Chemiresistive Gas Sensing Properties of Copper Substituted Zinc Ferrite Thin Films Deposited by Spray Pyrolysis

Gas sensors working at lower temperatures are considered better since they consume less energy. Many transition metal oxides have received greater attention in the development of potential gas sensors. In this work, we deposited copper substituted zinc ferrite thin films by spray pyrolysis at an optimized 375°C substrate temperature. The structural and physical properties of films were characterized by x-ray diffractometry (XRD), Field emission scanning electron microscopy (FE-SEM), and spectroscopic ellipsometry (SE). The chemiresistive gas sensing study revealed the effect of copper content on gas response and operating temperature. The zinc ferrite thin film sensor with no copper content shows a 25.1% response at 150°C operating temperature, but the film with 10% copper substitution (i.e. Cu0.1Zn0.9Fe2O4) shows a higher response (47.5%) at a lower 120°C operating temperature with satisfactory selectivity to SO2 gas. The optimized thin film sensor shows a linear response for exposed gas in the range 5 ppm to 200 ppm, which afterward bends to saturation. The mechanism of saturation of response is discussed in the paper. The results offer a potentially attractive candidate material for effective sensing of SO2 gas at a relatively low operating temperature.