Mechanistic studies of the decomposition of trimethylaluminum on heated surfaces

The decomposition of trimethylaluminum (TMA) on copper, aluminum, quartz, and gallium arsenide substrates has been studied as a function of substrate temperature from 550–900 K under low pressure conditions. Detection of gaseous products was carried out by laser multiphoton ionization mass spectrometry (MPI/MS) for methyl radical and aluminum species and electron impact mass spectrometry (EI/MS) for stable species. The methyl radical was the sole gaseous reaction product observed above these substrates, with an apparent activation energy for production of 13±2 kcal/mol. Neither ethane nor methane was observed at the low pressures employed in these experiments, with either helium or hydrogen as carrier gases. A mechanism is proposed to explain these results.