Study on infrared emissivity of ZnO:Al (ZAO) thin films prepared by sol-gel process

ZnO:Al (ZAO) thin films were deposited on quartz glass substrates by sol-gel process. The effects of annealing temperature and Al doping concentration on the infrared emissivity of the films were investigated. The microstructures and morphologies were analyzed through X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively, and the infrared emissivities in the band of 8-14μm were tested by spectrum radiometer. The results indicate that the crystal structure of the ZAO films is hexagonal wurtzite without other phase, which is the same as undoped ZnO film. Annealing temperature is found to be the critical parameter affecting the average infrared emissivity (ε) of ZAO film in the band of 8-14μm. The infrared emissivity of the films decreases as the annealing temperature and Al doping concentration increase.