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

K.Morgenstern, G.Rosenfeld, B.Poelsema, G.Comsa: Physical Review Letters, 1995, 74[11], 2058-61