The CVD of Other Interstitial-Metal Carbides

The CVD of other refractory metal carbides is essentially similar to that of TiC. The metal halide is reacted with a hydrocarbon, usually methane, although propane, propene and toluene have been used also. Pressure varies from 1 kPa to 1 atm. (composition closest to stoichiometry are usually obtained at the lower pressures). 

Metal Chlorination. With the exception of titanium and vanadium chlorides (TiCl4 and VCI4), the chlorides of the refractory metals are solids at room temperature and it is often expedient to chlorinate the metal in situ with chlorine or HCl as shown schematically in Fig. 15.3. A typical reaction is the formation of hafhium chloride as follows  

The reaction occurs between 500°C and 600°C and is exothermic. It is only necessary to heat the metal (in the form of sponge or chips) to the starting temperature, after which it becomes self-sustaining. 

Deposition Reactions. The most conunon deposition reactions are similar to reaction 1  

Molybdenum carbide (M02C) by the decomposition of molybdenum carbonyl (Mo(CO)6)l l 

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