Luminescence properties from erbium oxide nanocrystals dispersed in titania/organically modified silane composite sol-gel thin films

Luminescence properties from erbium (III) oxide nanocrystals dispersed in titania/organically modified silane composite thin films were studied. Erbium oxide nanocrystals were prepared by an inverse microemulsion technique. A strong room-temperature photoluminescence was observed at 1.531 μm, with the full width at half maximum (FWHM) of 22 nm due to intra-atomic transitions between ⁴I_13/2 and ⁴I_15/2 levels in the erbium (III) ion. The shape, peak position, and FWHM of the photoluminescence signals from the composite thin films were quite comparable to those prepared by other methods. The photoluminescence peak of the composite thin films showed a maximum intensity at the heat-treatment temperature of 300°C. A room-temperature green up-conversion emission at 543 nm (⁴S_3/2 → ⁴I_15/2) was observed for the composite thin films with different heat-treatment temperatures upon excitation at 993 nm. The up-conversion emission mechanism was explained by means of an energy-level diagram and the lifetime of the visible up-conversion emission was measured.