Bidirectional heterostructures consisting of graphene and lateral MoS/WS composites: a first-principles study.

First-principles calculations have been performed to explore the structural and electronic properties of bidirectional heterostructures composed of graphene and (MoS) /(WS) ( = 1, 2, 3) lateral composites and compare them with those of heterobilayers formed by graphene and pristine MS (M = Mo, W). The band gaps of the lateral heterostructures lie between those of pristine MoS and WS. The weak coupling between the two layers can induce a tiny band-gap opening of graphene and formation of an n-type Schottky contact at the G-(MoS) /(WS) interface. Moreover, the combination ratio of MoS/WS can control the electronic properties of G-(MoS) /(WS) . By applying external electric fields, the band gaps of (MoS) /(WS) ( = 0, 1, 2, 3, 4) monolayers undergo a direct-indirect transition, and semiconductor-metal transitions can be found in WS. External electric fields can also be used effectively to tune the binding energies, charge transfers, and band structures (the types of Schottky and Ohmic contacts) of G-(MoS) /(WS) heterostructures. These findings suggest that G-(MoS) /(WS) heterostructures can serve as high-performance nano-electronic devices.