PREDICTED GROWTH MODE FOR METAL HOMOEPITAXY ON THE FCC(111) SURFACE

In an attempt to understand homoepitaxial growth on fee (111) surfaces , the potential energy barriers for both inter- and intralayer diffusi on are calculated for Ag, Au, Cu, Ni, Pd and Pt using a corrected effe ctive medium theory in its simplest form, namely MD/MC-CEM theory. The se metals exhibit two different characteristic behaviors, classified b y the relative magnitude of the barriers between the two kinds of diff usion: (i) for Ag, Au, Cu and Ni, the interlayer diffusion barrier is always larger than the intralayer one, even for small islands or near kink sites at step edges; and (ii) for Pd and Pt, the reverse situatio n is true, with the interlayer diffusion barrier decreasing further fo r small islands or near a kink site. We therefore predict that under ' 'natural'' conditions, the first group of metals will grow three-dimen sionally over the whole temperature range until the step-flow regime i s reached. In particular, re-entrant growth is not expected to occur a t low temperatures. By contrast, for the second group of metals we pre dict that a two-dimensional growth regime exists below step-flow, and re-entrant layer-by-layer growth is possible at low temperature due to the extremely low barrier for small islands or near kink sites. These predictions are consistent with all available experiments, which have investigated the AE, Cu and Pt systems. We suggest that further exper iments are desirable, in particular for Pd growth on Pd(111). We also point out that the reduced barriers for interlayer diffusion, due to t he small size of the island and to the presence of kinks, have a commo n physical origin.