Raman Scattering of Acoustical Modes of Silicon Nanoparticles Embedded In Silica Matrix

The Raman scattering from acoustical phonons of silicon quantum dots in glass matrix was investigated. Two peaks that correspond to symmetric and quadrupolar spheroidal vibrations were found. A model calculation for in- and off-resonance scattering conditions was used, which considered the homogeneous broadening due to interaction with matrix and the inhomogeneous broadening due to particle size distribution. A strong dependence of the light-to-vibration coupling coefficient on the particles size was needed for fitting the Raman data. This result suggests that resonance with electronic transitions of the silicon nanoparticles is important for excitation at 514.5 nm. The size distribution obtained from the Raman data is in agreement with the results of high-resolution transmission electron microscopy.