Equilibrium Shape and Size of Supported Heteroepitaxial Nanoislands

摘要

We study the equilibrium shape, shape transitions and optimal size ofstrained heteroepitaxial nanoislands with a two-dimensional atomistic modelusing simply adjustable interatomic pair potentials. We map out the globalphase diagram as a function of substrate-adsorbate misfit and interaction. Thisphase diagram reveals all the phases corresponding to different well-knowngrowth modes. In particular, for large enough misfits and attractive substratethere is a Stranski-Krastanow regime, where nano-sized islands grow on top ofwetting films. We analyze the various terms contributing to the total islandenergy in detail, and show how the competition between them leads to theoptimal shape and size of the islands. Finally, we also develop an analyticinterpolation formula for the various contributions to the total energy ofstrained nanoislands.