Doping domains in graphene on gold substrates: First-principles and scanning tunneling spectroscopy studies

Abstract

We have studied the graphene/gold interface by means of density functional theory (DFT) and scanning tunneling spectroscopy (STS). Weak interaction between graphene and the underlying gold surface preserves Dirac cones in the band structure, but they can be shifted with respect to the Fermi level of the whole system, which results in effective doping of graphene. DFT calculations revealed that the interface is extremely sensitive to the adsorption distance and to the structure of a metal's surface. On the other hand, STS experiments have shown the presence of energetic heterogeneity in terms of the changes in the local density of states (LDOS) measured at different places on the sample. They have been identified to be domains of doping by comparing measured and simulated LDOS. Domains of zero-doping and $p$-type (0.25--0.55 eV) doping have been then associated with the heterogeneous character of the gold surface. All these results demonstrate the possibility of engineering the electronic properties of graphene, especially tuning the doping across one flake, which can be useful for applications of graphene in electronic devices.