The discovery of a 2H-3C solid state transformation in silicon carbide single crystals

Abstract

Needle-shaped single crystals of 2H (wurtzite type) SiC, grown by a vapour-liquid-solid mechanism, are transformed to the 3C (sphalerite type) structure on annealing in argon at temperatures above 1400°C. The temperature at which the structural transformation is induced varies from one crystal to another ranging from 1400°C to 1800°C. The structure of the crystals before and after the heat-treatment was identified by X-ray diffraction photographs. The discovery of this transformation explains the absence of the ABAB… packing in the structure of SiC polytypes formed at high temperatures above 2000°C and suggests that cubic SiC is the stable modification, at least over a temperature- range from 1400°C to about 1800°C.