Excitation of Tm 3+ by the energy transfer from Si nanocrystals

Abstract

Photoluminescence (PL) properties of SiO 2 films containing Si nanocrystals (nc-Si) and Tm 3+ were studied. The average size of nc-Si was changed over wide range in order to tune the exciton energy of nc-Si to the energy separations between the discrete electronic states of Tm 3+. At room temperature, the samples exhibited broad PL peaks located at an energy region between 1.35 and 1.6 eV corresponding to the recombination of the excitons in nc-Si, and sharp peaks at 1.57 and 0.69 eV corresponding to the intra-4f shell transition of Tm 3+. The intensity of the Tm 3+ related PL showed a strong dependence on the size of nc-Si. This result implies that only nc-Si which are smaller than a threshold size can efficiently excite Tm 3+. At low temperatures, the spectral shape of nc-Si PL was strongly modified by doping Tm. From the analysis of the modified spectral shape, the spectroscopic evidence of the resonant energy transfer from nc-Si to Tm 3+ was obtained.