Ab initio structure and energetics for the molecular and dissociative adsorption of NH3 on Si(100)-2 x 1

Eyal Fattal, Michelle R. Radeke, Gregg Reynolds, Emily A. Carter

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We predict the structures and detailed energetics for the dissociative adsorption of NH3 to form NH2 and H adsorbed on a single Si dimer on the Si(100)-2 x 1 surface at the MRSDCI (multireference single and double excitation configuration interaction) level of theory. We predict that this dissociation involves two steps: (i) barrierless molecular chemisorption of NH3 followed by (ii) activated N-H bond cleavage of NH3(a) to form NH2(a) + H(a). While the second step involves a barrier, its relatively small height renders the overall reaction barrierless. The extremely high adsorption exothermicity (∼75 kcal/mol) results in a very high desorption barrier. These results can explain the experimentally determined high sticking probability of NH3, the observation of NH3(a) at low temperatures, and the observed stability of NH2(a) and H(a) on the Si(100) surface up to ∼600 K. Additionally, our CASSCF level (complete active space self-consistent-field) calculated geometries for the dissociatively adsorbed species agree with structures proposed to explain experimental data.

Original languageEnglish (US)
Pages (from-to)8658-8661
Number of pages4
JournalJournal of Physical Chemistry B
Issue number43
StatePublished - Oct 23 1997
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry


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