Prefactors for interlayer diffusion on Ag/Ag(111)

Abstract

Interlayer diffusion controls the transfer of atoms between layers in a film and isthe key factor determining whether growth is layer-by-layer or two-dimensional.Analysis of recent experimental data on Ag/Ag(111) taken at two sets oftemperatures provides similar values for the step edge barrier ΔEsbut not for the ratio of the prefactors νs/νt where νtis the prefactor for diffusion on a terrace and νs the prefactorat a step edge site. A prefactor ratio larger than 1, νs/νt > 1,is extracted from the measurements at low temperature (T < 150 K),while νs/νt ∼ 1 isfound in the experiments done at a higher temperature (T ∼ 300 K).Since the conclusion νs/νt ∼ 1 isbased on a steady state analysis of island decay, we examine whether thiscondition is fulfilled for Ag/Ag(111). We show that the low value of the terracediffusion barrier on Ag(111) (Et ≈ 0.1 eV)offers an alternative interpretation to the steady state analysis, i.e.an independent detachment model. Alternatively, we propose anindependent detachment model. Re-analysis of the data in terms ofthis model results also in νs/νt > 1, ingood agreement with the low temperature experiments.