view transmission electron microscopy (TEM) and atomic force microscopy (AFM). Damage generated during polishing using diamond abrasives with 0.5 µm particle size consists of dislocation loops with length up to 400 nm from the scratches. The total dislocation density was estimated at 5 × 10 10 dislocations cm −2 . TEM analysis of the Burgers vectors indicates that the initial perfect dislocations have a Burgers vector of b = a/3 11-20 -type with many dislocation dissociated into two partials with b = a/3 1-100 . The depth of damage was estimated to be up to 50 nm. 4H-SiC homoepitaxial layers grown on mechanically polished substrates without further surface treatment exhibit threading dislocation density along scratches in the order of 10 5 cm −1 .

Growth rates and relative stability of 6H- and 4H-SiC have been studied as a function of growth conditions during Halide Chemical Vapor Deposition (HCVD) process using silicon tetrachloride, propane and hydrogen as reactants. The growth temperature ranged from 2000 to 2150 oC. Silicon carbide crystals were deposited at growth rates in the 100-300 μm/hr range in both silicon- and carbon-supply limited regimes by adjusting flows of all three reactants. High resolution x-ray diffraction measurements show that the growth on Si-face of 6H- and C-face of 4H-SiC substrates resulted in single crystal 6H- and 4H-SiC polytype, respectively. The growth rate results have been interpreted using thermodynamic equilibrium calculations.