Mass-spectrometric monitoring of the thermally induced decomposition of trimethylgallium, tris(tert-butyl) gallium, and triethylantimony at low pressure conditions

The thermal decomposition of trimethylgallium (GaMe3), tris(tert-butyl)gallium (Ga'BU3) and triethylantimony (SbEt3) was investigated in a tubular hot-wall reactor coupled with a molecular-beam sampling mass spectrometer, and decomposition mechanisms were proposed. The obtained results confirm the predominance of the surface reactions and reveal that the radical decomposition path of Ga'BU3 and SbEt3, responsible for the formation of butane and ethane respectively, is restricted to a narrow temperature range in contrast to the molecular route that is responsible for the formation of the corresponding alkenes. GaMe3 decomposes above 480 'C, forming essentially methane and also ethane to a lesser extent, whereas Ga'Bu, decomposes starting 260 'C to form predominantly i-butane and i-butene as major species. The decomposition of SbEt3 starts at 400 'C and forms n-butane, ethane, and ethene. The selectivity to n-butane increases with the thermolysis temperature. The resulting activation energies of the relevant decomposition paths show good agreement with those among them that have been measured before by temperature-programmed desorption techniques.