ON A SURFACTANT-LIKE BEHAVIOR OF NI AG(100) DEPOSIT/

Auger experiments performed during the annealing at 620 K of one monol ayer of Ni, deposited at room temperature on a Ag(100) substrate, show a very rapid decrease of the Ni signal indicating an almost immediate disappearance of Ni atoms from the surface, whereas annealing at 770 K the reverse deposit Ag/Ni(100) does not lead to any dissolution of A g, even after a long time. This clearly non-Fickian behaviour can be u nderstood in terms of local equilibrium near the surface, by means of a recently developed microscopic kinetic model (KTBIM: kinetic tight-b inding Ising model) taking into account the driving forces of surface segregation. Moreover, the KTBIM simulation of the dissolution of addi tional Ni layers, successively deposited on Ag(100), reveals the exist ence of a ''floating'' Ag bi-layer which stays above the Ni deposit, a nalogous to a surfactant during semiconductor growth.