Electronic and optical properties of O-doped monolayer MoS2

The O-doping effects for monolayer molybdenum disulfide (MoS2) are systematically investigated by first-principle calculations. It is shown that the geometrical, electronic and optical properties are affected distinctively by the oxygen dopant. Structural analysis reveals a local contraction along c axis in the substituted cases. The substitution of oxygen for a sulfur atom in monolayer MoS2 leads to a transition from a direct K-K band gap to an indirect C-K band gap. And, the value of band gap decreases with increasing doping concentration. In addition, for the pure MoS2, strong covalent chemical bonds are formed on the Mo-S bonds, which is ascribed to the strong hybridization between Mo-4d and S-3p orbitals. After oxygen doping, the covalent bonding of Mo-S is distinctively weakened. More electrons are transferred from Mo to O because of the larger electronegativity of O, and the atomic populations of O atoms become larger than that of S atoms. Optical properties are also found to be affected distinctively by the oxygen dopant. An interesting blue-shift of the absorption threshold is observed in the O-doped systems. (C) 2015 Elsevier B.V. All rights reserved.