Effects of impurities on crystal growth processes

The mechanisms of adsorption of impurities during the growth of bulk crystals are surveyed. The impurities considered are foreign substances deliberately added to or inherently present in a growth medium. After a brief introduction to different growth models, the nature of impurities and types of impurity effects on growth kinetics, adsorption of impurities on F faces at relatively low and high impurity concentrations is first discussed. Here mechanisms of adsorption at kinks in steps and surface terrace in the presence of low concentrations of one impurity and two competitive impurities are presented. Then the concepts of adsorption of impurities involving the formation of two-dimensional in:purity layer and three-dimensional impurity clusters as growth promoters on a growing face are developed. Thereafter the mechanism of adsorption of impurities on S and K faces and the determination-of the adsorption mechanism on a growing face from the kinetic data are discussed, Finally, impurity effects on surface morphology of bulk crystals, and growth morphodroms of alkali halides are briefly reviewed. Copyright (C) 1996 Published by Elsevier Science Ltd