Regensburg 2010 – scientific programme
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O: Fachverband Oberflächenphysik
O 16: Organic, polymeric, biomolecular films - also with adsorbates
O 16.2: Talk
Monday, March 22, 2010, 15:15–15:30, H46
Photoisomerization of azobenzene on layer compound surfaces studied by photoelectron spectroscopy — •Eric Ludwig1, Jaroslaw Iwicki1, Kai Rossnagel1, Felix Köhler2, Rainer Herges2, and Lutz Kipp1 — 1Institut für Experimentelle und Angewandte Physik, Universität Kiel, D-24098 Kiel, Germany — 2Otto-Diels-Institut für Organische Chemie, Universität Kiel, D-24098 Kiel, Germany
Photoswitchable azobenzene and its derivative Disperse Orange 3 (DO3) molecules were deposited in situ under UHV conditions on the surfaces of the metallic and semiconducting layered crystals TiTe2 and HfS2, respectively. Due to weak van der Waals-like coupling between the layers these materials serve as excellent substrates for the analysis of adsorbed molecules and their possible photoswitching behavior. Coverages from sub-monolayer to several monolayers were realized. Photoelectron spectroscopy (PES) experiments were performed using a He discharge lamp and a SPECS Phoibos 150 analyzer. Results imply Stranski-Krastanov-like film growth of azobenzene on TiTe2. Comparison of PES spectra to outer valence green function calculations suggests dimer formation of DO3. To photoisomerize the adsorbed molecules, the samples were irradiated with a LED Power Pen (wavelength 365 nm, 3.5 W/cm2). Experimental data of azobenzene adsorbed on HfS2 shows that the molecules can be partially switched from the trans to the cis orientation. On TiTe2 no switching has been observed, presumably due to stronger molecule-substrate coupling. This work was supported by the DFG through SFB 677.