Sensitizing properties of amorphous Si clusters on the 1.54 microns luminescence of Er in Si-rich SiO2

In this letter, the role of amorphous Si clusters in the excitation of Er implanted in substoichiometric SiOx films will be elucidated. It will be shown that the temperature of the SiOx thermal process prior to Er implantation is crucial in determining the luminescence properties of the samples. In particular, the luminescence intensity at 1.54 mum is almost constant for SiOx samples not annealed or pre-annealed at temperatures lower than 800degreesC, reaches the maximum at 800degreesC, and decreases at higher temperatures. The structural properties of these samples have been studied by energy filtered transmission electron microscopy. It will be shown that for annealing temperatures lower than 1000degreesC, only amorphous Si nanoclusters are present. We demonstrate that a large density of small amorphous Si clusters produces the best luminescence performance and enhances the fraction of optically active Er.