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MOLECSYNCON Report Summary

Project ID: 335473
Funded under: FP7-IDEAS-ERC
Country: Netherlands

Mid-Term Report Summary - MOLECSYNCON (Controlling Tunneling Charge Transport with Organic Synthesis)

This project focuses on advancing the field of Molecular Electronics from basic studies on the length-dependence of tunneling junctions comprising simple molecules towards control over tunneling current by the synthetic manipulation of molecules; i.e., functionality. To accomplish this goal, we are investigating two phenomena: quantum-interference and electrostatics. The former causes dramatic changes in tunneling probability (conductivity) when electrons interfere with each other quantum mechanically, while the latter gives rise to non-linear current/voltage behavior. We control quantum-interference by altering the conjugation pathways of the "cores" of molecules and then manipulating the position of these features with functional groups on the "arms." That is, we are attempting to switch the effect on and off by controlling the electronic structure of the molecules without altering their lengths (to avoid distance-dependent effects). We control electrostatics by embedding dipole moments arising from electron donating and withdrawing groups positioned along the long-axis of the molecules. These dipole moments act collectively to shift the electrostatics within a junction, bringing states in and out of resonance with the electrodes and thereby affecting the conductance of the junction. All of the systems that we investigate comprise self-assembled monolayers; in this way, the junctions are assembled bottom-up rather than top-down, which is desirable for potential future applications because the devices, in part, fabricate themselves. We use two tools; liquid metal top-contacts composed of gallium and indium and gold nanowires that we fabricate mechanically, using self-assembled monolayers to define the gaps between them. The first tool allows the investigation of junctions and post facto spectroscopic analysis, while the latter enables the interaction of junctions with external stimuli (e.g., light).

The present state of the project is that we have a large pool of synthetic intermediates that we are combining to produce libraries of molecules that we will investigate using the aforementioned methods. We have completed the simpler molecules and acquired data from them and disseminated the results via publication.

Primary Achievements:

The observation of a through-space (as opposed to through-bond) effects in tunneling junctions comprising self-assembled monolayers.
The observation of dipole-induced asymmetry and shifts in transition voltages in same. (Transition voltages reflect the energy levels inside the junctions.)
The observation of light-induced gating (not switching) in same.

Secondary Achievements:

The observation of dipole-induced asymmetry and remarkably high and non-thermally activated transport in tunneling junctions comprising photo system I.
The bisecting of microfluidic channels with ultra-long metallic nanowires fabricated by nanoskiving, allowing access to the high-flow regime.
New methods for the construction of 3D nanostructures by nanoskiving.

Tertiary Achievements:

The development of software for processing and performing statistical analyses on conductance data from tunneling junctions.

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