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

Abstract

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.