Mechanism of bright red emission in Si nanoclusters

A bright photoluminescence around 1.7 eV is observed for post-annealed samples of 1 MeV Si2+ implanted in an SiO2 matrix. A super-linear power dependence of photoluminescence intensity accompanied by pulse shortening under continuous wave laser excitation is recorded without any spectral narrowing. An emission process comprised of an initial non-radiative recombination (time constant similar to 280-315 ps) of excited carriers in the defect states in SiO2 matrices to the conduction band minima of nc-Si, followed by a slower process of radiative recombination in the direct band transition for nc-Si along with a non-radiative Auger recombination (time constant similar to 2.67 ns) is proposed.