Electrical characterization of mica as an insulator for organic field-effect transistors

Electrical properties of conjugated polymer films, including poly(3-hexylthiophene)-2,5-diyl (P3HT), poly(3,3'-didodecylquarterthiophene) (PQT-12), and poly(triarylamine) (PTAA), on mica substrates have been studied. The test structure was similar to a standard organic field-effect transistor but with a 150-mu m-thick commercially available mica gate insulator/substrate, which allowed to obtain a field-effect mobility of P3HT as high as 0.08 cm(2)/Vs in the linear regime in ambient air. The influence of interface treatment, thermal annealing, and measurement conditions on the electrical properties of the P3HT films has been characterized and analyzed. We also studied the time dependence of the carrier concentration and mobility before and after a thermal annealing process. The results indicate that mica is a promising insulator for organic field-effect transistors, apart from already being one of the common thin-film materials widely used in electric capacitors. (C) 2008 Elsevier B.V. All rights reserved.