Investigation of the nano-structural properties of amorphous silicon carbon alloys by IBA technique, optical spectroscopy and GISAXS

Abstract

Amorphous hydrogenated silicon carbide thin films, a-Si 1− x C x :H, were deposited by magnetron sputtering with x between 0.05 and 0.4 and a wide range of hydrogen concentration. The samples were analysed using vibrational spectroscopies (FTIR, Raman), ion beam analysis techniques (IBA) such as Rutherford backscattering spectrometry (RBS), elastic recoil detection analysis (ERDA) and grazing incidence small angle X-ray scattering (GISAXS). IBA was used for estimation of composition, using several kinds of ions and beam energies in order to enhance the compositional resolution, in particular carbon to silicon ratio and hydrogen concentration. Combining IBA and vibrational spectroscopy, the volume contributions of pure silicon phase, carbon phase, silicon carbide and voids were estimated. Assuming that hydrogen atoms are bonded on the internal surface of the voids, the average volume per each Si–H or C–H bond was calculated. The typical values for our samples were 5–30 Å 3, corresponding to voids ranging from silicon polyvacancies to much larger ones. The analysis of GISAXS data indicates the presence of “particles” with dimensions between 1 and 5 nm, most probably voids, containing a large number of hydrogen atoms, or the domains of similar size, with much lower density than the rest of the material.