It was recalled that, in hetero-epitaxy, thin-film growth proceeded in two-dimensional layer-by-layer, three-dimensional island, or layer-plus-island modes depending, upon the growth conditions. Interlayer mass transport played a crucial role in determining the growth mode. Interlayer diffusion of Au atoms from Au islands grown on Ir(111) was investigated using scanning tunneling microscopy and kinetic Monte Carlo simulation. The scanning tunneling microscopic measurements revealed that the first Au layer on Ir(111) grows in a complete layer at 100K, whereas the Au layer grows in a three-dimensional fashion from the second Au layer at this temperature. Annealing these surfaces to 300K reduced the higher-layer islands, indicating that Au atoms undergo step-down diffusion. By measuring the density of the top-layer islands and comparing them with the kinetic Monte Carlo simulation results, the additional step-down diffusion barrier for Au atoms to descend from the Au islands was estimated to be 0.02eV on the first Au layer and 0.04eV on the second Au layer. The layer dependence of the additional step-down diffusion barrier was explained in terms of the lattice mismatch between Au and underlying layers.

Interlayer Diffusion of Au Atoms in a Heteroepitaxial System. S.Ogura, K.Fukutani: Journal of Physics - Condensed Matter, 2009, 21[47], 474210