Thorough characterizations of velocity-dependent deformation patterns of c-plane single crystal gallium nitride in nanoscratching

YP Wang and YY Zhang and SP Tan and CM Ke and YQ Wu and XP Xu, CERAMICS INTERNATIONAL, 51, 55593-55602 (2025).

DOI: 10.1016/j.ceramint.2025.09.280

This study investigates the deformation behavior of single crystal gallium nitride (GaN) under varying scratch velocities to elucidate the strain rate effect on the material removal mechanism. Nanoscratch experiments were conducted on (0001) plane (c-plane) GaN using a Berkovich indenter at velocities ranging from 0.1 to 100 mu m/s, spanning three orders of magnitude. The results indicate that GaN exhibits brittle deformation, characterized by surface and subsurface microcracks, as well as plastic deformation, involves phase transition, lattice distortion, stacking faults and dislocations. The critical normal load required for the transition from plastic to brittle in GaN increases with scratch velocity. Furthermore, reductions in both the width of scratch grooves and the thickness of the subsurface damage layer suggest that higher scratch velocities favor low-damage removal of GaN within the plastic regime. Molecular dynamics simulation results show a good agreement with experimental observations. Notably, to the best of our knowledge, this study is the first to characterize the scratch-induced damage from two complementary perspectives, restructuring a three-dimensional profile of the microdefects by correlating the scanning electron microscopy and transmission electron microscopy images. This approach provides deeper insights into determining the active slip systems and delineating the trajectories of crack propagation in GaN, with significant implications for advancing ultra-precision grinding techniques for GaN.

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