LINK BETWEEN THE SURFACE WETTING IN CU(AG) AND THE LAYER-BY-LAYER DISSOLUTION MODE OF A THICK AG DEPOSIT ON A CU SUBSTRATE

Using a mean field approximation to an energetic model derived from the electronic structure, the tight binding Ising model (TBIM), we study the AgcCu1-c (111) system in the Ag dilute limit. We find an infinite succession of first-order phase transitions when the bulk concentration approaches the solubility limit c(alpha)(T): the planes parallel to the surface, starting from the surface layer, change from almost pure Cu to almost pure Ag. The range of bulk concentration in which these transitions occur can be explored kinetically during the dissolution of a sufficiently thick Ag deposit over the (111) surface of Cu. We model such a dissolution using a kinetic model (KTBIM) whose stationary state is consistent with the equilibrium one (TBIM). It leads to a hardly non-Fickian behaviour, i.e.: an unusual layer-by-layer dissolution mode. The link between kinetics and equilibrium has to be found in the equilibrium profile of the coherent interphase boundary between two phases of concentration 1 - c(alpha) and c(alpha) respectively.