X-ray diffraction, Raman and photoluminescence studies of nanocrystalline cerium oxide thin films

Cerium oxide (CeO2) thin films were deposited on Si (100) and glass substrates at various oxygen partial pressures (2×10−5 mbar–3×10−1 mbar) and a substrate temperature of 673 K, by pulsed laser deposition (PLD). The structural, morphological and optical properties of the films were characterized by X-ray diffraction, Raman spectroscopy, high resolution transmission electron microscopy, atomic force microscopy, photoluminescence and UV–visible spectroscopy. XRD analysis revealed the polycrystalline and cubic structure of the CeO2 films with preferred orientation for (200) as the increase of oxygen partial pressure. The Raman studies indicated the formation of Ce–O with the systematic variation of peak intensity and FWHM with oxygen partial pressures. The high resolution transmission electron microscopy investigation confirmed the polycrystalline and cubic nature of the CeO2 films with (200) preferred orientation. The AFM studies showed the roughness (RMS) values of the films increased from 0.8 nm to 4.6 nm with increasing oxygen partial pressure from 2×10−5 mbar to 3×10−1 mbar. The photoluminescence (PL) investigation indicated the bandgap values in the range 3.05–3.10 eV with increasing oxygen partial pressures. The UV–visible spectroscopy analysis demonstrated that the refractive index of the films decreased from 2.41 to 1.72 with increasing oxygen partial pressures.