Ab Initio Study of Graphene/hBN Van der Waals Heterostructures: Effect of Electric Field, Twist Angles and p-n Doping on the Electronic Properties

Nanomaterials (Basel). 2022 Jun 20;12(12):2118. doi: 10.3390/nano12122118.

Abstract

In this work, we study the structural and electronic properties of boron nitride bilayers sandwiched between graphene sheets. Different stacking, twist angles, doping, as well as an applied external gate voltage, are reported to induce important changes in the electronic band structure near the Fermi level. Small electronic lateral gaps of the order of few meV can appear near the Dirac points K. We further discuss how the bandstructures change applying a perpendicular external electric field, showing how its application lifts the degeneracy of the Dirac cones and, in the twisted case, moves their crossing points away from the Fermi energy. Then, we consider the possibility of co-doping, in an asymmetric way, the two external graphene layers. This is a situation that could be realized in heterostructures deposited on a substrate. We show that the co-doping acts as an effective external electric field, breaking the Dirac cones degeneracy. Finally, our work demonstrates how, by playing with field strength and p-n co-doping, it is possible to tune the small lateral gaps, pointing towards a possible application of C/BN sandwich structures as nano-optical terahertz devices.

Keywords: THz nanodevices; Van der Waals heterostructures; density functional theory; graphene; h-BN.

Grants and funding

O.P., S.B. and M.P. acknowledge financial funding from the EU MSCA-RISE project DiSeTCom (HORIZON2020 GA 823728) and INFN project TIME2QUEST. M.P. acknowledges Tor Vergata University Project 2021 TESLA. F.B. acknowledges financial funding from the European Union’s Horizon 2020 research and innovation programme under Grant No. 824158 (EoCoE-II). The research leading to these results has received funding from the European Union Seventh Framework Program under Grant No. 785219 Graphene Core2. This publication is based upon work from COST Action TUMIEE CA17126, supported by COST (European Cooperation in Science and Technology.