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 language | English |
|---|---|
| Pages (from-to) | 5434-5439 |
| Number of pages | 6 |
| Journal | Journal of Physical Chemistry Letters |
| Volume | 10 |
| Issue number | 18 |
| DOIs | |
| Publication status | Published - Sep 19 2019 |
Fingerprint
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 journal › Article
}
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 -