Vibrational Sum Frequency Generation Spectroscopy Measurement of the Rotational Barrier of Methyl Groups on Methyl-Terminated Silicon(111) Surfaces

Dhritiman Bhattacharyya, Angelo Montenegro, Noah T. Plymale, Chayan Dutta, Nathan S. Lewis, Alexander V. Benderskii

Research output: Contribution to journalArticle

Abstract

The methyl-terminated Si(111) surface possesses a 3-fold in-plane symmetry, with the methyl groups oriented perpendicular to the substrate. The propeller-like rotation of the methyl groups is hindered at room temperature and proceeds via 120° jumps between three isoenergetic minima in registry with the crystalline Si substrate. We have used line-shape analysis of polarization-selected vibrational sum frequency generation spectroscopy to determine the rotational relaxation rate of the surface methyl groups and have measured the temperature dependence of the relaxation rate between 20 and 120 °C. By fitting the measured rate to an Arrhenius dependence, we extracted an activation energy (the rotational barrier) of 830 ± 360 cm-1 and an attempt frequency of (2.9 ± 4.2) × 1013 s-1 for the methyl rotation process. Comparison with the harmonic frequency of a methyl group in a 3-fold cosine potential suggests that the hindered rotation occurs via uncorrelated jumps of single methyl groups rather than concerted gear-like rotation.

Original languageEnglish
Pages (from-to)5434-5439
Number of pages6
JournalJournal of Physical Chemistry Letters
Volume10
Issue number18
DOIs
Publication statusPublished - Sep 19 2019

Fingerprint

Vibrational spectra
Silicon
Spectroscopy
silicon
spectroscopy
Propellers
Substrates
propellers
Gears
Activation energy
line shape
Polarization
Crystalline materials
Temperature
activation energy
harmonics
temperature dependence
symmetry
room temperature
polarization

ASJC Scopus subject areas

  • Materials Science(all)
  • Physical and Theoretical Chemistry

Cite this

Vibrational Sum Frequency Generation Spectroscopy Measurement of the Rotational Barrier of Methyl Groups on Methyl-Terminated Silicon(111) Surfaces. / Bhattacharyya, Dhritiman; Montenegro, Angelo; Plymale, Noah T.; Dutta, Chayan; Lewis, Nathan S.; Benderskii, Alexander V.

In: Journal of Physical Chemistry Letters, Vol. 10, No. 18, 19.09.2019, p. 5434-5439.

Research output: Contribution to journalArticle

Bhattacharyya, Dhritiman ; Montenegro, Angelo ; Plymale, Noah T. ; Dutta, Chayan ; Lewis, Nathan S. ; Benderskii, Alexander V. / Vibrational Sum Frequency Generation Spectroscopy Measurement of the Rotational Barrier of Methyl Groups on Methyl-Terminated Silicon(111) Surfaces. In: Journal of Physical Chemistry Letters. 2019 ; Vol. 10, No. 18. pp. 5434-5439.
@article{043be6ebe09a4f62bb412b08becc171c,
title = "Vibrational Sum Frequency Generation Spectroscopy Measurement of the Rotational Barrier of Methyl Groups on Methyl-Terminated Silicon(111) Surfaces",
abstract = "The methyl-terminated Si(111) surface possesses a 3-fold in-plane symmetry, with the methyl groups oriented perpendicular to the substrate. The propeller-like rotation of the methyl groups is hindered at room temperature and proceeds via 120° jumps between three isoenergetic minima in registry with the crystalline Si substrate. We have used line-shape analysis of polarization-selected vibrational sum frequency generation spectroscopy to determine the rotational relaxation rate of the surface methyl groups and have measured the temperature dependence of the relaxation rate between 20 and 120 °C. By fitting the measured rate to an Arrhenius dependence, we extracted an activation energy (the rotational barrier) of 830 ± 360 cm-1 and an attempt frequency of (2.9 ± 4.2) × 1013 s-1 for the methyl rotation process. Comparison with the harmonic frequency of a methyl group in a 3-fold cosine potential suggests that the hindered rotation occurs via uncorrelated jumps of single methyl groups rather than concerted gear-like rotation.",
author = "Dhritiman Bhattacharyya and Angelo Montenegro and Plymale, {Noah T.} and Chayan Dutta and Lewis, {Nathan S.} and Benderskii, {Alexander V.}",
year = "2019",
month = "9",
day = "19",
doi = "10.1021/acs.jpclett.9b01487",
language = "English",
volume = "10",
pages = "5434--5439",
journal = "Journal of Physical Chemistry Letters",
issn = "1948-7185",
publisher = "American Chemical Society",
number = "18",

}

TY - JOUR

T1 - Vibrational Sum Frequency Generation Spectroscopy Measurement of the Rotational Barrier of Methyl Groups on Methyl-Terminated Silicon(111) Surfaces

AU - Bhattacharyya, Dhritiman

AU - Montenegro, Angelo

AU - Plymale, Noah T.

AU - Dutta, Chayan

AU - Lewis, Nathan S.

AU - Benderskii, Alexander V.

PY - 2019/9/19

Y1 - 2019/9/19

N2 - The methyl-terminated Si(111) surface possesses a 3-fold in-plane symmetry, with the methyl groups oriented perpendicular to the substrate. The propeller-like rotation of the methyl groups is hindered at room temperature and proceeds via 120° jumps between three isoenergetic minima in registry with the crystalline Si substrate. We have used line-shape analysis of polarization-selected vibrational sum frequency generation spectroscopy to determine the rotational relaxation rate of the surface methyl groups and have measured the temperature dependence of the relaxation rate between 20 and 120 °C. By fitting the measured rate to an Arrhenius dependence, we extracted an activation energy (the rotational barrier) of 830 ± 360 cm-1 and an attempt frequency of (2.9 ± 4.2) × 1013 s-1 for the methyl rotation process. Comparison with the harmonic frequency of a methyl group in a 3-fold cosine potential suggests that the hindered rotation occurs via uncorrelated jumps of single methyl groups rather than concerted gear-like rotation.

AB - The methyl-terminated Si(111) surface possesses a 3-fold in-plane symmetry, with the methyl groups oriented perpendicular to the substrate. The propeller-like rotation of the methyl groups is hindered at room temperature and proceeds via 120° jumps between three isoenergetic minima in registry with the crystalline Si substrate. We have used line-shape analysis of polarization-selected vibrational sum frequency generation spectroscopy to determine the rotational relaxation rate of the surface methyl groups and have measured the temperature dependence of the relaxation rate between 20 and 120 °C. By fitting the measured rate to an Arrhenius dependence, we extracted an activation energy (the rotational barrier) of 830 ± 360 cm-1 and an attempt frequency of (2.9 ± 4.2) × 1013 s-1 for the methyl rotation process. Comparison with the harmonic frequency of a methyl group in a 3-fold cosine potential suggests that the hindered rotation occurs via uncorrelated jumps of single methyl groups rather than concerted gear-like rotation.

UR - http://www.scopus.com/inward/record.url?scp=85072404270&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85072404270&partnerID=8YFLogxK

U2 - 10.1021/acs.jpclett.9b01487

DO - 10.1021/acs.jpclett.9b01487

M3 - Article

C2 - 31442376

AN - SCOPUS:85072404270

VL - 10

SP - 5434

EP - 5439

JO - Journal of Physical Chemistry Letters

JF - Journal of Physical Chemistry Letters

SN - 1948-7185

IS - 18

ER -