Optical properties of Ce-doped SiO2 films: From isolated Ce3+ ions to formation of cerium silicate

• Activation of isolated Ce3+ ions causes an increase of the Ce-related luminescence.
• Ce cluster formation at high annealing temperatures and decrease of luminescence.
• Cerium silicate formation at 1100 °C evidenced by both FTIR and XRD measurements.

The optical properties of Ce-doped SiO2 thin films were investigated by photoluminescence spectroscopy. Strong blue luminescence is obtained at room temperature from as-deposited films. The dependence of the luminescence on both Ce content and annealing temperature is then systematically studied. The luminescence is found to shift to higher wavelength as the annealing temperature increases. Moreover, the integrated luminescence intensity first increases for annealing temperatures between 500 °C and 900 °C as a result of the activation of Ce3+ ions and eventually decreases for higher temperatures which is interpreted by the formation of cerium clusters. At 1100 °C, the formation of a cerium silicate phase is observed by infrared absorption spectroscopy. X-ray diffraction measurements confirm the formation of an orthorhombic Ce6Si4(SiO4)2O13 compound.