Nanometer to Micron Scale Atomistic Mechanics of Silicon Using Atomistic Simulations at Accelerated Time Steps

Abstract

Atomistic simulations have a unique capability to reveal the material deformation mechanisms and the corresponding deformation-based constitutive behavior. However, atomistic simulations are limited by the accessible length and time scales. In the present work, an equivalent crystal lattice method is used to analyze atomistic mechanical deformation of nanometer- to micrometer-sized polycrystalline silicon (Si) samples at accelerated time steps. The equivalent crystal lattice method’s validity is verified by the results of classical molecular dynamics (MD) simulations at MD strain rates. The method is then used to predict material behavior at subcontinuum length scales. An extrapolation of the thin film polycrystalline silicon stress-strain relationships to lower strain-rate values indicates that the thin film peak stress values at the experimental strain rates are in agreement with experimental values. Analyses reveal that the peak stress values in the case of polycrystalline Si follow inverse Hall-Petch relation up to an average grain size 134.97 nm. In the case of both bulk and thin film polycrystalline Si with the thin film polycrystalline, Si showed significantly higher softening attributable to additional surface defects.