Influence of surfactants on atomic diffusion

We have used Monte Carlo simulations with realistic interatomic potentials, combined with experimental results obtained by He diffraction (thermal ene rgy atom scattering) and STM to investigate the effect of a surfactant agen t such as Pb on the mechanisms of atomic diffusion involved in epitaxial me tal growth. We find that the main role of the surfactant is to hinder fast diffusion by hopping over the surface, which is the dominant mechanism on a compact face such as Cu(111), and to promote exchange. As a side effect, t his facilitates interlayer diffusion and hence layer-by-layer growth, becau se islands are smaller and have rougher borders; adatoms reaching an edge h ave more opportunities to cross them by exchange with a step atom. (C) 2000 Elsevier Science B.V. All rights reserved.