Fabrication of nanostructured ZnO thin film sensor for NO2 monitoring

Nanocrystalline zinc oxide (ZnO) thin films were deposited onto glass substrates by a spin coating method. These films were characterized for their structural and morphological properties by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The ZnO films are oriented along (1 0 1) plane with the hexagonal crystal structure. These films were utilized in NO2 sensors. The dependence of the NO2 response on the operating temperature, NO2 concentration was investigated. The ZnO film showed selectivity for NO2 over H2S compared to NH3 (SNO2/SH2S=3.32SNO2/SH2S=3.32 and SNO2/SNH3=5.32SNO2/SNH3=5.32). The maximum gas response of 37.2% was achieved with 78% stability for ZnO films upon exposure of 100 ppm NO2 at operating temperature 200 °C.