SKM 2023 – scientific programme
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O: Fachverband Oberflächenphysik
O 55: Organic Molecules on Inorganic Substrates IV: Adsorption and Growth II
O 55.7: Talk
Wednesday, March 29, 2023, 16:45–17:00, CHE 91
Molecular orientation of DHTAP on the nanostructured Cu-CuO stripe phase — •Claudia López-Posadas1, Antony Thomas2, Thomas Leoni2, Olivier Siri2, Conrad Becker2, and Peter Zeppenfeld1 — 1Institute of Experimental Physics, Johannes Kepler University Linz, Altenberger Str. 69, 4040 Linz, Austria — 2Aix-Marseille University, CNRS, CINaM, UMR 7325, F-13288 Marseille, France
We have studied the preferential adsorption, structure and molecular orientation of 5,14-dihydro-5,7,12,14-tetraazapentacene (DHTAP) layers on the regularly patterned Cu-CuO stripe phase obtained by sub-monolayer oxygen adsorption on the Cu(110) surface. Using Reflectance Difference Spectroscopy (RDS) and Scanning Tunneling Microscopy (STM) we find that the DHTAP molecules preferentially adsorb on the Cu (110) stripes, where they are always lying flat with their long molecular axis aligned parallel to the [-110]-direction. In contrast, on the subsequently covered Cu(110)-(2x1)O stripes, the DHTAP molecules are aligned with their long molecular axis parallel to the [001]-direction. The evolution of the RDS signal allows to monitor the sequential adsorption and orientation of DHTAP during monolayer formation and the subsequent multilayer growth for different oxygen pre-coverages and, hence, different Cu and CuO stripe widths. Interestingly, beyond the first monolayer, the DHTAP molecules adopt a preferential orientation which critically depends on the initial oxygen coverage, revealing the influence of the Cu-CuO stripe width and the possibility to tune the overall optical anisotropy of these films.