Time evolution of a metallic ultra-thin film by surface electro-migration

Abstract

The morphological change of a thin film patch caused by surface electro-migration is investigated, with the use of a computer simulation based on the lattice gas model. In the Stranski-Krastanov mode the contribution of constituent atoms of an intermediate layer is also considered in the mass transport, in addition to adatoms on the intermediate layer. Three kinds of binding energies are introduced among atoms; between the intermediate layer and the substrate, between an adatom and the intermediate layer and between deposited atoms. The numerical results can explain well the difference observed in the behaviour for Ag/Si(111) and Ga/Si(111), and the criterion between the two kinds of behaviour is clarified. For Ga/Si(111) the effect of desorption is also considered. The surface electro-migration in the Volmer-Weber mode is studied for the first time, and the possibility of the diffusion motion of islands of deposited atoms directly on the substrate is found.