Regensburg 2007 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 25: Symposium: Real Time Growth Studies III
DS 25.6: Vortrag
Donnerstag, 29. März 2007, 17:15–17:30, H32
Optical Spectroscopy of Ultrathin Stacked Nanolayers Grown by Multiple Organic Heteroepitaxy — •Roman Forker1, Thomas Dienel1, Klaus Müllen2, and Torsten Fritz1 — 1Institut für Angewandte Photophysik, TU Dresden, 01062 Dresden, Germany — 2MPI für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
Highly ordered quaterrylene (QT) films in the (sub-) monolayer regime were examined by means of differential reflectance spectroscopy (DRS) while being epitaxially deposited on various substrates. This in situ technique provides unsurpassed sensitivity for the thickness-dependent optical analysis during film growth. From the DR spectra, the optical constants were extracted using a novel numerical algorithm [1]. Rather broad and structureless spectra were obtained on Au(111). This behaviour changes drastically by depositing a closed monolayer of hexabenzocoronene (HBC) on the Au(111) surface before growing the QT film on top: Well-resolved QT-monomers become visible up to one QT-monolayer, followed by a physical monomer-dimer transition [2, 3] indicated by the appearance of isosbestic points in the spectra. The results are discussed in terms of the different molecular orbital hybridization on Au(111) and on HBC. Structural characterization was done by means of STM and LEED showing closed layers of flat lying molecules.
[1] R. Nitsche et al., Phys. Rev. B 70 (2004), 195432.
[2] H. Proehl et al., Phys. Rev. Lett. 93 (2004), 097403.
[3] H. Proehl et al., Phys. Rev. B 71 (2005), 165207.