THEORETICAL INVESTIGATION OF RAMAN-SCATTERING FROM MICROCRYSTALLITES

A shift towards lower energy and broadening of Raman spectra of μc-Si films with decreasing the microcrystallite size are explained quantitatively with the relaxation of the momentum conservation rules due to the finite crystalline size and the diameter distribution of microcrystallites in the films. The dielectric correlation function in μc-Si films is introduced in the calculations of Raman spectra to show how the short correlation length for normal mode vibrations breaks the momentum conservation rule and the diameter distribution of microcrystallites affects the spectra. The quantitative agreement between the calculations and the experimental results indicates that there is no substantial phonon damping in microcrystallites, hence the spatial correlation of phonons extends to the microcrystallite boundaries. © 1990.