Molecular Dynamics Studies of Crystallization and Grain Boundary Formation in Silicon

摘要

Molecular dynamics calculations using Tersoff potential were carried out to investigate the formation of grain boundaries during crystallization of silicon. The model cell initially contained two separated small seed crystals that are randomly oriented in liquid silicon. The formation process of grain boundaries was classified into the following three stages. (1) Seed crystals were surrounded by {111} planes and grew along <111> direction. Rotations of seed crystals by preferential angles were observed. (2) The apex of the quadrangular pyramid made by (111) planes of the crystal moved forward along <010> direction and made contact with the neighboring crystal grain. (3) The non-crystallized region in front of {111} planes was crystallized and grain boundaries were formed. The formation of a stacking fault was recognized in this stage, and this stacking fault may be introduced to lower the potential energy of atoms around the interface of grain boundaries. The final atomistic structure of the calculated grain boundary was similar to that of the calculated amorphous silicon, suggesting an amorphous layer at the interface.