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Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P296
The dielectric function of zinc-tetraphenylporphyrin from near infrared to
vacuum ultraviolet energy
Daniel Lehmann 1 , John Sindu 1 , Ovidiu D. Gordan 1 , Marion Friedrich 1 ,
Christoph Cobet 2,3 , Simona Silaghi 3 , Norbert Esser 3 , Walter Braun 4 , Dietrich
R.T. Zahn 1
1 Institut für Physik, TU Chemnitz, Reichenhainerstr. 70, 09107 Chemnitz, Germany –
2 Institut für Festkörperphysik, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany –
3 ISAS Institute for Analytical Sciences, Albert-Einstein-Str. 9, 12489 Berlin, Germany
– 4 BESSY GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany
Zinc-meso-tetraphenylporphyrin (ZnTPP) layers are used in organic opto-electronic devices
such as organic light emitting devices (OLEDs) and organic photovoltaic (OPV)
solar cells as p-conducting active layer [1-2]. The dielectric properties of those layers
are crucial for the functionality of opto-electronic devices. Here we present the
dielectric function of ZnTPP in the range from 0.73 eV to 9.6 eV determined by Spectroscopic
Ellipsometry. The layers for this study were grown by Organic Molecular
Beam Deposition (OMBD) on silicon substrates. In the range from 0.73 eV to
5.0 eV the characterization was performed by Variable Angle Spectroscopic Ellipsometry
(VASE). The results show an anisotropic behaviour. The tilt angle of the molecules
with respect to the substrate was determined to be (29 ± 3) ◦ . This was verified by infrared
spectroscopy. Measurements in the range from 4.0 eV to 9.6 eV were performed
at the Vacuum-Ultraviolet-Ellipsometry beamline at the synchrotron radiation source
BESSY II. At an energy of 6.4 eV a strong absorption feature appears, which was not
reported before. Measurements with synchrotron radiation in the VUV energy range
are more sensitive for ultra-thin films due to the smaller wavelength. Results of ultrathin
ZnTPP films investigated at BESSY II are presented.
[1] K. Takahashi et al., Synthetic Met. 155 (2005) 51-55.
[2] Y. Kim et al., Solid-State Electron. 48 (2004) 633-644.