In situ mass spectroscopy studies of the decomposition of organometallic arsenic compounds in the presence of Ga(CH3)3 and Ga(C2H5)3

Abstract The gas phase decomposition and reaction mechanisms of As(CH 3 ) 3 (TMAs), As(C 2 H 5 ) 3 (TEAs), and H 2 AsC 4 H 9 (tBAs) in the presence of Ga(CH 3 ) 3 (TMG) and Ga(C 2 H 5 ) 3 (TEG) are studied by molecular beam mass spectroscopy sampling in an organometallic chemical vapor deposition (OMCVD) reactor. Experiments are reported for H 2 , D 2 , and He carrier gases. The 50% decomposition temperature of TMAs, TEAs, and tBAs are determined to be 765, 690, 560 K, respectively. TMAs decomposes via a unimolecular reaction involving the loss of methyl groups. TEAs pyrolizes with C 2 H 4 as the main hydrocarbon product regardless of the carrier gas used. When TEG and TMAs or TMG and TEAs are mixed, decreases in the decomposition temperature of the methyl compounds are observed. This effect is attributed to an exchange process between the methyl and the ethyl groups through the formation of an adduct. The primary decomposition path of tBAs is proposed to be via the loss of tert-butyl radicals and AsH 2 resulting in production of AsH 3 starting at 500 K with isobutene and isobutane as the main hydrocarbon products. Mass spectra of mixtures of TMG and tBAs show new peaks corresponding to methylarsenic fragments indicating the formation of an adduct.