Molecular Dynamics Simulation of the Crystal Orientation and Temperature Influences in the Hardness on Monocrystalline Silicon

A nanoindentation simulation using molecular dynamic (MD) method was carried out to investigate the hardness behavior of monocrystalline silicon with a spherical diamond indenter. In this study, Tersoff potential was used to model the interaction of silicon atoms in the specimen, and Morse potential was used to model the interaction between silicon atoms in the specimen and carbon atoms in the indenter. Simulation results indicate that the silicon in the indentation zone undergoes phase transformation from diamond cubic structure to body-centred tetragonal and amorphous structure upon loading of the diamond indenter. After the unloading of the indenter, the crystal lattice reconstructs, and the indented surface with a residual dimple forms due to unrecoverable plastic deformation. Comparison of the hardness of three different crystal surfaces of monocrystalline silicon shows that the (001) surface behaves the hardest, and the (111) surface behaves the softest. As for the influence of the indentation temperature, simulation results show that the silicon material softens and adhesiveness of silicon increases at higher indentation temperatures.