Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 35: Poster Session II (Polymeric biomolecular films; Nanostructures; Electronic structure; Spin-orbit interaction; Phase transitions; Surface chemical reactions; Heterogeneous catalysis; Particles and clusters; Surface magnetism; Electron and spin dynamics; Surface dynamics; Methods; Electronic structure theory; Functional molecules)

O 35.82: Poster

Tuesday, March 27, 2012, 18:15–21:45, Poster B

Photoemission studies of graphene on Pt(111) — •David Nobis, Daniel Niesner, and Thomas Fauster — Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen, Germany

Graphene can be grown on a variety of metal surfaces with different quality. On the Pt(111) surface graphene was prepared by decomposition of hydrocarbons. Ultraviolet photoelectron spectroscopy (UPS, 6.22 eV) and two-photon photoemission (2PPE, pump pulse 4.66 eV, probe pulse 1.55 eV) experiments were carried out on the graphene-covered surface.

The UPS experiments show a downward-dispersing state 260 meV below the Fermi level. This state fits well to a Shockley surface state from the bare Pt(111) surface calculated by the phase accumulation model. The graphene layer increases its binding energy.

By 2PPE the first two image-potential states with binding energies of 820 meV and 210 meV were observed. Lifetimes were determined to 13 fs and 79 fs and effective masses are close to the free-electron mass. Compared to the clean Pt(111) surface [1] the graphene layer enlarges the binding energy (mostly of n=1 image-potential state) and the lifetime of the image-potential states. This can be understood by the screening of the charge being dominated by the graphene. Angle-resolved spectra show maximum intensity around k_∥ = 0.1 Å⁻¹ which is attributed to a resonance with the Shockley surface state.
Link, S. et al., Phys. Rev. B 63 (2001) 115420