New insights in the electronic structure of doped graphene on adsorption with oxides of nitrogen

Abstract

The electronic effects produced by molecular adsorption of some environmentally potent oxides of nitrogen, N2O, NO, and NO2 on chemically modified surfaces of graphene are investigated, employing spin-polarized density functional calculations. Graphene surface is modified chemically with substitutional doping through boron, nitrogen, and co-doping, with combinations of boron and nitrogen. In the case of adsorption of the paramagnetic species, NO and NO2, rather exotic effects on adsorption are observed, with unusual electronic structure leading to flat bands in the band structure. The significant alterations of the electronic structure are primarily due to the adsorbate-adsorbent orbital mixing. The adsorption-induced dispersion-less flat bands are produced, eventually turning some of the doped, semiconducting surfaces into a metallic one. These dispersion-less bands are due to stronger interactions of the gaseous molecule with the surface leading to the localization of the molecule over the surface. It is observed that with the adsorption of paramagnetic oxides of nitrogen, the flat bands are introduced between the valence and the conduction band resulting in the loss of dispersion. For some of the configurational patterns of the dopant, chemically driven adsorption of the molecules onto the doped graphene surface take place, characterized by strong adsorption energies and charge transfers.