Epitaxy and thick-film formation on an attractive substrate: The systematics of a lattice-gas model

Abstract

A lattice-gas model consisting of an inert attractive substrate and an adatom gas with nearest-neighbor repulsion and next-nearest-neighbor attraction is studied by mean-field and Monte Carlo methods. Epitaxial (sublattice-ordered) phases appear in the surface phase diagram and it is possible to examine in this context the interplay between film formation (layering and wetting) and lateral ordering (epitaxy). For a given adatom/substrate pair, film buildup proceeds in the usual way, except that regions of epitaxy appear in the surface phase diagram. Strong enough substrate attraction produces high-density, compressed layers and quenches epitaxy. Because of the adatom-adatom nearest-neighbor repulsion, this compression can lead to a nonmonotonic dependence of wetting behavior on substrate strength and even to complete dewetting at $T=0\mathrm{}$ for certain strong substrates. The relation of these phenomena to various experimental observations is discussed.