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Vibrational Sum-Frequency Spectroscopic Investigation of the Structure and Azimuthal Anisotropy of Propynyl-Terminated Si(111) Surfaces

Dhar, Purnim and Plymale, Noah T. and Malyk, Sergey and Lewis, Nathan S. and Benderskii, Alexander V. (2017) Vibrational Sum-Frequency Spectroscopic Investigation of the Structure and Azimuthal Anisotropy of Propynyl-Terminated Si(111) Surfaces. Journal of Physical Chemistry C, 121 (31). pp. 16872-16878. ISSN 1932-7447. doi:10.1021/acs.jpcc.7b05256. https://resolver.caltech.edu/CaltechAUTHORS:20170710-143624667

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Abstract

Vibrational sum-frequency generation (VSFG) spectroscopy was used to investigate the orientation and azimuthal anisotropy of the C–H stretching modes for propynyl-terminated Si(111) surfaces, Si—C≡C—CH_3. VSFG spectra revealed symmetric and asymmetric C–H stretching modes in addition to a Fermi resonance mode resulting from the interaction of the asymmetric C–H bending overtone with the symmetric C–H stretching vibration. The polarization dependence of the C–H stretching modes was consistent with the propynyl groups oriented such that the Si—C≡C– bond is normal to the Si(111) surface. The azimuthal angle dependence of the resonant C–H stretching amplitude revealed no rotational anisotropy for the symmetric C–H stretching mode and a 3-fold rotational anisotropy for the asymmetric C–H stretching mode in registry with the 3-fold symmetric Si(111) substrate. The results are consistent with the expectation that the C–H stretching modes of a –CH_3 group are decoupled from the Si substrate due to a −C≡C– spacer. In contrast, the methyl-terminated Si(111) surface, Si–CH_3, was previously reported to have pronounced vibronic coupling of the methyl stretch modes to the electronic bath of bulk Si. Vacuum-annealing of propynyl-terminated Si(111) resulted in increased 3-fold azimuthal anisotropy for the symmetric stretch, suggesting that removal of propynyl groups from the surface upon annealing allowed the remaining propynyl groups to tilt away from the surface normal into one of three preferred directions toward the vacated neighbor sites.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/acs.jpcc.7b05256DOIArticle
http://pubs.acs.org/doi/abs/10.1021/acs.jpcc.7b05256PublisherArticle
http://pubs.acs.org/doi/suppl/10.1021/acs.jpcc.7b05256PublisherSupporting Information
ORCID:
AuthorORCID
Plymale, Noah T.0000-0003-2564-8009
Lewis, Nathan S.0000-0001-5245-0538
Benderskii, Alexander V.0000-0001-7031-2630
Additional Information:© 2017 American Chemical Society. Received: May 30, 2017; Revised: July 6, 2017; Published: July 10, 2017. A.V.B. acknowledges the Air Force Office of Scientific Research under grant No. FA9550-15-1-0184. N.S.L. acknowledges the National Science Foundation under grant No. CHE-1214152. N.T.P. acknowledges support from a National Science Foundation Graduate Research Fellowship. The authors declare no competing financial interest.
Funders:
Funding AgencyGrant Number
Air Force Office of Scientific Research (AFOSR)FA9550-15-1-0184
NSFCHE-1214152
NSF Graduate Research FellowshipUNSPECIFIED
Issue or Number:31
DOI:10.1021/acs.jpcc.7b05256
Record Number:CaltechAUTHORS:20170710-143624667
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20170710-143624667
Official Citation:Vibrational Sum-Frequency Spectroscopic Investigation of the Structure and Azimuthal Anisotropy of Propynyl-Terminated Si(111) Surfaces Purnim Dhar, Noah T. Plymale, Sergey Malyk, Nathan S. Lewis, and Alexander V. Benderskii The Journal of Physical Chemistry C 2017 121 (31), 16872-16878 DOI: 10.1021/acs.jpcc.7b05256
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78907
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:10 Jul 2017 21:47
Last Modified:15 Nov 2021 17:44

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