Due to the broken of inversion and mirror symmetry, Janus structures are believed to have abundant properties and can be applied in two-dimensional (2D) materials, but the research of 2D Janus materials is insufficient. In this work, Janus materials ZnXY₂ (X = Ge, Sn, Si and Y = S, Se, Te) monolayers are designed referring to group-III monochalcogenides. The electronic, mechanical and piezoelectric properties and stabilities of ZnXY₂ monolayers are investigated by the first-principles calculations. The electronic property shows that ZnXY₂ monolayers are semiconductors with wide direct band-gaps and large effective masses difference between holes and electrons. The mechanical property shows that ZnXY₂ monolayers possess low Young’s modulus, bending modulus and ductile properties, which is beneficial for applications in flexible nanodevices. The piezoelectric property shows that, compared with conventional Janus group-III monochalcogenides and bulk piezoelectric materials, ZnXY₂ monolayers exhibit higher in-plane and comparable out-of-plane piezoelectricity. The further analyzations indicate that the distances and electronegativity differences between atoms are two important influence factors to piezoelectricity. In summary, the flexibility, piezoelectricity, direct band-gaps and large effective mass difference make ZnXY₂ monolayers promising candidates for optoelectronics, photocatalysis, flexible nanodevices and electromechanical systems.

由于反转和镜像对称性的破缺，Janus结构被认为具有丰富的性质，可以应用于二维（2D）材料，但对二维Janus材料的研究还不够。在这项工作中，Janus 材料 ZnXY ₂（X = Ge、Sn、Si 和 Y = S、Se、Te）单层被设计为参考 III 族单硫属元素化物。通过第一性原理计算研究了ZnXY ₂单层的电子、机械和压电性能和稳定性。电子性质表明，ZnXY ₂单分子层是直接带隙较宽且空穴与电子之间的有效质量差较大的半导体。力学性能表明，ZnXY ₂单层具有低杨氏模量、弯曲模量和延展性，有利于在柔性纳米器件中的应用。压电性能表明，与传统的 Janus III 族单硫属化物和体压电材料相比，ZnXY ₂单层表现出更高的面内和可比的面外压电。进一步的分析表明，原子之间的距离和电负性差异是影响压电性的两个重要因素。总之，柔性、压电性、直接带隙和大的有效质量差异使 ZnXY ₂单层成为光电子学、光催化、柔性纳米器件和机电系统的有希望的候选者。