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DS: Fachverband Dünne Schichten

DS 16: Poster I

DS 16.8: Poster

Dienstag, 24. März 2009, 09:30–12:30, P5

Contact degradation of pentacene field-effect transistors — •Dagmawi Belaineh, Benedikt Gburek, and Veit Wagner — Jacobs University Bremen, School of Engineering and Science, Campus Ring 8, 28759 Bremen, Germany

The performance of organic semiconductors in organic field-effect transistors (OFETs) has been steadily increasing. One of the major hindrances in realizing reliable OFET devices is the degradation of the active organic semiconductor layer in air. The negative influence of the contact properties at the interface between the metallic contacts and the organic semiconductors on the transport properties of OFETs is a well known problem. Therefore it is crucial to investigate the degradation of the organic semiconductor at the contacts as compared to the sheet semiconductor. For this analysis OFETs with bottom-gate geometry were produced with gold source and drain electrodes patterned by optical lithography on n-doped Si/SiO₂ substrates, on top of which pentacene was deposited as the active layer in vacuum. The degradation of the active layer was observed over three months for samples stored in air and others kept in an oxygen and water free nitrogen-atmosphere. The contact properties were determined by the transmission line method, i.e. by analyzing the channel conductance in dependence of the channel length L=1 to 50 µm. We find that the contact resistance of samples kept in air increases significantly as compared to the sheet resistance. In parallel AFM measurements were performed to analyze the pentacene layer structure close to the contacts.