Room-temperature luminescence from rare-earth ions implanted into Si nanocrystals

Efficient room-temperature luminescence from rare earths contained in Si nanocrystals is reported. Si nanocrystals were formed by high-dose Si implantation into SiO2 followed by high-temperature annealing. Er implantation was then performed both in pure SiO2 and in SiO2 containing the nanocrystals. Luminescence measurements showed that the Er signal at 1.54 mu m is two orders of magnitude higher in the sample containing the nanocrystals than in pure SiO2. Excitation spectroscopy demonstrated that, while within SiO2 Er is excited through direct photon absorption, excitation within the nanocrystals occurs via an efficient carrier-mediated process. These data demonstrate that the non-radiative processes usually limiting Er luminescence in Si are almost absent within the nanocrystals. Extension to other rare earths (namely Tm, Yb and Nd) is reported showing that the wavelength of emission can be properly tuned. The implications of these results are discussed.