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

Abstract

Photoluminescence (PL) properties of SiO 2 films containing Si nanocrystals (nc-Si) and Nd 3+ ( Tm 3+ ) 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 Nd 3+ ( Tm 3+) . At room temperature, PL from the recombination of excitons confined in nc-Si and the intra-4 f shell transition of Nd 3+ ( Tm 3+ ) were observed simultaneously. The intensities of Nd 3+ and Tm 3+ PL were found to depend strongly on the size of nc-Si. These strong size-dependence suggests that nc-Si which are smaller than a threshold size can efficiently excite Nd 3+ ( Tm 3+ ). We also studied the temperature dependence for the sample with Tm 3+. At low temperature, PL spectra of the nc-Si was strongly modified. This modification gives the spectroscopic evidence of the resonant energy transfer to the third excited states of Tm 3+.