It was noted that transient enhanced diffusion, following ion implantation and annealing, was due largely to the formation of B-defect clusters. A search was made here for particularly stable B-defect clusters (up to B4I4). A tight-binding method, together with atomic-scale statics calculations, was used to study B and B-defect clusters which contained up to four B atoms and 4 self-interstitials within a matrix of crystalline Si. There was found to be a tendency to form a 4-atom ring which contained two Si self-interstitials and two B atoms. A general principle governing the stability of the cluster geometry was a maximization of the number of unstrained bonds (that is, those having Si-like bond lengths). The higher the number of unstrained bonds, the lower was the formation energy. Symmetry was found to play a lesser role in determining the preferred structure.

Identification of Stable Boron Clusters in c-Si using Tight-Binding Statics. W.Luo, P.Clancy: Journal of Applied Physics, 2001, 89[3], 1596-604