Regensburg 2019 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 16: Organic Thin Films, Organic-Inorganic Interfaces

DS 16.2: Vortrag

Mittwoch, 3. April 2019, 09:45–10:00, H39

Titanylphthalocyanine Films on Ag(111): an Epitaxial Metal/Organic Hetero-System with Exceptional Smooth Surface — •Michael Kothe, Felix Widdascheck, and Gregor Witte — Philipps-Universität, Marburg, Germany

The chemical and thermal robustness of titanyl-phthalocyanine (TiOPc) in combination with its high optical absorption favours its application as photoconductor or chromophore for light-harvesting in organic photovoltaic applications. Beside such device application there is a large interest in the controlled fabrication of smooth molecular spacer layers of controlled thickness in order to prepare molecular hetero-structures. While many pi-conjugated materials form highly ordered mono- and bilayer films on metallic (single crystalline) substrates, the films exhibit a notable roughness upon increasing film thickness. Here, we demonstrate that TiOPc forms extremely smooth films on Ag(111), not only in the mono- and bilayer regime but also for films exceeding a thickness of 10nm. Combining various techniques including atomic force and scanning tunnelling microscopy (AFM, STM), with X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and X-ray diffraction (XRD), we show that for substrate temperatures below 450 K TiOPc forms molecularly smooth films with a small overall film roughness. The analysis shows that the films are stabilized by molecular bilayers of alternatingly (up and down) oriented titanyl. Finally, we show that even the thick films are epitaxially oriented with respect to the azimuth direction of the Ag(111) surface.