Tunable hybridization between electronic states of graphene and a metal surface

We present an approach to monitor and control the strength of the hybridization between electronic states of graphene and metal surfaces. Inspecting the distribution of the $\pi$ band in a high-quality graphene layer synthesized on Ni(111) by angle-resolved photoemission, we observe a new “kink” feature that indicates a strong hybridization between the $\pi$ and the $d$ states of graphene and nickel, respectively. Upon deposition and gradual intercalation of potassium atoms into the graphene/Ni(111) interface, the kink feature becomes less pronounced, pointing at potassium mediated attenuation of the interaction between the graphene and the substrate.

Figure 1

(Color online) Epitaxial growth and functionalization of a graphene monolayer. (a) Clean Ni(111) surface. (b) Graphene monolayer grown by CVD. The unit cell with the nonequivalent $A$ and $B$ atoms is indicated. (c) Potassium atoms intercalate between the Ni(111) and the graphene. The corresponding XPS spectra for (d) a clean Ni(111) surface, (e) an epitaxially grown graphene monolayer on Ni(111), and (f) a potassium intercalated graphene monolayer with $\text{K}/\text{C}=0.69$.

Figure 2

(Color online) ARPES intensities of the band structure of (a) a pristine graphene monolayer and (b) a doped graphene monolayer. The thick and thin lines denote the TB calculations for the $\pi$ and $\sigma$ bands (for the parameters, see Table ). The on-site energy ${ϵ}_{2p}$ and the gap $\Delta$ are depicted.

Figure 3

(Color online) The region of the hybridization kink in the $\pi$ band of graphene for different doping levels as indicated by the K/C ratio. The kink is denoted by the arrow in (a). The dots depict the tight-binding calculations.