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US scientists develop single molecule diode, revolutionise nanoscale technology

An illustration of the molecule used by Columbia Engineering professor Latha Venkataraman to create the first single-molecule diode with a non-trivial rectification ratio overlaid on the raw current versus voltage data. Diodes are fundamental building blocks of integrated circuits; they allow current to flow in only one direction. (Photo Credit: Latha Venkataraman, Columbia Engineering)

An illustration of the molecule used by Columbia Engineering professor Latha Venkataraman to create the first single-molecule diode with a non-trivial rectification ratio.  (Photo Credit: Latha Venkataraman, Columbia Engineering)

Scientists have managed to develop a working diode made of a single molecule, first of its kind that will revolutionise the way nanoscale tech world functions.

Latha Venkataraman, associate professor of applied physics at the University of Columbia, Berkeley, says the device is 50 times better than any known nano device. “Our new device represents the ultimate in functional miniaturisation that can be achieved for an electronic device,” she said.

The decades-old idea of a single molecule device was coined by Arieh Aviram and Mark Ratner in 1974 to make it a rectifier or a device that converts AC current into DC current. The researchers were able to achieve the breaktrhough using concepts from chemistry and physics.

Upbeat with the success, she said her team would now focus on understanding the fundamental physics behind the device so that they can improve the rectification ratios of the device.

The molecular diode can create a current of 0.1 microamps or the amount of current that passes through a single molecule.

Latha Venkataraman

Their paper, “Single-Molecule Diodes with High On-Off Ratios through Environmental Control,” is published in Nature Nanotechnology.

Since a diode acts as an electricity valve, its structure needs to be asymmetric so that electricity flowing in one direction is different from the other but for a single-molecule diode, researchers have simply designed molecules that have asymmetric structures.

“While such asymmetric molecules do indeed display some diode-like properties, they are not effective,” explains Brian Capozzi, a PhD student with Venkataraman and lead author of the paper said.

They collaborated with Luis Campos’ group at Columbia and Jeffrey Neaton’s group at the Molecular Foundry at UC Berkeley to develop an asymmetry in the environment around the molecular junction.

With their results achieving rectification ratios as high as 250: 50 times higher than the previously known designs, and Latha Venkataraman says the new technique can be applied to all nanoscale devices, including those made with graphene electrodes.

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