Elastic response of monolayer Si1−xGex

Abstract

The elastic response of monolayer silicon-germanium alloys (${\mathrm{Si}}_{1\text{\ensuremath{-}}x}{\mathrm{Ge}}_{x}, 0\ensuremath{\le}x\ensuremath{\le}1$) is investigated using first-principles calculations. It is found that the atomic arrangement of monolayer ${\mathrm{Si}}_{1\text{\ensuremath{-}}x}{\mathrm{Ge}}_{x}$ alloys has a significant impact on their elastic anisotropy, which can be categorized by their crystal systems. The hexagonal ${\mathrm{Si}}_{1\text{\ensuremath{-}}x}{\mathrm{Ge}}_{x}$ is elastically isotropic because of high symmetry, while some rectangular and oblique ${\mathrm{Si}}_{1\text{\ensuremath{-}}x}{\mathrm{Ge}}_{x}$ are elastically anisotropic because of the presence of the zigzag interface. The degree of anisotropy is related to the width and ratio of silicene/germanene strips in the ${\mathrm{Si}}_{1\text{\ensuremath{-}}x}{\mathrm{Ge}}_{x}$ superlattice structure. This work provides a guideline for experimentally realizing this series of materials that may find applications in ${\mathrm{Si}}_{1\text{\ensuremath{-}}x}{\mathrm{Ge}}_{x}$-based optoelectronics and flexible electronics.