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Published online by Cambridge University Press: 21 February 2011
The morphological instability of an epitaxially-strained, thin film is studied by means of a discrete atom method in a dislocation-free, two-dimensional crystal. The instability of the film-substrate interface is also examined in conjunction with the migration of the free surface. The results show that a mobile film-substrate interface can accelerate merger between the two surfaces, and anisotropic effects facilitate island formation. In addition, the instability of a curved interface is discussed with the results on the morphological evolution of coherent precipitates. A circular, soft precipitate in an isotropic matrix undergoes a series of shape transitions before reaching its equilibrium shape. As in the strained thin film case, transition begins with interfacial waves induced by the coherency strain. The waves then develop small lobes, which coarsen into a lower density of larger lobes. The larger lobes eventually coarsen as the equilibrium shape is approached. Anisotropic effects suppress some of the interfacial waves.