CO2 gas sensing properties of DC reactive magnetron sputtered ZnO thin film

Nanostructured ZnO thin films were deposited on glass substrates using a DC reactive magnetron sputtering technique. Thin films of three different thicknesses viz 40, 100 and 300 nm were prepared and subsequently annealed at 450 °C. The structural, topographical, and optical characteristics of all the three annealed films were studied using X-ray diffractometer (XRD), Atomic Force Microscope (AFM) UV-visible and photoluminescence spectrophotometers. The carbon dioxide (CO2) gas sensing behavior of these films was investigated in detail in the concentration range of 500-10,000 ppm. The sensing performance was optimized with respect to the ZnO film thickness as well as the operating temperature. ZnO film with 40 nm thickness showed better response characteristics at the operating temperature of 300 °C than that of thicker ZnO films. A maximum sensitivity (%) of 1.13 with a response and recovery time of 20 s was observed towards 1000 ppm of CO2.