Transparent thin-film transistors with pentacene channel, AlO_x gate, and NiO_x electrodes

We report on the fabrication of pentacene-based transparent thin-film transistors (TTFT) that consist of Ni Ox, Al Ox, and indium-tin-oxide (ITO) for the source-drain (S/D) electrode, gate dielectric, and gate electrode, respectively. The Ni Ox S/D electrodes of which the work function is well matched to that of pentacene were deposited on a 50-nm -thick pentacene channel by thermal evaporation of NiO powder and showed a moderately low but still effective transmittance of ∼25% in the visible range along with a good sheet resistance of ∼60 Ω/□. The maximum saturation current of our pentacene-based TTFT was about 15 μA at a gate bias of -40 V showing a high field effect mobility of 0.9 cm2 Vs in the dark, and the on/off current ratio of our TTFT was about 5× 105. It is concluded that jointly adopting Ni Ox for the S/D electrode and Al Ox for gate dielectric realizes a high-quality pentacene-based TTFT.