Codeposition of SiC and C from Mixtures of Methyltrichlorosilane and Ethylene in Hydrogen

The variation of the deposition rate and of the composition of the material deposited from CH 3 SiCl 3 −C 2 H 4 −H 2 mixtures with the operating conditions (feed composition and temperature) is investigated. Chemical vapor deposition (CVD) experiments are carried out at subatmospheric pressure in a hot-wall CVD reactor, in which the deposition rate is measured in situ gravimetrically. Methyltrichlorosilane (MTS) is used as the silicon and carbon source, and in order to enhance the incorporation of carbon in the deposit, ethylene is employed as an additional source of carbon. One of the most interesting findings of the study is that the deposition of carbon is dramatically enhanced by the presence of silicon compounds in the gas phase. The MTS/C 2 H 4 /H 2 system is found to be capable of producing high-quality SiC/C composite coatings at temperatures much lower than when CH 4 is used as the additional carbon source. When the mole fraction of C 2 H 4 is increased in the feed, it is possible to gradually change the deposit from pure SiC to a material where carbon is the major component. However, multiplicity of steady states may be present under some conditions, and in such a case, the deposition rate and the deposit composition may go through abrupt changes as some of the operating parameters are varied.