Room temperature ozone sensing with conductivity and work function sensors based on indium oxide

Indium oxide thin films were deposited on silicon substrates for work function sensing as well as on alumina (Pt) conductivity sensors. The correlation of work function and conductivity measurements due to ozone in dry and humid air reveal that a chemisorption state dominates the sensor effects at temperatures below 200 /spl deg/C. The influence of humidity is found to be comparatively small for these films. The work function method provides a sensitivity maximum at low concentrations of some ppb of ozone stable down to a substrate temperature of 40 /spl deg/C. However, thermal desorption cycles will be necessary even for restricted use of such sensors. For HSGFET work function sensors with a In/sub 2/O/sub 3/-Si/sub 3/N/sub 4/ system a response of 120 mV from 100 ppb of ozone in humid air is estimated for heaterless operation at room temperature.