Dresden 2009 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 16: Poster I

DS 16.7: Poster

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

Insulator Thickness Dependence of Organic Field-Effect Transistors. — •Atefeh Yousefi Amin, Arne Hoppe, Benedikt Gburek, and Veit Wagner — Jacobs University Bremen, School of Engineering and Science, Campus Ring 1, 28759 Bremen, Germany

Organic electronics and especially organic field effect transistors (OFETs) present a promising route for future cost-efficient electronics. A crucial point in the fabrication of OFETs is to find insulators which combine low leakage current with high capacitance. To allow for low voltage operation, i.e. below 20 V, typically insulator thicknesses below 1 μm are required. In this study OFETs were fabricated in top-gate architecture with poly-methylmethacrylate (PMMA) of different molecular weight as organic gate insulator and a thiophene-based semiconductor. Both were deposited by spin-coating under atmospheric conditions.

According to theory the FET capacitance, which is inversely proportional to the insulator thickness, is directly related to the drain-source current. Therefore a thinner insulator layer results in a lower value of the threshold voltage and higher source drain current. The dependence of device characteristics on the insulator thickness was analyzed. In addition the homogeneity of the insulator film was found to be crucial for low leakage current. This layer homogeneity for fixed film thickness was found to be tunable by the right combination of molecular weight, solution concentration and coating speed. The minimum value of PMMA thickness for the reproducible production of short-circuit free devices was found at about 400 nm.