High Conductance Ratio in Molecular Optical Switching of Functionalized Nanoparticle Self-Assembled Nanodevices

TL;DR

This study demonstrates a light-controlled molecular switch in nanoparticle networks with a record high conductance ratio, combining experimental fabrication and molecular dynamics simulations to understand the switching mechanism.

Contribution

It introduces a novel light-switchable nanoparticle device with high conductance ratios and provides microscopic insights through molecular dynamics simulations.

Findings

Achieved up to 620 on/off conductance ratio in light-induced switching.

Reversible switching between cis and trans molecular conformations.

Correlated molecular conformation changes with conductance variations.

Abstract

Self-assembled functionalized nano particles are at the focus of a number of potential applications, in particular for molecular scale electronics devices. Here we perform experiments of self-assembly of 10 nm Au nano particles (NPs), functionalized by a dense layer of azobenzene-bithiophene (AzBT) molecules, with the aim of building a light-switchable device with memristive properties. We fabricate planar nanodevices consisting of NP self-assembled network (NPSANs) contacted by nanoelectrodes separated by interelectrode gaps ranging from 30 to 100 nm. We demonstrate the light-induced reversible switching of the electrical conductance in these AzBT NPSANs with a record on/off conductance ratio up to 620, an average value of ca. 30 and with 85% of the devices having a ratio above 10. Molecular dynamics simulation of the structure and dynamics of the interface between molecular monolayers chemisorbed on the nano particle surface are performed and compared to the experimental findings. The properties of the contact interface are shown to be strongly correlated to the molecular conformation which in the case of AzBT molecules, can reversibly switched between a cis and a trans form by means of light irradiations of well-defined wavelength. Molecular dynamics simulations provide a microscopic explanation for the experimental observation of the reduction of the on/off current ratio between the two isomers, compared to experiments performed on flat self-assembled monolayers contacted by a conducting cAFM tip.