Investigations of Some Physical Properties and Sensing Properties of Fluorine-Doped Alpha-Iron (III) Oxide Thin Films

Abstract

Fluorine-doped α-Fe₂O₃ nanostructure films were synthesized by a facile Chemical Spray Pyrolysis (CSP) technique at a substrate temperature of 400 °C using standard glass slides. The fluorine dopant concentration was varied incrementally at 0%, 2%, and 4% by weight in order to systematically investigate its influence on the structural, morphological, and optical properties of the deposited films. X-ray diffraction (XRD) analyses exhibit well-defined diffraction peaks corresponding to the (017), (113), (119), and (220) planes, confirming the successful formation of the pure α-Fe₂O₃ (hematite) phase without any detectable secondary phases. The average crystallite size of hematite increased from 13.98 nm to 16.78 nm with rising fluorine content, indicating enhanced crystal growth and improved crystallinity due to doping. Atomic Force Microscopy (AFM) images reveal uniformly distributed grains with a smooth surface texture free of cracks or pinholes. Furthermore, the surface morphology and grain dimensions were noticeably altered as the dopant concentration increased. Optical characterization demonstrated a progressive decrease in transmittance with fluorine incorporation, reaching 65% at 600 nm, accompanied by a clear blue shift in the optical band gap, indicating modified electronic transitions and enhanced optical activity in the doped films.