Structural investigation of nanocrystalline graphene grown on (6√3 × 6√3)R30°-reconstructed SiC surfaces by molecular beam epitaxy

Growth of nanocrystalline graphene films on (6 p 3◊6 p 3)R30 - reconstructed SiC surfaces was achieved by molecular beam epitaxy, enabling the investigation of quasi-homoepitaxial growth. The structural quality of the graphene films, which is investigated by Raman spectroscopy, increases with growth time. X-ray photoelectron spectroscopy proves that the SiC surface reconstruction persists throughout the growth process and that the synthesized films consist of sp 2 -bonded carbon. Interestingly, grazing incidence x-ray diffraction measurements show that the graphene domains possess one single in- plane orientation, are aligned to the substrate, and offer a noticeably contracted lattice parameter of 2.450A. We correlate this contraction with theoretically calculated reference values (all-electron density functional calculations based