X-ray studies of self-assembled organic monolayers grown on hydrogen-terminated Si(111)

Hua Jin, C. Reagan Kinser, Paul A. Bertin, Donald E. Kramer, Joseph A. Libera, Mark C Hersam, Sonbinh T. Nguyen, Michael J. Bedzyk

Research output: Contribution to journalArticle

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Abstract

The structure of self-assembled monolayers (SAMs) of undecylenic acid methyl ester (SAM-1) and undec10-enoic acid 2-bromo-ethyl ester (SAM-2) grown on hydrogen-passivated Si(111) were studied by X-ray reflectivity (XRR), X-ray standing waves (XSW), X-ray fluorescence (XRF), atomic force microscopy, and X-ray photoelectron spectroscopy (XPS). The two different SAMs were grown by immersion of H-Si(111) substrates into the two different concentrated esters. UV irradiation during immersion was used to create Si dangling bond sites that act as initiators of the surface free-radical addition process that leads to film growth. The XRR structural analysis reveals that the molecules of SAM-1 and SAM-2 respectively have area densities corresponding to 50% and 57% of the density of Si(111) surface dangling bonds and produce films with less than 4 Å root-mean-square roughness that have layer thicknesses of 12.2 and 13.2 Å. Considering the molecular lengths, these thicknesses correspond to a 38° and 23° tilt angle for the respective molecules. For SAM-2/Si(111) samples, XRF analysis reveals a 0.58 monolayer (ML) Br total coverage. Single-crystal Bragg diffraction XSW analysis reveals (unexpectedly) that 0.48 ML of these Br atoms are at a Si( 111) lattice position height that is identical to the T 1 site that was previously found by XSW analysis for Br adsorbed onto Si(111) from a methanol solution and from ultrahigh vacuum. From the combined XPS, XRR, XRF, and XSW evidence, it is concluded that Br abstraction by reactive surface dangling bonds competes with olefin addition to the surface.

Original languageEnglish
Pages (from-to)6252-6258
Number of pages7
JournalLangmuir
Volume20
Issue number15
DOIs
Publication statusPublished - Jul 20 2004

Fingerprint

Hydrogen
Monolayers
Self assembled monolayers
X rays
hydrogen
Dangling bonds
x rays
standing waves
Esters
Fluorescence
esters
X ray photoelectron spectroscopy
reflectance
fluorescence
submerging
Molecules
Acids
Alkenes
photoelectron spectroscopy
Ultrahigh vacuum

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Colloid and Surface Chemistry

Cite this

Jin, H., Kinser, C. R., Bertin, P. A., Kramer, D. E., Libera, J. A., Hersam, M. C., ... Bedzyk, M. J. (2004). X-ray studies of self-assembled organic monolayers grown on hydrogen-terminated Si(111). Langmuir, 20(15), 6252-6258. https://doi.org/10.1021/la0496690

X-ray studies of self-assembled organic monolayers grown on hydrogen-terminated Si(111). / Jin, Hua; Kinser, C. Reagan; Bertin, Paul A.; Kramer, Donald E.; Libera, Joseph A.; Hersam, Mark C; Nguyen, Sonbinh T.; Bedzyk, Michael J.

In: Langmuir, Vol. 20, No. 15, 20.07.2004, p. 6252-6258.

Research output: Contribution to journalArticle

Jin, H, Kinser, CR, Bertin, PA, Kramer, DE, Libera, JA, Hersam, MC, Nguyen, ST & Bedzyk, MJ 2004, 'X-ray studies of self-assembled organic monolayers grown on hydrogen-terminated Si(111)', Langmuir, vol. 20, no. 15, pp. 6252-6258. https://doi.org/10.1021/la0496690
Jin, Hua ; Kinser, C. Reagan ; Bertin, Paul A. ; Kramer, Donald E. ; Libera, Joseph A. ; Hersam, Mark C ; Nguyen, Sonbinh T. ; Bedzyk, Michael J. / X-ray studies of self-assembled organic monolayers grown on hydrogen-terminated Si(111). In: Langmuir. 2004 ; Vol. 20, No. 15. pp. 6252-6258.
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