Tunable donor and acceptor impurity states in a WSe2 monolayer by adsorption of common gas molecules

Abstract

A gas sensor of common gas molecules, such as CO, H₂O, NH₃, O₂, NO and NO₂ on a WSe₂ monolayer is investigated systematically by using first-principle calculations. The results show that the effects of NH₃, H₂O, CO adsorption on the electronic structures of the WSe₂ monolayer are not obvious; while the adsorption of O₂, NO and NO₂ molecules has an obvious influences on electronic structures of the WSe₂ monolayer. Moreover, our calculations show that NH₃ acts as a charge donor, whereas O₂, CO, H₂O, NO and NO₂ gas molecules act as an acceptor impurity. In particular, our results also show that NO₂ molecule adsorptions can result in an effective p-type doping in the WSe₂ monolayer. These results suggest that the carrier type can be tuned effectively in the monolayer WSe₂ by adsorption of common gas molecules.