Dynamics of vacancy island coalescence on Ag(111)

The reshaping of two-dimensional vacancy islands during coalescence has been studied experimentally on a Ag(111) surface at room temperature using a fast scanning tunneling microscope. Different stages of the coalescence event have been found: the initial break-up of the narrow region separating the two islands (neck formation), the subsequent widening of the neck until an elongated shape has evolved, and the final relaxation to the equilibrium shape, which is an equilateral hexagon with rounded corners. The relaxation time for reshaping is found to be a strong function of the island size: for coalescence events involving islands of a similar size it scales roughly with the third to fourth power of the island diameter.