Back-gate ZnO nanowire field-effect transistors each with a top Ω shaped Au contact

We have fabricated depletion and enhancement modes (D-mode and E-mode) back-gate metal-insulator-semiconductor field-effect-transistors (MISFETs), using two kinds of ZnO nanowires (NWs) labeled as A and B, respectively. The NWs A and B were synthesized via the vapor phase transport method with ZnO∕C admixture and Zn as the sources, respectively. Each of the MISFETs has a top Ω shaped Au contact on the conductive channel. Compared to that without any top Au contact, the on/off ratio (∼106) of the ZnO NW A MISFET increases by a factor of 103, and is the highest one among the back-gate ZnO NW MISFETs ever reported; while the ZnO NW B MISFET changes from D-mode to E-mode when a top Au contact is added. The effects of the Au∕ZnO NW contacts on the performances of the NW A and B MISFETs were discussed.