Spectrally resolved energy transfer from excitons in Si nanocrystals to Er ions

Abstract

The energy transfer from Si nanocrystals (Si-nc’s) to Er ions was studied spectroscopically. At low temperatures, inhomogeneously broadened photoluminescence bands of Si-nc’s were partially quenched and some dips were observed. A comparison of the quenched spectra with a photoluminescence excitation spectrum revealed that the dips are due to the resonant energy transfer from excitons in Si-nc’s to Er ions. For the energy transfer to the ${}^{4}I_{11∕2}$ state of Er ions, two dips, one very clear and the other indistinctive, were observed, while to the ${}^{4}I_{9∕2}$ state, two dips with comparable depth were observed. Modification of the band structure of Si-nc’s by the quantum size effects is responsible for the different dip structures, depending on to which states the energy transfer is made.