Hydrogen-Coverage-Dependent Stark Effect in Bilayer Graphene and Graphene/BN Nanofilms

Abstract

Hydrogenation and electric field are used to tailor the electronic structures of hybrid graphene/hexagonal boron nitride (Gr/BN) and bilayer graphene (Gr/Gr). Without hydrogen adsorption, the electronic structure of Gr/BN is only slightly affected by the electric field, but energy gaps are induced in Gr/Gr because of the breaking of inversion symmetry. Under partial hydrogenation conditions, more interlayer bonds tend to form in Gr/BN than that in Gr/Gr because of the inherent Coulomb attraction, and a band gap is created in Gr/BN even at low hydrogen coverage. The electronic structures of partially hydrogenated Gr/BN and Gr/Gr are both rather insensitive to the electric fields. Under full hydrogenation conditions, Gr/BN and Gr/Gr evolve into diamond-like nanofilms: Gr/BN-BC (interlayer B–C bonding) and Gr/Gr-CC (C–C bonding). Because of the interface-dipole-induced electric field, the band gap of Gr/BN-BC is rather small compared to that of the Gr/Gr-CC. Depending on the direction of the external electric field, the band gap of Gr/BN-BC is linearly increased or decreased, whereas that of Gr/Gr-CC is only decreased. These electric-field-induced band gap modulations in Gr/BN and Gr/Gr as well as their hydrogenation derivatives are results of the Stark effect; they are dependent on the hydrogen coverage and can be understood in terms of the charge distribution of the valence-band maximum and conduction-band minimum