Direct evidence for the β-hydride elimination mechanism in the decomposition of triethylgallium on GaAs(100)

Abstract

Decomposition of the surface ethyl group formed by dissociative adsorption of triethylgallium (TEGa) on GaAs(100) is investigated using temperature programmed desorption. Deuterium labeling indicates that decomposition of the surface ethyl group proceeds exclusively through a β-hydride elimination reaction mechanism without any scrambling between α- and β-hydrogens. For undeuterated TEGa (TEGa-d 0), the surface ethyl group decomposes and desorbs simultaneously as C 2H 4 and H 2 at 600 K. For perdeuterated TEGa (TEGa-d 15), the desorption of C 2D 4 and D 2 occurs at a slightly higher temperature (630 K). Partially deuterated TEGa (TEGa-d 6), with deuterium on the α-carbons, results in H 2 and C 2H 2D 2 as desorption products at 600 K. A kinetic isotope effect of 8 ± 5 kJ mol −1 for hydride versus deuteride transfer is determined, which is consistent with cleavage of the C βH bond in the transition state, and with tunneling.