Gas sensing performance of sprayed NiO thin films toward NO2 gas

Abstract

Nickel oxide thin films were obtained by a cost-effective chemical spray pyrolysis approach on glass substrates using nickel chloride as starting precursor with different deposition times. The X-ray diffraction investigation indicated that the obtained films were polycrystalline cubic structure with preferred orientation along (111) plane. Scanning electron microscopy images for sprayed NiO layers at deposition time of 5 and 10 min exhibit a porous structure with randomly oriented honeycomb like morphology. The optical direct band-gap energy Eg of sprayed NiO films was around 3.4–3.5 eV for all deposited samples and optical transmittance decreases with increasing the deposition time. Gas sensing performance was tested for the detection of nitrogen dioxide (NO2) at different operating temperatures and NO2 concentrations. It was found that the sprayed NiO thin film at deposition time of 5 min shows the maximum sensitivity of 57.3% for 20 ppm NO2 at 200 °C as operating temperature with good stability and selectivity. This study suggests that the sprayed NiO thin film is a good candidate material for NO2 detection at a relatively low operating temperature.