Ta2O5 as gate dielectric material for low-voltage organic thin-film transistors

In this paper we report the use of Ta2O5 as gate dielectric material for organic thin-film transistors. Ta2O5 has already attracted a lot of attention as insulating material for VLSI applications. We have deposited Ta2O5 thin-films with different thickness by means of electron-beam evaporation. Being a relatively low-temperature process, this method is particularly suitable for organic thin-film transistor fabrication on plastic substrates. Deposition and patterning are achieved in one step by the use of shadow masks. The dielectric can be evaporated on top of the semiconducting layer. In this way a large variety of structures can be realized. Poly(3-hexylthiophene) was used as semiconducting material in the transistor structure. Such transistors are operating at voltages smaller than -3 V. Having a high dielectric constant (epsilon(r) = 21), Ta2O5 facilitates the charge carrier accumulation in the transistor channel at much lower electrical fields. The properties of the dielectric material as well as the operation of the organic transistors with a Ta2O5 gate dielectric are discussed. (C) 2002 Elsevier Science B.V. All rights reserved.