Simulation of kinetically limited nucleation and growth at monatomic step edges

A kinetic Monte Carlo (KMC) numerical approach was used to investigate initial stages of kinetically controlled nucleation and growth on electrodes. Deposition, surface diffusion, nucleation, and growth were simulated for a pristine system consisting of metal ions in solution adjacent to a face-centered-cubic (fcc) surface that is initially configured with a series of parallel, monatomic step edges. Simulations were carried out with an atomic-scale, solid-on-solid KMC algorithm, in which the deposited atoms occupied the sites of a fcc lattice. One series of simulations was carried out for metal deposition onto a substrate of the same metal. The results were characterized according to a dimensionless quantity, Lambda, that represented the ratio of the rate of surface diffusion to the rate of deposition. It was found for large values of Lambda that the deposit grew at the monatomic step edges, whereas for small values of Lambda the step edges played no role in the nucleation of islands. A second series of simulations was carried out for deposition onto a foreign substrate. The growth modes associated with various combinations of system parameters was explored. (c) 2007 The Electrochemical Society.