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J Chem Phys. 2014 Nov 7;141(17):174701. doi: 10.1063/1.4899841.

Dissociative adsorption of CH₃X (X = Br and Cl) on a silicon(100) surface revisited by density functional theory.

Author information

1
Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, People's Republic of China.
2
Lash Miller Chemical Laboratories, Department of Chemistry and Institute of Optical Sciences, University of Toronto, Toronto, Ontario M5S 3H6, Canada.

Abstract

During the dissociative adsorption on a solid surface, the substrate usually participates in a passive manner to accommodate fragments produced upon the cleavage of the internal bond(s) of a (transient) molecular adsorbate. This simple picture, however, neglects the flexibility of surface atoms. Here, we report a Density Functional Theory study to revisit our early studies of the dissociative adsorption of CH3X (X = Br and Cl) on Si(100). We have identified a new reaction pathway, which involves a flip of a silicon dimer; this new pathway agrees better with experiments. For our main exemplar of CH3Br, insights have been gained using a simple model that involves a three-atom reactive center, Br-C-Si. When the silicon dimer flips, the interaction between C and Si in the Br-C-Si center is enhanced, evident in the increased energy-split of the frontier orbitals. We also examine how the dissociation dynamics of CH3Br is altered on a heterodimer (Si-Al, Si-P, and Si-Ge) in a Si(100) surface. In each case, we conclude, on the basis of computed reaction pathways, that no heterodimer flipping is involved before the system transverses the transition state to dissociative adsorption.

PMID:
25381532
DOI:
10.1063/1.4899841

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