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 O3 were investigated. The differences in the mechanisms of interaction between the oxide surface and O3 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 O3 and the oxide surfaces can be used for measuring the properties of oxide sensor regarding these gases.