Effect of dilution gas flow on low pressure CVD boron-doped carbon coatings

Taking BCl₃-C₃-H₆-H₂ as gas-phase reaction system, boron-doped carbon coating was prepared by means of low pressure chemical vapor deposition. The effects of Ar gas dilution flow on deposition rates, morphologies, compositions and bonding states of the deposits were investigated. The results show that under different Ar gas dilution flow, deposition rates of boron-doped carbon are almost same, morphologies of the deposits is transferred from compact structure to delaminated structure; boron element content increases a little, while carbon element content decreases a little; B element bonding states in deposits present mainly B-sub-C and BC₂O. In combination of chemical reaction and gas diffusion theory, action mechanism of dilution gas was discussed. The PyC dominates deposition reaction, which reduce the effect of dilution gas flow on deposition rate. The difference of diffusion coefficients of BCl₃ and C₃H₆ precursors in Ar gas can cause morphologies and compositions of the deposits changed.