Tuning metal-graphene interaction by non-metal intercalation: a case study of the graphene/oxygen/Ni (111) system

Epitaxial growth of graphene on transition metal surfaces has been proposed as one of the most promising methods for large-scale preparation of high-quality graphene. However, the presence of the substrate could significantly affect the intrinsic electronic structure of graphene and intercalation of metals is an established route for decoupling the graphene from the substrate. Taking a graphene/Ni(111) surface as an example, we suggest reactive oxygen as an effective intercalation element to recover the linear dispersion of graphene based on density functional theory calculation, in which vdW interactions are treated using the optB88vdW functional. The possible intercalation configurations at different coverage are considered and the geometry and electronic structure are analyzed in detail. Our results indicate that the energy favorable structures change from top-fcc to bridge-top configuration after oxygen intercalation and the binding between the graphene and the O/Ni(111) substrate becomes stronger at high oxygen coverage even than pure Ni(111) substrate. Most interestingly, the electronic structure of pristine graphene is found to be almost restored, especially for the bridge-top configuration after oxygen intercalation, and the Dirac points move towards the high energy region relative to the Fermi level. A graphene/oxygen/Ni (111) system is thus suggested as a p-type doped strongly bound Dirac system. Detailed analysis using projected energy band and differential charge density indicates that the intercalated oxygen atoms react with the Ni (111) surface strongly, which not only blocks the strong interaction between Ni and graphene but also passivates oxygen 2p states. The intercalation mechanisms distinguished from the conventional metal intercalation will be useful to understand other complex intercalation systems.