Interlayer coupling and external electric field controllable electronic structures and Schottky contact of HfSeX (X = S, Se)/graphene van der Waals heterostructures

Abstract

Graphene-based van der Waals heterostructures (vdWHs) owing to their remarkable physical properties and extensive application attract much attention. However, the Schottky barrier height (SBH) at the interface limits the charge injection effect. Here, we investigate the geometry, electronic structures, contact behavior and optical properties of the HfSeX/graphene (HfSeX/G, X = S, Se) vdWHs via first-principles calculations. The effect of interlayer coupling and external electric field (Efield) on the HfSeX/G are examined. Our results show that the Dirac cones of graphene are well preserved in all modes due to weak van der Waals interaction and a small bandgap is opened in graphene. The SBH of n-type Schottky contact types (SCT) HfSe2/G, SHfSe/G and SeHfS/G vdWHs are 0.100, 0.085 and 0.114 eV, respectively. Both the interlayer distance and Efield can induce the n-type SCT of the Janus HfSSe/G to transfer to p-type, and large Efield can cause an Ohmic contact. The HfSeX/G heterostructures enhance light absorption intensity in visible-light region compared with isolate graphene and HfSeX monolayers. The work provides a valuable theoretical guidance for designing Schottky-based devices of the HfSeX/G heterostructures, as well as indicates that the heterostructures have a flexible application prospect in further optoelectronic and field effect transistors devices.