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

Abstract

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.