Growth Control And Characterization Of Wide Band Gap Silicon-Carbon Films

Silicon-carbon films have been grown by reactive hydrogen magnetron sputtering at a substrate temperature of 730°C, with different values of carbon-to-silicon sputtered area ratio, rc. The layers were investigated by infrared spectroscopy, Raman scattering, x-ray photoelectron spectroscopy and optical absorption. For rc below 30%, almost only Si nanocrystallites were formed with a few fraction of amorphous SiC, whereas for rc exceeding 30%, a drastic change was noticed, leading to the achievement of SiC crystals in the layers. These latter were found of near-stoichiometric composition with an atomic ratio C/Si ˜1.04. The results suggest that the excess C is of graphitic-like configuration being likely located in the intergrain regions, in addition to some silicon-oxygen bonds. These features are accompanied by an abrupt widening of the band gap in the transition region that is consistent with the formation of SiC nanocrystals. The large value measured for the band gap (≥3 eV) is thought to be due to more than one origin, such as size effect of SiC, Si-O bonds and possible presence of different SiC polytypes.