New molecular wires for single-molecule electronic devices

August 29, 2018, Tokyo Institute of Technology
The proposed wire is 'doped' with a ruthenium unit that enhances its conductance to unprecedented levels compared with previously reported similar molecular wires. Credit: Journal of the American Chemical Society

Scientists at Tokyo Institute of Technology designed a new type of molecular wire doped with organometallic ruthenium to achieve unprecedentedly higher conductance than earlier molecular wires. The origin of high conductance in these wires is fundamentally different from similar molecular devices and suggests a potential strategy for developing highly conducting "doped" molecular wires.

Since their conception, researchers have tried to shrink electronic devices to unprecedented sizes, even to the point of fabricating them from a few molecules. Molecular wires are among the building blocks of such minuscule contraptions, and many researchers have been developing strategies to synthesize highly conductive, stable wires from carefully designed molecules.

A team of researchers from Tokyo Institute of Technology, including Yuya Tanaka, designed a novel in the form of a metal electrode-molecule-metal electrode (MMM) junction including a polyyne, an organic chain-like molecule, "doped" with a ruthenium-based unit Ru(dppe)2. The proposed design, featured in the cover of the Journal of the American Chemical Society, is based on engineering the energy levels of the conducting orbitals of the atoms of the wire, considering the characteristics of gold electrodes.

Using scanning tunneling microscopy, the team confirmed that the conductance of these molecular wires was equal to or higher than those of previously reported organic molecular wires, including similar wires "doped" with iron units. Motivated by these results, the researchers then went on to investigate the origin of the proposed wire's superior conductance. They found that the observed conducting properties were fundamentally different from previously reported similar MMM junctions and were derived from orbital splitting. In other words, orbital splitting induces changes in the original electron orbitals of the atoms to define a new "hybrid" orbital facilitating electron transfer between the metal electrodes and the wire molecules. According to Tanaka, "such orbital splitting behavior has rarely been reported for any other MMM junction."

Since a narrow gap between the highest (HOMO) and lowest (LUMO) occupied molecular orbitals is a crucial factor for enhancing of molecular wires, the proposed synthesis protocol adopts a new technique to exploit this knowledge, as Tanaka adds "The present study reveals a new strategy to realize molecular wires with an extremely narrow HOMO?LUMO gap via MMM junction formation."

This explanation for the fundamentally different conducting properties of the proposed wires facilitate the strategic development of novel molecular components, which could be the building blocks of future minuscule electronic devices.

Explore further: Building molecular wires, one atom at a time

More information: Yuya Tanaka et al, "Doping" of Polyyne with an Organometallic Fragment Leads to Highly Conductive Metallapolyyne Molecular Wire, Journal of the American Chemical Society (2018). DOI: 10.1021/jacs.8b04484

Related Stories

Building molecular wires, one atom at a time

January 17, 2018

Electronic devices are getting smaller and smaller. Early computers filled entire rooms. Today you can hold one in the palm of your hand. Now the field of molecular electronics is taking miniaturization to the next level. ...

Single polymer chains as molecular wires

February 27, 2009

The research team of Leonhard Grill at Freie Universität Berlin - in collaboration with the synthetic chemistry group of Stefan Hecht from Humboldt University of Berlin and the theoretical physics group of Christian ...

Researchers discover switching function in molecular wire

October 27, 2017

The increasing miniaturisation in electronics will result in components which consist of only a few molecules, or even just one molecule. Tiny wires are required to connect these to an electrical circuit at the nano level. ...

Recommended for you

Engineers develop first method for controlling nanomotors

September 19, 2018

In a breakthrough for nanotechnology, engineers at The University of Texas at Austin have developed the first method for selecting and switching the mechanical motion of nanomotors among multiple modes with simple visible ...

How medicine literally gets under your skin

September 19, 2018

If drugs are to enter the body painlessly and efficiently, they can be administered via skin patches. Researchers at Empa and the University of Fribourg are currently developing nano-containers for therapeutic agents that ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.