Regensburg 2007 – scientific programme

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DS: Fachverband Dünne Schichten

DS 25: Symposium: Real Time Growth Studies III

DS 25.8: Talk

Thursday, March 29, 2007, 18:15–18:30, H32

In- situ measurements to analyze the intermolecular coupling and film growth of organic semiconductor thin films — •Derck Schlettwein, Christian Kelting, Harry Brinkmann, Wilfried Michaelis, and Karsten Hesse — Institut für Angewandte Physik, Justus-Liebig-Universität Gießen, 35392 Gießen

Intermolecular coupling of electronic pi-systems in thin films of organic semiconductors is of fundamental relevance for both the understanding of physical characteristics and their utilization in electronic devices. Optical absorbance is well- suited to probe them already during film growth, in particular when backed up by electron diffraction studies. Subtle changes in the film structure can be detected in changes of the observed band splitting. Thin films of modified phthalocyanines are a good example since spectra could already be obtained in the monolayer thickness range. Also, the average orientation relative to the substrate surface was extracted from relative intensities and the conclusions are supported by independent measurements of (ex-situ) spectral ellipsometry [1]. Aside from intermolecular coupling but not independent from it, microscopic growth characteristics of the films are of high relevance for technical applications. Measurements of the electrical conduction during film growth turned out very useful to discuss the formation of conduction pathways and hence the growth mode of films. Thus we could distinguish between layer vs. island growth. In a number of cases we observed the formation of ultrathin conductive channels in the monolayer range, interesting for technical application. [1] cooperation with the group of D.R.T. Zahn, TU Chemnitz.