Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 25: Organic films II
O 25.4: Vortrag
Dienstag, 28. März 2006, 16:30–16:45, PHY C213
Intermolecular, interface, and dipole-dipole interactions in organic thin films — •Achim Schöll1, Selami Yilmaz1, Christoph Stadler1, Satoshi Kera2, and Eberhard Umbach1 — 1Exp. Phys. II, Univ. Würzburg, Germany — 2Faculty of Engineering, Chiba Univ., Japan
The interactions at metal-organic interfaces are of crucial importance for electronic devices, since they influence the layer morphology and the charge carrier transport through the interface due to the formation of interface dipoles and band off sets. We present a high-resolution PES and NEXAFS study on the adsorption behaviour and interface interaction of ordered thin films of the molecules titanyl- (TiO-Pc) and vanadyl-phthalocyanine (VO-Pc), which offer the possibility to tune the work function change of metal surfaces due to their high static dipole moments. Strong changes in the XPS and NEXAFS data of TiO-Pc consistently show the chemisorptive bonding of the first layer. In addition, UPS and work function measurements clearly indicate a parallel orientation of the molecular dipoles which increases the work function by ~0.1 eV in comparison to non-polar adsorbates. A further increase of the coverage leads to the formation of a second layer with anti-parallel dipoles and reduced work function. The careful analysis of the high-resolution XPS and NEXAFS data shows no significant covalent contribution to the intermolecular interaction. However, the desorption temperature of the second layer is increased by more than 150 K in respect to the multilayer, which is attributed to dipole-dipole interaction. This project is financed by the BMBF under contract 05KS4WWC/2.