Molecular dynamics simulation on crystal defects of single-crystal silicon during elliptical vibration cutting

In recent years, elliptical vibration cutting (EVC) has become a promising technique to fabricate high quality surface of single-crystal silicon. However, our understanding for its cutting mechanism, especially the evolution of the crystal defects in subsurface workpiece is insufficient. In this paper, molecular dynamics simulation was carried out to explore the formation mechanism of crystal defects in single-crystal silicon during EVC. A three-dimensional MD model was adopted to demonstrate the interaction between subsurface damage and tool movement in one vibration cycle. The results indicate that the formation mechanism of surface morphology including elastic recovery and side flow is greatly determined by the cutting stage in EVC. Meanwhile, the preferred slip motion during subsurface damage formation is distinct in the extrusion and shear stage. Furthermore, the influence of cutting temperature and speed on the formation of crystal defects was investigated. It is found that at elevated temperature, the proportion of the Shockley partial dislocations are apparently increased, and recrystallization process is apparently promoted on the interface of the distorted/crystal region. As the speed ratio increases, the generation and propagation of the crystal defects are suppressed, which is advantageous for suppressing the subsurface damage. These findings provide a comprehensive theoretical basis for improving the understanding in the formation mechanism of crystal defects of single-crystal silicon in EVC.