NO2 Gas Sensing Performance of Co-Doped NiO Thin Film Sensors

Undoped and Co-doped NiO thin films were synthesized via a simple solvothermal route. The undoped NiO thin film sensor exhibited responses of approximately 144-216% to 0.5-10 ppm of NO2 at 250 degrees C. In contrast, the Co-doped NiO thin film sensor showed responses of approximately 206-722% to 0.5-10 ppm of NO2 at 250 degrees C. Therefore, the NO2 gas sensing performance of the NiO thin film sensor was enhanced remarkably by Co doping. Both the undoped and Co-doped NiO thin film sensors showed selectivity for NO2 gas over other gases. The underlying mechanism of the enhanced NO2 gas sensing of NiO thin films by Co-doping can be explained based on a combination of a surface depletion mechanism and a potential barrier-controlled carrier transport mechanism related to the Co3O4-NiO junction as well as a catalytic mechanism.