Annealing effects of highly homogeneous a-Si1−xCx:H

We report the effect of annealing on the properties of amorphous hydrogenated silicon carbide thin films. The samples were deposited onto different substrates by plasma enhanced chemical vapor deposition at temperatures between 300 and 350 °C. The gaseous mixture was formed by silane and methane, at the ‘silane starving plasma regime’, and diluted with hydrogen. Rutherford backscattering and Fourier transform infrared spectrometry were used, respectively, to determine the atomic composition and chemical bonds of the samples. The film’s structure was analyzed by means of X-ray absorption fine structure and X-ray diffraction. For temperatures higher than 600 °C, amorphous silicon carbide films annealed under inert atmosphere (Ar or N₂) clearly changed their structural and compositional properties due to carbon loss and oxidation, caused by the presence of some oxygen in the annealing system. At 1000 °C, crystallization of the films becomes evident but only stoichiometric films deposited on single crystalline Si1 0 0] substrates presented epitaxial formation of SiC crystals, showing that the crystallization process is substrate dependent. Films annealed in high-vacuum also changed their structural properties for annealing temperatures higher than 600 °C, but no traces of oxidation were observed or variations in their silicon or carbon content. At 1200 °C the stoichiometric films are fully polycrystalline, showing the existence of only a SiC phase. The XANES signal of samples deposited onto different substrates and annealed under high-vacuum also show that crystallization is highly substrate dependent.