Surface control of luminescence in silicon nanoparticles

Abstract

The intensity of visible photoluminescence from thin films of silicon nanoparticles is shown to be dependent upon the degree of surface passivation on the nanoparticles, while the emission energy is independent of the specific chemical nature of the passivating species. Nanoparticles are deposited into films using a pulsed laser ablation supersonic expansion source. Surface chemistry is controlled with a variety of postdeposition processing steps, including acid, methanol, and iodine treatments. These steps are then correlated with the visible photoluminescence behavior of the sample and the surface chemistry as characterized by x-ray photoelectron spectroscopy. Surface passivation controls the emission intensity through the elimination of competing nonradiative carrier relaxation pathways. The chemical nature of the passivating species does not determine the emission energy and can be easily changed with no anomalous photoluminescence behavior resulting. All results are consistent with a simple quantum confinement model of emission where particle size determines emission energy and surface passivation determines emission intensity.