Giant piezoelectricity of monolayer group Ⅳ monochalcogenides: SnSe, SnS, GeSe, and GeS

摘要

We predict enormous, anisotropic piezoelectric effects in intrinsic monolayer group Ⅳ monochalcogenides (MX, M=Sn or Ge, X=Se or S), including SnSe, SnS, GeSe, and GeS. Using first-principle simulations based on the modern theory of polarization, we find that their piezoelectric coefficients are about one to two orders of magnitude larger than those of other 2D materials, such as MoS_2 and GaSe, and bulk quartz and AlN which are widely used in industry. This enhancement is a result of the unique "puckered" C_(2v) symmetry and electronic structure of monolayer group Ⅳ monochalcogenides. Given the achieved experimental advances in the fabrication of monolayers, their flexible character, and ability to withstand enormous strain, these 2D structures with giant piezoelectric effects may be promising for a broad range of applications such as nano-sized sensors, piezo-tronics, and energy harvesting in portable electronic devices.