Regensburg 2007 – scientific programme

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DS: Fachverband Dünne Schichten

DS 15: Poster Session

DS 15.5: Poster

Tuesday, March 27, 2007, 15:00–17:00, Poster B

Low temperature reflection anisotropy spectroscopy investigation of vanadyl phthalocyanine — •Michael Fronk, Björn Bräuer, Dietrich Zahn, and Georgeta Salvan — Chemnitz University of Technology, D-09107 Chemnitz, Germany

Magneto optical Kerr effect (MOKE) spectroscopy is often used to characterise metallic films but there are hardly any reports about investigations on organic layers. It would thus be interesting to prove whether MOKE spectroscopy is a suitable technique to detect magnetic phase transitions in organic materials. Here thin films of a paramagnetic metal phthalocyanine molecule, namely vanadyl phthalocyanine, are investigated. The films are grown on Si(111) by vacuum evaporation. The MOKE spectra are recorded in the spectral range from 1.5 eV to 5.5 eV with a home-made set-up that analyses the change in the polarisation state of the reflected light upon applying an external magnetic field perpendicular to the sample surface. In addition to MOKE, the optical anisotropy of the film can lead to a noticeable change in the polarisation state of the reflected light. The effect of the optical anisotropy, however, is independent of the applied magnetic field and in a first approach the two effects sum up. As a first step in this work the optical anisotropy of the films is investigated in the temperature range from 300 K to 7.5 K. With decreasing temperature all spectral features show slight changes in their relative intensity. The most pronounced changes are observed in the sub-structure of the Q band related feature when cooling down from 300 K to 100 K.