Structural and optical properties of pure SnO and VO/SnO nanocomposite thin films for gas sensing application

In this study, pure SnO and VO/SnO nanocomposite thin film NH sensors with varying VO contents were successfully prepared by spray pyrolysis method. The prepared thin films were characterized by X-ray diffraction, Field emission scanning electron microscopy, Energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, stylus profilometry and Ultra violet–Visible and transmittance spectroscopies. NH gas sensing property was also studied. XRD results suggested that all the thin films exhibited a tetragonal rutile crystal structure, while the average crystallite size increases with VO content. FESEM images of the thin films showed the presence of both nano and micro-sized grains in the range ~ 53–194 nm. EDX spectra confirmed the inclusion of VO into the SnO matrix. The vibrational bands associated with the thin films were verified from the FTIR spectra. Thickness measurements revealed that the thickness increases with VO content. Change in transparency and bandgap narrowing were also noticed from the transmittance and UV–Vis spectra. NH gas sensing measurements suggested that the transient resistance of VO/SnO thin film was lower than pure SnO. Further, in the operating temperature 300 °C and 100 ppm NH3 gas, the sensor response of VO/ SnO thin film (99.13) is found to be higher than pure SnO thin film (92.34). Also, the response and recovery times of pure SnO thin film (30 and 44 s) are lower than VO/SnO thin film (39 and 180 s). These results indicate that VO/SnO thin film could serve as a suitable material for NH gas sensing application.