Resonant excitation of Er3+ by the energy transfer from Si nanocrystals

Abstract

Photoluminescence (PL) properties of SiO2 films containing Si nanocrystals (nc-Si) and Er were studied. The average size of nc-Si was changed in a wide range in order to tune the exciton energy of nc-Si to the energy separations between the discrete electronic states of Er3+. PL from exciton recombination in nc-Si and the intra-4f shell transition of Er3+ were observed simultaneously. At low temperatures, periodic features were observed in the PL spectrum of nc-Si. The period agreed well with the optical phonon energy of Si. The appearance of the phonon structure implies that nc-Si which satisfy the energy conservation rule during the energy transfer process can resonantly excite Er3+. For the PL from Er3+, a delay was observed after the pulsed excitation of nc-Si hosts. The rise time of the PL showed strong size dependence. The effects of the quantum confinement of excitons in nc-Si on the energy transfer process are discussed.