Formation and structure of vacancy defects in silicon: Combined metropolis monte carlo, tight-binding molecular dynamics, and density functional theory calculations

We present the formation and structure of vacancy clusters (Vn,n≤48) in crystalline Si based on combined Metropolis Monte Carlo, tight-binding molecular dynamics, and density functional theory calculations. In this size regime, vacancy clusters are predicted to favor fourfold coordination by nullifying dangling bonds created by Si lattice-atom removal. Our results also highlight the identification of a stable high-symmetry V32 configuration that exhibits a complex but ordered tetrahedral core/shell shape. When n>25, fourfold-coordinated (FC) clusters commonly show the core/shell figure while smaller FC clusters (10<n<25) exhibit the trace of the high-symmetry V12 structure that exhibits four identical voidlike structural units surrounding a tetragonal core. In addition, our study reveals that the formation of thermodynamically favored FC clusters can be kinetically facile.