Molecular dynamics analysis for micro notch effects of single crystal silicon thin film

Nano-sized materials are widely used for semiconductors and micro-electro-mechanical systems (MEMS) well. It is significant that the physical and mechanical properties of these materials are clarified. In this study, the molecular dynamics analysis of single crystal silicon thin film was conducted, and the effects of notch depth against the deformation and fracture behavior were investigated. The specimen size was about 10 nm × 5 nm × 2.5 nm and the notch depth was from about 0.5 to 4.0 nm in the loading direction of |110|. For making the thin film, the periodic boundary condition applied in depth z direction. In the stress-strain relationship, a normal stress for a loading direction increased with the increase of an applied strain. After that, the normal stress became small rapidly. As the notch depth was increased, the stiffness and maximum stress calculated were decreased. The stiffness calculated by the molecular dynamics were smaller than that by the finite element method, however the tendency, which the stiffness was decreased with increasing the notch depth, was agreed with the result calculated by finite element method. The fracture plane was perpendicular to the loading direction. A fracture criterion was that the atomic stress of notch root became a critical value. The critical stress was different from the other loading direction.