Effect of the heat treatment on the infrared emissivity of indium tin oxide (ITO) films

Indium tin oxide (ITO) films were deposited on glass substrates at temperatures ranging from 100 °C to 400 °C by direct current magnetron sputtering. The mean infrared emissivities at the waveband of 8–14 μm were measured in process of heating and cooling between room temperature and 350 °C. Microstructure and phases of ITO films before (Group A) and after (Group B) heat treatment were characterized by SEM and XRD, respectively. Electrical properties were characterized with a four-point probe method and by Hall measurement system. During heat treatment, the infrared emissivity of the film increases with the increase of temperature, and decreases with the decrease of temperature. While, the infrared emissivity of the films decreases slightly around 250 °C in heating process. On the other hand, after heat treatment, the crystalline phases of the films have no obvious change. However, both the resistivity and the infrared emissivity of all films decrease.