Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 51: Metal Substrates: Adsorption of Organic/Bio Molecules III

O 51.2: Vortrag

Mittwoch, 27. Februar 2008, 15:30–15:45, MA 041

Ultra-thin films of α-sexithiophene on Au(001) at room and elevated temperature — •Anke Höfer, Klaus Duncker, Mario Kiel, Sebastian Wedekind, René Hammer, and Wolf Widdra — Institute of Physics, Martin-Luther-Universität Halle-Wittenberg

The rodlike, π-conjugated molecule α-sexithiophene (α-6T) is widely used in organic electronics, in which the performance of the devices strongly depends on molecular order. Ultra-thin films of α-6T on Au(001) have been studied by scanning tunneling microscopy (STM) in UHV. At room temperature in the monolayer regime two different highly ordered adsorption phases coexist which are related to quenching (phase D) and conservation (phase L) of the underlying substrate reconstruction. As the molecular structure of D is identical to one found on Ag(001), the other one is similar to that observed on Au(111) [1]. Both structures show different homochiral domains necessitating chiral self-recognition of the adsorbed molecules. Thermally induced both phases disappear at 400 K, whereas the transition of L is irreversible. In-situ observations at elevated temperatures from 410 K up to 630 K show the formation of a molecular network, which is interpreted as result of thiophene polymerization. The onset temperature of polymerization differs for the surface areas with quenched and conserved reconstruction.

[1] M. Kiel, K. Duncker, Ch. Hagendorf, W. Widdra, Phys. Rev. B 75, 195439 (2007)