Spin-dependent band-gap driven by nitrogen and oxygen functional groups in zigzag graphene nanoribbons

Abstract

We investigated the role of nitrogen and oxygen functional groups on the electronic and magnetic properties of zigzag graphene nanoribbons (ZGNRs) using spin-polarized first-principles density functional theory calculations. Twenty four functional groups of nitrogen, oxygen, and nitrogen-oxygen configurations were attached to the edge of ZGNRs. We analyze the band structure, spin-resolved bandgap, charge transfer, magnetic ordering, and binding energy. Similar to the pristine ZGNR, an indirect bandgap semiconducting behavior dominated in functionalized ribbons, except for carbonyl, pyrane, and pyridinium groups, that displays a metallic behavior. Spin-resolved band gap calculations revealed a strong dependence on the functional groups. Carbonyl groups showed a half-metallicity behavior with only spin up states at the Fermi level. In general, the functionalized ribbons displayed ferromagnetic alignment along the edges, but antiferromagnetic alignment between them, resulting in a total null magnetization. We showed some exceptions, the carbonyl, pyrane, lactam, pyridine N-oxide, and pyridinium functional groups induced significant changes in the magnetic arrangement, not only along the edge where they were attached but also to the opposite side. We have also incorporated a pentagon-heptagon pair or a single pentagon defect at the edge to explore the quinone, pyrone, and pyridone functional groups.