Step-Edge Barriers on Pt(111): An Atomistic View

The escape of platinum from Pt(111) islands has been examined in the field ion microscope to obtain a direct view of atomic events. No effective barrier to the escape of platinum clusters larger than dimers is found at step edges, but incorporation of individual adatoms is nevertheless more effective at low temperatures. From the temperature dependence of the rate of atom disappearance from Pt(111) islands, the additional step-edge barrier is found as $0.06\pm 0.01\mathrm{eV}$, quite small compared with the diffusion barrier of 0.26 eV, and in sharp contrast with deductions from growth experiments.