Preparation and characterisation of Si nanocrystallites embedded in a silica matrix

Si nanocrystallites embedded in a silica matrix have been prepared by the s ol-gel route using triethoxysilane as the precursor. The different steps of formation of silicon during thermal treatment of the gels were observed by X-ray diffraction, Raman and Si-29 MAS NMR spectroscopy. The gels were fir st pre-heal-treated under vacuum at different temperatures (500 degrees C, 700 degrees C and 1000 degrees C) and then densified under pressure at 1320 degrees C. TEM and low frequency inelastic Raman measurements indicate tha t the size of the Si particles increases with the temperature of the pre-he at treatment. The only materials to show luminescence in the visible range were those containing residual Si-OH bonds.