Dresden 2014 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 37: Posters: Plasmonics, Electronic Structure and Spin-Orbit Interaction, Semiconductor and Insulator Surfaces, Nanostructures
O 37.85: Poster
Dienstag, 1. April 2014, 18:30–22:00, P2
Pentacene adsorption and oxidation on a cobalt oxide bilayer film — •Marina Schuler, Pascal Ferstl, Lutz Hammer, and M.Alexander Schneider — Lehrstuhl f. Festkörperphysik, FAU Erlangen-Nürnberg, 91058 Erlangen
As a prototypical example of the adsorption of functional organic molecules on an oxide surface we investigate pentacene on a bilayer of CoO epitaxially grown on Ir(100) [1] by STM and TDS in UHV. At 300 K the molecules adsorb flat-lying and a maximum areal density of 0.66 molecules per nm2 is obtainable before multi-layer growth sets in. For single-layer coverage we observe a well-defined rotational alignment of the molecules with respect to the crystallographic axes of the CoO layer. The lateral binding configuration, in contrast, is variable on the atomic scale, since the molecules always bridge many inequivalent sites of CoO. From the absence of any lateral long-range order of the molecular film even after annealing to 400 K we conclude that the molecule-substrate interaction is dominating.
Pentacene starts to get oxidized by the CoO film already at 420 K, the molecules decompose into CO2, H2O, CO and H2. In the beginning of the reaction the oxide layer gradually transforms into ordered sub-oxide structures. At higher temperatures and lower oxygen content of the cobalt oxide layer the dominant reaction products shift from CO2 and H2O to CO and H2. We note that the sub-oxides can be reoxidised in the same temperature regime, hence a full catalytic cycle of molecule oxidation is achievable.
[1] C. Tröppner, et al., PRB 86, 235407 (2012)