Effect of polymer gate dielectric surface viscoelasticity on pentacene thin-film transistor performance

Pentacene is one of the most studied semiconductor for organic thin-film transistors (OTFTs), and enhanced understanding of pentacene-based TFTs has significantly advanced the organic electronics. We report here the crucial effect of the polymer gate dielectric glass transition temperature (T _g) on pentacene film growth mode, microstructure, and the resulting TFT performance. Nanoscopically-confmed thin polymer films are known to exhibit reduced glass-transition temperatures versus the corresponding bulk values, and we demonstrate here that pentacene films grown on polymer gate dielectrics at temperatures well below their bulk T_g exhibit morphological/ microstructural transitions and OTFT performance discontinuities at well-defined growth temperatures [defined as the surface T_g, or T_g(s)] characteristic of the underlying polymer structure and independent of the film thickness. The results argue mat realistic OTFT response must take into account this fundamental polymer property, and that TFT measurements represent a new probe of polymer surface thermal properties.