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Regensburg 2000 – scientific programme

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O: Oberflächenphysik

O 11: Postersession (Eröffnung)

O 11.59: Poster

Monday, March 27, 2000, 19:00–22:00, Bereich C

HREELS study of electronic and vibrational excitations in K-dosed PTCDA films on Ag(110) — •V. Shklover1, F.S. Tautz2, S. Schmitt1, S. Sloboshanin2, M. Sokolowski1, J.A. Schaefer2, and E. Umbach11Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074 Würzburg — 2Institut für Physik, Technische Universität Ilmenau, PF 100565, 98684 Ilmenau

Alkali metal doping of organic semiconductors is widely used to increase their conductivity. We have studied the electronic and vibrational excitations of K-doped films of PTCDA on Ag(110) by HREELS and LEED as a function of K concentration and annealing temperature. HREEL spectra in the range of electronic excitations show that for K concentrations up to approximately 2 K atoms/PTCDA and for annealing temperatures up to 400 K hybrid HOMO-LUMO states are formed as broad features at 0.8 eV due to charge transfer. In the vibrational spectra their formation corresponds to the appearence of strong peaks at 47.6, 66, 130, 150 and 191 meV. The increase of K concentration and/or annealing temperature results in the disappearance of the charge transfer transitions and the formation of chemically bound K-PTCDA complexes with dominating features at 1.8, 2.3 and 3.5 eV. Corresponding changes are observed in the vibrational spectra and in the LEED patterns.

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