Enhanced NO2 sensing using ZnO–TiO2 nanocomposite thin films

Highlights: ► The TiO2 addition in ZnO was concluded to enhance the conductivity and NO2 sensitivity of the nanocomposite thin films. ► Pure TiO2 thin film did not exhibit sensitivity towards NO2 gas at operating temperature ∼250 °C in N2 (0.4 ± 0.03 mbar). ► The addition of TiO2 in ZnO enhanced NO2 sensitivity up to 2% addition which decreased further with TiO2 addition. ► ZnO–2%TiO2 was observed to enhance the NO2 sensing signal for 20 ppm by 22 times compared to the pure ZnO thin film. ► The sensor response of films of ZnO–2%TiO2 showed 68% reduction in the response time for 20 ppm of NO2 sensing. -- Abstract: ZnO–TiO2 nanocomposites were synthesized using a wet chemical route with concentration of 1–10% (w/w) of TiO2 in ZnO. Spin coating was used to deposit the thin films of these nanocomposites on a glass substrate. These nanocomposite thin films were tested for NO2 gas detection at an operating temperature of 250 °C in N2 atmosphere (0.4 ± 0.03 mbar). The nanocomposite thin film of composition ZnO–2%TiO2 is observed to enhance the NO2 gas detection signal for 20 ppm concentration by 22 times in comparison to the pure ZnO thin film. The sensor response of films of the above composition (ZnO–2%TiO2) showed a significant reduction of 68% in the response time and the difference between response and recovery time by 97% for 20 ppm of NO2 sensing. The results are analyzed and discussed in the light of data obtained from various characterization techniques e.g. X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), current–voltage (I–V) characteristics and gas sensing characteristics