Bidirectional heterostructures consisting of graphene and lateral MoS 2 /WS 2 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 2 ) X /(WS 2 ) 4- X ( X = 1, 2, 3) lateral composites and compare them with those of heterobilayers formed by graphene and pristine MS 2 (M = Mo, W). The band gaps of the lateral heterostructures lie between those of pristine MoS 2 and WS 2 . 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 2 ) X /(WS 2 ) 4- X interface. Moreover, the combination ratio of MoS 2 /WS 2 can control the electronic properties of G-(MoS 2 ) X /(WS 2 ) 4- X . By applying external electric fields, the band gaps of (MoS 2 ) X /(WS 2 ) 4- X ( X = 0, 1, 2, 3, 4) monolayers undergo a direct-indirect transition, and semiconductor-metal transitions can be found in WS 2 . 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 2 ) X /(WS 2 ) 4- X heterostructures. These findings suggest that G-(MoS 2 ) X /(WS 2 ) 4- X heterostructures can serve as high-performance nano-electronic devices.