Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 3: Inorganic/Organic Interfaces: Growth I
O 3.8: Talk
Monday, March 16, 2015, 12:15–12:30, MA 005
Thermally and photoinduced polymerization of ultrathin sexithiophene films — •Anke Sander1,3, Rene Hammer1, Klaus Duncker1, Stefan Förster1, and Wolf Widdra1,2 — 1Martin-Luther-Universität Halle-Wittenberg, Halle, Germany — 2Max Planck Institute of Microstructure Physics, Halle, Germany — 3present address: Unite Mixte de Physique CNRS/Thales, Palaiseau, France
Due to their semiconducting properties, polythiophenes are highly promising for use in organic electronics. Apart from their direct deposition onto a substrate, one could also deposit smaller thiophene compounds and form covalent bonds between them by further processing which additionally enables a manipulation of the morphology.
This study addresses the polymerization of ultrathin sexithiophene (6T) films on Ag(001) and Au(001). Annealing of initially well-ordered films leads to local reactions between neighboring molecules. Depending on the surface temperature and the annealing time, long unbranched polythiophene polymers or branched polymer networks are formed. In general, the onset temperature and the complexity of structure formation depend on the strength of interaction with the underlying substrate. Here, on both substrates the polymerization occurs at temperatures significantly lower than found for crystalline powder. Similar structural changes and 6T polymerization are found upon exposure to UV radiation in the range from 3.0 to 4.2 eV. The observed reactions induced by thermal annealing as well as by UV excitation are explained by a polymerization via formation of cation radicals that necessitates the interplay with metallic substrate states.