Studies of the optoelectronic properties of ZnO thin films

ZnO thin films have been deposited on quartz glass, sapphire, and glass substrates by the sol-gel technique and subjected to different annealing ambients. X-ray diffraction measurements show that all the films are hexagonal wurtzite type. The variations in photoluminescence (PL) and photoconductivity (PC) properties have been correlated to the structural and microstructural changes due to different substrates and annealing ambients. The maximum photoresponse has been observed for the films on quartz substrates. The violet emission in the PL spectra is enhanced for vacuum and nitrogen annealed films. The maximum ultraviolet (UV) photoresponse and photo-to-dark current ratio is observed for ZnO films annealed in air.