Impact of calcination temperature on the structure, optical and photoluminescence properties of NanocrystallineCerium oxide thin films

Abstract

Nanocrystalline cerium oxide films were effectively synthesized on glass substrates via hydrothermal and dip coating techniques at various calcination temperatures (CT) from 300 to 550 °C. Impact of CT on the structure, surface morphology, optical and photoluminescence (PL) properties of cerium oxide (CeOx) films has been investigated. The grazing incident in-plane X-ray diffraction (GIIXD) analysis revealed that thin films acquire cubic fluorite nanostructure of CeO2, with average crystallite size in the range of 3.77–7.63 nm for films of different CT. XPS results revealed the existence of amorphous Ce2O3 in nanostructure CeOx films with crystalline CeO2 phase that was identified by GIIXD results. AFM images manifestations of CeOx thin film at various temperatures with tinny nanoparticles which agglomerate as spherical grains appear randomly distributed with surface roughness ranging from 0.42 to 0.488 μm for films of different CT. Optical properties indicated a narrowing in direct and indirect band gaps of nanocrystalline films than bulk CeO2 to show some fluctuation with the influence of CT that affected with lowering in Ce3+/Ce4+ ratio. Other optical parameters were analysed with the influence of calcination temperatures CT. Photoluminescence (PL) studies indicate the presence of most intense PL emission peak appears at 419 nm revealed the fundamental transition of direct band gap of CeO2, in addition to some other PL emission peaks in the visible range attributed to structural and oxygen vacancies defects states among Ce4f and O 2p bands.