Ce doped In2O3 sensors for nitrogen dioxide with reduced cross-sensitivity to oxygen at low operation temperatures

Indium oxide nanoparticles prepared by precipitation method have a high defect concentration of oxygen vacancies. As a result, the surface electron conduction is dominated by an accumulation layer model, which is intrinsically sensitive to nitrogen oxides (NOx) vapors with the detection limit down to 100 ppb, even at room temperature in the absence of oxygen. However, the absorbed oxygen inhibits further interactions between NOx and Indium atoms, and the sensitivity is significantly restricted accordingly. In order to enhance the response, more surface defects were introduced by doping indium oxide with Ce by a Sol-Gel process. It was indicated that the surface electron concentration and the mechanism of accumulation layer transportation are regulated by the donor doping. Test results showed that the response of doped In2O3 sensors to nitrogen dioxide was two times higher than that of pure In2O3 senors.