Electronic and optical properties of sulfur vacancy-defect monolayer PtS2: A first-principles study

Abstract

In this work, Density Functional Theory (DFT) simulations are performed to study the sulfur vacancy in monolayer PtS2. The structural, electronic, and optical properties of monolayer PtS2 with sulfur vacancy have been investigated. The sulfur vacancy slightly affects the structure near the vacancy and the remaining atoms show inward relaxation. The formation energies of a single sulfur vacancy are 1.65–1.73 eV in S-rich conditions and 0.69–0.77 eV in the Pt-rich environment. The sulfur vacancy induced three defect bands in the bandgap. It is found that when the concentration of Vs increases, then the gap between the highest occupied and lowest unoccupied state decreases. The sulfur vacancy increases the in-plane static dielectric constant and causes extra ε2//peaks which appear in the range of 0.5–1.8 eV, i.e., infrared absorption. Finally, we show that an O atom, O2 molecule, and three hydrogens can cause the partial passivation of sulfur vacancy. Though the three schemes cannot remove all the defective states of the gap, the bandgaps of the defective PtS2 monolayer became similar to the perfect one. We suggest that the proposed passivation methods may further facilitate their practical applications.