Indium oxide thin films were deposited on silicon substrates for work
function sensing as well as on alumina (Pt) conductivity sensors. A co
rrelation 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 h
umidity is found to be comparatively small for these films. The work f
unction method provides a sensitivity maximum at low concentrations of
some ppb of ozone stable down to a substrate temperature of 40 degree
s C. For HSGFET work function sensors with an In2O3-Si3N4 system a res
ponse of 120 mV from 100 ppb of ozone in humid air is estimated for he
aterless operation at room temperature. However, thermal desorption cy
cles will be necessary even for a restricted use of such sensors based
on sputtered In2O3 films. (C) 1998 Elsevier Science S.A. All rights r
eserved.