Photoluminescence decay dynamics of silver/porous-silicon nanocomposites formed by metal-assisted etching

We investigate the photoluminescence (PL) properties of silver/porous-silicon (Ag/PSi) nanocomposites prepared by metal-assisted etching in image solution, on the basis of steady-state and time-resolved PL spectroscopy measurements. The PL intensity and peak position are strongly dependent on the image concentration. Time-resolved PL measurements reveal that the nonradiative rate decreases with an increase in the image concentration for the Ag/PSi nanocomposites. It is found from x-ray photoelectron spectroscopy measurements that the decrease in the nonradiative rate is caused by the formation of image layers on the PSi surfaces. Further, the number of light-emitting Si nanocrystals in the nanocomposites, which is estimated from the PL decay rate and PL intensity, increases with the image concentration. From the wavelength dependence of the PL decay rate, it is found that the nonradiative rate is considerably dispersive, i.e., the shorter the wavelength, the higher the nonradiative rate.