Impact of surface phase coexistence on the development of step-free areas on Si(111)

The step-flow growth condition of Si on Si(111) near the (7×7)-"1×1" surface phase transition temperature T_C are analyzed within the framework of Burton--Cabrera--Frank theory. In particular, coexistence of both surface phases well below T_C and their specific influence on the step-flow growth behavior are considered. We presume that under dynamical condition of growth, the surface initially covered by only the (7×7) phase separates into domains surrounded by "1×1" areas. On such a surface, the overall supersaturation should be reduced drastically compared to a surface with only (7×7), resulting in much larger critical terrace width for nucleation.