Berlin 2008 – wissenschaftliches Programm

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SYSA: Symposium Tayloring Organic Interfaces: Molecular Structures and Applications

SYSA 5: Poster Session SYSA

SYSA 5.15: Poster

Dienstag, 26. Februar 2008, 14:30–20:00, Poster A

Luminescence line shifts of ultrathin rubrene layers on epitaxial aluminium oxide — •Mathias Müller, Olga Krylova, and Moritz Sokolowski — Institut für physikalische und theoretische Physik, Universität Bonn, Wegelerstraße 12, 53111 Bonn

We have investigated the photoluminescence properties of rubrene films on an ultrathin layer of aluminium oxide under UHV-conditions. The ultrathin alumina layer was grown epitaxially on Ni₃Al(111) by heating of the sample under low oxygen pressure. Afterwards rubrene films of varying thickness (d) were evaporated onto the alumina. The photoluminescence (PL) was measured at 40 K using an argon-ion-laser for excitation and an N₂ cooled CCD-Spectrometer for detection. PL-Spectra could be detected from d=0,6 Å upwards. Both the positions and the intensities of the transitions show strong changes depending on the nominal film thickness. With increasing film thickness the intensity decreases by three orders of magnitude whereas the entire spectrum shifts continuously to smaller wavenumbers (1200 cm⁻¹ for d=0,6 Å to 79 Å). These changes are tentatively interpreted as an emission from the center of small clusters, that have been formed on the surface. Funding by DFG research unit 557 is gratefully acknowledged.