Raman scattering technique in characterization of glasses containing nanoparticles for integrated optoelectronics

Low frequency Raman scattering on the acoustic vibrational modes of nanoparticles has been used for determining the size of dielectric, semiconductor and metal nanoparticles embedded in glass. This contribution reports on application of low-frequency Raman scattering on acoustical vibrational modes of nanoparticles. The theoretical background as well as the experimental results of free non-interacting nanoparticles as well as glass containing different nanoparticles for optoelectronics will be presented. The approach is based on a 1/v dependence of the Raman light of the vibration coupling coefficient and on the fact that each nanocrystallite of diameter D vibrates with its eigenfrequency v~1/D. The Raman scattering spectra are analyzed using confined acoustical vibrations model. The model-calculation considered homogeneous broadening of the confined acoustical modes due to interaction of the particles with matrix and inhomogeneous broadening due to the contribution of the Raman scattering from the particles of different sizes. The low frequency Raman spectra of different nanoparticles (nc-TiO2, nc-SnO2, nc-CdSxSe1-x, and nc-Si) prepared by Physical Vapour Deposition, thermal quenching and thereafter annealing of glass and sol-gel techniques was used for determination of particles size distribution and results were compared to TEM. The Raman spectroscopy technique has proved to be a simple and fast method that has favorable statistical characteristics due to the macroscopic probe volume and makes in situ measurements possible.