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Dresden 2009 – scientific programme

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O: Fachverband Oberflächenphysik

O 30: Metal substrates: Adsorption of organic / bio molecules IV

O 30.1: Talk

Wednesday, March 25, 2009, 10:30–10:45, SCH A118

Evidence of Charge Transfer in UHV-Deposited Coronene-hexaone and Hexamethoxycoronene Sandwich LayersK. Medjanik1, S. Naghavi2, R. Rieger3, D. Kutnyakhov1, S.A. Nepijko1, •G. Schönhense1, V. Alijani2, C. Felser2, M. Baumgarten3, and K. Müllen31Institut für Physik, Universität Mainz — 2Institute for Analytic and Anorganic Chemistry Univ. Mainz — 3Max-Planck-Institute for Polymer Research, Mainz

The electronic structure of UHV-deposited sandwich layers of the donor hexamethoxycoronene and the acceptor coronene-hexaone on Au has been studied by UPS. In a donor-acceptor multilayer superstructure a new signal close to the Fermi energy arises that is absent in films of the pure species. The electron injection barrier of the acceptor is lowered such that charge transfer occurs into its LUMO. The charge depletion in the donor molecules leads to a shift of their HOMO position to higher binding energies by 0.26eV. A significant band bending occurs due to the polar interface between the metal and the organic film as discussed by Koch [1]. In turn, the UPS signal of the charge transfer complex rises significantly above that of the Au substrate (by 0.35eV in the as-deposited multilayer film and by 0.55eV upon annealing of the film at 80°C). In AFM and optical microscopy we observe triangular-shaped nanocrystals with dendritic growth mode.

Funded by DFG through Transregio SFB TRR 49 (B8)

[1] N. Koch, J. Phys. Cond. Matt. 20 (2008) 184008

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