Simulating changes of packing structures, locally loading states and mechanical behaviors for Si lattices with double vacancies at elevated temperatures

Abstract

The vacancy defects in silicon matrix have important influences on processing or manufacturing novel microelectronic devices as well as their performances related to structures and mechanical properties. Molecular dynamics simulations were performed for the evolution of the atomic packing structures and locally loading states as well as tensile tests for silicon matrixes having three types of double vacancies at atomic scale. Through analysis from Young's modulus, Poisson's ratios, Lode-Nadai parameters and atomic strain energy density as well as visually packing images, the simulation results show that there exists just one type of adjacent vacancies at room temperature, and the external energy provided from high temperature results in vacancy's migration. On heating, the matrixes having vacancies present apparent different stages from elasticity to plasticity, and their temperature regimes are identified. Under applying uniaxial tension at room temperature, the strain energy density of the matrix near the vacancies is significantly higher than those in the other regions in the elasticity stage. There are differences of the elongation and tensile strength of the matrixes having different types of vacancies.