Transmission infrared spectra of CH3-, CD3-, and C10H21-Ge(111) surfaces

David Knapp, Bruce S. Brunschwig, Nathan S Lewis

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

The surface chemistry of CH3-, CD3-, and C 10H21-Ge(111) surfaces prepared through a bromination/alkylation method have been investigated by infrared spectroscopy. Well-ordered CH3-Ge(111) surfaces could be prepared only if, prior to bromination, the surface was etched with 6.0 M HCl or with a two-step etch of H2O2 (1.5 M)/HF (5.1 M) followed by a short HF (6.0 M) etch. The etching method used to make the Ge precursor surface, and the formation of a bromine-terminated intermediate Ge surface, were of critical importance to obtain clear, unambiguous infrared absorption peaks on the methyl-terminated Ge surfaces. Polarization-dependent absorption peaks observed at 1232 cm-1 for CH3-Ge(111) surfaces and at 951 cm -1 for CD3-Ge(111) surfaces were assigned to the methyl "umbrella" vibrational mode. A polarization-dependent peak at 2121 cm-1 for CD3-Ge(111) surfaces was assigned to the symmetric methyl stretching mode. Polarization-independent absorption peaks at 755 cm-1 for CH3-Ge(111) and at 577 cm-1 for CD3-Ge(111) were assigned to the methyl rocking mode. These findings provide spectroscopic evidence that the methyl monolayer structure on the alkylated Ge is well-ordered and similar to that on analogous Si(111) surfaces, despite differences in the composition of the precursor surfaces. The X-ray photoelectron spectra of CH3-Ge(111) surfaces, however, were not highly dependent upon the etching method and showed a constant C 1s:Ge 3d ratio, independent of the etching method. The infrared spectra of C10H 21-Ge(111) surfaces were also not sensitive to the initial etching method. Hence, while the final packing density of the alkyl groups on the surface was similar for all etch methods studied, not all methods yielded a well-ordered Ge(111)/overlayer interface.

Original languageEnglish
Pages (from-to)16389-16397
Number of pages9
JournalJournal of Physical Chemistry C
Volume115
Issue number33
DOIs
Publication statusPublished - Aug 25 2011

Fingerprint

Infrared transmission
infrared spectra
Etching
etching
bromination
Polarization
polarization
Bromine
Alkylation
Infrared absorption
packing density
alkylation
Photoelectrons
Surface chemistry
bromine
Stretching

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

Transmission infrared spectra of CH3-, CD3-, and C10H21-Ge(111) surfaces. / Knapp, David; Brunschwig, Bruce S.; Lewis, Nathan S.

In: Journal of Physical Chemistry C, Vol. 115, No. 33, 25.08.2011, p. 16389-16397.

Research output: Contribution to journalArticle

Knapp, David ; Brunschwig, Bruce S. ; Lewis, Nathan S. / Transmission infrared spectra of CH3-, CD3-, and C10H21-Ge(111) surfaces. In: Journal of Physical Chemistry C. 2011 ; Vol. 115, No. 33. pp. 16389-16397.
@article{2e6864987e324573909fa68a1b588e3d,
title = "Transmission infrared spectra of CH3-, CD3-, and C10H21-Ge(111) surfaces",
abstract = "The surface chemistry of CH3-, CD3-, and C 10H21-Ge(111) surfaces prepared through a bromination/alkylation method have been investigated by infrared spectroscopy. Well-ordered CH3-Ge(111) surfaces could be prepared only if, prior to bromination, the surface was etched with 6.0 M HCl or with a two-step etch of H2O2 (1.5 M)/HF (5.1 M) followed by a short HF (6.0 M) etch. The etching method used to make the Ge precursor surface, and the formation of a bromine-terminated intermediate Ge surface, were of critical importance to obtain clear, unambiguous infrared absorption peaks on the methyl-terminated Ge surfaces. Polarization-dependent absorption peaks observed at 1232 cm-1 for CH3-Ge(111) surfaces and at 951 cm -1 for CD3-Ge(111) surfaces were assigned to the methyl {"}umbrella{"} vibrational mode. A polarization-dependent peak at 2121 cm-1 for CD3-Ge(111) surfaces was assigned to the symmetric methyl stretching mode. Polarization-independent absorption peaks at 755 cm-1 for CH3-Ge(111) and at 577 cm-1 for CD3-Ge(111) were assigned to the methyl rocking mode. These findings provide spectroscopic evidence that the methyl monolayer structure on the alkylated Ge is well-ordered and similar to that on analogous Si(111) surfaces, despite differences in the composition of the precursor surfaces. The X-ray photoelectron spectra of CH3-Ge(111) surfaces, however, were not highly dependent upon the etching method and showed a constant C 1s:Ge 3d ratio, independent of the etching method. The infrared spectra of C10H 21-Ge(111) surfaces were also not sensitive to the initial etching method. Hence, while the final packing density of the alkyl groups on the surface was similar for all etch methods studied, not all methods yielded a well-ordered Ge(111)/overlayer interface.",
author = "David Knapp and Brunschwig, {Bruce S.} and Lewis, {Nathan S}",
year = "2011",
month = "8",
day = "25",
doi = "10.1021/jp110550t",
language = "English",
volume = "115",
pages = "16389--16397",
journal = "Journal of Physical Chemistry C",
issn = "1932-7447",
publisher = "American Chemical Society",
number = "33",

}

TY - JOUR

T1 - Transmission infrared spectra of CH3-, CD3-, and C10H21-Ge(111) surfaces

AU - Knapp, David

AU - Brunschwig, Bruce S.

AU - Lewis, Nathan S

PY - 2011/8/25

Y1 - 2011/8/25

N2 - The surface chemistry of CH3-, CD3-, and C 10H21-Ge(111) surfaces prepared through a bromination/alkylation method have been investigated by infrared spectroscopy. Well-ordered CH3-Ge(111) surfaces could be prepared only if, prior to bromination, the surface was etched with 6.0 M HCl or with a two-step etch of H2O2 (1.5 M)/HF (5.1 M) followed by a short HF (6.0 M) etch. The etching method used to make the Ge precursor surface, and the formation of a bromine-terminated intermediate Ge surface, were of critical importance to obtain clear, unambiguous infrared absorption peaks on the methyl-terminated Ge surfaces. Polarization-dependent absorption peaks observed at 1232 cm-1 for CH3-Ge(111) surfaces and at 951 cm -1 for CD3-Ge(111) surfaces were assigned to the methyl "umbrella" vibrational mode. A polarization-dependent peak at 2121 cm-1 for CD3-Ge(111) surfaces was assigned to the symmetric methyl stretching mode. Polarization-independent absorption peaks at 755 cm-1 for CH3-Ge(111) and at 577 cm-1 for CD3-Ge(111) were assigned to the methyl rocking mode. These findings provide spectroscopic evidence that the methyl monolayer structure on the alkylated Ge is well-ordered and similar to that on analogous Si(111) surfaces, despite differences in the composition of the precursor surfaces. The X-ray photoelectron spectra of CH3-Ge(111) surfaces, however, were not highly dependent upon the etching method and showed a constant C 1s:Ge 3d ratio, independent of the etching method. The infrared spectra of C10H 21-Ge(111) surfaces were also not sensitive to the initial etching method. Hence, while the final packing density of the alkyl groups on the surface was similar for all etch methods studied, not all methods yielded a well-ordered Ge(111)/overlayer interface.

AB - The surface chemistry of CH3-, CD3-, and C 10H21-Ge(111) surfaces prepared through a bromination/alkylation method have been investigated by infrared spectroscopy. Well-ordered CH3-Ge(111) surfaces could be prepared only if, prior to bromination, the surface was etched with 6.0 M HCl or with a two-step etch of H2O2 (1.5 M)/HF (5.1 M) followed by a short HF (6.0 M) etch. The etching method used to make the Ge precursor surface, and the formation of a bromine-terminated intermediate Ge surface, were of critical importance to obtain clear, unambiguous infrared absorption peaks on the methyl-terminated Ge surfaces. Polarization-dependent absorption peaks observed at 1232 cm-1 for CH3-Ge(111) surfaces and at 951 cm -1 for CD3-Ge(111) surfaces were assigned to the methyl "umbrella" vibrational mode. A polarization-dependent peak at 2121 cm-1 for CD3-Ge(111) surfaces was assigned to the symmetric methyl stretching mode. Polarization-independent absorption peaks at 755 cm-1 for CH3-Ge(111) and at 577 cm-1 for CD3-Ge(111) were assigned to the methyl rocking mode. These findings provide spectroscopic evidence that the methyl monolayer structure on the alkylated Ge is well-ordered and similar to that on analogous Si(111) surfaces, despite differences in the composition of the precursor surfaces. The X-ray photoelectron spectra of CH3-Ge(111) surfaces, however, were not highly dependent upon the etching method and showed a constant C 1s:Ge 3d ratio, independent of the etching method. The infrared spectra of C10H 21-Ge(111) surfaces were also not sensitive to the initial etching method. Hence, while the final packing density of the alkyl groups on the surface was similar for all etch methods studied, not all methods yielded a well-ordered Ge(111)/overlayer interface.

UR - http://www.scopus.com/inward/record.url?scp=80051933646&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=80051933646&partnerID=8YFLogxK

U2 - 10.1021/jp110550t

DO - 10.1021/jp110550t

M3 - Article

AN - SCOPUS:80051933646

VL - 115

SP - 16389

EP - 16397

JO - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

SN - 1932-7447

IS - 33

ER -