Effect of Iron Doping on the Structural and Optical Properties of CeO₂ Films

Undoped and Fe-doped CeO₂ thin films were fabricated by spin coating on F-doped tin oxide glass substrates followed by annealing at 500 °C for 15 h. The concentration of the dopant was varied from 2 to 10 % iron by weight (metal basic). Glancing angle X-ray diffraction and laser Raman microspectroscopy indicated that the films consisted only of CeO₂ without any impurity phases of Fe_xO_y. The thickness of the films was determined by dual-beam focused ion beam milling to be ~150 nm for undoped film, while Fe-doped CeO₂ films have thickness of ~200 nm for all dopant samples. The transmission spectra from UV–visible spectrophotometry showed a redshift of the absorption edge of the doped films, and the optical indirect band gap of the films decreased from 3.48 to 3.20 eV with increasing dopant concentration. Furthermore, the results have been proposed in the diagram of electron–hole trapping.