Regensburg 2007 – wissenschaftliches Programm
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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices
SYOE 8: Poster Session SYOE
SYOE 8.25: Poster
Dienstag, 27. März 2007, 18:00–20:00, Poster B
Growth of sexithiophene (6T) films studied by reflectance difference spectroscopy — •L.D. Sun1, S. Berkebile2, G. Weidlinger1, G. Koller2, F.P. Netzer2, M.G. Ramsey2, M. Hohage1, and P. Zeppenfeld1 — 1Institute of experimental physics, Johannes Kepler University Linz, Linz, Austria — 2Institute of Physics, Karl-Franzens University Graz, Graz, Austria
As a linear differential optical method, reflectance difference spectroscopy (RDS) is extremely sensitive to any kind of optical transition which is polarization dependent, from single molecule excitation to excitons of molecular aggregates. Here, we report our in-situ RDS investigation of 6T film growth on anisotropic substrates, namely Cu(110)-(2x1)O and TiO2(110). The orientation of 6T molecule and the optical property of 6T thin film have been monitored over the entire range of the film thickness up to several nm. At submonolayer coverage, the optical property of the film is close to that of single molecule. However, already when the thickness of the film approach to one completed monolayer, exitonic state represented by Davydov splitting sets in. Following the evolution of RD spectrum, the growth mode and the film morphology can be deduced. For 6T grows on Cu(110)-(2x1)O , all molecules in the film are uniaxially aligned with their long molecular axes parallel to the CuO rows and to the Cu substrate surface. Similar growth mode has also been observed for 6T growth on TiO2(110) at liquid nitrogen temperature. However the 6T growth on TiO2(110) at room temperature shows a different behavior.