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The interaction of organic adsorbate vibrations with substrate lattice waves in methyl-Si(111)-(1 × 1)

Brown, Ryan D. and Hund, Zachary M. and Campi, Davide and O'Leary, Leslie E. and Lewis, Nathan S. and Bernasconi, M. and Benedek, G. and Sibener, S. J. (2014) The interaction of organic adsorbate vibrations with substrate lattice waves in methyl-Si(111)-(1 × 1). Journal of Chemical Physics, 141 (2). Art. No. 024702. ISSN 0021-9606. doi:10.1063/1.4886810. https://resolver.caltech.edu/CaltechAUTHORS:20140911-100847244

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Abstract

A combined helium atom scattering and density functional perturbation theory study has been performed to elucidate the surface phonon dispersion relations for both the CH_3-Si(111)-(1 × 1) and CD_3-Si(111)-(1 × 1) surfaces. The combination of experimental and theoretical methods has allowed characterization of the interactions between the low energy vibrations of the adsorbate and the lattice waves of the underlying substrate, as well as characterization of the interactions between neighboring methyl groups, across the entire wavevector resolved vibrational energy spectrum of each system. The Rayleigh wave was found to hybridize with the surface rocking libration near the surface Brillouin zone edge at both the M-point and K-point. The calculations indicated that the range of possible energies for the potential barrier to the methyl rotation about the Si-C axis is sufficient to prevent the free rotation of the methyl groups at a room temperature interface. The density functional perturbation theory calculations revealed several other surface phonons that experienced mode-splitting arising from the mutual interaction of adjacent methyl groups. The theory identified a Lucas pair that exists just below the silicon optical bands. For both the CH_3- and CD_3-terminated Si(111) surfaces, the deformations of the methyl groups were examined and compared to previous experimental and theoretical work on the nature of the surface vibrations. The calculations indicated a splitting of the asymmetric deformation of the methyl group near the zone edges due to steric interactions of adjacent methyl groups. The observed shifts in vibrational energies of the -CD_3 groups were consistent with the expected effect of isotopic substitution in this system.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://scitation.aip.org/content/aip/journal/jcp/141/2/10.1063/1.4886810PublisherArticle
http://dx.doi.org/10.1063/1.4886810DOIArticle
ORCID:
AuthorORCID
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 2014 AIP Publishing LLC. Received 1 May 2014; accepted 23 June 2014; published online 9 July 2014. S.J.S. acknowledges support from the Air Force Office of Scientific Research (AFOSR) Grant No. FA9550-10-1-0219, and the Material Research Science and Engineering Center at the University of Chicago for infrastructure support, and N.S.L. acknowledges support from the National Science Foundation (NSF) (CHE-1214152).
Funders:
Funding AgencyGrant Number
Air Force Office of Scientific Research (AFOSR)FA9550-10-1-0219
University of Chicago Material Research Science and Engineering CenterUNSPECIFIED
NSFCHE-1214152
Issue or Number:2
DOI:10.1063/1.4886810
Record Number:CaltechAUTHORS:20140911-100847244
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20140911-100847244
Official Citation:The interaction of organic adsorbate vibrations with substrate lattice waves in methyl-Si(111)-(1 × 1) Ryan D. Brown, Zachary M. Hund, Davide Campi, Leslie E. O’Leary, Nathan S. Lewis, M. Bernasconi, G. Benedek and S. J. Sibener J. Chem. Phys. 141, 024702 (2014); http://dx.doi.org/10.1063/1.4886810
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49585
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:11 Sep 2014 18:44
Last Modified:10 Nov 2021 18:46

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