Study on TiO2-doped ZnO thick film gas sensors enhanced by UV light at room temperature

The gas-sensing properties of titanium oxide (TiO₂)-doped zinc oxide (ZnO) thick film sensor specimens to typical ethanol vapor under UV light activation at room temperature have been investigated. Zinc nanoparticles were mixed with commercial TiO₂ in various weight percentage (0%, 1%, 5%, and 10%) and sintered at 650 °C for 2 h to prepare the thick film sensors. The sensors exhibit better photosensitivity and gas sensitivity to ethanol analyte. The response and recovery times are within 8 s. TiO₂ doping can improve the sensors stability and reproducibility. X-ray diffraction (XRD) and scanning electron microscopy (SEM) characterization of the film materials revealed that Zn₂TiO₄ and TiO₂ phases hindered the rod- or needle-like structure growth and subsequently affected the gas sensitivity. UV absorption spectra of the sensing film material completely dispersed in ethanol solution exhibited that the red shifts were caused with the doping of a small amount of TiO₂ into ZnO then blue shift was caused with higher TiO₂ level. The results of the UV spectra are well consistent with the photosensitive performance. The maximum sensitivity can be achieved by doping the amount of TiO₂ (5 wt%).