Thermal decomposition of hydrides and organometallic compounds

One of the earliest studies of deposition from organometallics was the discovery that when some metal alkyls, such as lead tetramethyl Pb(CH3)4, 

This makes possible numerous further decomposition reactions involving the hydrogen atom as an intermediate in chain reactions. 

As an example of carbon bond strengths the data for the stages in the atomization of methane are shown below, together for the less accurate data for silane 

The above data are correct to about 20 kJ mole-1, but it will be seen that the general trend among these more covalent bonds does appear to be a decrease in stability from carbon to silicon, i.e. the same way as was found for more ionic bonds in the halides. Thermodynamic data for metallorganic methyl compounds used in the production of semiconductor systems are shown in Table 2.3. 

The preparation of semiconductors by thermal decomposition would appear to be impossible because of the high amount of energy required to break all of the metal-carbon bonds before the atomic species could be formed. However, the thermal method is successful because the reaction to form free methyl radicals, which combine to form ethane, lowers the energetic requirements for the formation of gallium, for example, according to the equation 

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