Dresden 2009 – scientific programme

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O: Fachverband Oberflächenphysik

O 22: Focused Session: Epitaxial Graphene III

O 22.1: Topical Talk

Tuesday, March 24, 2009, 10:30–11:00, SCH 251

Structural and electronic properties of graphene on Ru(0001) — •Sebastian Günther — Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 11, 81377 München, Germany

STM on clean and Au covered graphene on Ru(0001) revealed a surprisingly large apparent height corrugation of 0.8-1.2 Å within the unit cell of the imaged moiré structure with a size of ~ (11x11) Ru lattice spacings. Up to then graphene was thought to be a rather flat 2-dim network, weakly interacting with metal substrates. In order to understand whether graphene can form a strongly corrugated layer on a transition metal substrate and what type of interaction between carbon and substrate is formed, we performed ARPES measurements, SXRD and a LEED I(V) analysis. In ARPES strong electronic interaction between C and Ru could be evidenced by the observation of a large gap of the graphene pi-band at the K-point of the brillouin zone. Further details of the electronic structure were found and will be discussed. The geometric configuration of the g-Ru(0001) was addressed by SXRD and LEED I(V) measurements. SXRD proved that in fact the periodic moiré consists of a much larger unit cell of (25x25) g on (23x23) Ru size with a superimposed (2x2) symmetry. Crystal truncation rod data indicated pronounced buckling of the underlying Ru atoms evidencing strong interaction of C and Ru atoms. Finally, a LEED I(V) analysis proved both the large height modulation of the graphene layer of ~ 1.5 Å as well as strong vertical and lateral atom displacements in the underlying Ru layers.