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Free keywords:
Graphene, nanocrystalline graphene, silicon carbide, buffer layer, molecular beam epitaxy,
grazing incidence diffraction, density functional theory
Abstract:
Growth of nanocrystalline graphene films on (6√3×6√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 sp2-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 2.446 Å. We correlate this contraction with theoretically calculated reference values (all-electron density
functional calculations based on the van der Waals corrected PBE functional) for the
lattice parameter contraction induced in ideal, free-standing graphene sheets by:
substrate-induced buckling, the edges of limited-size flakes, and typical point defects
(monovacancies, divacancies, Stone-Wales defects).
