Effects of particle size and excitation spectrum on the photoluminescence of silicon nanocrystals formed by ion implantation

Abstract

Ion implantation was used to synthesize two specimens of SiO 2 containing silicon nanocrystals with different average sizes. Although the luminescence spectra of the two specimens were slightly different, selective excitation experiments tuned to specific regions of the absorption spectrum do not indicate any direct particle-size dependence of the luminescence. The spectrum is, however, highly sensitive to the excitation power, due to the more rapid recombination dynamics at higher frequencies. The luminescence lifetime was slightly smaller for the larger nanoparticles. These results are consistent with a sub-gap recombination mechanism for silicon nanocrystals embedded in a matrix of SiO 2. Tuning the wavelength of emission from light-emitting devices based on these materials is therefore not likely to be achieved by controlling the particle size; such tunability may instead be realized by techniques such as doping or otherwise chemically modifying silicon nanocomposites.