Repairing sulfur vacancies in the MoS2 monolayer by using CO, NO and NO2 molecules

As-grown transition metal dichalcogenides are usually chalcogen deficient and contain a high density of chalcogen vacancies, which are harmful to the electronic properties of these materials. Based on the first-principles calculation, in this study the repairing of the S vacancy in the MoS2 monolayer has been investigated by using CO, NO and NO2 molecules. For CO and NO, the repairing process consists of the first molecule filling the S vacancy and the removing of the extra O atom by the second molecule. However, for NO2, when the molecule fills the S vacancy, it is dissociated directly to form an O-doped MoS2 monolayer. After the repair, the C, N and O-doped MoS2 monolayers can be obtained by the adsorption of CO, NO, and NO2 molecules, respectively. And in particular, the electronic properties of these materials can be significantly improved by N and O doping. Furthermore, according to the calculated energy, the process of S vacancy repairing with CO, NO and NO2 should be easily achieved at room temperature. This study presents a promising strategy for repairing MoS2 nanosheets and improving their electronic properties, which may also apply to other transition metal dichalcogenides.