1. School of Mechanical Engineering, Jiangnan University, Wuxi 214122, China
2. School of Mechanical and Electrical Engineering, Wuxi Vocational Institute of Commerce , Wuxi 214153, China
et al.
Gallium nitride (GaN) crystals have gained extensive usage in diverse fields such as new energy vehicles, aerospace and military applications. However, the inherent characteristics of GaN, characterized by its hardness and brittleness, adversely affect its processing efficiency. To overcome this limitation and achieve efficient and robust removal of GaN, it is paramount to investigate the influence of indenter shape on material damage during nanofabrication. Molecular dynamics simulations are employed to simulate indentation and scratching experiments on the Ga surface of GaN. The aim is to analyze the influence of employing both spherical and Berkovich indenters with different orientation to distribution and progression of atomic packing, crystal slip and dislocations throughout the machining process. It turns out that the distribution of edge dislocations is predominantly influenced by the contact interface between the indenter’s periphery and the material during the nanoindentation process. In the case of the spherical indenter, atomic slip predominantly occurs along <11-20> crystallographic direction families. For Berkovich indenter, the sharp edges are effective in suppressing slip and dislocation expansion of atoms in that direction. When the one edge of the indenter face to the [11-20] direction, atomic slip and dislocation phenomena are mitigated, and slip and atomic packing are primarily observed perpendicular to the three edges of the indenter. During the scratching process, edge dislocations undergo three main processes: initial generation, extended formation and destructive reorganization. The spherical indenter produces the most dislocations, whereas the Berkovich indenter has moderate dislocations when the sharp angle is forward, and the subsurface amorphous deformation zones are uniform, with less atomic packing.