Internal Displacement and Elastic Properties of Atomic System II. 2nd Report, Evalution of Elastic Constants of Nano-scale Thin Silicon Films.

Abstract

The elastic properties of thin silicon films were investigated using the Martin's method, which is useful for obtaining the internal displacement and elastic constants. It was found that a 1.6 nm thin film becomes very soft compared with the bulk value. Newly defined atomic elastic constants showed that the internal displacement of the atoms within 2-3 surface layers reduces elastic constants near the surface and throughout the thin film. The films with a thickness of about 20 nm or less become soft due to the effect of the internal displacement of the surface atoms. Thin films with a thickness of 2 nm or less become soft due to the the change in the atomic bonding properties. The macro-micro boundary is about 10 nm in thickness if a 10% decrease in elastic constants is defined as the boundary.