Structural and optical properties of pure SnO₂ and V₂O₅/SnO₂ nanocomposite thin films for gas sensing application

In this study, pure SnO₂ and V₂O₅/SnO₂ nanocomposite thin film NH₃ sensors with varying V₂O₅ 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. NH₃ 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 V₂O₅ 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 V₂O₅ into the SnO₂ matrix. The vibrational bands associated with the thin films were verified from the FTIR spectra. Thickness measurements revealed that the thickness increases with V₂O₅ content. Change in transparency and bandgap narrowing were also noticed from the transmittance and UV–Vis spectra. NH₃ gas sensing measurements suggested that the transient resistance of V₂O₅/SnO₂ thin film was lower than pure SnO₂. Further, in the operating temperature 300 °C and 100 ppm NH3 gas, the sensor response of V₂O₅/ SnO₂ thin film (99.13) is found to be higher than pure SnO₂ thin film (92.34). Also, the response and recovery times of pure SnO₂ thin film (30 and 44 s) are lower than V₂O₅/SnO₂ thin film (39 and 180 s). These results indicate that V₂O₅/SnO₂ thin film could serve as a suitable material for NH₃ gas sensing application.