Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 27: Graphene II
O 27.1: Vortrag
Dienstag, 27. März 2012, 10:30–10:45, MA 041
How clusters bind to the graphene moiré on Ir(111) - XPS compared to DFT — •Timm Gerber1, Jan Knudsen2, Peter J. Feibelman3, Elin Grånäs2, Karina Schulte4, Patrick Stratmann1, Jesper N. Andersen2, and Thomas Michely1 — 1II. Physikalisches Institut, Universität zu Köln — 2Division of Synchrotron Radiation Research, Lund University — 3Sandia National Laboratories, Albuquerque, New Mexico — 4MAX-lab, Lund University
Our understanding of metal-atom cluster adsorption on graphene on Ir(111) is based on elementary chemical ideas, rehybridization and buckling, supported by density functional theory (DFT) calculations. We have tested the DFT picture by comparing calculated core level spectra to X-ray photoemission spectroscopy (XPS) measurements. For pristine graphene, which forms a gently undulating moiré on Ir(111), DFT predicts a 140 meV modulation of C 1s core level shifts (CLS), consistent with the measured spectrum. With Pt clusters adsorbed, measured Pt 4f CLS of the adsorbed clusters also support the calculations. The modulation of the C 1s spectrum is strengthened with clusters adsorbed, and C-atom ionization potentials under and in the vicinity of the Pt clusters are shifted enough to be experimentally distinguished as a broad shoulder of positive C 1s CLS. Further, DFT calculations imply that sp2 to sp3 rehybridization of C-atoms below the Pt cluster induce a 1.1 eV CLS-splitting between Pt and Ir bonded C atoms; this prediction is also consistent with the XPS data.