Prefactors for interlayer diffusion on Ag/Ag(111)

Interlayer diffusion controls the transfer of atoms between layers in a film and is the 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 of temperatures provides similar values for the step edge barrier ΔEs but not for the ratio of the prefactors νs/νt where νt is the prefactor for diffusion on a terrace and νs the prefactor at 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 is found in the experiments done at a higher temperature (T ∼ 300 K). Since the conclusion νs/νt ∼ 1 is based on a steady state analysis of island decay, we examine whether this condition is fulfilled for Ag/Ag(111). We show that the low value of the terrace diffusion 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 an independent detachment model. Re-analysis of the data in terms of this model results also in νs/νt > 1, in good agreement with the low temperature experiments