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

摘要

We report the existence of layering transitions induced by superficial segregation in Cu(Ag)(001). 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 x 1) square structure to almost pure Ag planes with a pseudo-hexagonal c(IO x 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 x 2) --> (I x 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. (C) 2001 Elsevier Science B.V. All rights reserved. References: 24