An EELS and EXELFS study of amorphous hydrogenated silicon carbide

Abstract

A series of thin films of amorphous hydrogenated silicon carbide (a-Si∶C∶H) produced by RF plasma decomposition of propane and silane has been studied by electron energy-loss spectroscopy (EELS) and extended energy-loss fine structure (EXELFS) studies. The composition of the films has been determined by EELS and the nearest neighbour spacings have been determined by EXELFS. These results, along with the energy of the plasmon loss peaks, have been compared with the deposition conditions for each film. The results show that for a large gas ratio (C3H8/(C3H8+SiH4)) the films have a high proportion of carbon and are similar to a-C∶H in structure, whereas those films prepared with Y = 0.4 or 0.5 have nearest neighbour spacings consistent with those for tetrahedrally bonded carbon. The films prepared with lowest Y have nearest neighbour spacings similar to those for amorphous silicon carbide. The results for a-Si∶C∶H have been compared with the results of EELS and EXELFS of CVD diamond films, amorphous carbon and amorphous silicon.