Conductivity and work function ozone 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. A correlation of work function and conductivity measurements due to ozone in dry and humid air reveal that a chemisorption state dominates both sensor effects at temperatures below 200 degrees 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 degrees C. For HSGFET work function sensors with an In2O3-Si3N4 system a response of 120 mV from 100 ppb of ozone in humid air is estimated for heaterless operation at room temperature. However, thermal desorption cycles will be necessary even for a restricted use of such sensors based on sputtered In2O3 films. (C) 1998 Elsevier Science S.A. All rights reserved.