Monte Carlo simulation applicable to the growth of rough metal overlayers: Parametric relationships related to the electrochemical roughening

Monte Carlo simulations of growth modes of overlayers built up from a finite number of particles randomly distributed in a confined space are presented. These results are applicable to the growth of metal overlayers on a metal substrate, particularly for an understanding of the development and the structure of the rough metal surfaces resulting from the electroreduction of metal-oxide layers. The roughness factor of the deposited overlayers increases with both the number and the sticking probability of depositing particles, and decreases on increasing their surface diffusion length. Otherwise, the roughness factor appears to be practically independent of the number of particles in the critical nucleus. The morphology of the deposits changes gradually from that of a compact cluster arrangement to that of a dendritic one. Correspondingly, the roughness factor increases considerably as either the sticking probability increases or the diffusion length decreases. Data obtained for the electrochemical growth of Au and Pt overlayers on metal surfaces as derived from combined scanning-tunneling-microscopy and scanning-electron-microscopy imaging are used to test the validity of the conclusions resulting from the Monte Carlo simulation.