Monique Pauthe, Estela Bernstein, Jean Dumas, Lucien Saviot, Annie Pradel and Michel Ribes
Si nanocrystallites embedded in a silica matrix have been prepared by the sol-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 29Si MAS NMR spectroscopy. The gels were first pre-heat-treated under vacuum at different temperatures (500°C, 700
°C and 1000
°C) and then densified under pressure at 1320
°C. TEM and low frequency inelastic Raman measurements indicate that the size of the Si particles increases with the temperature of the pre-heat treatment. The only materials to show luminescence in the visible range were those containing residual Si}}n1OH bonds.