Towards molecular electronics with large-area molecular junctions

Abstract

Electronic transport through single molecules has been studied extensively by academic and industrial research groups. Discrete tunnel junctions, or molecular diodes, have been reported using scanning probes, break junctions, metallic crossbars and nanopores. For technological applications, molecular tunnel junctions must be reliable, stable and reproducible. The conductance per molecule, however, typically varies by many orders of magnitude. Self-assembled monolayers (SAMs) may offer a promising route to the fabrication of reliable devices, and charge transport through SAMs of alkanethiols within nanopores is well understood, with non-resonant tunnelling dominating the transport mechanism. Unfortunately, electrical shorts in SAMs are often formed upon vapour deposition of the top electrode, which limits the diameter of the nanopore diodes to about 45 nm. Here we demonstrate a method to manufacture molecular junctions with diameters up to 100 microm with high yields (> 95 per cent). The junctions show excellent stability and reproducibility, and the conductance per unit area is similar to that obtained for benchmark nanopore diodes. Our technique involves processing the molecular junctions in the holes of a lithographically patterned photoresist, and then inserting a conducting polymer interlayer between the SAM and the metal top electrode. This simple approach is potentially low-cost and could pave the way for practical molecular electronics.

Molecules on Si: Electronics with Chemistry

“…Reported temperature dependence of transport varies from none [55,172,174,175] to positive (i.e., thermal activation). [34,55,96] In MIM junctions, a pseudo-metallic temperature response is generally attributed to conductance via metallic filaments penetrating the monolayer.…”

“…Excellent reproducibility was reported also, for alkyls on Au, with poly(3,4-ethylenedioxythiophene) poly(styrene sulfonic acid) PEDOT-PSS top contacts. [174] The stability of a given junction under repeating scan cycles is another important indicator of junction reliability. For example alkyl thiols on GaAs could be measured only once before contact oxidization led to transport deterioration.…”

In Situ Mapping of the Molecular Arrangement of Amphiphilic Dye Molecules at the TiO2 Surface of Dye-Sensitized Solar Cells

“…[1][2][3][4][5] SAM functionalization provides a powerful, yet simple way to manipulate the chemical, electrical and optical properties of surfaces, with the ability to tune the material's macroscopic properties. 6 This is the case for dye-sensitized solar cells (DSCs) where a SAM of dye molecules sensitizes a semiconductor in order to harvest light.…”

A Toolbox for Controlling the Energetics and Localization of Electronic States in Self‐Assembled Organic Monolayers

“…In many instances, a convenient way for tuning the characteristics of such interfaces is by using molecular (mono)layers. These can even adopt the role of functional elements in devices, for example, in highly efficient organic monolayer transistors1, 2 or as self‐assembled monolayer (SAM) based devices in the field of molecular electronics 3, 4, 5, 6, 7, 8, 9, 10, 11. The spatial localization and energetics of the electronic states in these layers play a crucial role, as the states serve as “channels” for the electrical current 12, 13.…”