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

Luminescent thin films were fabricated using CeO2 as a host crystal and Eu3+ and Sm3+ as activators. The films were deposited on glass substrates by a spin-on/pyrolysis technique at temperatures up to 700 °C using ethanolic solutions of rare-earth acetates. A cubic fluorite-type CeO2 phase was formed at the deposition temperatures between 400 and 700 °C. Increases in the temperature promoted the grain growth of CeO2 and improved its crystallinity. Eu3+ was practically doped in the CeO2 lattice as indicated by a dominant magnetic-dipole D05→F17 transition in a site with inversion symmetry. The efficiency of ultraviolet light excitation at 330–340 nm was promoted by the charge transfer from O2− to Ce4+ and the subsequent energy transfer to Eu3+ in photoluminescence. Sm3+ doping was found to cause unusual emissions with a dominant G5/24→H5/26 transition centered at 573 nm.