Silicon carbide and silicon rich carbide (SiC and SRC) thin films were prepared by PECVD and annealed at 1100 °C. Such a treatment, when applied to SiC/SRC multilayers, aimed at the formation of silicon nanocrystals, that have attracted considerable attention as tunable band-gap materials for photovoltaic applications. Optical and structural techniques (X-ray photoelectron spectroscopy, Reflectance and Transmittance, Fourier Transformed Infrared Spectroscopy) were used to evidence the formation, during the annealing treatment in nominally inert atmosphere, of a parasitic ternary SiOxCy surface compound, that consumed part of the originally deposited material and behaved as a preferential conductive path with respect to the nanocrystal layer in horizontal electrical conductivity measurements. The SiOxCy compound was HF-resistant, with composition dependent on the underlying matrix. It gave rise to a Si …