Amorphous and nanocrystalline SiC films enriched by oxygen were deposited by a PECVD technique using
methyltrichlorosilane as a gas-precursor at substrate temperature in the range of 200-350 °C. X-ray diffraction (XRD) of
the film deposited at 350°C exhibited the presence of SiC nano-crystallites. In this film the bright blue
photoluminescence (PL) with spectrum that has a double-peak structure at 415 and 437 nm was obsearved at room
temperature. The film was annealed at 650 and 850 °C in vacuum. Annealing at 650 °C strongly enhanced blue-white
photoemission with maximum intensity around 470 cm<sup>-1</sup>. Moderate annealing was found to lead to strengthening the C-H,
C-C and Si-C bonds as well as to increasing of a size of SiC grains embedded in the amorphous Si:C:O:H matrix. A
further increase of annealing temperature up to 850 °C caused a drop of PL.
Basing on an analysis of experimental data and first principles simulations of several hydrogenated SiC and Si
nanoclusters, we suggest that the blue PL in as-deposited nc-SiC:H film and related Si-based nanostructures can be
assigned to the radiative recombination in a radiative center (RC) located at the nanocrystallite surface, whereas the
excitation of electron-hole pares occurs in nanocrystallite cores. It follows from our calculations that O-O structural
groups can be considered as a radiative recombination centers. The recombination at band tails of the amorphous Si:C:O:H tissue (or at the oxygen-related defect states in a-SiO<sub>x</sub>, in the case of Si nanostructures) gives rise to a shoulder around 470 nm.