Brownian motion of vacancy islands on Ag(111)

The motion of monatomic deep vacancy islands on crystal surfaces is studied both theoretically and experimentally. A new theoretical model was developed which allows the microscopic mechanism of mass transportation to be developed from measuring the diffusion coefficients of the vacancy islands as a function of their size. This model is applied to experimental results obtained with a fast scanning tunneling microscope on Ag(111) at room temperature. The observed scaling is consistent with a mechanism where the microscopic mass transport is dominated by diffusion of adatoms across the vacancy island rather than along the island boundary.