Synthesis and characterization of Fe-doped ZnO films for enhanced NO2 gas-sensing applications

Zinc oxide films doped with iron (Fe-doped ZnO) were fabricated via spray pyrolysis technique by utilizing zinc nitrate and ferric chloride as the source materials. The film manifests a hexagonal wurtzite crystalline structure. Variations in the atomic dimensions of ZnO matrix were observed with an escalation in dopant concentration ranging from 0 to 5 at.% (atomic percent). The incorporation of Fe into the lattice was found to influence the optical transmittance properties and resulted in a decrement of the optical bandgap from 3.28 eV to 2.90 eV. X-ray diffraction (XRD) analysis confirmed that the films are monophasic, retaining a wurtzite structure characteristic of pure ZnO. Comprehensive material characterization was conducted by utilizing a suite of analytical techniques, including scanning electron microscopy (SEM), ultraviolet–visible (UV–Vis) spectroscopy and X-ray photoelectron spectroscopy (XPS), to substantiate the successful synthesis of the nanocomposite and to evaluate various attributes such as surface area, structural and morphological features, chemical composition, and purity. The gas-sensing efficacy of the Fe-doped ZnO films towards nitrogen dioxide (NO₂) was assessed, revealing a significant gas response of 31.81% at an operational temperature of 400 degrees Celsius for a NO₂ concentration of 100 parts per million (ppm). This gas-sensing performance is characterized by prompt response and recovery times, recorded at 23 s and 61 s, respectively. In addition, it was determined that the sensor response is contingent upon the operating temperature.