Monte Carlo simulation of kinetically limited electrodeposition on a surface with metal seed clusters

Kinetic Monte Carlo (KMC) simulations were carried out to simulate kinetic-limited electrodeposition of a metal (M) onto an array of pre-existing metal clusters on a substrate (S) of a second conducting material. Electrochemical reaction and surface diffusion were accounted for in a KMC code which tracked deposit growth with a (2+1)-dimensional approach. Beginning with various arrangements of ten-atom metal seed clusters on a substrate platform of 300 × 300 fcc lattice sites, KMC simulations were carried out to investigate the evolution of the surface morphology. The influence of the number (spacing) of pre-existing seed clusters, the applied potential, and the metal-substrate surface diffusion energy barrier were investigated. It was found that when 16 or fewer seed clusters were present on the surface prior to electrodeposition, the resulting nucleation distribution was dominated by secondary nuclei formed during deposition. For substrates with a metal-substrate surface diffusion energy barrier greater than 3.5 × 10^-20 J, it was more difficult to control the uniform growth of the seed clusters owing to the nucleation of secondary clusters. At lower applied potentials it was found that larger nuclei could be grown with a more controlled size distribution because fewer secondary nuclei were formed. Furthermore, it was found that larger clusters with a more controlled size distribution can be grown when more clusters are seeded onto the surface because the deposited atoms were more likely to attach to existing clusters, than to form secondary nuclei.