First-Principles Study of Electronic and Optical Properties and Photocatalytic Performance of MS (M: Ge, Sn) Monolayer under Strain ☆

This study explores the mechanical, optoelectrical and photocatalytic properties of GeS and SnS structures by Density Function Theory (DFT) through Quantum Espresso software. The results show that the GeS and SnS structures are the semiconductor materials at equilibrium with band gaps of 1.75 eV and 1.4 eV, respectively. The band gap of these two structures tends to increase under the tensile strain and decrease under the compressive strain. Especially, at the strain of -10%, the band gap of GeS decreases dramatically and becomes metallic, while the SnS still maintains the semiconductor properties. The absorption coefficient is changed significantly in the ultraviolet region under the biaxial strain. Besides, our calculations also show that the GeS and SnS have photocatalytic properties and can become good candidates for overall water-splitting under the tensile strain. The results obtained from this study are the basis for application in microelectromechanical and optoelectronic devices and cleaning technology.