Ultraviolet photodetection characteristics of Zinc oxide thin films and nanostructures

ZnO thin films were deposited by using RF sputtering technique at 150W and 4×10^-3 mbar pressure. Post-deposition rapid thermal annealing of ZnO thin films were carried out at 1000°C for 600sec. ZnO nanostructures (nanowires/nanorods) were hydrothermally grown by using equimolar solution of Zinc nitrate and hexamethyltetramine. Morphology of ZnO thin films and nanostructures were investigated using scanning electron microscope. A comparative study on the ultraviolet photodetection behaviour of ZnO thin films and nanostructures were carried out by adopting current-voltage measurement technique at room temperature. ZnO annealed films have shown relatively lower transient photocurrent decay as compared to as- deposited film, which may be due to the faster evacuation of the charge carries. However, in case of ZnO nanorods transient photocurrent decay is relatively slow than that of nanowires, which is attributed to delayed readsorption of oxygen molecules onto the nanorods surface due to its larger width.