Structure and luminescent properties of CeO2:rare earth (RE=Eu3+ and Sm3+) thin films

Abstract

Luminescent thin films were fabricated using ${\mathrm{CeO}}_2$ as a host crystal and ${\mathrm{Eu}}^{\text{3+}}$ and ${\mathrm{Sm}}^{\text{3+}}$ as activators. The films were deposited on glass substrates by a spin-on/pyrolysis technique at temperatures up to $\text{700\hspace{0.05em}°}\mathrm{C}$ using ethanolic solutions of rare-earth acetates. A cubic fluorite-type ${\mathrm{CeO}}_2$ phase was formed at the deposition temperatures between 400 and $\text{700\hspace{0.05em}°}\mathrm{C}.$ Increases in the temperature promoted the grain growth of ${\mathrm{CeO}}_2$ and improved its crystallinity. ${\mathrm{Eu}}^{\text{3+}}$ was practically doped in the ${\mathrm{CeO}}_2$ lattice as indicated by a dominant magnetic-dipole ${}^5{D}_0{\to }^7{F}_1$ transition in a site with inversion symmetry. The efficiency of ultraviolet light excitation at 330–340 nm was promoted by the charge transfer from ${\mathrm{O}}^{\text{2−}}$ to ${\mathrm{Ce}}^{\text{4+}}$ and the subsequent energy transfer to ${\mathrm{Eu}}^{\text{3+}}$ in photoluminescence. ${\mathrm{Sm}}^{\text{3+}}$ doping was found to cause unusual emissions with a dominant ${}^4{G}_{\text{5/2}}{\to }^6{H}_{\text{5/2}}$ transition centered at 573 nm.