Medium range ordering of amorphous silicon-carbon alloys studied by GISAXS, optical spectroscopy and IBA

Abstract

The nano-structural properties of non-stoichiometric hydrogenated amorphous silicon carbide thin films, deposited by magnetron sputtering and PECVD (plasma enhanced chemical vapour deposition) in a wide range of hydrogen and carbon concentration, were analysed by GISAXS (grazing incidence small angle X-ray scattering), optical spectroscopy and IBA (ion beam analysis). The GISAXS was performed on ELETTRA synchrotron radiation source, Trieste (Italy). All of the measured specimens showed the presence of ‘particles’ with mean dimensions between 1.5 and 4.5 nm while the size distribution of ‘particles’ varied from sample to sample between 1 and 2.5 nm. In order to determine the constitution of the ‘particles’, the specimens were examined by vibrational spectroscopy (Raman and IR spectroscopy) when estimating the local structural and chemical ordering and IBA (ion beam analysis) e.g. RBS (Rutherford back scattering) and ERDA (elastic recoil detection analysis) when estimating the composition of films. The results suggest that the ‘particles’ are agglomerates of small voids, whose size increases with carbon to silicon ratio and whose distribution broadens with hydrogen concentration.