The photoluminescence from (Eu, Yb) co-doped silicon-rich Si oxides

We report on photoluminescence (PL) properties of europium (Eu) and ytterbium (Yb) co-doped silicon-rich oxide films with different Si excess and after various annealings. The dominating PL signal of Eu changed gradually from that of Eu3+ ions to Eu2+ by raising the annealing temperature from 700 to 1200 °C. Transmission electron microscopy revealed that amorphous Eu, Yb, Si, O containing precipitates have been formed in the Si-rich oxide during 1000-1200 °C annealing and these precipitates are considered to be responsible for the Eu2+-related luminescence. The variation of PL intensity from Yb3+ ions with annealing in N2,was correlated with the PL intensity from Eu. The PL of films can be altered considerably by oxidizing at different temperatures, which is discussed in terms of defects in the host oxide and excitation energy transfer.