Mechanically Strengthened Amorphous Silicon by Phosphorus: A Molecular Dynamics Simulation and Experimental Study

Abstract

The effects of phosphorus (P), one of the most common impurities in silicon(Si), on the mechanical responses of amorphous Si (a-Si) have been investigated numerically and experimentally. Tensile behaviors of P doped a-Si films were investigated using classical Molecular Dynamics(MD) simulations prescribed by Modified Embedded Atom Method(MEAM) formalism. The validity of this potential was verified by comparing our simulation results with accessible higher level calculations and experimental data. By conducting uniaxial tension simulations, it was revealed that the stiffness, yield strength and flow stress of bulk P-doped a-Si are increased, and that the ductibility of a-Si film is evidently enhanced by P. Two factors account for this observation. One goes to larger bond strength of P-Si than that of Si-Si, and the other is the higher compactness of a-Si after introducing P impurities, both of which are in good agreement with experiments. Nanoindentation technology was applied to acquire the knowledge about how P impurities influence the indentation responses of a-Si. We observed a larger stiffness and stronger resistance to nanoindentation destruction as the concentration of P grew, consistent with MD conclusions though the enhanced ductibility from MD calculations needs further work to verify.