Influence of irradiation-induced point defects on nanotribological properties of m-plane GaN investigated using molecular dynamics simulation

Molecular dynamics (MD) simulation toward the irradiation cascade collision of GaN (10-10) by using different primary knock-on atom (PKA) energies was performed. Simulation results showed that point defects comprising vacancies and interstitials in pairs increased with increased PKA energy. The number of stable defects after cascade collision was linearly related to the PKA energy, which well agreed with the Norgett-Robinson-Torrens equation. Then, we investigated the effect of irradiation-induced point defects on the nanotribological properties and subsurface damage of the GaN (10-10) workpiece by MD simulation of nanoscratching. The irradiationinduced point defects induced a significant change in the wear morphology, as well as more slight wear and a lower coefficient of friction, compared with non-irradiated GaN. The irradiated GaN also exhibited fewer chips and smoother surfaces than the non-irradiated one after scratching. The number of deformed atoms of GaN increased with increased PKA energy, suggesting that irradiation can suppress the atomic/near-atomic scale deformation of GaN crystal under certain conditions. The presence of point defects can, to some extent, hinder the development of dislocations and differentiate the scratching-induced subsurface damage. This study provided atomic-scale insight into the effect of irradiation point defects on the nanotribological behavior of GaN.