Effect Annealing Temperature on Pure and Al-Doped Iron Oxide Thin Films for Formaldehyde Gas Sensing Application

The present study employs chemical spray pyrolysis to prepare pure and Al-doped α -Fe 2 O 3 thin films with different aluminium concentrations. Subsequently, annealed at 450 °C and investigated the effect of annealing temperature on structural, morphological, optical, chemical and gas sensing properties. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) studies were adapted to examine the morphologies and microstructural properties of the α -Fe 2 O 3 -based thin films. All the films were polycrystalline with rhombohedral structure, and the (104) plane was confirmed to be the favoured orientation. Deposited thin films were seen to have agglomerated, superimposed sphere-like particles on their surfaces in AFM and FESEM micrographs. Raman spectroscopy analysis and XPS were used to examine the film’s symmetry and structural characteristics. The optical band gap of the deposited thin films is determined using a Tauc plot.Pure and Al-doped thin film’s formaldehyde sensing capability was examined based on aluminium (Al) doping concentration. The results of the experiments showed that the gas-detecting capabilities have been significantly enhanced by the optimal content of Al added to the α -Fe 2 O 3 lattice.