Activation energies for diffusion of small heteroepitaxial islands by nucleation and motion of a dislocation across the island are calculated using a Frenkel-Kontorova model. At “magic island sizes” the activation barriers for heteroepitaxial island diffusion are dramatically lowered. Total energy calculations and molecular dynamics simulations using the embedded atom method confirm the existence of a rapid diffusion process for two-dimensional islands. A signature of this process is a strongly temperature dependent activation energy for diffusion.

• Received 5 April 1996

DOI:https://doi.org/10.1103/PhysRevLett.77.885