GROWTH OF AU ON NI(110) - A SEMIEMPIRICAL MODELING OF SURFACE ALLOY PHASES

Recent experiments using scanning tunneling microscopy show evidence for the formation of surface alloys of otherwise immiscible metals. Such is the case for Au deposited in Ni(110), where experiments by Pleth Nielsen et al. [Phys. Rev. Lett. 71, 754 (1993)] indicate that at low Au coverage (<0.5 ML), Au atoms replace Ni atoms in the surface layer forming a surface alloy while the Ni atoms form islands on the surface. In this paper, we present results of a theoretical modeling of this phenomenon using the recently developed Bozzolo-Ferrante-Smith method for alloys. We provide results of an extensive analysis of the growth process that strongly support the conclusions drawn from the experiment: at very low coverages, there is a tendency for dimer formation on the overlayer, which later exchange positions with Ni atoms in the surface layer, thus accounting for the large number of substituted dimers. Ni island formation as well as other alternative short-range-order patterns are discussed. © 1995 The American Physical Society.