Going beyond the self-assembled monolayer: Metal intercalated dithiol multilayers and their conductance

Hicham Hamoudi, Kohei Uosaki, Katsuhiko Ariga, Vladimir A. Esaulov

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Abstract

A study of the self-assembly of silver atom intercalated 5,5′-bis(mercaptomethyl)-2,2′-bipyridine (BPD; HS-CH2-(C5H3N)2-CH2-SH) and 1,4-benzenedimethanethiol (BDMT; HS-CH2-(C6H4)-CH2-SH)) dithiol (DT) multilayers on gold is presented. The bilayer of these SAMs can be obtained starting from the exposure of a DT monolayer to a concentrated silver ion solution. After grafting the silver atoms on the sulfur end group, the incubation of the resulting DT-Ag SAM in a DT solution leads to the formation of a DT-Ag-DT bilayer. This process was extended to make a multilayer structure. The corresponding changes in these self-assembled layers on Au are characterized by X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE) measurements, and I-V characteristics. Our interpretation of evolution in the absorbed layer are based on changes in intensities of peaks in XPS related to S bound to substrate or Ag and in -SH groups, as well as changes in thickness and absorption features in SE measurements. The latter show the evolution in absorbance wavelength as a function of thickness and indicate a decrease in the HOMO-LUMO gap from about 4.5 eV to 4 eV. The I-V characteristics show a significant bias dependence on the number of the BPD layers and there appears to be a transition from tunneling to a hopping regime when going from the single to the multiple layers.

Original languageEnglish
Pages (from-to)39657-39666
Number of pages10
JournalRSC Advances
Volume4
Issue number75
DOIs
Publication statusPublished - 2014
Externally publishedYes

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ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Chemistry(all)

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