The improved phonon confinement model developed previously [11] is applied for definition of germanium nanocrystal sizes from the analysis of its Raman scattering spectra. The calculations based on the model allow determining the sizes of germanium nanocrystals more precisely from the analysis of their Raman spectra. In some cases, the comparative analysis of Raman data and electron microscopy data is carried out, and good agreement is observed.

Silicon nitride films of different stoichiometric composition were studied using Raman spectroscopy. A Raman signal due to Si–Si, Si–N bond vibrations in silicon nanoclusters was detected in as-deposited films. The appearance of Raman peaks in the range 493–514 ${\mathrm{cm}}^{\mathrm{-1}}$ after thermal and pulse laser treatments was interpreted as formation of silicon nanocrystals with sizes from 1.3 up to 5 nm depending on treatment parameters. Thermal treatment at $\text{1200\hspace{0.17em}°}\mathrm{C}$ allowed Si atom diffusion and its gathering in Si nanocrystals, meanwhile 5 ns pulse laser irradiation leads to crystallization of preexisting silicon nanoclusters inside the as-deposited ${\mathrm{SiN}}_x$ films.

We develop a model for calculating the Raman scattering spectra from phonons confined in for silicon nanocrystals, which is based on the familiar approach taking into account the uncertainty in the quasi-momentum of phonons localized in the nanocrystals. The model is considerably improved by taking into account dispersion of phonons not only in the magnitude of the quasi-momentum, but also in its direction. A significant refinement of the model is also due to the fact that phonon dispersion is calculated using the widely approved Keating model instead of being approximated by empirical expressions as was done in earlier approaches. The calculations based on this model make it possible to determine the sizes of silicon nanocrystals more precisely from analysis of the experimental Raman spectra.

In this letter, we report on accurate comparative measurements of Raman scattering from bulk crystalline Si and from hydrogenated amorphous Si thin films before and after their pulse laser annealing, performed for the purpose of Si crystalline grain formation. Being accompanied by the respective optical transmittance/reflectance measurements, these data allowed us to estimate the integrated Raman scattering cross section ratios of crystalline and microcrystalline Si to hydrogenated amorphous Si and to compare the results with those known from the literature. For crystalline Si, the obtained ratio is equal to 0.75, while for microcrystalline Si, it is equal to at least 2. Our results are found to contradict the proposed earlier exponential decay dependence of the integrated Raman scattering cross section ratio of microcrystalline to amorphous Si on the crystalline grain size. The physical reasons, which support our findings, are discussed.