SnO2 thin film sensor with enhanced response for NO2 gas at lower temperatures

Semiconducting SnO2 thin films having higher value of electrical conductivity have been deposited using RF sputtering technique in the reactive gas environment (30% O2 + 70% Ar) using a metallic tin (Sn) target for detection of oxidizing NO2 gas. The effect of growth pressure (12–18 mTorr) on the surface morphology and structural property of SnO2 film was studied using Atomic force microscopy (AFM), Scanning electron microscopy (SEM) and X-ray Diffraction (XRD) respectively. Film deposited at 16 mTorr sputtering pressure was porous with rough microstructure and exhibits high sensor response (∼2.9 × 104) towards 50 ppm NO2 gas at a comparatively low operating temperature (∼100 °C). The sensor response was found to increase linearly from 1.31 × 102 to 2.9 × 104 while the response time decrease from 12.4 to 1.6 min with increase in the concentration of NO2 gas from 1 to 50 ppm. The reaction kinetics of target NO2 gas on the surface of SnO2 thin film at the Sn sites play important role in enhancing the response characteristics at lower operating temperature (∼100 °C). The results obtained in the present study are encouraging for realization of SnO2 thin film based sensor for efficient detection of NO2 gas with low power consumption.