Enhanced ultraviolet photo-response of nanostructure zinc oxide (ZnO) thin film irradiated with pulsed laser

Ultravoilet (UV) photodetectors have been fabricated by rf magnetron sputtered ZnO films. The average grain size of ZnO films were 15-20 nm. Photo-response (I_on/I_off) of as-grown ZnO film of thickness 100 nm was maximum (3.8 times 10³) having relatively small response time ~90 ms for UV intensity of 140 muW/cm² (lambda= 365 nm). ZnO films were irradiated by pulsed Nd:YAG laser corresponding to both fundamental wavelength (1064 nm) and forth harmonics (266 nm) to modify its defects profiles. Response was found to increase with increasing number of irradiating pulses upto 6000, and thereafter starts decreasing. Laser (lambda=266 nm) irradiated detector exhibits enhanced response (3.7 times 10⁴) with fast response speed (30 ms), showing its promising application for detection of low intensity UV photons.