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

Group IV monochalcogenides M X ( = Ge, Sn; = 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 M X . Based on analysis on the orbital-projected band structure, the VBMs are found to be dominantly contributed from the p z orbital of atom, while the CBM is mainly dominated by p x or p y orbital of atom. 2D SnS has the largest anisotropy ratio due to the lacking of orbital contribution which increases the anisotropy. Moreover, the electron/hole effective masses along the direction have the steeper tendency of increase under the uniaxial tensile strain compared to those along direction.