Molecular dynamics simulation and experimental investigation on deformation anisotropy of gallium nitride Ga-plane and N-plane nano- scratching
J Song and H Zhou and YM Xu and W Jiang and CW Zhang, SOLID STATE COMMUNICATIONS, 353, 114866 (2022).
Gallium nitride(GaN) is a typical anisotropic material. Therefore, in order to guide the processing of GaN, it is important to investigate the effect of anisotropy on its frictional properties and deformation mechanism. Hexagonal wurtzite c-GaN has a periodicity of 60 degrees; therefore, in this study, only the 1010 and 1210 crystal directions of the Ga and N planes were investigated through molecular dynamics simulations, and corresponding nano-scratch experiments were conducted to validate the simulation results. The results indicated that the entire scratching process could be divided into three phases: elastic deformation, plastic deformation, and brittle fracture. The GaN N-plane 1210 crystal direction was the first to undergo plastic and brittle deformation, and the incision depth corresponding to the elastic-plastic transition was 0.62 nm and the normal force was 264.1 nN. The brittle- plastic transition corresponded to an incision depth of 55 nm and normal force of 1.4 mN. At the same time, when brittle-plastic transition occurred, the friction coefficient of the material increased abruptly, and the corresponding friction coefficient of the N plane was generally larger than that of the Ga plane. Moreover, distribution of cracks was determined by scanning electron microscopy. In terms of deformation mechanism, when scratching along the 1010 crystal direction, the removed materials got mainly accumulated on both sides of the scratched groove; when scratching along the 1210 crystal direction, the removed material mainly got accumulated in front of the indenter.
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