Simulation study of nucleation mechanism of grown-in dislocations near grain boundary during solidification of silicon

Abstract

We carried out molecular dynamics (MD) simulations of directional solidification of silicon with carbon impurity to study the nucleation mechanism of grown-in dislocations near Σ27 grain boundary. We find that carbon impurity atoms segregate to crystal boundary groove. A stacking fault composed of two consecutive {111} bi-layer plane twinnings nucleates near the carbon segregation site in the grain boundary groove. Then Shockley partial dislocations composed of 5-5-8-atom rings are formed between stacking fault area and normal stacking area. These dislocations originate from the grain boundary, pass through the crystal, extend to the solid-liquid interface and expand with the movement of the solid-liquid interface, indicating that they are grown-in dislocations formed during the directional solidification of silicon. Our study is expected to provide a theoretical basis for further reducing the dislocation density of multicrystalline silicon (mc-Si).