Mechanism of O3 and NO2 detection and selectivity of In2O3 sensors

The gas-sensitive properties of the sol-gel prepared In2O3, In2O3-NiO, and In2O3-MoO3 thin film sensors at the detection of NO2 and O-3 were investigated. The differences in the mechanisms of interaction between the oxide surface and O-3 and NO2 molecules are discussed. The activity and selectivity of oxides substantially depend on the metal-oxygen binding energy in the oxide lattice. The introduction of dopants into In2O3, which increases the metal-oxygen binding energy as well as creates adsorption centers with the high affinity to oxygen (Mo5+), leads to the shift of NO2 detection temperature at In2O3-sensors to the high temperature range. In the case of nonstoichiometric In2O3 films, the optimal ozone detection temperature is low. The observed differences of the interaction between NO2 and O-3 and the oxide surfaces can be used for measuring the properties of oxide sensor regarding these gases. (C) 2001 Elsevier Science B.V. All rights reserved.