Excitation of Er ions by the energy transfer from Si nanocrystals

Abstract

Incorporation of Si nanocrystal into Er-doped glasses strongly enhances the IR luminescence of Er<SUP>3+</SUP>. The enhancement is believed to be due to the energy transfer from nc-Si. However, the mechanism of the interaction between nc-Si and Er<SUP>3+</SUP> has not been fully understood. In this work, we have studied the interaction between nc-Si and Er<SUP>3+</SUP> by photoluminescence (PL) spectroscopy and PL decay dynamics. In order to tune the luminescence energy of nc-Si to the energy separations between the discrete electronic sates of Er<SUP>3+</SUP>, the size of nc-Si was changed in a wide range; the PL energy of nc-Si was changed from 1.2 to 1.5 eV. At low temperatures, periodic features were observed in the PL spectra of nc-Si. The observation of the features is the first spectroscopic evidence that indicates the strong coupling between nc-Si and Er<SUP>3+</SUP>. Furthermore, size dependence of the energy transfer rate was estimated from the delay time of the Er<SUP>3+</SUP>. The effects of quantum confinement of excitons in nc-Si on the high PL efficiency of Er<SUP>3+</SUP> are discussed.