Effects of size and surface on the elasticity of silicon nanoplates: Molecular dynamics and semi-continuum approaches

Abstract In this paper, the size effects on the elastic behavior of single crystal silicon nanoplates terminated by {100} surfaces is studied by means of molecular dynamics (MD) using a modified embedded atom method. The results indicate that the {100} surfaces undergo 2 × 1-type reconstruction, which significantly influences the mechanical properties of nanoplates. The simulations are carried out at room temperature and structural relaxation is performed. The effective Young ' s modulus, in extensional mode, is determined for different thicknesses. The surface energy, surface stress and surface elasticity of layers near the surfaces (non-bulk layers) are obtained. These surface properties are used as inputs for a recently developed two-dimensional plane-stress semi-continuum framework. The framework can be seen as the link between the surface effects calculated by atomistic simulations and the overall elastic behavior. The surface properties of nanoplates of a few layers are shown to deviate from thicker plates, suggesting a size dependence of surface parameters and, especially, surface energy. For thicknesses below 3 nm, there is a difference between the effective Young ' s modulus, calculated by the semi-continuum approach and that calculated directly by MD. The difference is due to the size dependence of surface parameters.