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

Abstract

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.