Organic Thin-Film Transistors Based on Vapor-Deposition Polymerized Gate Insulators

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In this study, we demonstrated that organic thin-film transistors (OTFTs) can be fabricated by using organic gate insulators using a vapor deposition polymerization (VDP) process. We found that electrical output characteristics in our organic thin-film transistors using a staggered-inverted top-contact structure show a saturated slope in the saturation region and a subthreshold nonlinearity in the triode region. The field-effect mobility, threshold voltage, and on-off current ratio of OTFTs using 4,4$'$-oxydiphthalic anhydride[ODPA]-4,4$'$-oxydianiline[ODA] and 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride[6FDA]-[ODA] as gate insulators with a thickness of 0.45 μm were about 0.13–0.5 cm2/Vs, $-7$ V, and $10^{4}$, respectively. To form polyimide as a gate insulator, the VDP process was also introduced instead of a spin-coating process, in which a polyimide film was codeposited by the high-vacuum thermal evaporation of ODPA and ODA, 6FDA and ODA, and cured at 150°C for 1 h followed by 200°C for 1 h after codeposition. To explain the differences in the electrical characteristics caused by the insulators, the morphology of pentacene on the polyimide from ODPA-ODA was compared with that from 6FDA-ODA, respectively.
2005-01-15