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Molecular rectification in metal-SAM-metal oxide-metal junctions
Christian A Nijhuis1, William F Reus, George M Whitesides
1Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Journal of the American Chemical Society
|November 26, 2009
Summary
Ferrocene-terminated self-assembled monolayers (SAMs) exhibit significant current rectification in tunneling junctions. This study demonstrates their potential for electronic applications, outperforming SAMs without ferrocene.
Area of Science:
- Materials Science
- Nanotechnology
- Electrochemistry
Background:
- Self-assembled monolayers (SAMs) are crucial for molecular electronics.
- Ferrocene (Fc) is a redox-active molecule with potential for electronic applications.
- Efficient charge transport and rectification in molecular junctions are key research areas.
Purpose of the Study:
- To compare the charge transport and rectification properties of ferrocene-terminated SAMs (SC(11)Fc) with non-ferrocene terminated SAMs (SC(n-1)CH(3)).
- To establish a high-yield method for fabricating stable SAM-based tunneling junctions.
- To analyze the rectification behavior statistically for physical-organic insights.
Main Methods:
- Fabrication of SAMs of SC(11)Fc and SC(n-1)CH(3) on template-stripped silver (Ag(TS)) surfaces.
- Formation of soft electrical contacts using a eutectic alloy of gallium and indium (EGaIn) with a native gallium oxide skin.
- Measurement of current density (J) versus applied voltage (V) to determine rectification ratios (R).
- Statistical analysis of a large number of data points (N = 300-1000).
Main Results:
- SC(11)Fc SAMs formed stable tunneling junctions with high yields (70-90%).
- SC(11)Fc junctions exhibited significant current rectification with R ≈ 1.0 x 10^2.
- Control junctions with SC(n-1)CH(3) SAMs showed minimal rectification (R ≈ 1.5-2.1).
- Statistical analysis confirmed the significance of rectification in Fc-containing junctions.
Conclusions:
- Ferrocene head groups in SAMs are essential for achieving significant current rectification.
- The EGaIn contact method provides a high-yield, stable platform for SAM-based molecular electronics.
- These findings support the use of Fc-functionalized SAMs in molecular electronic devices and physical-organic studies.
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