Tuning electronic properties of the S₂/graphene heterojunction by strains from density functional theory

Based on the density functional calculations, the structural and electronic properties of the WS₂/graphene heterojunction under different strains are investigated. The calculated results show that unlike the free mono-layer WS₂, the monolayer WS₂ in the equilibrium WS₂/graphene heterojunctionis characterized by indirect band gap due to the weak van der Waals interaction. The height of the schottky barrier for the WS₂/graphene heterojunction is 0.13 eV, which is lower than the conventional metal/MoS₂ contact. Moreover, the band properties and height of schottky barrier for WS₂/graphene heterojunction can be tuned by strain. It is found that the height of the schottky barrier can be tuned to be near zero under an in-plane compressive strain, and the band gap of the WS₂ in the heterojunction is turned into a direct band gap from the indirect band gap with the increasing schottky barrier height under an in-plane tensile strain. Our calculation results may provide a potential guidance for designing and fabricating the WS₂-based field effect transistors.