Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 20: Inorganic/Organic Interfaces: Growth III

O 20.3: Talk

Tuesday, March 17, 2015, 11:00–11:15, MA 005

Growth of α-sexithiophene (α-6T) on a textured rutile TiO₂(110) surface — •Thorsten Wagner, Michael Mühlegger, Ebrahim Ghanbari, and Peter Zeppenfeld — Johannes Kepler University Linz, Austria

Titanium dioxide (TiO₂) is a wide band gap semiconductor with applications as photocatalyst, in solar energy converters, and in electronic devices based on organic thin films. In this work, we studied the growth of the prototype organic semiconductor α-sexithiophene (α-6T, C₂₄H₁₄S₆) on the (110) surface of rutile TiO₂ single crystals. In particular, we used the real-time imaging capabilities of Photoelectron Emission Microscopy (PEEM) to study side-by-side the growth of α-6T on a well prepared part of the surface and on a part of the surface with was modified by ion bombardment. To texture the surface, first several cycles of oxygen exposure, annealing, and sputtering were carried out. Finally, one part of the sample was sputtered with Ar⁺-ions for 5 min while the other part was protected by an aperture.
The ion bombardment of the TiO₂ surface introduces oxygen vacancies. Morphological changes of the surface and these oxygen vacancies can modify the growth of the organic dye molecules α-6T as demonstrated by Ivanco et al. By imaging spectroscopy we can confirm the local modification of the TiO₂ surface upon sputtering. Local transients of the PEEM intensity were obtained during deposition of the organic material. Finally, the individual crystallites were probed by imaging spectroscopy to study their electronic properties.