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, Λ, that represented the ratio of the rate of surface diffusion to the rate of deposition. It was found for large values of Λ that the deposit grew at the monatomic step edges, whereas for small values of Λ 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.