Study of tertiarybutylphosphine pyrolysis using a deuterated source

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Abstract
The pyrolysis of tertiarybutylphosphine (TBP) and the reaction mechanism for the organometallic vapor-phase epitaxial growth of GaP using TBP and trimethylgallium (TMGa) in a He ambient have been studied. A deuterated TBP source (C4H9PD2) was used to label the reaction products and to distinguish possible mechanisms. The reaction was found to be independent of the ambient, and C4H9D was found to be a major product species. However, its relative concentration was determined to increase as the input concentration of the reactant increased. The concentration of C4H9D is even higher when the pyrolysis was catalyzed by GaP surfaces. However, the addition of TMGa retarded both the production of C4H9D and the pyrolysis of TBP. Another species, CH3D, becomes the major deuterated product observed under these conditions. The results lead to the following conclusions: (1) an important reaction for TBP pyrolysis is of second order: the tert-butyl radical (C4H9) attacks TBP; (2) the PH and PH2 species on GaP surfaces, products from the scission of TBP, enhance the pyrolysis of TBP; (3) the same species also attack the adsorbed TMGa, leading to the growth of GaP crystals.