Microstructure of the surfactantlike effect in Ni/Ag(100) and (111)

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Abstract
Recent experiments on Ni/Ag systems have shown that the growth mode can be a floating monosubstrate or bisubstrate layer burying the deposited film. We study this surfactant effect by both mean-field and Monte Carlo kinetic approaches. The kinetic tight-binding Ising model in mean-field approximation gives quasisteady profiles consistent with local equilibrium concepts. In this framework, we find two and one capping Ag monolayers for Ag(100) and Ag(111), respectively, on a mostly pure Ni monolayer. Monte Carlo simulations reveal that this Ni ``sandwich'' structure is in fact made of embedded Ni precipitates with low interface energy regular polyhedra shapes. The cluster distribution is found to be larger for the less compact surface [i.e., (100)] and to obey the ``Ostwald ripening'' law.