ANNEALING TREATMENT OF ZnO THIN FILMS DEPOSITED BY SOL–GEL METHOD

Highly transparent ZnO thin films were deposited on glass substrates by using a simple and inexpensive multi-step sol–gel spin coating process. This research investigated the effects of annealing temperature in the range from 350–600°C on the microstructure, surface morphology and optical properties of thin films by using XRD, SEM and transmittance spectra. The XRD results showed that the c-axis orientation of ZnO thin films was improved with the increase of annealing temperature. The grain size increases from 16.6–19.7 nm with the increase in temperature. The transmittance spectra indicated that the transmittance and direct optical band gap Eg of the films showed a decreased trend with annealing temperature. It is found that the tensile stress exist in the films, which decreases with the increase in annealing temperature up to 500°C, on further increasing the annealing temperature up to 600°C, the stress in the film changes from tensile to compressive nature.