Local structure and oxygen absorption in a-Si 1−x C x ( x < 0·4) alloys grown on silicon by plasma enhanced chemical vapour deposition

The results of the structural analysis of amorphous hydrogenated silicon carbide layers obtained in a glow discharge from SiH₄ and CH₄ gas precursors are reported. The investigations are focused on the low range of C content with the aim of determining the local structure and chemical ordering for small x values. The main results indicate an increase in the mean number of H atoms per Si atom as the C concentration increases. In addition, as C is depositedfrom plasma methyl precursors (CH₃), the high total H content of the films is responsible for a less densified structure, with the presence of voids. The influence of O absorption on the microstructure of the films after degradation in ambient conditions has also been studied. The concentration of O as afunction of depth and its preference for C or Si environments has been determined and discussed. Despite the presence of voids, H saturation of bonds is found to be responsible for the good resistance to oxidation.

MST/3318