Research on the material removal mechanism of vibration-assisted nano-scratch on single-crystal GaN by molecular dynamics

Single-crystal gallium nitride (GaN) is a semiconductor material with high hardness and high brittleness. To reveal the differences in the micro-mechanisms of material removal during conventional grinding and ultrasonic vibration-assisted grinding, and to provide guidance for the high-efficiency, high-quality planarization processing of single-crystal GaN, this study uses molecular dynamics (MD) simulation methods to establish a model of single-crystal GaN being scratched by a single abrasive grain with/without ultrasonic vibration assistance. The study compares the differences in surface morphology and subsurface damage formation mechanisms of single-crystal GaN under conditions with and without ultrasonic assistance. The results indicate that, compared to conventional grinding, the periodic ultrasonic vibrations effectively reduce the normal force and result in a more uniform distribution of stress and temperature, thereby mitigating local stress concentration and thermal accumulation effects. Ultrasonic vibration alters the motion of the abrasive grain, increasing the effective contact area and material removal range, reducing the number of residual atoms in the machining area, and lowering the chip pile-up height at the abrasive grain's leading edge. Additionally, the micro-shear deformation induced by ultrasonic vibrations helps suppress brittle fracture phenomena caused by excessive local stress, thus reducing the thickness of the subsurface damage layer. These findings provide new insights into the microscopic mechanisms of material removal in high-efficiency, high-quality grinding processes of single-crystal GaN.