An "inverse" growth of Ag(111) on Cu(001) obtained by superficial segregation

We report the existence of layering transitions induced by superficial segr egation in Cu(Ag)(001). Moreover, Monte Carlo (MC) simulations in conjuncti on with a N-body potential show that these chemical transitions are coupled with structural ones. Thus, the first three surface planes transform succe ssively from almost pure Cu planes with a (1 x 1) square structure to almos t pure Ag planes with a pseudo-hexagonal c(IO x 2) superstructure. We find a large hysteresis effect for the transitions affecting the surface underla yers, partly due to the difficulty to re-incorporate a given number of adat oms during the reverse transition c(10 x 2) --> (I x 1). A matching of the MC results on a lattice gas model allows us to discuss the relative influen ce of the chemical effect and of the structural one on the layering transit ions. (C) 2001 Elsevier Science B.V. All rights reserved.