Synthesis and Characterization of Atomically Flat Methyl-Terminated Ge(111) Surfaces

Keith T. Wong, Youn Geun Kim, Manuel P. Soriaga, Bruce S. Brunschwig, Nathan S Lewis

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Atomically flat, terraced H-Ge(111) was prepared by annealing in H2(g) at 850 °C. The formation of monohydride Ge-H bonds oriented normal to the surface was indicated by angle-dependent Fourier-transform infrared (FTIR) spectroscopy. Subsequent reaction in CCl3Br(l) formed Br-terminated Ge(111), as shown by the disappearance of the Ge-H absorption in the FTIR spectra concomitant with the appearance of Br photoelectron peaks in X-ray photoelectron (XP) spectra. The Br-Ge(111) surface was methylated by reaction with (CH3)2Mg. These surfaces exhibited a peak at 568 cm-1 in the high-resolution electron energy loss spectrum, consistent with the formation of a Ge-C bond. The absorption peaks in the FTIR spectra assigned to methyl "umbrella" and rocking modes were dependent on the angle of the incident light, indicating that the methyl groups were bonded directly atop surface Ge atoms. Atomic-force micrographs of CH3-Ge(111) surfaces indicated that the surface remained atomically flat after methylation. Electrochemical scanning-tunneling microscopy showed well-ordered methyl groups that covered nearly all of the surface. Low-energy electron diffraction images showed sharp, bright diffraction spots with a 3-fold symmetry, indicating a high degree of order with no evidence of surface reconstruction. A C 1s peak at 284.1 eV was observed in the XP spectra, consistent with the formation of a C-Ge bond. Annealing in ultrahigh vacuum revealed a thermal stability limit of ∼400 °C of the surficial CH3-Ge(111) groups. CH3-Ge(111) surfaces showed significantly greater resistance to oxidation in air than H-Ge(111) surfaces. (Chemical Equation Presented)

Original languageEnglish
Pages (from-to)9006-9014
Number of pages9
JournalJournal of the American Chemical Society
Volume137
Issue number28
DOIs
Publication statusPublished - Jul 22 2015

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Fourier Analysis
Electrochemical Scanning Microscopy
Scanning Tunnelling Microscopy
X-Rays
Electrons
Fourier Transform Infrared Spectroscopy
Vacuum
Methylation
Hot Temperature
Air
Photoelectrons
Light
Fourier transforms
Annealing
Infrared radiation
X rays
Surface reconstruction
Low energy electron diffraction
Ultrahigh vacuum
Scanning tunneling microscopy

ASJC Scopus subject areas

  • Chemistry(all)
  • Catalysis
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Synthesis and Characterization of Atomically Flat Methyl-Terminated Ge(111) Surfaces. / Wong, Keith T.; Kim, Youn Geun; Soriaga, Manuel P.; Brunschwig, Bruce S.; Lewis, Nathan S.

In: Journal of the American Chemical Society, Vol. 137, No. 28, 22.07.2015, p. 9006-9014.

Research output: Contribution to journalArticle

Wong, Keith T. ; Kim, Youn Geun ; Soriaga, Manuel P. ; Brunschwig, Bruce S. ; Lewis, Nathan S. / Synthesis and Characterization of Atomically Flat Methyl-Terminated Ge(111) Surfaces. In: Journal of the American Chemical Society. 2015 ; Vol. 137, No. 28. pp. 9006-9014.
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