Dislocation Structure Transformation of (111) Twist Grain Boundaries in Silicon

Abstract

Grain boundaries (GBs) play a crucial role in determining the performance of nanocrystalline and polycrystalline silicon. In this paper, we investigate the structural transformation of silicon (111) twist GBs through hybrid molecular statics (RBTs method, namely, the rigid body translations) and molecular dynamics (NPT ensemble, namely, isobaric–isothermal ensemble) simulation. By considering the dislocation structures and energetics as a function of both misorientation angle and temperature, it is revealed that the transformation between the shuffle and glide GB structures is jointly governed by a critical temperature and a critical angle, and different structural and energetic characteristics are exhibited under four combination conditions of two. The shuffle GB will transform into the glide GB above the critical temperature, and the critical temperature increases linearly with the misorientation angle. Meanwhile, glide GB structures above a critical angle (θ ≥ 12°) could transform to a hybrid structure with mixed glide and shuffle characteristics, and this angle varies linearly with increasing temperature. It is found that the transformation is primarily driven by the dislocation core energy difference between the shuffle and glide GBs. There are two lines dividing the entire angle-temperature surface into four regions, each with different structures and energy characteristics. The atomistic insights provided in this study could be useful for optimizing polycrystalline silicon materials under high-temperature processing conditions.