First- and second-order Raman scattering in nanocrystalline silicon

Confinement effects on first-order and second-order Raman scattering in nanocrystalline silicon are presented. The average dimension of the nanocrystals has been determined by an analysis of the first-order Raman spectra using the phenomenological phonon confinement model. The second-order acoustic bands 2LA and 2TA do not seem to be influenced by confinement effects and are similar to those in the bulk. The second-order optic bands are broadened and shifted in comparison to those in the bulk. The ratio of the integrated intensities $I{(2\mathrm{T}\mathrm{O})}_{\mathrm{int}}/I{(\mathrm{TO})}_{\mathrm{int}}$ depends upon the nanocrystal size and varies between the crystalline and amorphous limits.