Vapor Growth Mechanism of a Crystal Surface Covered with a Quasi-liquid Layer - Effect of Self-diffusion Coefficient of the Quasi-liquid Layer on the Growth Rate

For several years, progress has been made in understanding surface melting as well as surface roughening of various crystals such as ice, lead, rare gases etc. A so-called quasi-liquid layer (QLL), caused by surface melting, is expected to influence the vapor growth mechanism of crystals at temperatures not far below their melting points. The effect of the self-diffusion coefficient D of a QLL on the growth rate is investigated in this study. It is shown that the condensation coefficient aQLL involved in the Hertz—Knudsen equation decreases with a decrease in D because of difficulty of rearrangement of molecules from QLL to crystal and this effect appears more clearly for crystals with larger equilibrium vapor pressure. The expression for the rate of spiral growth of the surface covered with QLL is also derived as a function of supersaturation.