COMPARATIVE-STUDY OF VARIOUS METAL-OXIDE-BASED GAS-SENSOR ARCHITECTURES

Reactively sputtered SnOx and InOx thin films, plain and surface doped with Pt, have been covered with layers of various insulating films an d catalysts. Test gases used are carbon monoxide, methane, ethanol, bu tane and propane. Filters used are alumina (Al2O3), silicon oxide (SiO 2) and tungsten trioxide (WO3). Palladium has also been added on the s urface of alumina filters, while platinum is added on the surface of m etal-oxide sensor films. Response to hydrocarbons, and especially to b utane and propane is found to be enhanced with the addition of noble m etals on the sensing film or on the filter. It is also found that a WO 3 filter improves the carbon monoxide sensitivity at low working tempe ratures and reduces the sensor response to ethanol with respect to oth er test gases. The behaviour of indium-oxide-based sensors is qualitat ively very similar to that of tin-oxide-based sensors.