Fabrication approaches to ZnO nanowire devices

To date, most of the work on ZnO nanostructures has focused on the synthesis methods and there have been only a few reports of the electrical characteristics. We report on fabrication methods for obtaining device functionality from single ZnO nanorods. A key aspect is the use of sonication to facilitate transfer of the nanorods from the initial substrate on which they are grown to another substrate for device fabrication. Examples of devices fabricated using this method are briefly described, including metal-oxide semiconductor field effect depletion-mode transistors with good saturation behavior, a threshold voltage of ∼-3 V, and a maximum transconductance of order 0.3 mS/mm and Pt Schottky diodes with excellent ideality factors of 1.1 at 25°C and very low (1.5 × 10^-10 A, equivalent to 2.35 Acm^-2, at -10 V) reverse currents. The photoresponse showed only a minor component with long decay times (tens of seconds) thought to originate from surface states. These results show the ability to manipulate the electron transport in nanoscale ZnO devices.