Integrated solid-state gas sensors based on SnO2(Pd) for CO detection

Abstract Thin films of polycrystalline Pd-doped tin dioxide SnO 2 (Pd), widely used as sensitive element in gas sensors devices for atmospheric pollutant as CO, have been deposited on Si substrates through the ultrasonic aerosol pyrolysis technique. It is firstly shown that the sensitivity S =( G − G 0 )/ G 0 to CO at low temperature (80–120°C), measured on steady state regime by conductance–temperature characteristics, depends on the concentration x of Pd incorporated into the film and on the SnO 2 grain size D . The highest sensitivity S corresponds to a very sharp ( x , D ) domain. Secondly, the films synthesised under these optimal conditions have been integrated to a silicon-based prototype of micro-sensor. This device provides stable response in dynamic regime ( S =17) at low temperature (∼100°C) to 50 ppm CO by using a short-term annealing ( T annealing =350°C, t annealing =5 min) before each measurement.