Effect of hydrogen on the photoluminescence of Si nanocrystals embedded ina SiO2 matrix

Hydrogen passivation of Si nanocrystals is shown to result in a redshift of photoluminescence (PL) emission spectra, as well as the more commonly obse rved intensity increase. The shift is reversible, with spectra returning to their unpassivated values as hydrogen is removed from the samples by annea ling. The magnitude of the redshift also depends on the implant fluence emp loyed for nanocrystal synthesis, increasing with increasing fluence or part icle size. These data are shown to be consistent with a model in which larg er crystallites are assumed to contain a greater number of nonradiative def ects, i.e., the number of nonradiative defects is assumed to scale with the surface area or volume of a nanocrystal. Hydrogen passivation then results in a disproportionate increase in emission from larger crystallites, givin g rise to an apparent redshift in the composite PL emission spectrum. (C) 2 001 American Institute of Physics.