An atomistic insight into nanometric cutting of single crystalline gallium nitride via molecular dynamics simulation

Single crystalline gallium nitride (GaN) devices require ultra-precision machining to maintain in-service performance prior to its application. Understanding the cutting-induced deformation and material removal of GaN is essential for developing efficient machining technologies for this crystal. This work investigates the nanometric cutting of single crystalline GaN via molecular dynamics simulation. The results demonstrate the dominant role of the atomic slip in the cutting of GaN crystal, which remarkably affects the orientation dependence of its deformation behaviour. The cutting along a [-1100] or m [-2110] orientation evokes the slip on {-1100}-plane, tending toward a straight cutting chip with slight phase transition, less amorphization and shorter dislocations induced. Cutting stress and forces indicate that the cuttings along these two orientations are convenient for material removal. In the a [-1100], or c [-2110], or m [-2110] oriented cutting, dislocation propagates along the slip direction in the uncut chip ahead of the cutter, suggesting better surface quality could be expected. The simulation shows that the cutting with a parallel feed path enables a shear-dominated removal, thus it can be used to gain higher surface integrity. This study provides an atomistic understanding of the nanometric cutting of GaN, which is valuable for improving the machining technology of this crystal.