Influence of short-range adatom-adatom interactions on the surface diffusion of Cu on Cu(111)

Abstract

The EAM potential set up by Mishin et al. [Phys. Rev. B 63 224106 (2001)] is used to study some elementary processes in the homoepitaxy of $\mathrm{Cu}$ on $\mathrm{Cu}(111)$. After having checked its ability to reproduce surface physical quantities, this potential is applied to an investigation of the energetics, the vibrations and the surface diffusion of ${\mathrm{Cu}}_{N}$ close-packed adislands $(1\ensuremath{\leqslant}N\ensuremath{\leqslant}7)$. In each case we determine the most stable configurations, the corresponding activation barriers, the local vibrational spectra, and the Vineyard prefactors. In particular it is found that, at room temperature, dimers and trimers are still very mobile and move by concerted jumps much faster than tetramers while heptamers can be considered as immobile. The very good agreement of our results with scanning tunneling microscopy observations justifies the use of Mishin et al. potential for treating surface diffusion. This allowed us to study in details the influence of the lateral atomic environment of the adatoms along its diffusion path. An effective lateral pair interaction model is set up which is able to predict the existence of a saddle point along the path and to give a very good estimation of the activation barrier height. This model will be very useful in kinetic Monte Carlo simulations of homoepitaxial growth of $\mathrm{Cu}(111)$.