Effect of nickel ions on sensitivity of In2O3 thin film sensors to NO2

The effect of Ni2+ ions on the properties of sol-gel obtained In2O3 thin film sensors under detection of low concentrations of NO2 had been investigated. Doping of In2O3 thin films with Ni2+ ions leads to the increase of their sensitivity to NO2. According to electron microscopy, electron and X-ray diffraction results, Ni2+ ions substitute In3+ ions in the cationic sites of In2O3 crystal lattice with the formation of In2-xNixO3 solid solution containing higher In2+ ions concentration as compared with In2O3. At exposure of In2O3 and In2O3-Ni2+ surfaces with NO2 oxidation of In2O3, lattice defects (i.e., In2+ ions) occur. Thus, interaction with NO2 leads to changes of oxide stoichiometry and electric conductivity conformably, causing In2O3 and In2O3-Ni2+ sensors response. Higher In2O3-Ni2+ sensitivity to NO2 correlates with higher In2+ ions concentration as compared with In2O3. (C) 1999 Elsevier Science S.A. All rights reserved.