Stress-Assisted Amorphization and Dislocation-Mediated Plasticity in Silicon near Its Melting Point: A Molecular Dynamics Study

Whether the plasticity of silicon at high temperatures originates from dislocation slip or solid-state phase transition remains difficult to investigate directly through experimental observation due to its microscopic nature. Using molecular dynamics simulations, we investigated the deformation behavior of silicon crystals along four typical crystallographic directions at a reduced temperature of T/Tm = 0.88 (Tm denotes the melting point of silicon predicted by the Tersoff potential). The results indicate that prior to yielding, compressive stress induces uniform amorphization throughout the crystal. Once the critical stress is exceeded, Shockley partial dislocations nucleate on the {111} crystal planes, initiating plastic flow, while the amorphous phase undergoes recrystallization during stress relaxation. These findings demonstrate that at high temperatures, the plasticity of silicon involves both stress-assisted amorphization and dislocation-mediated plasticity, which occur sequentially rather than competing with one another. This study provides an atomic-scale rationale that consolidates the long-standing process guidance for suppressing dislocation defects in the directional solidification growth of multicrystalline silicon.