Analysis of the nano-structural properties of thin film silicon-carbon alloys

Amorphous hydrogenated silicon-carbon thin films with high hydrogen content (20-40 at%) and carbon to silicon ratio between 0.2 and 0.4, were deposited by sputtering a silicon target in a gas mixture containing hydrogen and carbon atoms. The samples were heated up to 1050 °C in order to form crystal-like structures. The structural ordering on an atomic level was estimated by Fourier Transform Infrared (FTIR) and Raman spectroscopy while the homogeneity on the nano-scale was examined by Grazing Incidence Small Angle X-ray Scattering (GISAXS), performed on the ELETTRA synchrotron radiation source, Trieste (Italy). GISAXS spectra of all of measured specimens indicate the presence of “particles” in the “bulk” of the films, with size distribution between 0.8 and 1.5 nm and mean values between 2.8 and 4.8 nm. By comparison with results of vibrational spectroscopy, the “particles” in an amorphous phase were identified as void agglomerates while in annealed samples they are most probably nano-crystals of SiC.