Regensburg 2007 – scientific programme
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DS: Fachverband Dünne Schichten
DS 2: Organic Thin Films II
DS 2.6: Talk
Monday, March 26, 2007, 12:30–12:45, H32
Sub-nm control of the inter-layer spacing in thin films of intercalated rod-like conjugated molecules — •Jörn-Oliver Vogel1, Ricarda Opitz1, Ingo Salzmann1, Steffen Duhm1, Bert Nickel2, Jürgen Rabe1, and Norbert Koch1 — 1Humboldt-Universität zu Berlin, Berlin, Deutschland — 2Ludwig-Maximilians-Universität, München, Deutschland
We present evidence for the mutual intercalation of three rod-like molecular materials, which are widely used as active layers in molecular electronics: α-sexithiophene (6T), its alkylated analogue α,ω-dihexylsexithiophene (DH6T), and p-sexiphenyl (6P). We co-deposited pairs of these molecular materials by organic molecular beam deposition on silicon oxide and Mylar (a polymeric gate insulator used in all-organic thin film transistors) and studied the properties of the resulting thin film samples by atomic force microscopy (AFM), X-ray diffraction (XRD), and infrared spectroscopy (IR). As a key result, we found evidence for mutual intercalation of the pairs 6T/DH6T and 6P/DH6T in thin films and no indications for phase separation. Furthermore, the inter-layer distance of neighbouring molecular layers could be varied almost linearly as function of the molecular mixing ratio in the range of ca. 2.3 nm to ca. 3.7 nm, which was brought about by the conformational flexibility of the DH6T hexyl-chains. Thus, vapour phase co-deposition of appropriate molecular material pairs appears to be a promising route towards controlling inter-layer spacing with sub-nm precision.