Turning around a molecular diode.
WORK RECENTLY PUBLISHED IN NATURE COMMUNICATIONS
In a collaboration project led by Prof. Christian Nijhuis (Graphene Research Centre/National University of Singapore), we have investigated the electrical conductance of tunnel junctions formed by self-assembled monolayers (SAM) of molecules that act as current diodes.
A challenge in molecular electronics is to control the strength of the molecule-electrode coupling to optimise device performance. In this work we show that non-covalent contacts between the active molecular component (in this case, ferrocenyl of a ferrocenyl-alkanethiol SAM and the electrodes allow for robust non-covalent coupling with low energy broadening of the molecular level, precisely what is required to maximise performance of a molecular diode. In contrast, strong chemisorbed contacts through the ferrocenyl result in large energy broadening, leakage currents, and poor device performance. By gradually shifting the ferrocenyl from the top to the bottom of the SAM, we were able to turn around a molecular diode by controlling the ferrocenyl-electrode coupling parameters and to estimate the shape of the electrostatic potential profile across the molecules. Our demonstrated control of the molecule-electrode coupling is important for the rational design of materials that rely on charge transport across organic-inorganic interfaces
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