Tuning of structural, optical, and impedance properties of CeO₂ thin films by incorporation palladium ions

Thin films of pure and Pd-doped CeO₂ with different doping concentrations deposited via sol gel spin coating technique. The influence of Pd doping level (0, 2, 4 and 8%) on the physical characteristics was investigated of nanocrystalline CeO₂ thin films. From X-ray diffraction (XRD) pattern, the (111) preferred oriented CeO₂ cubic structure was observed in all thin films. Crystallite size decreased with increasing Pd doping from 67.41 to 41.67 nm, whereas the crystallinity of thin film increased with doping level. The field emission scanning electron microscopy (FESEM) analyses showed the uniform distribution of nanospherical grains, decreased in size and agglomerated of nanocrystallite with increasing Pd doping. Energy-dispersive X-ray (EDX) results revealed that the weight percentage of un-doped and Pd-doped CeO₂ thin films was confirmed and very close to that in mixed precursor. The energy bandgap values of prepared thin films were measured as a function of Pd doping centration using UV–Vis spectroscopy. Energy bandgap as well as the transmission of CeO₂ were increased with Pd doping level. The PL spectra show noticeable variations in intensity and red shift of the emission peaks upon Pd doping. These effects have been associated with structural modifications and defect states Pd-doped CeO₂ thin films. The Nyquist plots suggest that the ionic conductivity through the grains is responsible in the conduction mechanism of the thin films.