Received: April 24, 2007

In Final Form: September 10, 2007

Abstract:

The interaction of the polyhedral oligomeric silsesquioxane (POSS) T₈, (HSiO_3/2)₈ with the Si(100) surface has been studied using a cluster model, represented by the single dimer Si₉H₁₂ to represent the surface. Hartree-Fock (HF), density functional theory (DFT), and multi-configuration self-consistent field (MCSCF) wavefunctions have been used to optimize the geometries of stationary points on the potential energy surface. The HF and MCSCF wavefunctions are augmented by second-order perturbation theory for improved relative energies. The POSS reacts with the Si(100) surface saturating dangling bonds on the surface, yielding two possible addition products. One of these forms a Si-Si bond between the POSS and the dimer at the same time that a hydrogen atom is transferred from the POSS to the adjacent silicon atom of the same dimer, with no structural modification of the cage. The other product involves the opening of the POSS cage with the corresponding formation of a pair of Si-Si and Si-O bonds with the surface. The former mechanism produces a lower-energy product, whereas the second reaction channel has a lower-energy barrier, which actually vanishes when dynamic correlation energy is included in the calculation.

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