Effects of interlayer coupling and electric fields on the electronic structures of graphene and MoS2 heterobilayers

Combining the electronic structures of graphene and molybdenum disulphide (MoS2) monolayers in two-dimensional (2D) ultrathin graphene and MoS2 heterostructures has been realized experimentally for novel nanoelectronic devices. Here, first-principles calculations are performed to investigate the effects of interlayer coupling and the electric field on the electronic structures of graphene and MoS2 heterobilayers (G/MoS2 HBLs). We find that an n-type Schottky contact is formed at the G/MoS2 interface with a small Schottky barrier of 0.23 eV, because the work function of graphene is close to the electron affinity of MoS2. Furthermore, increasing the interfacial distances between graphene and MoS2 can reduce the n-type Schottky barriers at the G/MoS2 interface. But applying the electric field perpendicular to the G/MoS2 HBL can not only control the Schottky barriers but also the Schottky contacts (n-type and p-type) and Ohmic contacts (n-type) at the G/MoS2 interface. Tunable p-type doping in graphene is easily achieved at negative electric fields because electrons can easily transfer from the Dirac point of graphene to the conduction band of MoS2.