WHAT DOES AN EVAPORATING SURFACE LOOK LIKE

The Burton, Cabrera and Frank model for step flow is discussed in the case of evaporation, taking into account vacancy formation. In this fr amework, the criterion for nucleation of polyvacancies (''Lochkeime'') on an evaporating vicinal surface with step-step separation l is foun d to be roughly kappal > betagamma, where gamma is the step stiffness, 1/kappa = square-root Dtau(v), D is the adatom diffusion constant, ta u(v) is the average residence time of adatoms on the surface before de sorption and 1/beta = k(B)T. Application to silicon is discussed.