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

Auger experiments performed during the annealing at 620 K of one monolayer 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 Ag, even after a long time. This clearly non-Fickian behaviour can be understood in terms of local equilibrium near the surface, by means of a recently developed microscopic kinetic model (KTBIM: kinetic tight-binding Ising model) taking into account the driving forces of surface segregation. Moreover, the KTBIM simulation of the dissolution of additional Ni layers, successively deposited on Ag(100), reveals the existence of a ''floating'' Ag bi-layer which stays above the Ni deposit, analogous to a surfactant during semiconductor growth.