Gas-phase chemistry of metalorganic and nitrogen-bearing compounds

The gas-phase chemistry and reactions between trimethyl gallium ((CH3)(3))G a, TMGa) and ammonia (NH3) were investigated by the use of quantum chemical calculations employing density functional theory techniques. Reactive inte rmediates and reaction pathways originating from the initial formation of t he gas-phase adduct between TMGa and NH3 were identified. The lowest activa tion Gibbs free energy for the formation of methane For these reactions inv olving the TMGa:NH, adduct is 34 kcal/mol. In addition, a further reaction intermediate was identified having the stoichiometry TMGa:(CH3)(2)GaNH2 :NH 3, and this intermediate eliminates methane with a low Gibbs free energy ac tivation barrier of 20 kcal:mol. Therefore, it appears that the production of methane from TMGa and NH, may be an autocatalytic process. The implicati ons for reactor design and growth are discussed. (C) 2000 Elsevier Science B.V. All rights reserved.