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

Wong, Keith T. and Kim, Youn-Geun and Soriaga, Manuel P. and Brunschwig, Bruce S. and Lewis, Nathan S. (2015) Synthesis and Characterization of Atomically Flat Methyl-Terminated Ge(111) Surfaces. Journal of the American Chemical Society, 137 (28). pp. 9006-9014. ISSN 0002-7863. doi:10.1021/jacs.5b03339.

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Atomically flat, terraced H–Ge(111) was prepared by annealing in H_2(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 CCl_3Br(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 (CH_3)_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 CH_3–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 CH_3–Ge(111) groups. CH_3–Ge(111) surfaces showed significantly greater resistance to oxidation in air than H–Ge(111) surfaces.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Kim, Youn-Geun0000-0002-5936-6520
Soriaga, Manuel P.0000-0002-0077-6226
Brunschwig, Bruce S.0000-0002-6135-6727
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 2015 American Chemical Society. Received: March 31, 2015; publication Date (Web): July 8, 2015. This work was supported by the National Science Foundation grant CHE-1214152 and by the Gordon and Betty Moore Foundation (GBMF1225). The research was in part carried out in the Molecular Materials Research Center of the Beckman Institute of the California Institute of Technology and in part through the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993, which provided support for Y.-G.K. and M.P.S. to perform the EC-STM experiments. The authors declare no competing financial interest.
Funding AgencyGrant Number
Gordon and Betty Moore FoundationGBMF1225
Department of Energy (DOE)DE-SC0004993
Issue or Number:28
Record Number:CaltechAUTHORS:20150714-134139272
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Official Citation:Synthesis and Characterization of Atomically Flat Methyl-Terminated Ge(111) Surfaces Keith T. Wong, Youn-Geun Kim, Manuel P. Soriaga, Bruce S. Brunschwig, and Nathan S. Lewis Journal of the American Chemical Society 2015 137 (28), 9006-9014 DOI: 10.1021/jacs.5b03339
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58885
Deposited On:15 Jul 2015 19:19
Last Modified:10 Nov 2021 22:11

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