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