Semiconductor Device-Based Sensors for Gas, Chemical, and Biomedical Applications

ZnO Thin-Film and Nanowire-Based Sensor Applications 189

© 2011 by Taylor & Francis Group, LLC

UV illumination produces an ohmic characteristic. This is similar to the result reported by Keem

et al., who showed that the above-bandgap light lowered the potential barrier between the Schottky

contact and the ZnO nanowire. In their case, however, the photoresponse recovery times were very

long (>10

4

s), which was ascribed to the dominance of surface states, whereas our recovery times

were limited by turn-off of the Hg lamp and suggest the conduction in our nanowires is dominated

by bulk transport.

Figure5.34 shows the reverse current characterist ...