MBE Alloy Clustering Kinetics - A Stochastic Model Study

Abstract

ABSTRACTA theoretical study of alloy clustering in an hypothetical diamond cubic alloy, 00.560.5 in which thermodynamics favors phase separation is performed based on a master equation approach. The a-b atom pair interaction is assumed weaker and repulsive (-0.25 eV). It is shown that below 375°C, due to negligible surface migration, there is no clustering of the alloy, but, the surface roughness is very large. In the intermediate temperature range of 300 – 625°C, with increasing temperature, surface migration increases, resulting in more clustering and decreased surface roughness. Above 500°C, due to very high surface migration, complete phase separation and smooth surface result. It is shown that the conventional MBE growth techniques are incompatible with the growth of good quality heterostructures which consist of alloys having large poistive enthalpy of mixing.