Revealing the correlation relation between conducting channels in self-assembled monolayer tunnel junctions

Abstract

Molecular tunnel junctions, with single molecules or molecular monolayers as the functional electronic components, have been working as an ideal platform to investigate charge transport across nanometer-scale distance. Compared with the single molecule case, molecular monolayer tunnel junctions involve a bunch of molecules for charge transport and thus have multiple conducting channels. As all conducting channels are involved in the measured electrical characteristics, it is extremely difficult to reveal the behaviour of individual conducting channels in molecular monolayer tunnel junctions. Here, by monitoring tunnelling induced light emission, we have revealed the correlation relation among multiple conducting channels in molecular monolayer tunnel junctions. The light emission from individual conducting channels (or emission spots) shows two distinct correlation behaviours: positive correlation and negative correlation. Such a correlation relation is quite universal and does not depend on the bias voltage or the emission spot number. Based on a resistor circuit model, the positive and negative correlations are well understood by the dynamic changes of interface contact and molecular conformations, respectively. Our findings provide new possibilities to identify and manipulate the contribution of individual conducting channels in molecular monolayer tunnel junctions.