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Volumn 22, Issue 6, 2006, Pages 2578-2587

Alkanethiols on platinum: Multicomponent self-assembled monolayers

Author keywords

[No Author keywords available]

Indexed keywords

ALKANETHIOLS; DODECANETHIOL; SELF ASSEMBLED MONOLAYERS (SAM); SPECTROSCOPIC ELLIPSOMETRY (SE);

EID: 33645514247     PISSN: 07437463     EISSN: None     Source Type: Journal    
DOI: 10.1021/la050928a     Document Type: Article
Times cited : (111)

References (83)
  • 16
    • 33645524022 scopus 로고    scopus 로고
    • note
    • The total fwhm is the sum of Gaussian and Loremzian contributions. The Lorentzian fwhm was 0.1 eV for C Is and O Is and 0.25 eV for S 2p. For C Is components C2 and C3, the total fwhm was fixed to that of Cl (1.2-1.3 eV). For S 2p components, we used a spin-orbit intensity ratio of 0.5 and an energy splitting of 1.2 eV.; the total fwhm was 0.98 eV for SI and S2, 1.48 eV for S3.
  • 37
    • 33645534038 scopus 로고    scopus 로고
    • note
    • Normalizing elemental XPS signals by the corresponding Scofield factors (ref 36) is a standard way to correct for element-dependent photoelectric cross sections, the major factor that determines element-specific XPS intensities. This normalization ignores any spatial distribution of the elements, but provides a practical way to compare elemental intensities, as such Scofield-adjusted intensity ratios often appear in quantitative XPS analysis models (see Appendix).
  • 40
    • 33645530250 scopus 로고    scopus 로고
    • note
    • The Tougaard model with parameters established for SAMs/Au (ref 26) predicts intensities of inelastic backgrounds to be much lower than the observed high-BE shoulders of S 2p peaks. The asymmetric S 2p peak shapes thus correspond to multiple S 2p components.
  • 41
    • 33645532519 scopus 로고    scopus 로고
    • note
    • The spectra were analyzed by nonlinear least-squares fitting to multiple Lorentzian lines, except in the case of the UVO-Pt substrate, in which a Gaussian line shape was required.
  • 44
    • 33645513086 scopus 로고    scopus 로고
    • note
    • The oxygen-free deposition on TS-Pt substrates resulted in the lowest overall O 1s signals in our study. For C6SH/TS-Pt, the Scofield-adjusted Intensity ratios (same units as in Table SI2) are 227 for the C2 and C3 components, 220 for O Is, and 101 for S2, The total intensity of the oxidized C components is equal to the total 0 signal; thus, the data are consistent with essentially no PtO, on the surface while S2 is still present.
  • 45
    • 33645516435 scopus 로고    scopus 로고
    • note
    • Each of the alkanethiol molecules contains two chemically distinct carbon atoms: one bound to the sulfur headgroup and one in the methyl group. The former is likely to have a BE higher than the alkyl carbons of the main C1 peak. The C2/C1 intensity ratios in fits to our data (Figure 6), however, are about one-half of what would be expected for ideal SAMs of respective thicknesses. An additional component of the appropriate intensity and BE shift of < 1 eV can be added without sacrificing the quality of the fits to account for the headgroup-bound carbons. The C2 and C3 components then must be interpreted as due to adventitious and/or solvent molecules, In the literature, assignment of C Is components with BE shifts of 1.2-1.6 eV (C2) and 2.7-3.6 eV (C3) varies, e.g., refs 6 and 27.
  • 56
    • 33645500309 scopus 로고    scopus 로고
    • note
    • Uncertainties are one standard deviation averaged over five measurement series.
  • 57
    • 33645514323 scopus 로고    scopus 로고
    • note
    • The unique extraction of dielectric constants from ultrathin (≤10 nm) films is problematic as the film thickness and index become correlated. The correlation coefficient between thickness and the real pan of the index (n) was ∼0,93. However, the estimated parameters are considered unique, as the statistical estimate of the fit uncertainties on thickness and n, accounting for the off-diagonal elements of the error matrix, are comparable to (∼50% smaller than) the reported uncertainties based on multiple data sets.
  • 63
    • 33645508359 scopus 로고    scopus 로고
    • note
    • The BE reported in ref 65 for S 2p in bulk PtS is 162.9 eV is closer to S2 rather than S1. Only for bulk PtSz is the BE comparable at 162.4 eV (ref 66), but creating a stoichiometry similar to PtS: at the surface would require C-S bond scission for the majority of alkylthiolates, i.e., such an assignment for SI is incompatible with the rest of the data.
  • 75
    • 33645518510 scopus 로고    scopus 로고
    • M.S. Thesis, University of New Orleans, New Orleans, LA
    • Sweeney, T. M. M.S. Thesis, University of New Orleans, New Orleans, LA, 2004
    • (2004)
    • Sweeney, T.M.1
  • 76
    • 33645524404 scopus 로고    scopus 로고
    • Yang, M.; Laracuente, A. R.; Whitman, L. J. Unpublished results, 2005
    • Yang, M.; Laracuente, A. R.; Whitman, L. J. Unpublished results, 2005.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.