Control of the energy gap in a molecular junction for making a molecular rectifier*

Molecular junctions are the constitutive components of Molecular Electronics circuits. For any potential application, the energy gap in the junction, i.e., the accumulated energy difference between the electrode Fermi level and the two frontier energy levels of the molecule, is a key property. In this presentation, we show that the gap of the molecule inserted between electrodes can differ largely from the gap of the same molecule, at the isolated level. It can be widely compressed by the alignment mechanism at each metal/molecule interface.

This behavior is important to consider for characterizing and designing molecular junctions. We show that this is particularly true for a new mechanism of rectification that we recently introduced. This latter opposes resonant to non-resonant tunneling and is based on the control of the energy gap in junction. We show that both the structure of the molecule and the anchoring group drive the value of this gap, at equilibrium and under bias. In the end, this will highlight the crucial importance, and benefit, of the contact for Molecular Electronics.

[1] Van Dyck, Ratner, J. Phys. Chem. C, 2017, 10.1021/acs.jpcc.6b07855
[2] Van Dyck, Ratner, Nano Letters, 2015, 10.1021/nl504091v