Molecular Dynamics Investigation on the Phosphorus Doping Effects on the Mechanical Properties of Crystal Silicon

Abstract

The effects of phosphorus (P), one of the most common impurities in silicon (Si), on the mechanical responses of crystal Si (c-Si) under tension are investigated using molecular dynamics with a Modified Embedded Atom Method (MEAM) potential. Tensile tests at 300K are applied for bulk c-Si with uniformly distributed and aggregated P impurities, notched c-Si films with P doping on the crack tip or at the middle of the crack propagation path. For bulk c-Si, local defects come into being around P, then rapidly nucleate and propagate, finally lead to brittle fracture. The fracture threshold decreases as the concentration increases, no matter P atoms are uniformly distributed or regionally aggregated. However, for notched c-Si film, P can evidently enhance its fracture strength by blocking the origin and propagation of cracks. With regard to Si-based micro/nano structures, fracture usually starts from the surface, indicating that P impurities play a critical role on the surface.