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DS: Fachverband Dünne Schichten

DS 15: [HL] Organic Semiconductors: Transistors and OLEDs (Joint Session DS/CPP/HL/O)

DS 15.6: Vortrag

Dienstag, 23. März 2010, 10:45–11:00, H15

Thickness dependence of contact and sheet resistance of thiophene and pentacene based organic field effect transistors — •Torsten Balster, Steve Pittner, Dagmawi Belaineh, Arne Hoppe, and Veit Wagner — School of Engineering and Science, Campus Ring 1, Jacobs University Bremen, 28759 Bremen, Germany

The electrical properties of evaporated organic semiconductors in dependence on the film thickness are affected by the growth mode of the thin film. While dihexyl-substituted oligothiophenes (DHnT) show a typical layer-by-layer growth mode on hexamethyldisilazane(HMDS)-treated silicon oxide, pentacene exhibits 3-dimensional growth. The growth mode as determined by AFM investigations is also reflected in the integral in-situ IV-measurements during growth. DHnT shows oscillatory behaviour in the mobility and the contact resistance within the first two monolayers, whereas the pentacene saturates without oscillations for 10nm. The total contact resistance with gold electrodes has been evaluated by the transfer line method. Furthermore the potential barriers at source and drain contact are determined separately by a four probe setup. For this purpose, additional sense fingers are prepared within the channel allowing the direct access to the channel potential. Major contact effects are identified for channel length smaller than 10 microns.