In situ kinetic analysis of SiC filaments CVD

An in situ kinetic study of the SiC-based filament CVD from DCMS/H₂ and DCMS/C₃H₆/H₂ mixtures has been carried out. The results evidenced a low temperature regime (T<1150 °C) controlled by surface chemical reactions and a high temperature domain (T> 1150 °C) governed by the diffusion of reactive species to the substrate (mass transfer regime). The addition of propene to the DCMS/H₂ mixture leads to the decrease of the deposition rate, the increase of the activation energy (within the surface reaction limited regime) and the increase of the C/Si (at.) ratio. The dilution of DCMS in H₂ promotes the co-deposition of free silicon. Conversely, the addition of propene results in lower amounts of free silicon or even traces of free carbon for high deposition temperatures. The increase of the C/Si (at.) ratio observed in presence of propene might be related to the inhibition of the deposition of Si-rich species derived from DCMS, through reactions with propene or related unsaturated hydrocarbons in the gas phase.