Tailoring electronic and optical parameters of bilayer graphene through boron and nitrogen atom co-substitution; an ab-initio study

Abstract

Bilayer graphene (BLG) system substituted with boron (B) and nitrogen (N) atoms of different concentration is investigated in this study using first-principles study density functional theory (FPS-DFT). The effects of B/N impurity co-substitution on electronic and optical behaviors of BLG are systematically studied. The band gap of pure BLG obtained during this study agrees well with previous experimental studies. Formation energies for B/N co-doped BLG systems indicate that the, impurity substitution process in BLG is exothermic and stable B/N atom-doped BLG systems can be realized experimentally. Charge difference calculations suggest that, the dopant B and N atoms placed in different layers of BLG, try to deplete the electrons in the space between graphene layers and the charge density is localized at the dopant sites. It is discovered through electronic parameters that, individual B/N substitution in BLG, moves Dirac cone into conduction/valence bands, while providing a limited energy gap at the Dirac point. On the other hand, when B/N impurities are placed in BLG, lattice symmetry of BLG breaks, dispersion relation near the Fermi level (EF) is disturbed and a fixed energy gap emerges in its electronic structure. BLG optical parameters contain same profile as that of SLG, except that all the parameters show increased intensities. When B/N atoms are co-doped in BLG, the absorption spectra is improved in low electron energy range and higher static reflectivity is observed. From the results generated during this study, it can be generalized that B/N atoms can be considered as ideal doping impurities for BLG systems, as they not only produce stable and functional BLG systems, but also preserve the intrinsic properties of graphene material. Further experimental studies can be performed on the systems discussed in this work, in order to synthesize multilayer graphene systems; those are functional for nano/opto electronic device applications.