2024-03-16 15:00:13
Leveraging light to control electronic properties, Columbia Engineering’s new single-molecule devices with direct metal-metal contacts mark a significant advance in molecular electronics, promising miniaturization and improved efficiency in electronic components. Credit: Venkatraman Lab
In a recently published study by Nature Communication, Columbia Engineering researchers announced the creation of highly tunable single-molecule devices in which the molecule is attached to leads by using direct metal-to-metal contacts. Their innovative approach uses light to control the electronic properties of the devices and opens the door to wider use of metal-metal contacts that can facilitate electron transport across a single-molecule device.
the challenge
As devices continue to shrink, their electronic components must be miniaturized. Single-molecule devices, which use organic molecules as their conductive channels, have the potential to solve the miniaturization and functionalization challenges faced by traditional ones. Semiconductors. Such devices offer the exciting possibility of external control through light, but – so far – researchers have been unable to demonstrate this.
“With this work, we have opened up a new dimension in molecular electronics, where light can be used to control how a molecule binds within the gap between two metal electrodes,” said Lata Venkataraman, a pioneer in molecular electronics and Lawrence Gassman Professor of Applied Physics and Professor of Chemistry at Columbia Engineering. “It’s like turning on a switch in nanometers, which open up all kinds of possibilities for designing smarter and more efficient electronic components.”
the approach
Venkataraman’s group has been investigating the fundamental properties of single-molecule devices for nearly two decades, exploring the interplay between physics, chemistry and engineering at the nanoscale. Its fundamental focus is on building circuits with a single molecule, a molecule connected to two electrodes, with diverse functionality, where the circuit structure is defined with atomic precision.
Her group, as well as those creating functional devices with graphene, a two-dimensional carbon-based material, knew that making good electrical connections between metal electrodes and carbon systems was a big challenge. One solution would be to use organometallic molecules and design methods to connect electrical conductors to the metal atoms within the molecule. Towards this goal, they decided to investigate the use of procaine molecules containing organometallic iron, which are also considered tiny building blocks in the world of nanotechnology. Just as Lego pieces can be stacked together to form complex structures, propane molecules can be used as building blocks to build extremely small electronic devices. The team used a molecule terminated by a ferrocene group consisting of two carbon-based cyclopentadienyl rings carrying an iron atom. They then used light to leverage the electrochemical properties of the ferrocene-based molecules to make a direct connection between the depleted iron center and the gold (Au) electrode when the molecule was in an oxidized state (that is, when the iron atom lost one electron). In this state, they discovered that the ferrocine can bind to the gold electrodes used to connect the molecule to the external circuits. Technically, the ferrocene oxidation enabled the binding of Au0 to the Fe3+ center.
“By harnessing light-induced oxidation, we have found a way to manipulate these tiny building blocks at room temperature, opening doors to a future where light can be used to control the behavior of electronic devices at the molecular level,” said the head of the study. Author Woojung Lee, who is a Ph.D. student in Venkararaman’s lab.
possible effect
Venkataraman’s new approach will allow her team to expand the types of molecular termination (contact) chemistry they can use to create single-molecule devices. This study also shows the ability to turn this contact on and off by using light to change the oxidation state of ferrocene, demonstrating a single-molecule device based on light-switchable ferrocene. The light-controlled devices can pave the way for the development of sensors and switches that respond to specific light wavelengths, offering more diverse and efficient components for a wide range of technologies.
the group
This work was a collaborative effort involving synthesis, measurements and calculations. The synthesis was done primarily at Columbia by Michael Inkpen, who was a postdoctoral fellow in Venkataraman’s group and is now an assistant professor at the University of Southern California. All measurements were made by Woojung Lee, a graduate student in Venkataraman’s group. The calculations were performed both by graduate students in the Venkataraman group and by collaborators from the University of Regensburg in Germany.
What next
The researchers are now exploring the practical applications of single-molecule devices controlled by light. This can include optimizing device performance, studying their behavior in different environmental conditions, and perfecting additional functions that enable a metal-to-metal interface.
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