The crystallite sizes in the nc-Si layer in a multilayered, silicon thin
film, calculated with a deconvolution of the Raman LO–TO mode,
showed excellent agreement with the average crystallite sizes determined
from the size distributions of smaller crystallites obtained
directly from HRTEM images. The small discrepancies can be explained
by the spherical approximation of the crystallites that is used in the
calculation for the crystallite size from the Raman results and due to
difficulties in measuring the larger crystallites in the HRTEMimages due
to overlapping. The fraction of small crystallites estimated from the
integrated area of the TO mode for small and large crystallites is smaller
than that observed using HRTEMdue to the different detection limits of
both methods for a structural analysis. The measured energy distribution
of the absorption coefficient can be approximated by the superposition
of the absorption in the amorphous layer and in the crystalline
layer, and is correlated to the crystallite fraction. Larger nanocrystals
have α(E) similar to c-Si and contribute to an increase in the absorption
of the pure amorphous layer in the low-energy region of the spectrum
(1.2–1.7 eV). Small nanocrystals, with sizes of approximately 2 nm, have
a much larger optical gap than c-Si, an indirect optical transition for