Diffusion and stability of small vacancy clusters on Cu(100) - A simulation study

The stability and mobility of small vacancy clusters on the Cu(1 0 0) surface has been investigated using temperature-accelerated dynamics simulation. The rate-limiting step for cluster dissociation is found to involve two-atom shearing, a mechanism previously discovered in the diffusion of small adatom islands. The tetramer vacancy cluster is found to be very stable and to have low diffusivity, suggesting that it may have an important role in the morphological evolution of growing surfaces. The filling of the tetramer vacancy cluster by single adatoms is also investigated, and the similarities to adatom accommodation at downward step-edges are highlighted.