Differences on carbon content and chemical bonds in a-Si1−xCx:H were observed and analyzed in carbon rich and silicon rich films, deposited by plasma enhanced chemical vapor deposition from mixtures of silane and methane. The influence of the radio frequency low power density regime on the film’s properties was investigated. The content of Si, C, and H in the solid phase was obtained by Rutherford back scattering and forward recoil spectrometry. The bondings were analyzed by Fourier transform infrared spectroscopy. Quantitative analysis on the film’s chemical composition was performed combining the vibrational spectra with the stoichiometry data. The results showed that under “silane starving plasma” conditions, a carbon content as high as 70 at. % is achieved and the main carbon bonds are tetragonal C–H, C–H2, and Si–C.
The correlation between composition, microstructure, and optical properties of a-Si,-.,C,:H thin films with different stoichiometries was established. The alloys were deposited by radio frequency glow discharge under "starving" plasma conditions from mixtures of SiH4 and CH,. The samples were characterized by small angle x-ray scattering, ultraviolet.-visible and infrared spectrometry, and Auger elect.ron spectroscopy. The results showed the presence of microvoids with sizes between-3 A and ~8 A. The relative microvoid volume fraction displayed a maximum for x around 55 at. % and decreased for higher values of x. High carbon content alloys (x-70 at. %) not only have a lower relative microvoid volume fraction, but show optical gaps as high as 3.7 eV, high resistivity, and very low refractive index, indicating the presence of a diamond-like CC structure. These remarkable results are attributed to the deposition under "starving" plasma conditions.
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