The evolution of the fraction of Er ions sensitized by Si nanostructures in silicon-rich silicon oxide thin films.

hotoluminescence (PL) and time-resolved PL experiments as a function of the elaboration process are performed on Er-doped silicon-rich silicon oxide (SRO:Er) thin films grown under NH3atmosphere. These PL measurements of the Er3+emission at 1.54?m under non-resonant pumping with the Er f-f transitions are obtained for different Er3+concentrations, ranging from 0.05 to 1.4 at.%, and various post-growth annealing temperatures of the layers. High resolution transmission electron microscopy (HRTEM) and energy-filtered TEM (EFTEM) analysis show a high density of Si nanostructures composed of amorphous and crystalline nanoclusters varying from 2.7×1018to 1018cm-3as a function of the post-growth annealing temperature. Measurements of PL lifetime and effective Er excitation cross section for all the samples under non-resonant optical excitation with the Er3+ atomic energy levels show that the number of Er3+ions sensitized by the silicon-rich matrix decreases as the annealing temperature is increased from 500 to 1050oC. The origin of this effect is attributed to the reduction of the density of sensitizers for Er ions in the SRO matrix when the annealing temperature increases. Finally, extended x-ray absorption fine-structure spectroscopy (EXAFS) shows a strong correlation between the number of emitters and the mean local order around the erbium ions