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The Valence Electronic Structure of N-Doped P-Sexiphenyl

Published online by Cambridge University Press:  10 February 2011

U. Theissl
Affiliation:
Institut f. Festkörperphysik, TU-Graz, A-8010 Graz, Austria
E.J.W. List
Affiliation:
Institut f. Festkörperphysik, TU-Graz, A-8010 Graz, Austria
N. Koch
Affiliation:
Institut f. Festkörperphysik, TU-Graz, A-8010 Graz, Austria LS Physik kondensierter Materie, Universität Potsdam, D-14469 Potsdam, Germany
A. Vollmer
Affiliation:
Institut f.Physikalische u. Theoretische Chemie, Freie Universität Berlin, D-14195 BerlinGermany
S. Schrader
Affiliation:
LS Physik kondensierter Materie, Universität Potsdam, D-14469 Potsdam, Germany
J.-J. Pireaux
Affiliation:
Laboratoire Interdisciplinaire de Spectroscopie Electronique –Facultés Universitaires Notre-Dame de la Paix, B-5000 Namur, Belgium
G. Leising
Affiliation:
Institut f. Festkörperphysik, TU-Graz, A-8010 Graz, Austria
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Abstract

Thin films of p-sexiphenyl (6P) were doped with increasing amounts of potassium in situ, and the change in the valence electronic structure of 6P upon the alkali metal deposition was followed with ultraviolet photoelectron spectroscopy. We observe the evolution of new intragap emissions, which are attributed to the formation of bipolarons, even for very low doping concentrations. The low binding energy intra-gap emission exhibits a pronounced asymmetric lineshape, in contrast to the findings when cesium is used as dopant. In order to investigate whether this lineshape is due to different emissive electronic species in the bulk and on the surface of the 6P film the take-off angle for the photoelectrons was varied. As no change in the lineshape is found when going from normal to near-grazing emission we can exclude that charged 6P molecules in the bulk and on the surface yield different valence electronic spectra. Therefore, the characteristic lineshape of the low binding energy emission is proposed to be related to the interaction of the doped organic molecule with the different counterions.

Type
Research Article
Copyright
Copyright © Materials Research Society 1999

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References

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