The mechanism of energy transfer from Si nanocrystals to Er ions in SiO2Different mechanisms depending on Er concentration

The mechanism of energy transfer from silicon nanocrystals (Si-nc’s) to erbium (Er) ions is studied by analyzing time transient of Er photoluminescence at 1.54 μm. It is shown that two different energy transfer mechanisms, i.e., fast and slow, exist in SiO2 films containing Si-nc’s and Er ions, and that the ratio of slow to fast processes depends on size of Si-nc’s and Er concentration. A quantitative analysis reveals that Er ions located within about 1.5 nm from the surface of Si-nc’s are excited by the fast process, and those located within about 2.5 nm by the slow process if no Er ions exist within 1.5 nm from the surface. Er ions staying outside these regions cannot be sensitized by Si-nc’s.