On the chemical vapour deposition of Ti3SiC2 from TiCl4-SiCl4-CH4-H2 gas mixtures

In the ternary system Ti-Si-C, the ternary compound Ti₃SiC₂ seems to exhibit promising thermal and mechanical properties. Its synthesis as a thin film from the vapour phase is very difficult owing to the complexity of the system. A contribution to the knowledge of the CVD of Ti₃SiC₂ from a TiCl₄-SiCl₄-CH₄-H₂ gas mixture is proposed on the basis of a thermodynamic approach. This approach is based on a reliable estimation of Ti₃SiC₂ thermodynamic data in good accordance with recent experimental results on its thermal stability. A first equilibrium calculation for the deposition on an inert substrate shows the influence of the experimental parameters on the composition of both the deposit and the gas phase. As a result, the deposition of Ti₃SiC₂ can be favoured by an excess of TiCl₄ ( 45%), a rather low pressure (10–20 kPa), high temperature ( 1273 K) and low H₂ dilution ratio. On the basis of equilibrium calculations for various reactive substrates, complex mechanisms of Ti₃SiC₂ deposition are pointed out, with intermediate steps of substrate consumption, e.g. the formation of TiC from a carbon substrate or TiSi₂ from a silicon substrate.