Load-Dependent Nanoscale Material Removal Behaviors of β-Ga2O3(100) Surface in Single-Point Diamond Scratching: From Plastic Plowing to Brittle Fracture

This study investigates nanoscale material removal behavior and its correlation with subsurface damage of (100)-oriented β-Ga2O3 subjected to single-point diamond scratching across a range of normal loads. Using multi-scale characterizations, we elucidate the load-dependent transition from elastic deformation to plasticity-dominated removal and, ultimately, to brittle fracture. Under low-load conditions, β-Ga2O3 exhibits a fully plasticity-dominated removal mechanism, characterized by smooth groove formation with surface pile-up and a crack-free subsurface containing only dislocations and stacking faults, suggesting that ductile-regime processing is achievable under appropriate mechanical conditions. As the normal load increases, the material enters a ductile–brittle transition regime, where plastic flow coexists with the initiation of micro shear cracks, accompanied by unstable fluctuations in the friction coefficient. Under high-load conditions, extensive brittle fracture becomes dominant, characterized by severe subsurface mixed cracking and large-scale material spalling. This research contributes to a deeper understanding of the machinability of β-Ga2O3 materials with high hardness and brittleness in ultraprecision surface processing.