First principles study of van der Waals heterobilayers

This paper presents a comparative first principles study of van der Waals heterobilayers derived from the coupling of graphene to silicon carbide and hexagonal boron nitride monolayer. Using the local, semi-local, and van der Waals interaction-corrected density functional theory, it found that the adhesion energy of graphene on SiC and h-BN monolayer is invariant under dispersion corrections. On the other hand, considerably more accurate interlayer distances are obtained using the semi-empirical DFT-D3 correction, whereas non-local corrections consistently yield higher adhesion energies of 3.70 and 2.84 mRyd per carbon for graphene on SiC and h-BN monolayer substrates. It is also observed that the anisotropy induced band gap depends on the evolution of the stacking sequence of heterobilayers under persistent strain. It is suggested that the delicate minimisation of the overlap interactions between interlayer π-bonds induces localised charge puddles in the interfacial electronic structure and opens up a band gap. Using the dependence of the induced band gap on network anisotropy, it is shown that the size of the band gap is tunable by controlling the stacking sequence and the strength of the dipole-induced electric field within the heterobilayer interface.