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Structural properties of a-Si(1-x)C(x):H by SAXS and IR spectroscopy

The a-Si(1-x)C(x):H thin films, with carbon concentrations up to x=0.3 deposited by means of a DC magnetron sputtering source, using benzene vapour as the origin of carbon atoms, were analysed by small-angle X-ray scattering (SAXS) and IR spectroscopy. The incorporation of carbon atoms in a-Si:H results in the appearance of IR absorption related to the Si-C and C-H bonds and a slight decrease of absorption related to Si-H bonds. By increaseing the carbon concentration, stretching frequency of Si-H bonds increases. This frequency, which is related to the described changes, is considered to be the consequence of an increasing void volume ratio and/or void volume per each Si-H oscillator. The SAXS data of pure a-Si:H indicate "particles" with giro radius Rg 0 1.27 nm, which increases with the carbon content up to Rg = 2.05 nm. These "particles" are attributed to the clusters of small voids with dimensions up to several silicon vacancies.

a-Si(1-x)C(x):H thin films; different carbon concentrations; DC magnetron sputtering; small angle X-ray scattering (SAXS); IR spectroscopy; stretching frequency of Si:H bonds; clusters of small voids

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