Experimental study of the chemical vapor deposition from CH3SiHCl2/H2: Application to the synthesis of monolithic SiC tubes

The deposition rate, composition and microstructure of the CVD-SiC coatings were investigated as a function of the substrate temperature and the gas flow rates. A Fourier transformed infrared (FTIR) spectroscopy analysis was carried out at the reactor outlet to characterize the gas phase reactions. The FTIR analysis of pure species from the Si-C-Cl-H system as well as ab initio calculations at the density functional theory (DFT) level allowed the assignment of the main IR features in the experimental spectra and the quantitative analysis of the complex gas mixture. This study has led to the proposal of a simplified dichloromethylsilane decomposition scheme which is consistent with the influence of the CVD parameters on the nature of the gas phase and the coating. The deposition rate, the Si/C atomic ratio, the SiC crystalline state and the surface morphology are indeed strongly related to the CH3SiHCl2 decomposition rate and the further progress of homogeneous reactions.