IMPURITY BLOCKING OF GROWTH STEPS - EXPERIMENTS AND THEORY

According to an early model by Cabrera and Vermilyea, a low density of immobile impurities, adsorbed on a crystal surface may block step pro pagation completely at low supersaturations. This phenomenon of a ''de ad zone'' for crystal growth has been studied experimentally by in sit u measurements of the velocity of [100] steps on (001) K2Cr2O7 growing from aqueous solution as a function of supersaturation and temperatur e. Theoretical studies were carried out for [100] steps on the (001) f ace of a Kossel crystal, using the Monte Carlo technique. An overview of recent results and some implications for the science of crystal gro wth are given.