Effect of Smoothening Electrodes for Revealing Finer Molecular Information in Charge Transport

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2017-04-11
Authors
Kadoma, Atte
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Altmetrics
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Materials Science and Engineering
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In molecular electronics, molecules are the building blocks of electrical circuits. Within this field, the study of self-assembled monolayers (SAMs) continues to gain interest. Self-assembled monolayers arise from spontaneous organization of chemi-sorbed molecules into ordered and well-defined layers on a surface. We seek to understand how charge tunnels through organic monolayers and the role of the monolayer in this process. To study charge transport by tunneling, a eutectic indium gallium (EGaIn) top electrode passes current onto a substrate (bottom electrode) through the SAM. Different preparation methods of the EGaIn electrode have led to variances in observed current density and have led to discrepancies in inferences related to the SAM structure in charge transport—for example, in the odd-even effect. By polishing the electrode with an acetic acid solution, we developed a universal method to address the disparities. The polished EGaIn tip in combination with ultra-flat substrate (AuTi-TS) led to significant improvement in sensitivity to molecular interface properties. Heat maps and related Gaussian distributions generated from this improved platform showed sharp and symmetric distributions. Similar trends in wetting confirm the observed results were sensitive to both bulk and interface properties of the SAMs. With the development of this method, we gain better fundamental molecular level information on SAMs. This has the potential to contribute to the use of SAMs in electronic-chemical sensor fabrication.

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