Dirac cones in graphene grown on a half-filled 4d-band transition metal

Abstract

New opportunities for structural and electronic properties engineering of graphene can be achieved by tuning the interfacial interaction, which is ruled by the interplay between d-band filling and geometry of the support. Here, is demonstrated the growth of graphene, featuring Dirac cones around the Fermi level, on the rectangular (110) surfaces of Rh, a half-filled 4d-band transition metal element. The analysis of the structural properties by low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) shows that domains with a continuum of possible graphene-substrate orientations with angular scatter of around 10° coexist in graphene/Rh(110) surfaces. Within each domain, surface structure is characterized by a distinct stripe-like moiré pattern. The interfacial chemistry analysis, by microprobeX-ray photoelectron spectroscopy (μ-XPS), of all the rotational domains studied, demonstrates the existence of two main levels of interfacial interaction strength, similar to previously reported graphene-metal systems characterized by the absence of Dirac cones around the Fermi level. However, the band structures of these domains probed by micro angle resolved photoelectron spectroscopy (μ-ARPES) present Dirac cones, with Fermi velocities comparable with those previously reported on weakly coupled graphene layers. Both the unique properties of graphene/Rh(110) surfaces and the prospect to obtain novel graphene-metal interfaces through the interplay between d-band filling and geometry, are expected to open new opportunities to study phenomena up to now masked behind the interaction with the substrate.