Down-conversion luminescence from (Ce, Yb) co-doped oxygen-rich silicon oxides

We have studied down-conversion photoluminescence (PL) from (Ce, Yb) co-doped "oxygen rich" silicon oxide films prepared by sputtering and annealing. The Ce³⁺ ∼510 nm PL is sensitive to the Ce concentration of the films and is much stronger for 3 at. % Ce than for 2 at. % Ce after annealing at 1200 °C. The PL emission and excitation spectroscopy results indicate that the excitation of Yb³⁺ is mainly through an energy transfer from Ce³⁺ to Yb³⁺, oxide defects also play a role in the excitation of Yb³⁺ after lower temperature (∼800 °C) annealing. The Ce³⁺ 510 nm photon excites mostly only one Yb³⁺ 980 nm photon. Temperature-dependent PL measurements suggest that the energy transfer from Ce³⁺ to Yb³⁺ is partly thermally activated.