LOCAL-STRUCTURE AND OXYGEN ABSORPTION IN A-SI1-XCX (X-LESS-THAN-0-CENTER-DOT-4) ALLOYS GROWN ON SILICON BY PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION

The results of the structural analysis of amorphous hydrogenated silic on carbide layers obtained in a glow discharge from SiH4 and CH4 gas p recursors are reported. The investigations are focused on the low rang e of C content with the aim of determining the local structure and che mical ordering for small x values. The main results indicate an increa se in the mean number of H atoms per Si atom as the C concentration in creases. In addition, as C is deposited from 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 a bsorption on the microstructure of the films after degradation in ambi ent conditions has also been studied. The concentration of O as a func tion of depth and its preference for C or Si environments has been det ermined and discussed. Despite the presence of voids, H saturation of bonds is found to be responsible for the good resistance to oxidation.