  A modified phonon confinement model considering the size distribution, an
improved phonon dispersion curve and a confinement function is developed for
the calculation of size dependent Raman spectra of the silicon (Si)
nanocrystals. The model is capable in simultaneous calculation of the Raman
shift, intensity and linewidth. The calculated size dependent redshift and
linewidth of Raman spectra are in good agreement with the available
experimental data in literature and better than previously reported theoretical
results. The rapid rise in the redshift and linewidth for relatively smaller Si
nanocrystals are well reproduced. The asymmetric behavior of Raman spectra is
also obtained from the present model.
