Supramolecular tunneling junctions


Wimbush, K.S. (2012) Supramolecular tunneling junctions. thesis.

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Abstract:In this study a variety of supramolecular tunneling junctions were created. The basis of these junctions was a self-assembled monolayer of heptathioether functionalized ß-cyclodextrin (ßCD) formed on an ultra-flat Au surface, i.e., the bottom electrode. This gave a well-defined hexagonally packed ßCD monolayer, which was coined as a 'supramolecular platform'.

Adsorbed on the supramolecular platform were dendritic molecules that varied in core structure and/or terminal functionality. To complete the junction, a top-electrode of eutectic gallium indium was contacted the dendrimers. By changing the chemical structure of the dendrimer in the junction, it was possible to study the mechanism of charge transport as a function of molecular structure.

Statistical relevant numbers of current vs. voltage I(V) measurements performed across the different supramolecular tunneling junctions allowed for the use of the rectification ratio (R), where R=│J(-2.0 V)│/│J(+2.0 V)│, to compare the charge transport characteristics of the junctions with different dendritic molecules. This allowed for the formulation and verification of the mechanism of charge transport across the tunneling junctions, and the influence that the electrode can have on the charge transport characteristics of the junction.

Finally, by using the tip of a Scanning Tunneling Microscope, instead of a top electrode of (Ga2O3)EGaIn, it was possible to investigate the charge transport characteristics at the single molecule level, which are averaged out in large-rea junctions.
Item Type:Thesis
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