Construction of Cr2O3:ZnO Nanostructured Thin Film Prepared by Pulsed Laser Deposition Technique for NO2 Gas Sensor

Rhombohedral structure of chromium oxide (Cr2O3) thin-film doped hexagonal zinc oxide (ZnO) nanoparticles have been prepared using pulsed laser deposition technique at a different weight percent of ZnO from 0 to 9 wt%. The results of X-ray diffraction analysis shown that the doped films are polycrystalline, and the average crystallite size of the synthesized thin films is found to be dependent on the ZnO concentration. The surface morphology of the prepared thin films was characterized by atomic force microscopy. The optical properties are investigated using ultraviolet-visible light (UV-Vis) absorption spectroscopy. The optical bandgap ranged from 2.45 to 2.68 eV, showing the shift towards longer-wavelength compared to bulk Cr2O3 ( 3 eV). The sensitivity, response, and recovery times of the sensor towards nitrogen dioxide (NO2) gas were studied and discussed. The sensitivity increase with increasing the doping concentration, and started to decrease when ZnO concentrations reach 7 wt%. The optimal ZnO concentrations for NO2 gas sensitivity is 5 wt%, which attain maximum sensitivity of 87.5% at temperature of 523 K.