Effect of Electric Field on the Structural and Electronic Properties of the Graphene/Hexagonal Boron Nitride Heterobilayer

Abstract

The rapid advancement of nanoelectronics has intensified the search for atomically thin materials with tunable electronic properties suitable for high-performance devices. Van der Waals heterostructures composed of complementary two-dimensional materials provide a versatile platform for engineering band structures and controlling charge transport at the nanoscale. The study investigates the characteristics of a graphene sheet deposited on a hexagonal boron nitride (h-BN) layer. The study highlights that although graphene possesses exceptional properties, the absence of an intrinsic energy gap limits its applications, hence the interest in Van der Waals heterostructures such as graphene/h-BN for inducing a tunable electronic gap through symmetry breaking. The methodology relies on first-principles calculations using density functional theory (DFT) with the SIESTA code for structural properties and Quantum Espresso for electronic properties, employing the PBE approximation and van der Waals TS corrections. The comparative study of four stacking orders (AA, AA', AB, and BA) reveals that the AB configuration constitutes the most stable ground state with an equilibrium interlayer distance of 3.39 Å, while the other stackings exhibit larger distances ranging from 3.50 Å to 3.511 Å. Analysis of the sliding dynamics shows specific energy barriers for the wheelchair and zigzag paths, which are modified by the application of an electric field. On the electronic level, the interaction between the layers lifts the degeneracy of the Dirac cones and causes the opening of a 0.0143 eV (approximately 14.3 meV) gap for the AB stacking in the absence of a field. The results highlight a monotonic decrease in this band gap under the influence of a perpendicular electric field, from 0.014256 eV to 0.010025 eV as the field strength increases from 0 to 1 V/Å. This evolution is attributed to a change in band alignment due to induced polarisation, with the electric field partially counterbalancing the symmetry breaking. The geometric study under a 1 V/Å field confirms the stability of the structure, with unchanged intralayer distances (approximately 1.427 Å for C–C and B–N) and a stable average interlayer distance around 3.74 Å. In conclusion, the study asserts that the graphene/h-BN synergy allows for precise control of physical properties, positioning this material as a promising candidate for terahertz nano-optical devices and information electronics.