p-type conduction in ZnO nanowire Schottky field-effect transistors with Pt metal electrodes

To obtain p-type conduction in a ZnO nanowire, field effect transistors were fabricated from a short ZnO nanowire with Pt contact electrodes. Since Pt metal has a high work function and is chemically inert, the Fermi level can align with the valence band side of the ZnO nanowire in such a way as to produce a high Schottky barrier. The current-voltage characteristics showed a non-linear behavior due to the high Schottky barrier between the ZnO nanowire and the Pt, and the gate transfer curves exhibited a weak p-type conduction behavior. To further enhance the hole conduction in the ZnO nanowire channel, we exposed the devices to F2 gas, which is effective at capturing electrons. The F2 adsorbed onto the ZnO FET and improved the hole conduction behavior relative to that of the intrinsic ZnO FET. A p-type gate response was obtained in the high source-drain bias voltage region.