The dynamics of a dense Pb wetting layer on the Si(111) surface was studied within the framework of a generalized Frenkel-Kontorova model. Instead of the typical diffusion by random hopping processes, a liquid-like collective motion of the Pb atoms within the dense wetting layer was found to give rise to ultra-fast kinetics of the wetting layer, even at low temperatures. A kinetic Monte Carlo simulation which included this collective spreading mechanism of the dense wetting layer quantitatively reproduced experimental observations.

Coverage-Dependent Collective Diffusion of a Dense Pb Wetting Layer on Si(111). L.Huang, C.Z.Wang, M.Z.Li, K.M.Ho: Physical Review Letters, 2012, 108[2], 026101