Abstract
Controlling charge transport through molecular tunnel junctions is of crucial importance for exploring basic physical and chemical mechanisms at the molecular level and realizing the applications of molecular devices. Here, through a combined experimental and theoretical investigation, we demonstrate redox control of cross-plane charge transport in a vertical gold/self-assembled monolayer (SAM)/graphene tunnel junction composed of a ferrocene-based SAM. When an oxidant/reductant or electrochemical control is applied to the outside surface of the neutral single-layer graphene top electrode, reversible redox reactions of ferrocene groups take place with charges crossing the graphene layer. This leads to counter anions on the outer surface of graphene, which balance the charges of ferrocene cations in the oxidized state. Correspondingly, the junctions switch between a high-conductance, neutral state with asymmetrical characteristics and a low-conductance, oxidized state with symmetrical characteristics, yielding a large on/off ratio (>100).
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•A vertical tunneling switch consisting of self-assembled monolayers•Space-separated chemical/electrochemical redox reactions across graphene•Reversible redox reactions in self-assembled monolayers switch the conductance•Interface optimizes the on-off ratio of redox-switchable molecular monolayer
Molecular tunneling devices are of considerable interest for future electronics with ultra-small dimensions and tunable functionalities. The ability to tailor charge transport through molecular tunnel junctions using various chemical physical and chemical mechanisms is essential for realizing functional systems. Here, we report a novel route for redox control of cross-plane charge transport in a vertical gold/self-assembled monolayer (SAM)/single-layer graphene (SLG) tunnel junction composed of a ferrocene-based SAM. With spatially separated chemical/electrochemical redox reactions across the SLG, the junction can switch between neutral and oxidized states with a large on/off conductance ratio. This redox control of charge transport opens a new path for exploring fundamental mechanisms and realizing new functionalities in molecular electronics.
Controlling charge transport through molecular-scale devices is of crucial importance. This article reports an effective route to tailor cross-plane charge transport in a vertical molecular tunneling junction through controlled chemical or electrochemical redox reaction in the self-assembled molecular monolayers buried under graphene. This redox control of the cross-plane charge transport is important for exploring fundamental mechanisms and realizing new functionalities in molecular electronics.