Step barrier effects during early stages of the kinetic roughening of fcc(111) surfaces

The influence of the additional Ehrlich-Schwoebel step barrier and temperature on the early stages of kinetic roughening and mound formation of fcc(111) surfaces is studied by means of kinetic Monte Carlo simulations. Increasing the Ehrlich-Schwoebel barrier, the growth mode develops from nearly layer-by-layer growth to statistical (Poisson) growth mode with the formation of wedding-cake-like shaped mounds. The evolution of the growth morphology is characterized by scaling laws with effective critical exponents. On the one hand, coarsening for growth without step barrier follows exponents n(eff) = 0.35 and beta(eff) = 0.20 for the characteristic lateral distance (coarsening exponent) and the rms roughness, respectively. On the other hand, coarsening is strongly suppressed for large step barriers (n(eff) = 0.05, beta(eff) = 0.52, Poisson growth) in agreement with different experimental results, e.g., for the formation of mounds during the homoepitaxy of Ag(111) and Pt(111). The lateral roughness on short distances is governed by the low roughness exponent a = 0.58 for all growth conditions independently of the growth mode.