Ab initio studies of the reactions of M(S-1,P-3, and P-1) with GeH4 (M=Cd,Hg)

The interaction of Cd(S-1:5s(2), P-3,P-1:5s(1)5p(1)) and Hg(S-1:6s(2), P-1, P-3:6s(1)6p(1)) with GeH4 were studied by means of Hartree-Fock self-consis tent field (SCF) and multiconfigurational SCF plus variational and multiref erence second order Moller-Plesset perturbational configuration interaction (CIPSI) calculations, using relativistic effective core potentials. It was found that both metal atoms in their P-3(ns(1)np(1)) state break spontaneo usly the Ge-H bond of the germane molecule, giving place to the MH+GeH3 (M = Cd, Hg) final products. For both atoms, the P-1(ns(1)np(1)) state is also inserted in the Ge-H bond and the corresponding interaction surface shows an avoided crossing with the lowest-lying X (1)A' potential surface adiabat ically linked with the M(S-1:ns(2)) + GeH4. This interaction leads eventual ly to the MH + GeH3 products. The HMGeH3 X (1)A(1) (M = Cd, Hg) intermediat e molecules, diabatically correlated with the M(P-1:ns(1)np(1)) + GeH4, whi ch lie 13.6 and 21 kcal/mol, respectively, above the ground state reactants , have been carefully characterized as well as the dissociation channels le ading to the MH + GeH3 and H + MGeH3 products. These products are reached f rom the HMGeH3 intermediates without activation barriers. Accurate energy d ifferences for all these species are reported. This work suggests that the simultaneous photoexcitation of Cd and Hg atoms in the presence of silane a nd germane molecules in the gas phase could be used to produce better quali ty a-SiGe:H thin films. (C) 2001 American Institute of Physics.