Effect of Ar dilution flow rate on LPCVD a boron-doped carbon coating from BCl₃-C₃H₆-H₂-Ar mixtures

A boron-doped carbon coating was deposited from a BCl₃-C ₃H₆-H₂-Ar system by LPCVD. The effects of the Ar dilution 110w rate on deposition rates, morphologies, compositions and bonding states were investigated. Deposition rates were almost the same, about 250 nm/h with different Ar dilution flow rate. Surface morphologies were also almost the same. The flat conchoidal aspect of the fracture surface transformed to a laminated structure with an increase in the Ar dilution flow rate. The carbon concentration was above 76.3 at.%, and the boron concentration was less than 17.9 at.%. The boron concentration increased with an increase in the Ar dilution flow rate, corresponding to a decreasing carbon concentration. The main bonding state of boron was B-sub-C and BC₂O. The whole deposition process was dominated by a PyC formation reaction, which led to almost the same deposition rate with different Ar dilution flow rates.