超声振动辅助抛光氮化镓分子动力学仿真分析

为了揭示超声振动辅助抛光（UVAP）氮化镓（GaN）的微观机理，为优化超声参数实现GaN材料高效去除和改善表面质量提供指导意见。采用分子动力学（MD）模拟方法研究了超声振动条件下单个磨粒在氮化镓（GaN）材料表面的划擦行为，并分析了超声振动周期和幅值对GaN材料去除行为的影响。结果表明，随UVAP振动周期的增大，平均切向力不断减小，平均法向力先增大后减小，损伤层厚度先降低后逐渐趋于平缓。振动周期为40 ps时，去除原子数量为常规抛光的5.6倍，同时损伤层深度仅为15.85 ?。而随着UVAP振幅的增加，平均切向力先减小后增大，平均法向力不断减小，划痕宽度和损伤层深度非线性增大。在振幅为8 ?时，损伤层深度与常规抛光基本保持一致，且去除原子数量相比常规抛光提升了4.6倍。UVAP较常规抛光能够降低平均磨削力，增大划痕宽度，提升去除原子数量，具有优异的抛光效果。UVAP振动周期和振幅的增大均会增加划痕底部的位错类型。此外，位错总长度的大小主要受振幅的影响，而与振动周期基本无关。通过调控UVAP振动周期和振幅分别为40 ps和8 ?，能够保证较好的表面质量和较高的材料去除效率。

Molecular dynamics simulation of ultrasonic vibration-assisted polishing of gallium nitride

The present work aims at investigating the microscopic mechanism of ultrasonic vibration-assisted polishing (UVAP) of gallium nitride (GaN) and providing guidelines for optimizing ultrasonic parameters to enhance material removal and surface quality. Thus, molecular dynamics (MD) method was applied to investigate the removal behavior of GaN material scratched by individual abrasive particles at different periods and amplitudes. As the rising of the UVAP vibration period, the average tangential force decreases, the average normal force initially increases and then decreases, and the thickness of the damage layer decreases and then tends to flatten out. With a vibration period of 40 ps, the number of atoms removed after UVAP is 5.6 times higher than conventional polishing, while the depth of the damaged layer is only 15.85 ?. Moreover, as the UVAP amplitude increases, the average tangential force decreases and then increases, the average normal force continuously decreases, and both the scratch width and damage layer thickness increase nonlinearly. Under 8 ? amplitude, the thickness of the damaged layer remained essentially the same as in conventional polishing, and the number of atoms removed after UVAP increased by a factor of 4.6 compared to conventional polishing. In summary, UVAP offers advantages over conventional polishing, including reduced average grinding force, increased scratch width, and improved atom removal, resulting in excellent polishing results. Both increasing the UVAP vibration period and amplitude rising the types of dislocations at the bottom of the scratch. In addition, the total length of dislocations is mainly influenced by the amplitude, while the vibration period has less impact. Finally, better surface quality and higher material removal efficiency can be ensured by regulating the UVAP vibration period and amplitude to 40 ps and 8 ?, respectively.