Edge and substrate-induced bandgap in zigzag graphene nanoribbons on the hexagonal nitride boron 8-ZGNR/h-BN(0001)

Abstract

The results of DFT (GGA-PBEsol) and DFT(PBE)-D2 study of the band structure of zigzag graphene nanoribbons on hexagonal nitride boron 8-ZGNR/h-BN(0001) are presented, suitable as potential base for new materials for spintronics. It offers a study of regularities in the changes of the valence band electron structure and the induction of the energy gap in the series 8-ZGNR → 8-ZGNR/h-BN(0001) → graphene/h-BN(0001). The peculiarities of the spin state at the Fermi level, the roles of the edge effect and the effect of substrate in formation of the band gap in 8-ZGNR/h-BN(0001) system are discussed. Our calculations shown that vdW-correction plays an important role in the adsorption of GNR on h-BN and results in reduction of the interplanar distances in equilibrium systems ZGNRs/h-BN(0001). As a result of the structural changes we have obtained new values of the energy gap in the 8-ZGNR-AF and 8-ZGNR-AF/h-BN(0001) systems. The paper demonstrates appearance of 600 meV energy gap in the 8-ZGNR/h-BN(0001) interface. The contributions of nanoribbon edges and the substrate in formation of the gap have been differentiated for the first time. The estimations of local magnetic moments on carbon atoms are made. Shown that in case of ferromagnetic ordering substrate presense causes insignificant splitting of the bands. The splitting reached only (14-28 meV). Since the electronic states of a suspended GNR in point (k=π) are degenerate near the Fermi level, we can assume that the above splitting in 8-ZGNR/h-BN(0001) is only determined by the contribution of the h-BN(0001) substrate.