Gas sensing properties of nanocrystalline SnO2 thin films prepared by liquid flow deposition

Nanocrystalline SnO2 sensitive films were deposited on the Si substrates (0.5 cm×1 cm) by a simple and inexpensive method called “liquid flow deposition” (LFD). The precursor solution was steadily flowed pass the substrate placed in the deposition chamber. The deposition temperature was kept constant at 80±1 °C. Microstructural analysis using the electron microscopes showed that the as-deposited films contained the 50–200 nm particles. These particles were made up of ∼10 nm SnO2 crystals. Gas sensing characteristics were studied by measuring a resistance change when the films were exposed to 0.21 and 0.51% i-butane at elevated temperatures. The results showed that the sensitivity increased with increasing temperature to the maximum value at ∼300–400 °C. At the operating temperature of 300 °C, the sensors showed high sensitivity with response and recovery times being 4 and 1 min, respectively.