Theoretical prediction of new dissolution modes during metal heteroepitaxy

By means of the kinetic tight-binding Ising model we investigate the Ni/Ag dissolution modes resulting from the thermal interdiffusion between the two elements. For a thin deposit (1 ML) we show that the dissolution proceeds by the formation of encapsulated Ni precipitates covered by two pure Ag mon olayers. For a thick deposit (10 ML) we find two distinct layer-by-layer mo des depending on the annealing temperature. At high temperature the kinetic s start with the apparition of capping Ag monolayers on a buried almost int act Ni him (surfactant-layer-by-layer mode). Below a critical temperature T -c the dissolution proceeds without any Ag surface enrichment (layer-by-lay er mode). We find that T-c decreases when the surface driving forces which favour the segregation of the substrate elements increase. (C) 1999 Elsevie r Science B.V. All rights reserved.