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Charge Transport Measured Using the EGaIn Junction through Self-Assembled Monolayers Immersed in Organic Liquids
Yuan Li1,2, Samuel E Root2, Lee Belding2
1Department of Chemistry, Tsinghua University, Beijing100086, China.
The Journal of Physical Chemistry. B
|December 29, 2022
Summary
This study shows that molecular junctions formed in organic liquids are robust. Tunneling currents are reduced due to thin liquid films, suggesting a new surface analysis method.
Area of Science:
- Materials Science
- Surface Chemistry
- Nanotechnology
Background:
- Molecular junctions are crucial for understanding charge transport.
- Self-assembled monolayers (SAMs) on metal electrodes are widely studied.
- The influence of external environments on junction stability and transport is of interest.
Purpose of the Study:
- To investigate charge transport through molecular junctions immersed in various organic liquids.
- To assess the robustness and environmental effects on these junctions.
- To explore a new surface analysis technique using tunneling currents.
Main Methods:
- Fabrication of molecular junctions using template-stripped metal electrodes and SAMs.
- Measurement of tunneling current density under seven different external environments.
- Analysis of liquid film formation at the electrode-SAM interface using electrical breakdown and molecular dynamics simulations.
Main Results:
- Junctions formed in organic liquids exhibit comparable stability and yield to those formed in air.
- Current densities in perfluorocarbons were similar to air, while other organic liquids caused reductions up to 5 orders of magnitude.
- A thin liquid film (0.5-1.5 nm) at the interface was identified as the cause for reduced tunneling currents, consistent with surface force apparatus measurements.
Conclusions:
- The formation of structured liquid films at interfaces significantly impacts charge transport in molecular junctions.
- The EGaIn junction and tunneling measurements offer a novel approach for surface analysis.
- This method is applicable to studying weak molecular interactions and liquid film behavior near interfaces.
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