First-Principles Calculations of Angular and Strain Dependence on Effective Masses of Two-Dimensional Phosphorene Analogues (Monolayer α-Phase Group-IV Monochalcogenides MX)

Group IV monochalcogenides MX (M = Ge, Sn; X = S, Se)-semiconductor isostructure to black phosphorene-have recently emerged as promising two-dimensional materials for ultrathin-film photovoltaic applications owing to the fascinating electronic and optical properties. Herein, using first-principles calculations, we systematically investigate the orbital contribution electronic properties, angular and strain dependence on the carrier effective masses of monolayer MX. Based on analysis on the orbital-projected band structure, the VBMs are found to be dominantly contributed from the p(z) orbital of X atom, while the CBM is mainly dominated by p(x) or p(y) orbital of M atom. 2D SnS has the largest anisotropy ratio due to the lacking of s orbital contribution which increases the anisotropy. Moreover, the electron/hole effective masses along the x direction have the steeper tendency of increase under the uniaxial tensile strain compared to those along y direction.