van der Waals graphene/MoS2 heterostructures: tuning the electronic properties and Schottky barrier by applying a biaxial strain

Abstract

First principles calculations are performed to study the effects of the interlayer distance and biaxial strain on the electronic properties and contact properties of graphene/MoS₂ heterostructures. The interlayer interaction is weakened and the charge transfer from the graphene layer to the MoS₂ layer is reduced with increasing interlayer distance in graphene/MoS₂ heterostructures, resulting in a shift of the Fermi level to a high energy state. The n-type Schottky barrier is formed with Φ_SB,N values of 0.647 eV, 0.568 eV, 0.509 eV, and 0.418 eV when the interlayer distances are 3.209 Å, 3.346 Å, 3.482 Å, and 3.755 Å, respectively. The interlayer distance and charge density difference change slightly, but the electronic structure of the graphene/MoS₂ heterostructure changes obviously by applying the biaxial strain. For the biaxial strain from −4% to +6%, the Φ_SB,P gradually increases for the graphene/MoS₂ heterostructure, while the Φ_SB,N increases initially and then decreases. Moreover, the Φ_SB,N is only 0.080 eV under a biaxial strain of +6%, indicating that the Ohmic contact is nearly formed. The results demonstrate the significant effects of a biaxial strain on the physical properties of 2D heterostructures.