Dynamics of Redox Events in Molecular Junctions

Rani Arielly, Chemistry, Tel Aviv University, Tel Aviv, Israel

Redox molecular junctions are promising systems for nanoelectronics applications and yet they are still only marginally understood. The study of these systems has so far been conducted in solution, utilizing "electrolyte gating" to control their redox states, and as a result their steady state transistor-like conductance behavior. Here we explore the redox process of Au-6-(Ferrocenyl) hexanethiol (FHT)-Au type junctions at two distinctive time-scales of miliseconds and picoseconds governed by the change of temperature from 78K to 300K. At miliseconds time scales, redox events are revealed as a two-levels fluctuating (TLF) signal in current-time traces with potential-dependent amplitude and frequency. Using a theoretical model for signals with a telegraph-like noise, the current-time traces are analyzed to extract the various molecular parameters which define the dynamics of the system. At picoseconds time scales, redox events are spotted using femtoseconds pump-probe based Plasmonic excitations to the metallic leads. The delay time dependent signal is analyzed using a model for electronic tunneling in and out of the double energy barrier like monolayer whose parameters coincides with the TLF model parameters. The presented method, which can be applied to other types of redox molecules, offers a new approach to study the unexplored territory of molecular dynamics in molecular junctions.