Comparative X-ray standing wave analysis of metal-phosphonate multilayer films of dodecane and porphyrin molecular square

Joseph A. Libera, Richard W. Gurney, Craig Schwartz, Hua Jin, Tien Lin Lee, Sonbinh T. Nguyen, Joseph T. Hupp, Michael J. Bedzyk

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Abstract

The nanoscale structures of multilayer metal-phosphonate thin films prepared via a layer-by-layer assembly process using Zr 4+ and 1,12-dodecanediylbis(phosphonic acid) (DDBPA) or porphyrin square bis(phosphonic acid) (PSBPA) were studied using specular X-ray reflectivity (XRR), X-ray fluorescence, and long-period X-ray standing wave (XSW) analysis. The films were prepared in 1, 2, 3, 4, 6, and 8 layer series on both Si(001) substrates for XRR and on 18.6 nm period Si/Mo layered-synthetic microstructure X-ray mirrors for XSW. After functionalizing the SiO 2 substrate surfaces with a monolayer film terminated with phosphonate groups, the organic multilayer films were assembled by alternating immersions in (a) aqueous solutions containing Zr 4+or Hf 4+ (final metal layer only) cations and then (b) organic solvent solutions of PO 3-R-PO 3 4-, where R was DDBPA or PSBPA spacer molecule. The Hf 4+ cation served as the marker for the top surface of the films, whereas the Zf 4+ cation was present in all other layers. The PSBPA also contained Zn and Re atoms at its midline which served as heavy-atom markers for each layer. The long-period XSW generated by the 0th- (total external reflection) through 4th-order Bragg diffraction conditions made it possible to examine the Fourier transforms of the fluorescent atom distributions over a much larger q z range in reciprocal space which permitted simultaneous analysis of Hf, Zn/Re, and Zr atomic distributions.

Original languageEnglish
Pages (from-to)1441-1450
Number of pages10
JournalJournal of Physical Chemistry B
Volume109
Issue number4
DOIs
Publication statusPublished - Feb 3 2005

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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