Successive Ion Layer Adsorption and Reaction Method Developed ZnO Thin Films for NO2 Gas Sensing

The present investigation deals with the NO2 gas detection via nanostructured zinc oxide (ZnO) thin films harvested over a glass substrate via a simple and facile successive ion layer adsorption and reaction (SILAR) approach. ZnO nanostructured thin films are developed by different SILAR cycles (ZnO:15, ZnO:30, ZnO:45, ZnO:60). The physicochemical, optical, and morphological properties of prepared thin films are explored by various characterization techniques. The phase purity and grains size are confirmed by X-ray diffraction (XRD) and Scherrer formula, which reveal the hexagonal phase structure with variant grain size (approximate to 16-21 nm). The surface morphology of deposited films shows the well-dispersion of ZnO nanoparticles, which is picturized by field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), attenuated total reflectance (ATR). UV-Vis and FTIR spectroscopy elaborates on the optical properties and functional groups of ZnO films, respectively. Further, the sensing ability of ZnO thin films is studied with different concentrations (50-250 ppm) of NO2 gas in the span of 50 ppm by recording the resistance transient. The ZnO:30 thin-film displays an enhanced gas sensing response of 1.42 G omega at 100 degrees C compared to other synthesized films and at different temperature ranges. The ZnO:30 film shows the highly selective response toward the NO2 gas compared to other interference gas species. Thus, the present study highly recommends the investigated method for the ZnO thin film formation to be employed toward NO2 gas sensing.