N-channel operation of pentacene thin-film transistors with ultrathin polymer gate buffer layer

N -channel operation of pentacene thin-film transistors with ultrathin poly(methyl methacrylate) (PMMA) gate buffer layer and gold source–drain electrode was observed. We prepared pentacene thin-film transistors with an 8-nm thick PMMA buffer layer on SiO 2 gate insulators and obtained electron and hole field-effect mobilities of 5.3 × 10 −2 cm 2 /(V s) and 0.21 cm 2 /(V s), respectively, in a vacuum of 0.1 Pa. In spite of using gold electrodes with a high work function, the electron mobility was considerably improved in comparison with previous studies, because the ultrathin PMMA film could decrease electron traps on SiO 2 surfaces, and enhance the electron accumulation by applied gate voltages.