Metal–semiconductor transition of two-dimensional Mg2C monolayer induced by biaxial tensile strain

Abstract

Designing new two-dimensional (2D) materials with novel band topologies has continuously attracted intense interest in fundamental science and potential applications. Here, we report a unique 2D Mg₂C monolayer featuring quasi-planar hexa-coordinate magnesium and hexa-coordinate carbon, which can be tuned from a metal to a semiconductor. The system has been studied using density functional theory, including electronic structure calculations and molecular dynamics simulations. In the freestanding state, the Mg₂C monolayer behaves as a weak metal; however, by increasing the biaxial tensile strains, it can gradually be modulated to a gapless semimetal and then to a semiconductor. The Mg₂C monolayer exhibits excellent dynamic and thermal stabilities and is also the global minimum of the 2D Mg₂C system, implying the feasibility of its experimental synthesis. With unique band structures, the material may find applications in optoelectronics and electromechanics.