An “inverse” growth of Ag(1 1 1) on Cu(0 0 1) obtained by superficial segregation

Abstract

We report the existence of layering transitions induced by superficial segregation in Cu(Ag)(0 0 1). Moreover, Monte Carlo (MC) simulations in conjunction with a N-body potential show that these chemical transitions are coupled with structural ones. Thus, the first three surface planes transform successively from almost pure Cu planes with a (1×1) square structure to almost pure Ag planes with a pseudo-hexagonal c(10×2) superstructure. We find a large hysteresis effect for the transitions affecting the surface underlayers, partly due to the difficulty to re-incorporate a given number of adatoms during the reverse transition c(10×2)→(1×1). A matching of the MC results on a lattice gas model allows us to discuss the relative influence of the chemical effect and of the structural one on the layering transitions.