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O: Oberflächenphysik

O 2: Organische Dünnschichten I

O 2.6: Vortrag

Freitag, 4. März 2005, 12:00–12:15, TU EB301

Growth of thin para-sexiphenyl films on Cu(110) and Cu(110)-(2x1)O — •K. Maschek, Y. Hu, L.D. Sun, M. Hohage, and P. Zeppenfeld — Institut für Experimentalphysik, Johannes-Kepler-Universität Linz, Austria

Para-sexiphenyl (P6P) has attracted considerable interest as a promising candidate for future organic opto-electronic applications. Its molecular structure consists of a linear chain of six linked benzene rings showing strong π bond delocalization in the direction of the chains. Previous research shows that the optical absorption of P6P films depends strongly on the molecular orientation. On the other hand, Reflectance Difference Spectroscopy (RDS) has been demonstrated to be a powerful tool to measure the optical anisotropy at normal incidence. Here, we present a RDS investigation of para-sexiphenyl thin film growth on Cu(110) and Cu(110)-(2x1)O. The RDS spectra show a pronounced anisotropy of the P6P films formed on both substrates at room temperature, indicating preferential orientation of P6P molecules on these two atomically well defined substrates: On Cu(110), the P6P molecular chains align in the [110] direction, i.e., along the Cu atomic rows, while on the Cu(110)-(2x1)O surface, the molecules align in the orthogonal [001] direction, i.e., along the Cu-O rows formed on Cu(110). Additionally, the evolution of the RDS signal at different photon energies during growth provides detailed information about the growth mode of P6P on both substrates.