Pentacene thin-film transistors (TFT) were fabricated on aluminum foils using polymethyl methacrylate (PMMA) as gate dielectric. In such structure, the aluminum substrate acts as the gate electrode itself. A bottom gate inverted structure was used to study the influence of the dielectric and the aluminum substrate on the device performance.
Pentacene thin-films were deposited by thermal evaporation in high-vacuum at deposition rates around 3 Ås-1 and three different substrate temperatures (30, 60 and 90°C). The maximum process temperature achieved was 170°C, corresponding to the baking of polymethyl methacrylate. The TFTs exhibit field-effect mobility values of ∼ 10-3 cm2V-1s-1 and threshold voltage values around –15 V. The influence of the dielectric and the substrate temperature on the pentacene structure and device field-effect mobility is discussed.