Size-dependent near-infrared photoluminescence spectra of Si nanocrystals embedded in SiO2 matrices

Photoluminescence (PL) spectra of Si nanocrystals embedded in SiO2 films were measured as a function of the size. Samples were prepared by r.f. cosputtering of Si and SiO2 and post-annealing. The average particle sizes for all the samples were directly estimated by high-resolution transmission electron microscopic observations. For each sample, a broad PL peak was observed in the near-infrared region. As the average particle size decreased from 3.8 nm to 2.7 nm, the peak exhibited a blue shift from 1.42 eV to 1.54 eV and its intensity increased progressively. This strong size dependence of the PL peak suggests that the PL peak arises from the recombination of electrons and holes confined in the Si nanocrystals. (C) 1997 Elsevier Science Ltd.