Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 89: Metal Substrates: Epitaxy and Growth

O 89.11: Talk

Friday, February 29, 2008, 12:00–12:15, MA 041

DFT study of epitaxial graphene on Ru(0001) — •bin wang¹, marie-laure bocquet¹, stefano marchini², sebastian günther², and joost wintterlin² — ¹Laboratoire de Chimie, Ecole Normale Supérieure de Lyon, Lyon, France — ²Department Chemie, Ludwig-Maximilians-Universität München, München, Germany

Graphene is a flat monolayer of carbon atoms with a honeycomb lattice, which has been a rising star in materials science for its unique electronic structure. It can also grow on surfaces if the lattice constants of the surface and of graphene match. In case of lattice mismatch, as in the case of metal surfaces like Ru(0001) [1] or Ir(111) [2], epitaxial growth leads to a moiré structure. We have investigated epitaxial graphene on a Ru(0001) substrate by means of large-scale density functional theory (DFT) calculations. We show that, contrary to other substrates, the graphene electronic structure displays massive local changes, alternatingly varying between a zero gap and a band gap of 2 eV. This result is caused by alternating weak and strong contact areas of the graphene on the Ru surface, correlated with a large geometric buckling of 1.5 Å over the 30 Å periodic moiré superstructure. The mismatching lattice between graphene and the substrate thus leads to a changing symmetry and electronic structure that both vary regularly on the nanometer scale. The results are in good agreement with recent STM experiments [1].

[1] Marchini S., Günther S. & Wintterlin J., Phys. Rev. B. 76, 075429 (2007) [2] N'Diaye A.T., Bleikamp S., Feibelman P. J. & Michely T., Phys. Rev. Lett. 97, 216501 (2006)