Ex situ prepared Si nanocrystals embedded in silica glass:: Formation and characterization

In this article we present an alternative approach for the fabrication of silicon nanocrystals (Si-nc) prepared ex situ of the silicon dioxide (SiO(2)) host matrix. The Si-nc are scratched from porous silicon layers and incorporated into a host spin-on-glass SiO(2) based matrix. High-resolution transmission electron microscopy and Raman spectroscopy revealed Si-nc of 2-5 nm size. These nanocrystallites exhibit visible room temperature photoluminescence (PL) with a maximum at about 700 nm. The presence of the dopant in the host matrix is shown to induce a blueshift of the PL maxima due to modified surface states of the Si-nc. This approach allows the fabrication of self-supporting samples with very high Si-nc concentrations. A bright photoluminescence at room temperature is obtained on such materials. Finally, strong indication of optical gain at room temperature is shown for samples with high Si-nc concentrations in a phosphorus doped sol gel host matrix. (C) 2004 American Institute of Physics.