Role of ZnO-doping concentration on CuO thin film for promising NH3 gas detectors application by a thermal vaporization method

Abstract

This study included the fabrication of nanofilms of ZnO-doping concentration on CuO nanoparticles (NPs) by a thermal vaporization method. The film thickness is 50 ± 0.2 nm and is deposited on glass substrates at room temperature (RT). The deposited nanofilms exhibit no discernible peaks in X-ray diffraction (XRD) examination. The widening of the peak indicates a lack of long-range symmetry, resulting in a disordered nanocrystalline structure. This process yielded films with a homogeneous surface, as confirmed by atomic force microscope (AFM). As ZnO doping increased, roughness increased by 70.48%, the root mean square value increased by 72.55%, and the average grain diameter increased by 50.28%. The field emission scanning electron microscope (FESEM) analysis showed equally scattered CuO/ZnO nano-films. The optical characteristics of CuO/ZnO nano-films show ZnO presence. The absorbance and absorption coefficient are both increased. As ZnO concentrations increased, energy and transmittance band gaps reduced from 0.83 to 0.71 eV and 3.610 to 3.487 eV. The most significant reported sensitivity at RT to NH₃ at a concentration of 0.20 wt.% was 47.06% at an operating temperature of 100°C. This sensitivity was achieved within an answer time of 32.49 s, with a recuperation period of 29.61 s. The most excellent reported sensitivity at 573 K to NH₃ at a concentration of 0.20 wt.% was 45.05% at an operating temperature of 100°C achieved within an answer time of 33.75 s, with a recuperation period of 28.62 s and the most excellent reported sensitivity at 673 K to NH₃ at a concentration of 0.20 wt.% was 68.81% at operating temperature of 100°C achieved within an answer time of 27.81 s, with a recuperation period of 15.84 s, so that it is considered the best sensitivity for NH₃ detection. The sensitivity of the sample (0.20 wt.%) typically decreases as the temperature rises. This makes it seem like the gas-detector can interact with NH₃ gas without needing any activation energy and that the interaction is predicated on polarity and physical adsorption. Nevertheless, the sensitivity of the pure, 0.08, and 0.14 wt.% samples exhibited a positive correlation with temperature within a specific range. The findings regarding the structural and conductive characteristics of CuO/ZnO nano-films hold promising applications in advanced optoelectronic devices and gas sensors.