Reentrant morphological instability of epitaxial islands

The morphological stability of two-dimensional islands nucleated on a squar e-symmetry substrate during vacuum atom deposition is investigated by analy tic scaling arguments and kinetic Monte Carlo simulations. It is shown that nonequilibrium, dendritic-skeletal island shapes may he converted into com pact, equilibrium ones by increasing the deposition rate, in contrast with simple expectation. Our results imply that epitaxial islands generically sh ould undergo a reentrant morphological transition with varying deposition r ate. Stable, compact shares should in principle exist only at intermediate Values of the deposition rate. [S0163-1829(99)04848-1].