Tuning the Schottky contacts at the graphene/WS2 interface by electric field

Abstract

Using the first-principle calculations, we study the electronic structures of graphene/WS₂ van der Waals (vdW) heterostructures by applying an external electric field (E_ext) perpendicular to the heterobilayers. It is demonstrated that the intrinsic electronic properties of graphene and WS₂ are quite well preserved due to the weak vdW contact. We find that n-type Schottky contacts with a significantly small Schottky barrier are formed at the graphene/WS₂ interface and p-type (hole) doping in graphene occurs during the formation of graphene/WS₂ heterostructures. Moreover, the E_ext is effective to tune the Schottky contacts, which can transform the n-type into p-type and ohmic contact. Meanwhile, p-type (hole) doping in graphene is enhanced under negative E_ext and a large positive E_ext is required to achieve n-type (electron) doping in graphene. The E_ext can control not only the amount of charge transfer but also the direction of charge transfer at the graphene/WS₂ interface. The present study would open a new avenue for application of ultrathin graphene/WS₂ heterostructures in future nano- and optoelectronics.