Morphological instabilities of CBr₄ crystals during growth from vapors

We have studied the surface morphological instabilities of CBr₄ crystals during growth from vapors. We have found that the crystal-growth morphologies depend not only on temperature and supersaturation, but also sensitively on the total pressure of inert gas in the vapor. With increasing inert gas pressure, at otherwise the same growth conditions, crystals with initially smooth surfaces first develop cellular patterns and then evolve into dendritic structures. Although these cellulars and dendrites bear morphological similarity with those found in melt and solution-growth experiments (i.e., the product W²R=const, with W being either the width of a cellular or the radius of a dendritic tip, and R the growth rate at the corresponding solid front) the destabilizing mechanism appears to be more complex than that from bulk nutrient diffusion. We have found that the surface diffusion on the substrate also plays an important role in surface morphological instabilities in vapor crystal growth.