The Electronic Properties of O-Doped Pure and Sulfur Vacancy-Defect Monolayer WS(2): A First-Principles Study

Based on the density functional theory (DFT), the electronic properties of O-doped pure and sulfur vacancy-defect monolayer WS(2) are investigated by using the first-principles method. For the O-doped pure monolayer WS(2), four sizes (2 × 2 × 1, 3 × 3 × 1, 4 × 4 × 1 and 5 × 5 × 1) of supercell are discussed to probe the effects of O doping concentration on the electronic structure. For the 2 × 2 × 1 supercell with 12.5% O doping concentration, the band gap of O-doped pure WS(2) is reduced by 8.9% displaying an indirect band gap. The band gaps in 3 × 3 × 1 and 4 × 4 × 1 supercells are both opened to some extent, respectively, for 5.55% and 3.13% O doping concentrations, while the band gap in 5 × 5 × 1 supercell with 2.0% O doping concentration is quite close to that of the pure monolayer WS(2). Then, two typical point defects, including sulfur single-vacancy (V(S)) and sulfur divacancy (V(2S)), are introduced to probe the influences of O doping on the electronic properties of WS(2) monolayers. The observations from DFT calculations show that O doping can broaden the band gap of monolayer WS(2) with V(S) defect to a certain degree, but weaken the band gap of monolayer WS(2) with V(2S) defect. Doping O element into either pure or sulfur vacancy-defect monolayer WS(2) cannot change their band gaps significantly, however, it still can be regarded as a potential method to slightly tune the electronic properties of monolayer WS(2).