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Zinc Oxide Nanostructures
6.4 Results
Photoconductive response is a key parameter for a photodetector.
Response of our paper devices was measured using a conventional
365 nm UV lamp (Fig. 6.4a). The real time ON/OFF switching was
measured by turning the UV lamp on and off inside a dark room.
The measured photocurrent under the unfocused UV source shows
a fast rise upon exposure to UV light and a relatively slower fall
once the UV source is turned off as seen in Fig. 6.4b. Photocurrent
pulse shows good stability and reversibility. Under dark condition,
oxygen molecules are adsorbed on the NC surface and capture free
electrons from the n-type ZnO, making negatively charged O
2
ions
at the surface. This creates a low conductivity depletion layer near
the nanowire surface.
O
2
(g) + e
 O
2
(ad)
(b)
(a)
Figure 6.4 (a) IV curves of the lexible pencil-drawn UV sensor with and
without UV illumination, (b) Time-dependent photo response
of the lexible UV sensor at a bias voltage of 1 V under UV
irradiance from an unfocused UV lamp irradiating at 365 nm.

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