Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 36: Posters: Bio/organic Molecules on Surfaces, Graphene, Solid/liquid interfaces, Metal Substrates, Electronic Structure Theory

O 36.52: Poster

Dienstag, 1. April 2014, 18:30–22:00, P1

Two-photon photoemission study of gold-intercalated graphene on Ir(111) — •David Nobis, Daniel Niesner, and Thomas Fauster — Universität Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen, Germany

We have investigated gold-intercalated graphene on Ir(111) as well as gold on clean Ir(111) using UV photoelectron spectroscopy (UPS) and two-photon photoemission (2PPE). Up to 5 monolayers (MLs) of gold were intercalated at several temperatures.
The measured work function of the Au/Ir system approaches the value of Au(111) after the deposition of 4 MLs of gold. In the graphene-covered case the work function (4.88 eV with 5 MLs gold) remains larger than expected [1]. The UPS spectra of Au/Ir(111) show a gold-related, upward-dispersing surface state around 0.47 eV below the Fermi level.
In the 2PPE spectra two image-potential states (IPS) are found. The second IPS shows a resonant transition from the Au surface state. The energetic positions of the IPS in combination with the large work function is evidence for incomplete intercalation of the gold. From the energetic spacing of the IPS the local work function of the intercalated areas is extrapolated to 4.69 eV which agrees with the calculated value of 4.74 eV [1]. With this local work function the binding energies of the first two IPS (0.85 eV and 0.21 eV) agree well with those measured on other graphene-covered noble-metal surfaces [2].
[1] Khomyakov, P. A. et al., Phys. Rev. B 79 (2009) 195425
[2] Nobis, D. et al., Phys. Rev. B 88 (2013) 195435