Bond polarization and image-potential screening in adsorbed C6F6 on Cu(1 1 1) |
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Authors: | S Vijayalakshmi PS Kirchmann A Pietzsch W Wurth |
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Institution: | a Institut für Experimentalphysik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany b Department of Physics, FU Berlin, Arnimallee 14, D-14195 Berlin-Dahlem, Germany c Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, 606-8501 Kyoto, Japan |
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Abstract: | The orientation of hexafluorobenzene (C6F6) on the Cu(1 1 1) surface has been determined for different coverages with the help of near edge X-ray absorption fine structure (NEXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS). The adsorption geometry and the bonding mode of C6F6 differ significantly in comparison to its hydrocarbon analog C6H6. C6F6 is found to adsorb on Cu(1 1 1) with the ring plane parallel to the surface for coverages below 10 ML. Next to the distinct multilayer, bilayer and monolayer phases we also present evidence of sub-monolayer (i.e., 1/2 ML) coverage with different electronic structure. These findings are explained in a phenomenological model based on fluorine’s property as a σ-acceptor and a π-donor and the resulting bond polarization within the molecule, which is stabilized by image-potential screening within the substrate. |
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Keywords: | Hexafluorobenzene Cu(1 1 1) Adsorption Image-potential screening XPS NEXAFS |
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