SNINO-BASED CHLORINE GAS SENSOR

The dependence of the resistance of InSnO (ITO) layers on a small amount of chlorine gas in air is studied here. The chlorine-sensitive ITO films have been fabricated by reactive sputtering of In and Sn from a metal alloy target (In and Sn in the proportion 0.94:0.06 by weight) on silicon substrates. It is found that the chlorine gas in the ambient atmosphere makes the ITO resistance increase. The dependence of the resistance on chlorine concentration tends to saturate at concentrations above 3 ppm. The sensitivity maximum is observed at 30-degrees-C. The addition of Pt significantly increases the sensitivity and reduces the temperature of the sensitivity maximum. The response time is almost-equal-to 150 s at 90-degrees-C and decreases exponentially with increasing temperature. The results obtained are typical for gas sensors based on tin oxide or ITO and can be explained in terms of electron localization at surface adsorption centres dominated by chlorine molecules and the electric transport features at the polycrystalline film grain boundaries.