Regensburg 2007 – scientific programme
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DS: Fachverband Dünne Schichten
DS 1: Organic Thin Films I
DS 1.4: Talk
Monday, March 26, 2007, 10:15–10:30, H32
Molecular chains and carpets of sexithiophenes on Au(111) — •Hendrik Glowatzki1, Steffen Duhm1, Kai F. Braun2, Jürgen P. Rabe1, and Norbert Koch1 — 1Humboldt-Universität zu Berlin, Institut für Physik, Newtonstrasse 15, 12489 Berlin — 2Universität Hamburg, Institut für Angewandte Physik, 20355 Hamburg, Germany
We investigated two organic semiconductors sexithiophene (6T) and dihexylsexithiophene (DH6T) adsorbed on Au(111) in the (sub-)monolayer range by scanning tunneling microscopy (STM). At low coverage, 6T formed continuous chains of single molecular width along Au step edges, facilitated by 6T conformation changes. At monolayer coverage, substantially different structures were observed for the two molecules, despite the identical conjugated core. 6T formed rows of molecules with parallel long molecular axes, whereas DH6T formed lines along these axes, where the conjugated cores were embedded in a matrix of hexyl chains (brick-wall-like). Alkylation of 6T thus led to significantly reduced inter-molecular interactions of conjugated parts in the monolayer. Consequently, 6T formed a continuous "molecular carpet" on extended Au(111) terraces, whereas DH6T resembled a patchwork-like carpet, as domain boundaries were induced by the Au(111) herringbone surface structure.