Intrinsic piezoelectricity of monolayer group IV–V MX2: SiP2, SiAs2, GeP2, and GeAs2

Abstract

The intrinsic piezoelectric effect of the monolayer group IV–V MX2 (M = Si, Ge and X = P, As) is systematically investigated using the density functional theory based on first-principles calculations and the modern theory of polarization. We find that the piezoelectric coefficients d112D of the compounds are approximately one order of magnitude larger than those of other 2D materials, such as hexagonal boron nitride and MoS2, which have been widely studied both experimentally and theoretically. Furthermore, the coefficients d112D are always one order of magnitude larger than d122D, showing obvious anisotropy. Such strong anisotropy can be easily understood by the C2v symmetry and puckered configuration along the a direction, which leads to considerable flexibility. Our results show that these monolayers of group IV–V MX2 have potential for applications in nanosized sensors, piezotronics, and energy-harvesting in portable electronic nanodevices. Owing to the recent advances in synthesis technologies, it is expected that these monolayers may be put to a wide practical use in the future.