Abstract: Organic thin film transistors with C₆₀ as an n-type semiconductor have been fabricated. A tantalum pentoxide (Ta₂O_{5)/poly-methylmethacrylate (PMMA) double-layer structured gate dielectric was used. The Ta2}O₅ layer was prepared by using a simple solution-based and economical anodization technique. Our results demonstrate that double gate insulators can combine the advantage of Ta₂O₅ with high dielectric constant and polymer insulator for a better interface with the organic semiconductor. The performance of the device can be improved obviously with double gate insulators, compared to that obtained by using a single Ta₂O₅ or PMMA insulator. Then, a good performance n-type OTFT, which can work at 10 V with mobility, threshold voltage and on/off current ratio of, respectively, 0.26 cm²/(V.s), 3.2 V and 8.31 × 10⁴ , was obtained. Moreover, such an OTFT shows a negligible ``hysteresis effect'' contributing to the hydroxyl-free insulator surface.

Key words: organic thin film transistors, C₆₀, double gate dielectrics