COMPARATIVE PYROLYSIS STUDIES OF ETHYLARSINES

The pyrolysis of triethylarsine (TEAs), diethylarsine (DEAsH), and monoethylarsine (MEAsH2) has been studied at atmospheric pressure in a flow tube reactor using mass spectrometry. He and D2 selected as the carrier gases to determine ambient effects and to isotopically label the pyrolysis products. For some experiments, supplemental C2H5 and CH3 radicals, produced from pyrolysis of the co-reactants azoethane ((C2H5)2N2) and azomethane ((CH3)2N2), were added to investigate the roles of C2H5 and CH3 in the reactions. Significant D2 effects have been observed for pyrolysis of TEAs but not for DEAsH and MEAsH2. Pyrolysis of the lafter could be enhanced by adding C2H5 radicals while the TEAs was nearly unaffected. With the presence of supplemental CH3 radicals, > 85% decomposition was induced for each precursor. The products included DEAsD, rather than DEAsH, for TEAs pyrolysis in D2. However, DEAsH pyrolysis produced TEAs, and MEAsH2 decomposed to yield DEAsH and arsine, in both ambients. This suggests that a beta-elimination reaction is not a major step for any of the ethylarsine precursors. More likely, radical reactions occur. When trimethylgallium (TMGa) was added, the ethylarsine pyrolysis rates were accelerated due to the CH3 radicals produced from TMGa pyrolysis. In addition, heterogeneous reactions have been observed for pyrolysis of ethylarsines, especially when a GaAs surface was involved.