Preparation and characterisation of Si nanocrystallites embedded in a silica matrix

Abstract

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 ²⁹ Si 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.