Abstract
Understanding the electronic transport mechanisms in molecular junctions is of paramount importance to design molecular devices and circuits. In particular, the role of the different junction components contributing to the current decay—namely the attenuation factor—is yet to be clarified. In this short review, we discuss the main theoretical approaches to tackle this question in the non-resonant tunneling regime. We illustrate our purpose through standard symmetric junctions and through recent studies on hybrid molecular junctions using graphene electrodes. In each case, we highlight the contribution from the anchoring groups, the molecular backbone and the electrodes, respectively. In this respect, we consider different anchoring groups and asymmetric junctions. In light of these results, we discuss some perspectives to describe accurately the attenuation factors in molecular electronics.
Highlights
One of the main goals of molecular electronics is to mimic standard electronic circuits using molecules instead of p-n junctions like components based on silicon [1]
Levelwhich and, are in currently particular,used the in determination of the attenuation factor important may be aspect that can be stressed is that, below nm, it seems that there is no significant difference in the extrapolated to large molecular areas, which are currently used in molecular electronics devices
We have considered hybrid Au–graphene electrodes for two different anchoring groups in alkane-based molecular junctions and we have observed an important reduction in the attenuation factor
Summary
One of the main goals of molecular electronics is to mimic standard electronic circuits using molecules instead of p-n junctions like components based on silicon [1]. For smaller molecular chains, (i.e., below 5 nm) [7], the regime is not activated anymore and corresponds to the direct tunneling of the electrons through the molecular junction, provided that the applied voltage is lower than the characteristic electronic barrier of the system In this case, there is no temperature dependence, and it is a reasonable approximation to say that the current varies linearly with the voltage at low bias. A fundamental problem in electronic transport in molecules lies in the length dependence of the conductance in the molecular junction This dependence is reflected in the so-called attenuation factor, which is representative of the electronic current propagation in the molecular junction. I will summarize and draw some conclusions in the last section
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