Berlin 2005 – scientific programme
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DS: Dünne Schichten
DS 22: Optische Spektroskopie dünner Schichten II
DS 22.5: Talk
Tuesday, March 8, 2005, 15:30–15:45, TU HS110
In-situ RAS study of para-sexiphenyl film growth on metal and oxide surfaces — •L.D. Sun1, M. Hohage1, Y. Hu1, K. Maschek1, P. Zeppenfeld1, S. Berkebile2, F.P. Netzer2, and M.G. Ramsey2 — 1Institut für Experimentalphysik, Johannes-Kepler-Universität Linz, Austria — 2Institut für Experimentalphysik, Karl-Franzens-Universität Graz, Austria
Para-sexiphenyl (P6P) is an aromatic molecule, which is classified as a wide gap organic semiconductor with an electronic band gap of 3.1 eV. The molecule which consists of a linear chain of six linked benzene rings gives a strong intrinsic electronic and optical anisotropy. This fact allows probing the orientation of the P6P molecules by monitoring the polarization dependence of the optical absorption. Reflectance Anisotropy Spectroscopy (RAS), on the other hand, is a powerful tool to study the lateral optical anisotropy and its evolution of the growing thin films and the substrate beneath. Here, we present our RAS in-situ investigation of P6P films growth on oxide (TiO2(110)) and metal (Cu(110)) surfaces. The films have been prepared by physical vapour phase deposition in UHV under diverse conditions. Pronounced optical anisotropies arising from the optical absorption of P6P have been observed for the distinct films. In fact, based on the behaviour of the RAS feature contributed by the HOMO to LUMO transition of the P6P molecules, important information about the orientation and the conformation of the P6P molecules in the films can be obtained directly. Furthermore, the RDS is very sensitive to small quantities of P6P and therefore well suited for the investigation of the initial stages of P6P growth.