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.