Synthesis and characterization of Nd-doped CeO2 thin films grown by spray pyrolysis method: Structural, optical and electrochemical properties

Abstract

In the present research, we successfully synthesized thin films of Cerium Oxide (CeO2) and Neodymium (Nd) doped CeO2 on both glass and ITO substrates using the chemical spray pyrolysis method. Their structural, morphological, optical and electrochemical properties were experimentally studied. X-ray diffraction analyses showed that all the layers exhibited the cubic fluorite phase characteristic of CeO2. Raman spectroscopy reveals a downward F2g band shift in all Nd3+-doped CeO2 films due to oxygen vacancies. The asymmetry and broadening of the Raman modes arise from the injection of Nd3+ ions in CeO2 thin films, which leads to variations in the presence of Ce3+ and oxygen vacancies. Additionally, the morphology of the films changes with different levels of Nd-doping. The UV–Vis-NIR spectra obtained in the wavelength scale between 300 nm and 1800 nm showed a noticeable reduction in the band gap from 3.46 eV to 3.30 eV. The cyclic voltammetry (CV) results indicate that the addition of Nd improves the ion storage capacities (ISC) of the cerium oxide thin film. Even after the intercalation/deintercalation of lithium ions, the doped cerium oxide thin films remain fully transparent. These significant findings broaden the potential applications of this oxide, particularly for electrochromic devices.