Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 52: Metal substrates: Adsorption of organic / bio molecules VII
O 52.15: Vortrag
Donnerstag, 26. März 2009, 18:30–18:45, SCH A118
Adsorption Geometry of Non-Planar Phthalocyanines on Cu(111): Orientation of the Electric Dipole Moment — •A. Gerlach1, S. Duhm2, T. Hosokai1, F. Schreiber1, N. Koch2, O. Hofmann3, E. Zojer3, T.-L. Lee4, and J. Zegenhagen4 — 1Institut für Angewandte Physik, Universität Tübingen, Germany — 2Institut für Physik, Humboldt-Universität zu Berlin, Germany — 3Institut für Festkörperphysik, Technische Universität Graz, Austria — 4European Synchrotron Radiation Facility, Grenoble, France
The orientation of polar organic molecules on metal surfaces has important implications for the electronic properties of the first molecular layer. We have studied the orientational ordering of chlorogallium phthalocyanines (GaClPc) on Cu(111) using the X-ray standing wave technique, photoelectron spectroscopy and DFT calculations.
The XSW data indicate that for low coverages the majority of GaClPc molecules adsorb in a ’Cl-down’ configuration with a chlorine bonding distance of 1.88 Å. Since the gallium atoms are located at 4.21 Å, we find a Ga-Cl bond length close to the gas phase value. For higher coverages the XSW data indicate a co-existence of the ’Cl-down’ and ’Cl-up’ configuration on Cu(111).
Due to the alignment of the GaClPc molecules in the sub-monolayer regime their dipole moments are expected to contribute to the decrease of the work function. The non-monotonic change of the work function with increasing GaClPc coverage observed in UPS measurements can be traced back to the different adsorption geometries of GaClPc. The analysis is further supported by quantum chemical calculations.