Nanostructured cerium oxide thin films by nebulized spray pyrolysis (NSP) technique: Impact of surfactants on the structural, optical and compositional properties

Abstract

Cerium oxide thin films are deposited on glass substrates with different surfactants by nebulized spray pyrolysis technique. Their crystallographic structures, surface morphology, optical properties and I–V characteristics are analyzed as a function of surfactants. All films exhibit cubic fluorite structure with preferred orientations along (111) and (200) direction depending upon preparation conditions with an average grain size 37nm. Fourier Transform-Infra Red analysis confirmed the presence of terminal stretching (Ce=O) and phonon band (Ce–O) of the metal oxide network. The intensity of carbonation bands is diminished with the addition of amine groups. The films exhibit dense, smooth and crack-free tiny particles composed of closed chains, golf-ball, hollow spherical and slap shaped nanostructures with an average size 180nm. It also exhibits nicely separated well-outlined cones and spheres with rounded apex having an average roughness 121nm. Optical spectra reveal that the films are transparent (70%) in the visible region. Optical parameters like refractive index, optical conductivity and band gap are calculated for different surfactants. Photo Luminescence analysis indicates the presence of blue and green emission peaks in the visible region centered around ~425 and ~467nm attributed to the persistence of electron–phonon interaction between Ce4f and O2p bands. X-ray Photoelectron Spectroscopy analysis reveals the existence of Ce, O, Na and C atoms in the prepared films. It also brings out the dominant occurrence of Ce4+ rather than Ce3+ in the films. It is ensured that the rare earth compounds having unpaired electrons can give raise an extra satellite peak (923.5eV) due to photoelectron energy gain or loss assigned to finger print of CeO2 phase. The electrical conductivities are in the range 7.20×10−7 to 1.21×10−4S/cm for different surfactants.