Structural characterization of 4-bromostyrene self-assembled monolayers on Si(111)

Rajiv Basu, Jui Ching Lin, Chang Yong Kim, Matthew J. Schmitz, Nathan L. Yoder, Joshua A. Kellar, Michael J. Bedzyk, Mark C Hersam

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Organic functionalization of silicon holds promise for a variety of applications ranging from molecular electronics to biosensing. Because the performance and reliability of organosilicon devices will be intimately tied to the detailed structure of the organic adlayers, it is imperative to develop systematic strategies for forming and characterizing self-assembled monolayers (SAMs) on silicon with submolecular spatial resolution. In this study, we use 4-bromostyrene for the photochemical growth of Br-terminated SAMs on Si(111). A variety of experimental and theoretical techniques including atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), X-ray reflectivity (XRR), X-ray standing waves (XSW), X-ray fluorescence (XRF), and density functional theory (DFT) have been employed to determine the coverage and conformation of the 4-bromostryene molecules within the SAM. In particular, AFM verifies a continuous and atomically flat SAM, and the XRR data indicate a SAM thickness of 8.50 Å and a molecular coverage of 46% of the surface silicon atoms. Because the DFT calculations indicate a molecular length of 8.89 Å, the measured XRR thickness implies a molecular tilt angle of approximately 17°. The XRR analysis also suggests that the Br atoms are preserved on top of the SAM in agreement with XPS measurements that show bromine bound solely to carbon and not to silicon. XRF reveals a Br atomic coverage of 50%, again in close agreement to that found by XRR. Single-crystal Bragg diffraction XSW is used to generate a three-dimensional map of the Br distribution within the SAM, which in conjunction with the XRR result suggests that the 4-bromostyrene molecules are tilted such that the Br atoms are located over the T4 sites at a height of 8.50 Å above the top bulklike Si(111) layer. The direction of molecular tilt toward the T4 sites is consistent with that predicted by the DFT calculation. Overall, through this unique suite of complementary structural characterization techniques, it is concluded that the Br functional handle is preserved at the top of the SAM and is available for further substitutional chemistry.

Original languageEnglish
Pages (from-to)1905-1911
Number of pages7
JournalLangmuir
Volume23
Issue number4
DOIs
Publication statusPublished - Feb 13 2007

Fingerprint

Self assembled monolayers
X rays
Silicon
x rays
reflectance
Density functional theory
Atoms
Atomic force microscopy
silicon
X ray photoelectron spectroscopy
density functional theory
Fluorescence
standing waves
4-bromostyrene
Molecular electronics
Bromine
Molecules
photoelectron spectroscopy
atomic force microscopy
atoms

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Colloid and Surface Chemistry

Cite this

Basu, R., Lin, J. C., Kim, C. Y., Schmitz, M. J., Yoder, N. L., Kellar, J. A., ... Hersam, M. C. (2007). Structural characterization of 4-bromostyrene self-assembled monolayers on Si(111). Langmuir, 23(4), 1905-1911. https://doi.org/10.1021/la062759f

Structural characterization of 4-bromostyrene self-assembled monolayers on Si(111). / Basu, Rajiv; Lin, Jui Ching; Kim, Chang Yong; Schmitz, Matthew J.; Yoder, Nathan L.; Kellar, Joshua A.; Bedzyk, Michael J.; Hersam, Mark C.

In: Langmuir, Vol. 23, No. 4, 13.02.2007, p. 1905-1911.

Research output: Contribution to journalArticle

Basu, R, Lin, JC, Kim, CY, Schmitz, MJ, Yoder, NL, Kellar, JA, Bedzyk, MJ & Hersam, MC 2007, 'Structural characterization of 4-bromostyrene self-assembled monolayers on Si(111)', Langmuir, vol. 23, no. 4, pp. 1905-1911. https://doi.org/10.1021/la062759f
Basu R, Lin JC, Kim CY, Schmitz MJ, Yoder NL, Kellar JA et al. Structural characterization of 4-bromostyrene self-assembled monolayers on Si(111). Langmuir. 2007 Feb 13;23(4):1905-1911. https://doi.org/10.1021/la062759f
Basu, Rajiv ; Lin, Jui Ching ; Kim, Chang Yong ; Schmitz, Matthew J. ; Yoder, Nathan L. ; Kellar, Joshua A. ; Bedzyk, Michael J. ; Hersam, Mark C. / Structural characterization of 4-bromostyrene self-assembled monolayers on Si(111). In: Langmuir. 2007 ; Vol. 23, No. 4. pp. 1905-1911.
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