First-principles method based electronic transport properties of two-dimensional SnSe2(1-x)X2x alloys

Abstract

SnSe2 based layered 2-dimensional alloys have drawn much attention due to their excellent optical and electronic properties in which substitutional doping is a well-defined route to modulate functionalities of devices made up of these novel materials. Herein, by using the first-principles method based density functional theory in conjunction with Boltzmann transport equation, we systematically investigate the stability, electronic structure and transport properties of the monolayer of SnSe2(1−x)O2x and SnSe2(1−x)S2x alloys at 300 K. Our results reveal that oxygen and sulphur behave as iso-electronic dopants and they do not alter the intrinsic nature of the pristine monolayer SnSe2. The calculated indirect band gap of monolayer pristine SnSe2, SnSe2(1−x)O2x, and SnSe2(1−x)S2x is 0.79 eV, 0.78 eV, and 0.77 eV, respectively, at the compositional proportion x (0 ≤ x ≤ 0.125). These dopants create energy states near the band edge of the monolayer SnSe2. Moreover, the corresponding effective masses have been calculated at the curvature of the band edge using the least square fitting. Electrical conductivity (σ/τ ), Seebeck coefficient (S) and thermoelectric power factor (PF/τ ) are calculated as a function of chemical potential. At the studied chemical potential range, for the pristine monolayer SnSe2 the achieved maximum electrical conductivity, Seebeck coefficient, and thermoelectric power factor are 6.0×1019 Ω−1m−1s−1, 1.25 mV/K and 1.28×1011 Wm−1K−2s−1 respectively. Moreover, for SnSe2(1-x)O2x and SnSe2(1−x) S2x, the achieved electrical conductivity, Seebeck coefficient, and thermoelectric power factor are 4.5×1019 and 5.8×1019 Ω−1m−1s−1, 1.15 and 1.32 mV/K, and 7.2×1010 and 1.23×1011 Wm−1K−2s−1, respectively. This contribution provides an effective way to understand and improve the transport properties of 2D ternary semiconductor SnSe2(1−x)X2x alloys based devices which have potential applications in next-generation integrated optoelectronics due to their flexible and tunable band gap.