Tunable electronic structures in MPX3 (M = Zn, Cd; X = S, Se) monolayers by strain engineering

By density functional theory calculations, we systematically investigate the strain effect on electronic structures of MPX3 (M = Zn, Cd; X = S, Se) monolayers. An indirect-direct band gap transition occurs under compressive strains in ZnPS3, ZnPSe3, and CdPSe3, but CdPS3 always remains in an indirect band gap phase. The band gaps of MPX3 monolayers increase firstly and then decrease under compressive strain, while they only decrease in the case of tensile strain. In addition, we find that MPX3 monolayers are perfect substitutes for the unachievable two-dimensional MX (M = Zn, Cd; X = S, Se), due to their quite comparable electronic structures, such as their band gaps and effective masses. This indicates that MPX3 monolayers should be promising candidates in optoelectronic applications for tunable electronic structures by strain engineering.