It was recalled that the Ag-on-Ag(111) epitaxial system grew 3-dimensionally because of the existence of a relatively high excess diffusion barrier of 0.13eV at the step edges. Several experimental methods were developed in order to measure the step-edge barrier in this system, for a wide range of coverages. The probability of an atom moving from a higher to a lower layer depended upon both the barrier and the pre-factor, and it was therefore important to test whether the pre-factors for hopping over a step and for hopping on a terrace were different. The results of several experiments indicated that the ratio of the former pre-factor to the latter pre-factor was about 100.

Determination of Interlayer Diffusion Parameters for Ag/Ag(111). K.R.Roos, M.C.Tringides: Physical Review Letters, 2000, 85[7], 1480-3