A numerical study was made of the equilibrium shapes, shape transitions and dislocation nucleation of small strained epitaxial islands within a 2-dimensional atomistic model using simple interatomic pair potentials. The phase diagram for the equilibrium island shape, as a function of island size (up to 105 atoms) and lattice misfit with the substrate, was first mapped out. It was shown that nanoscopic islands had 4 generic equilibrium shapes, in contrast with the predictions of the continuum theory of elasticity. With increasing substrate-adsorbate attraction, islands were found that formed on top of a finite wetting layer; as observed in Stranski-Krastanow growth. The energy barriers and transition paths were also investigated for transitions between different shapes of the islands and for dislocation nucleation in initially coherent islands. It was found that dislocations nucleated spontaneously, at the edges of the adsorbate/substrate interface, above a critical size or lattice misfit.

Equilibrium Shape and Dislocation Nucleation in Strained Epitaxial Nano-Islands. J.Jalkanen, O.Trushin, E.Granato, S.C.Ying, T.Ala-Nissila: Physical Review B, 2005, 72[8], 081403 (4pp)