Characterization of Ag-doped ZnO thin film for its potential applications in optoelectronic devices

Ag-doped ZnO thin films have potential applications in many optoelectronic devices. In this work, Ag-doped ZnO thin films were prepared by a low-cost sol-gel method and the effect of annealing time on the optical and electrical properties of the samples was studied. The results showed that all the samples were pure ZnO phase with a wurtzite structure. As the annealing time increased, the ZnO grains grew up and the films became denser. In addition, photoluminescence behavior dependent strongly on the annealing time was found. These Ag-doped ZnO films exhibited co-emission of ultraviolet, green, and red light. Considering the results of X-ray photoelectron spectroscopy and other researchers' proposals, the green emission centered at 549 nm was suggested to be related to the zinc vacancy defects, and the red emission centered at 652 nm was probably associated with oxygen interstitials or oxygen species adsorbed on the ZnO surface. Electrical measurement results showed that Ag-doped ZnO films with annealing time longer than 10 min presented P-type conductivity, and as the annealing time increased, the resistivity decreased first and then increased again.