Berlin 2012 – scientific programme
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DS: Fachverband Dünne Schichten
DS 44: Poster IV: Thin film photovoltaics; Organic electronics and photovoltaics (jointly with CPP, HL, O); Organic thin films; Trends in atomic layer deposition (Focused session)
DS 44.34: Poster
Friday, March 30, 2012, 09:30–12:00, Poster E
Interrelation between Substrate Roughness and Thin-Film Structure of Functionalized Acenes on Graphite — •Tobias Breuer1, Ingo Salzmann2, Jan Götzen1, Martin Oehzelt2, Antonia Morherr1, Norbert Koch2, and Gregor Witte1 — 1AG Molekulare Festkörperphysik, Philipps-Universität Marburg, D-35032 Marburg — 2Institut für Physik, Humboldt-Universität zu Berlin, D-12489 Berlin
We analyzed the growth of differently modified pentacenes (perfluoropentacene (PFP) and pentacenetetrone (P-TET)) on graphite and demonstrate that both, the resulting morphology and the crystalline structure of the films, critically depend on the microroughness of the substrate. On well-ordered highly oriented pyrolytic graphite (HOPG) surfaces prepared by exfoliation, both molecular materials form exceptionally smooth films, which consist of large-area molecularly flat islands yielding an overall low roughness. Interestingly, in these films molecules adopt a recumbent orientation, while on defective substrates, created by brief ion sputtering, the molecules adopt an upright orientation and form nonconnected islands exhibiting a significantly increased film roughness. Our study not only underlines the possibility to prepare very smooth films on a weakly interacting substrate but also emphasizes the importance of a proper substrate preparation and the significance of precise knowledge of substrate-surface properties to control the resulting structure of organic films.
[1] J. Götzen et al., Phys. Rev. B 81, 0854406 (2010).
[2] T. Breuer et al., Cryst. Growth Des. 11, 4996 (2011).