Regensburg 2004 – scientific programme

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SYOH: Organic and Hybrid Systems for Future Electronics

SYOH 5: Poster

SYOH 5.64: Poster

Thursday, March 11, 2004, 18:00–21:00, B

Influence of contact metal on the serial resistance in organic field effect transistors — •U. Bass¹, M. Leufgen¹, T. Muck², J. Geurts¹, and V. Wagner² — ¹Physikalisches Institut der Universität Würzburg, EP III, Am Hubland, D-97074 Würzburg — ²International University Bremen, School of Engineering and Science, Campus Ring 8, D-28759 Bremen

The performance of organic field effect transistors (OFETs) depends essentially on the channel resistance of the organic material and the resistance between the organic material and the metal contacts. With improving film morphology and reducing channel lengths the relative influence of the contact resistance increases and becomes the dominating factor of the OFETs performance. We present a systematic study of various noble metals as source and drain contact materials for OFETs, based on DH4T. We applied gold and platinum, which both required a titanium adhesion layer, and palladium, which we could deposit directly on the SiO₂ substrate. The smallest contact resistance was obtained when using Pd. However, these contacts turned out to be rather vulnerable during the chemical processing prior to the deposition of the organic active layer. From the contacts with Ti adhesion layers, the Au results were superior to those of Pt. For a more detailed study of the Au/Ti system, we varied the Ti adhesion layer thickness from 10 nm down to 1 nm, yielding an increasing performance with decreasing Ti thickness. Finally, a reduction of the channel resistance of the DH4T film was achieved by employing a pretreatment of the SiO₂ substrate with octadecyltrichlorosilane (OTS) instead of hexamethyldisilane (HMDS).