Stabilities, Electronic and Piezoelectric Properties of Two-dimensional Tin Dichalcogenides Derived Janus Monolayers
Using first-principles calculations, stabilities, electronic structures and piezoelectric properties of the two-dimensional (2D) tin dichalcogenides derived Janus SnXY monolayers (X=O, S, Se, Te; Y=O, S, Se, Te; X≠Y) are systematically investigated. Apart from structural instability of the SnOTe, all the other Janus monolayers are proved to be thermodynamically, dynamically and mechanically stable. Electronic property calculations demonstrate that Te-participated Janus systems are always metallic and the other systems have the band gap in the range of 0.33 - 1.74 eV. Appropriate valence band maximum positions guarantee these semiconducting Janus monolayers be applied as effective catalysts for oxygen reduction reaction. Due to losing the inversion symmetry, Janus materials exhibit a piezoelectric property. Surprisingly, the largest predicted in-plane piezoelectric coefficient d11 for the SnOSe is as high as 27.3 pm/V, which is one order of magnitude greater than those of reported fashionable piezoelectric materials, such as quartz, MoS2, etc. Our results indicate that 2D tin dichalcogenides derived Janus monolayers are strong candidates for future atomically thin piezoelectric applications in the fields of transducers, sensors, and energy harvesting devices.