Improved crystalline structure and H2S sensing performance of CuO-Au-SnO2 thin film using SiO2 additive concentration

In situ SiO2-doped SnO2 thin films were successfully prepared by liquid phase deposition. The influence of SiO2 additive as an inhibitor on the surface morphology and the grain size for the thin film has been investigated. These results show that the morphology of SnO2 film changes significantly by increasing the concentration of H2SiF6 solution which decreases the grain size of SnO2. The stoichiometric analysis of Si content in the SnO2 film prepared from various Si/Sn molar ratios has also been estimated. For the sensing performance of H2S gas, the SiO2-doped Cu-Au-SnO2 sensor presents better sensitivity to H2S gas compared with Cu-Au-SnO2 sensor due to the fact that the distribution of SiO2 particles in grain boundaries of nano-crystallines SnO2 inhibited the grain growth (<6 nm) and formed a porous film. By increasing the Si/Sn molar ratio, the SiO2-doped Cu-Au-SnO2 gas sensors (Si/Sn = 0.5) exhibit a good sensitivity (S = 67), a short response time (t90% < 3 s) and a good gas concentration characteristic (α = 0.6074). Consequently, the improvement of the nano-crystalline structures and high sensitivity for sensing films can be achieved by introducing SiO2 additive into the SnO2 film prepared by LPD method.