Quantum effects in two-dimensional silicon carbide

Abstract

Two-dimensional (2D) silicon carbide is an emergent direct band-gap semiconductor, recently synthesized, with potential applications in electronic devices and optoelectronics. Here, we study nuclear quantum effects in this 2D material by means of path-integral molecular dynamics (PIMD) simulations in the temperature range from 25 to 1500 K. Interatomic interactions are modeled by a tight-binding Hamiltonian fitted to density-functional calculations. Quantum atomic delocalization combined with anharmonicity of the vibrational modes cause changes in structural and thermal properties of 2D SiC, which we quantify by comparison of PIMD results with those derived from classical molecular dynamics simulations, as well as with those given by a quantum harmonic approximation. Nuclear quantum effects are found to be appreciable in structural properties such as the layer area and interatomic distances. Moreover, we consider a real area for the SiC sheet, which takes into account bending and rippling at finite temperatures. Differences between this area and the in-plane area are discussed in the context of quantum atomic dynamics. The bending constant (κ=1.0eV) and the 2D modulus of hydrostatic compression (Bxy = 5.5 eV/Å 2) are clearly lower than the corresponding values for graphene. This study paves the way for a deeper understanding of the elastic and mechanical properties of 2D SiC.