ON THE CHEMICAL-VAPOR-DEPOSITION OF TI3SIC2 FROM TICL4SICL4-CH4-H-2 GAS-MIXTURES .1. A THERMODYNAMIC APPROACH

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-H-2 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(greater than or equal to 45%), a rather low pressure (10-20 kPa), high temperature (greater than or equal to 1273 K) and low H-2 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,