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The Nano-structural Propeties of Hydrogenated a-Si and Si-C Thin Films Alloys by GISAXS and Vibrational Spectroscopy

Amorphous hydrogenated silicon with high hydrogen content (10-40 at %) and non-stehiometric silicon-carbon thin films with variation of carbon to silicon ratio up to 0.3, were deposited by using magnetron sputtering source. The Si1-xCx thin films were partially crystallised after deposition by thermal annealing up to 10500 C. The structural ordering was estimated by FTIR (Fourier Transform Infrared), Raman spectroscopy and GISAXS (Grazing Incidence Small Angle X-ray Scattering) which is performed on ELETTRA synchrotron radiation source, Trieste (Italy). The GISAXS spectra of all of the measured specimens indicate presence of "particles" in the “ bulk” of the films, while comparison with vibration spectroscopy indicates different type of scattering centres. For the a-Sigh samples, “ particles “ are most probably voids agglomerates with variation in size between 3 and 6 nanometres and size distribution between 0.9 and 1.8 nm. The mean value of the size distribution of the particles increases while it’ s width slightly decreases with hydrogen content in the film, indicating better structural ordering which is consistent with results of Raman spectroscopy that show decrease of ITA/ITO ratio and narrowing of TO Raman peak by increase of hydrogen content. The result is discussed as a consequence of beneficial influence of hydrogen bombardment during the film growth. For Si1-xCx thin films, the “ particles” are assumed to be SiC nano-crystals with size between 2 and 14 nm. The crystals are larger in films with higher carbon concentration and they grow faster in direction parallel to the surface than in that which is perpendicular to it.

amorphous silicon carbide; nano-structure; GISAXS; FTIR; Raman

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