The influence of water on the charge transport through self-assembled monolayers junctions fabricated by EGaIn technique

Abstract

Eutectic Gallium-Indium (EGaIn) is a promising technique to fabricate self-assembled monolayers (SAMs)-based molecular devices. However, several abnormal signals had been reported in previous measurements on the as-fabricated devices, like the offset of zero-bias current and others. To date, the limited study has been taken to explore the origin of the offset, which prevents the understanding of electrical transport through large-area molecular tunneling junctions, and hinders the development of high-performance devices. To explore the offset of zero-bias current, we built a new EGaIn automatic instrument platform, which allowed a systematic study on the electrical behavior of SAMs of n-alkanethiolate (n = 14, 16, 18). The measurements showed that the ambient water affected charge transport through as-fabricated molecular junctions. With the presence of water, a primary cell was established at the interface between SAMs and EGaIn/GaOx, which generated an internal potential and caused the offset of zero-bias current when the geometry contact area of the molecular junction is smaller than 600 μm2.