We have studied the decay of two-dimensional Ag islands on Ag(111) at room temperature by scanning tunneling microscopy. The results are in accordance with the classical continuum theory used to describe the time evolution of cluster sizes in an ensemble of clusters (Ostwald ripening), but they do not follow the simple power laws commonly used as limiting expressions of the classical theory. We show that deviations from the simple behavior are, in fact, expected for the island sizes studied ( $<5000\mathrm{}$ atoms) and for reasonable values of line tensions on metal surfaces.

• Received 6 November 1995

DOI:https://doi.org/10.1103/PhysRevLett.76.2113