Atomistic simulation of structural phase transformations in monocrystalline silicon induced by nanoindentation

Structural phase transformations of silicon during nanoindentation were investigated in detail at the atomic level. The molecular dynamics simulations of nanoindentation on the (100) and (111) surface of single crystalline silicon were simulated, and this supported the theoretical prediction of the anisotropic behaviour of structural phase transformations. Simulations showed that microscopic aspects of phase transformation varied according to the crystallographic orientation of the contact surface and were directly linked to the slip system of silicon. In the transformed region along the centreline, the crystalline structure of Si-II and the amorphous structure were observed when silicon was loaded in the [100] and [111] directions, respectively. Simultaneously, metastable phases with fourfold coordination, such as Si-III and Si-XII, were formed by the inhomogeneous distortion in the slip direction of silicon and observed along the direction. Additionally, our results indicated that the deviatoric stress added to the hydrostatic pressure induced by loading was an indispensable factor for the structural phase transformation to Si-II during nanoindentation on the (100) surface.