Phase-field crystal modeling of shape transition of strained islands in heteroepitaxy

The phase-field crystal(PFC) model is employed to study the shape transition of strained islands in heteroepitaxy on vicinal substrates.The influences of both substrate vicinal angles β and the lattice mismatch ξ are discussed.The increase of substrate vicinal angles is found to be capable of significantly changing the surface nanostructures of epitaxial films.The surface morphology of films undergoes a series of transitions that include Stranski-Krastonov(SK) islands,the couple growth of islands and the step flow as well as the formation of step bunching.In addition,the larger ξ indicates an increased strained island density after coarsening,and results in the incoherent growth of strained islands with the creation of misfit dislocations.Coarsening,coalescence and faceting of strained islands are also observed.Some facets in the shape transition of strained islands are found to be stable and can be determined by β and crystal symmetry of the film.