The stacking order of multilayer graphene has a profound influence on its electronic properties. In particular, it has been predicted that a rhombohedral stacking sequence displays a very flat conducting surface state: the longer the sequence, the flatter the band. In such a flat band, the role of electron-electron correlation is enhanced, possibly resulting in high Tc superconductivity, magnetic order, or charge density wave order. Here we demonstrate that rhombohedral multilayers are easily obtained by epitaxial growth on 3C-SiC(111) on a 2° off-axis 6H-SiC(0001). The resulting samples contain rhombohedral sequences of five layers on 70% of the surface. We confirm the presence of the flat band at the Fermi level by scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy, in close agreement with the predictions of density functional theory calculations.

Nitrogen doping of graphene is of great interest for both fundamental research to explore the effect of dopants on a 2D electrical conductor and applications such as lithium storage, composites, and nanoelectronic devices. Here, we report on the modifications of the electronic properties of epitaxial graphene thanks to the introduction, during the growth, of nitrogen-atom substitution in the carbon honeycomb lattice. High-resolution transmission microscopy and low-energy electron microscopy investigations indicate that the nitrogen-doped graphene is uniform at large scale. The substitution of nitrogen atoms in the graphene planes was confirmed by high-resolution X-ray photoelectron spectroscopy, which reveals several atomic configurations for the nitrogen atoms: graphitic-like, pyridine-like, and pyrrolic-like. Angle-resolved photoemission measurements show that the N-doped graphene exhibits large n-type carrier concentrations of 2.6 × 10(13) cm(-2), about 4 times more than what is found for pristine graphene, grown under similar pressure conditions. Our experiments demonstrate that a small amount of dopants (<1%) can significantly tune the electronic properties of graphene by shifting the Dirac cone about 0.3 eV toward higher binding energies with respect to the π band of pristine graphene, which is a key feature for envisioning applications in nanoelectronics.