Excitation of Er atoms by energy transfer from Si nanocrystallites embedded in SiO2 matrices fabricated by laser ablation

We have investigated excitation of Er3+ ions via energy transfer from Si nanocrystallites embedded in SiO2 films. The Er-doped films were fabricated using a laser ablation technique. We found that a photoluminescence (PL) excitation spectra of Er3+ ions coincides with that of Si nanocrystallites. Thus, it is evident that Er3+ ions are excited via the luminescent singlet state in Si nanocrystallites. Furthermore, we obtained the results that support the energy transfer mechanism. PL intensity of Er3+ ions increases with Er concentration while that of Si nanocrystallites decrease inversely. PL intensity of Er3+ ions increases with temperature from cryogenic to room temperature under photo-excitation at power density higher than 110 mW/cm2. The increase is characteristic of the luminescent state in Si nanocrystallites but not any state in Er3+ ions.