title: Comparative X-ray standing wave analysis of metal-phosphonate multilayer films of dodecane and porphyrin molecular square.
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 Zr(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.
authors.affiliation: Department of Materials Science and Engineering, and The Nanoscale Science and Engineering Center, Northwestern University, 2220 Campus Drive, Evanston, IL 60208, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Libera
authors.forename: Richard W
authors.initials: RW
authors.lastname: Gurney
authors.forename: Craig
authors.initials: C
authors.lastname: Schwartz
authors.forename: Hua
authors.initials: H
authors.lastname: Jin
authors.forename: Tien-Lin
authors.initials: TL
authors.lastname: Lee
authors.forename: SonBinh T
authors.initials: ST
authors.lastname: Nguyen
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Hupp
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Bedzyk
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D006195:Hafnium / Q000032:analysis*; D008567:Membranes, Artificial; D063065:Organophosphonates / Q000032:analysis* / Q000737:chemistry; D011166:Porphyrins / Q000737:chemistry*; D012211:Rhenium / Q000737:chemistry; D013057:Spectrum Analysis; D014965:X-Rays; D015040:Zirconium / Q000032:analysis*
chemical_list: C520680:1,12-dodecanediylbis(phosphonic acid); D000473:Alkanes; D008567:Membranes, Artificial; D063065:Organophosphonates; D011166:Porphyrins; C007548:n-dodecane; D012211:Rhenium; D015040:Zirconium; D006195:Hafnium