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

Abstract

A study of the self-assembly of silver atom intercalated 5,5 0 -bis(mercaptomethyl)-2,2 0 -bipyridine (BPD; HS-CH 2 -(C 5 H 3 N) 2 -CH 2 -SH) and 1,4-benzenedimethanethiol (BDMT; HS-CH 2 -(C 6 H 4 )-CH 2 -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.

Selfassembly of α,ω‐dithiols on surfaces and metal dithiol heterostructures

“…In the following, to illustrate in more detail these applications of metal dithiol heterostructures we discuss the making, composition and functional properties, including electrical conductivity and optical properties of some of these ensembles. We describe results of some recent works involving DT SAMs, which uses the preparation protocol in liquid phase described in section above. Finally as an illustration of a rather different approach, we also stop briefly on metal dithiol structures prepared without usage of a self assembled monolayers but by dithiol attachment to metals in solution as in some works mentioned above.…”

Static and dynamic electronic characterization of organic monolayers grafted on a silicon surface

“…When a moderate positive voltage is applied to the semiconductor (e.g., when the AFM tip is grounded), the transport occurs by tunneling through the molecular barrier. Scheme 3-c shows that the electrons have to cross a trapezoidal barrier, in which case the transport is described by 45,[68][69][70][71]…”

Direct covalent grafting of an organic radical core on gold and silver

“…Amongst these materials, covalently self-assembled monolayers (SAMs) [16][17][18][19] gained tremendous interest due to their ease of fabrication process and effectiveness to integrate organic molecules on inorganic (metallic) substrates. Importantly, organic radicals based SAMs 20 (r-SAMs) have emerged as potential building units for spintronic materials, which could be applied for downscaling the memory devices.…”