Optical and Morphology Mechanism of CeO2 Thin Films Prepared by Ultrasonic Spray Pyrolysis Method

Cerium oxide (CeO2) thin films were successfully fabricated on glass substrates via spray pyrolysis at 350°C with varying molarities (0.025, 0.05 and 0.1 M). We employed various characterisation techniques to assess how molarity influences these thin films' microstructural, optical, morphological, and surface properties. The as-synthesized samples exhibited a distinct face-centred cubic fluorite structure oriented along the (2 0 0) crystallographic plane. Raman spectroscopy provided insights into imperfections, with the longitudinal optical mode confirming the presence of oxygen vacancies. The peak asymmetry and width in the Raman spectra were associated with the existence of Ce+3 ions and oxygen vacancies. Photoluminescence spectra (PL) illustrated an excitation peak at 400 nm and two emission peaks at 525 nm and 600 nm. Our scanning electron microscopy (SEM) images illustrated how molarity affected the morphologies of the samples, while atomic force microscopy (AFM) allowed us to investigate the film's surface morphologies and roughness values. Transmittance analysis within UV-Vis spectral range indicated that these samples were transparent, with transmittance levels ranging from 20% to 60%. Furthermore, we observed a decrease in the band gap energy (Eg) with increasing molarity. These findings hold significant promise for expanding the applications of cerium oxide in technological devices.