Nanoscale Electrical Probes on a Single Facet of a ZnO Microwire: Device Fabrication and Local Electrical Characteristics

The electrical properties of a single facet of an individual ZnO microwire were investigated. Electrode patterns with a Hall bar structure were deposited on the surface of the top facet of the ZnO microwire. Using a suspended and cross-linked poly(methyl methacrylate) ribbon structure, it was possible to define the electrical connections only at the top surface, while avoiding those on the other five sides of the ZnO microwire. Current-voltage characteristics were examined, and Hall measurements were conducted with various magnetic fields. Through our device structure, the electrical properties could be directly probed at specific points on the ZnO surface in a reliable manner. The estimated electrical characteristics demonstrate that the carrier concentration and mobility of the ZnO surface varied along the axial direction of the wire. These results indicate that the charge carrier concentration on the surface of the micro-/nanowire can be sensitively changed according to the synthesis environment. In addition, it is worth noting that the nanoscale local Hall probes, fabricated by our technique, could probe the very slight variation of carrier concentration, which is difficult to detect by a standard transport measurement along the wire.