Effects of yttrium codoping on photoluminescence of erbium-doped TiO2 films

${\mathrm{Er}}^{\text{3+}}–{\mathrm{Y}}^{\text{3+}}$ codoped ${\mathrm{TiO}}_{\mathrm{2}}$ films were prepared on a fused silica substrate by the sol–gel process. The effect of ${\mathrm{Y}}^{\text{3+}}$ codoping on the ∼1.54 μm photoluminescence (PL) properties of ${\mathrm{Er}}^{\text{3+}}$ -doped ${\mathrm{TiO}}_{\mathrm{2}}$ films are investigated. Enhancement of PL properties due to ${\mathrm{Y}}^{\text{3+}}$ codoping by a factor of 10 for intensity and of 1.5 for the full width at half maximum in comparison with the ${\mathrm{Er}}^{\text{3+}}–{\mathrm{Al}}^{\mathrm{3+}}$ codoped ${\mathrm{SiO}}_{\mathrm{2}}$ system has been observed in the film annealed at ${\mathrm{Er}}^{\text{3+}}:{\mathrm{Y}}^{\text{3+}}:{\mathrm{Ti}}^{\mathrm{4+}}\text{=5:30(∼50):100.}$ Extended x-ray absorption fine structure measurements show that the local chemical environment of ${\mathrm{Er}}^{\text{3+}}$ ions in the ${\mathrm{Er}}^{\text{3+}}–{\mathrm{Y}}^{\text{3+}}$ codoped ${\mathrm{TiO}}_{\mathrm{2}}$ films is similar to that in ${\mathrm{Er}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}.$ The average spatial distance between ${\mathrm{Er}}^{\text{3+}}$ ions is enlarged due to the partial substitution of ${\mathrm{Y}}^{\text{3+}}$ for ${\mathrm{Er}}^{\text{3+}}$ ions in the ${\mathrm{Er}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ -like local structure. It is believed that the more intense PL emission of the ${\mathrm{Er}}^{\text{3+}}–{\mathrm{Y}}^{\text{3+}}$ codoped ${\mathrm{TiO}}_{\mathrm{2}}$ films can be attributed to the better dispersion and distorted local structure of ${\mathrm{Er}}^{\text{3+}}$ ions in the ${\mathrm{TiO}}_{\mathrm{2}}$ host matrix by yttrium codoping.