Impurity-induced ferromagnetism and metallicity of WS2 monolayer

We perform a first-principles study of electronic structure and magnetic properties of V, Nb and Ta-doped WS2 monolayers. Formation energy calculations reveal that all the doped systems are thermodynamically more preferred under S-rich condition than W-rich condition, and that under either condition the incorporation of 5d Ta dopant into monolayer is the most favorable, followed by the incorporation of 4d Nb and 3d V. Electronic structure analysis reveals that all the doped systems show p-type doping and metallic character, i.e. metallicity in the V-doped case, while half-metallicity in the Nb and Ta-doped cases. Furthermore, ferromagnetism is induced by the impurities, which mainly comes from the coupling between unpaired d orbitals of the dopants and the nearest neighbors of W 5d and S 3p states. These findings indicate that doping metals in WS2 monolayers may act as a useful way to tailor the electronic structure of two-dimensional materials for many device applications.