Berlin 2008 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 18: Poster: Towards Molecular Spintronics, Organic Thin Films, Optical Layers, Vibrational Spectroscopy, Tayloring organic interfaces

DS 18.36: Poster

Dienstag, 26. Februar 2008, 14:30–19:30, Poster A

Study of perylene films by Fourier transform infrared spectroscopy — •li ding, kostiantyn v. shportko, philip schulz, azadeh farahzadi, and matthias wuttig — Institute of physics (IA), RWTH Aachen University, 52056, Aachen, Germany

Organic semiconductors has attracted considerable attention recent years due to their potential application in electronic devices. Fourier transform infrared spectroscopy (FTIR), as a useful tool to study vibrational properties of molecules, contains information on the molecular orientation in films [1]. Since the molecular stacking has a significant impact on the electronic and optical properties of films, it is of great interest to understand the molecular orientation in thin films [2].

Thermally evaporated perylene films are grown on a silver layer deposited on glass substrates. Infrared reflectance spectra of perylene films on Ag/glass have been measured with the incident angle from 20° to 70°. The change of absorption intensities at different incident angles indicates that the average orientation of perylene molecules on Ag/glass tends to be perpendicular to the substrate surface. XRD pattern shows that thick perylene films are highly crystalline. We have compared the absorption frequencies and intensities of perylene film with those of isolated molecules. Some new frequencies are seen in the spectrum of crystalline perylene film, which are attributed to the dimer structure in the crystalline phase.

[1] D. L. Allara, J. D. Swalen, J. Phys. Chem. 86, 2700 (1982).

[2] K. Akers, R. Aroca, A. Hor, R.O. Loutfy, J. Phys. Chem. 91, 2954 (1987).