THE INVESTIGATION OF SILICON CARBIDE BY A TRAVELLING SOLVENT METHOD.
Final rept. 1 Mar 65-31 Jan 67,
TYCO LABS INC WALTHAM MASS
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The crystallization of SiC from molten alloy mixtures of Cr-SiC, Cr5-Si3-SiC, and CrSi2-SiC of varying compositions was investigated. The resulting crystals were analyzed for their polytype structure and crystal morphology. Cubic beta SiC was obtained preferably from dilute solutions in molten Cr5Si3 when rapidly cooled. The amount of alpha-SiC increased for slower cooling rates it was also greater for the other alloy mixtures. Structure identification was achieved by X-ray precession methods and by crystal morphology analysis. Etching in ClF3 gas at 400 C was used for the determination of polarity of SiC deposited from either molten alloy or from CH3SiCl3-H2 gaseous mixtures. This etch proved superior to previously used conventional etches in surface and dislocation studies. Epitaxial deposition was studied in detail with respect to substrate influence and structure propagation. Considerations on the crystal growth mechanism and on necessary requirements as dictated by morphology conditions are presented. It is stated that crystal growth and desired polytype formation can be well monitored by proper control of growth conditions as derived from morphology considerations, if it can be done at all. Author