CBR4 VAPOR GROWTH MORPHOLOGIES NEAR THE POLYMORPHIC TRANSITION POINT .1. SINGLE-CRYSTALS

The morphology of CBr4 single crystals was investigated during growth from the vapor with high resolution microscopy and image processing. We observed the rounding of corners and edges with increasing temperature at fixed supersaturation, on approaching but distinctively below the monoclinic-to-cubic phase transition. As the supersaturation was increased at fixed crystal temperature, the thermally rounded features resharpened. This rounding and resharpening could successively be induced with increases in temperature and supersaturation, respectively. In addition to the rounding of features formed by pre-existing facets, new facets formed on temperature increase. These findings are interpreted in terms of surface roughening theory and computer simulation results.