Vibrational Sum Frequency Spectroscopic Investigation of the Azimuthal Anisotropy and Rotational Dynamics of Methyl-Terminated Silicon(111) Surfaces
Abstract
Polarization-selected vibrational sum frequency generation spectroscopy (SFG) has been used to investigate the molecular orientation of methyl groups on CH_(3)-terminated Si(111) surfaces. The symmetric and asymmetric C–H stretch modes of the surface-bound methyl group were observed by SFG. Both methyl stretches showed a pronounced azimuthal anisotropy of the 3-fold symmetry in registry with the signal from the Si(111) substrate, indicating that the propeller-like rotation of the methyl groups was hindered at room temperature. The difference in the SFG line widths for the CH_3 asymmetric stretch that was observed for different polarization combinations (SPS and PPP for SFG, visible, and IR) indicated that the rotation proceeded on a 1–2 ps time scale, as compared to the 100 fs rotational dephasing of a free methyl rotor at room temperature.
Additional Information
© 2012 American Chemical Society. Received: July 6, 2012; Revised: November 9, 2012; Published: December 14, 2012. This research was supported by the AFOSR, Grant No. FA9550-09-1-0547 (AVB), and by the NSF, CHE-0911682 (NSL). L.E.O. graciously thanks the financial support of the Link Foundation Energy Fellowship.Attached Files
Published - jp3067298.pdf
Supplemental Material - jp3067298_si_001.pdf
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Additional details
- Eprint ID
- 37124
- Resolver ID
- CaltechAUTHORS:20130225-163026469
- FA9550-09-1-0547
- Air Force Office of Scientific Research (AFOSR)
- CHE-0911682
- NSF
- Link Foundation
- Created
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2013-02-26Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field