Nearly 62 years after researchers at Bell Labs demonstrated the first functional transistor, scientists say they have made another major breakthrough.

Researchers showed the first functional transistor made from a single molecule. The transistor, which has a benzene molecule attached to gold contacts, could behave just like a silicon transistor.

The molecule's different energy states can be manipulated by varying the voltage applied to it through the contacts. And by manipulating the energy states, researchers were able to control the current passing through it.

The transistor, or semiconductor device that can amplify or switch electrical signals, was first developed to replace vacuum tubes. On Dec. 23, 1947, John Bardeen and Walter Brattain (who'd built on research by colleague William Shockley) showed a working transistor that was the culmination of more than a decade's worth of effort.

Vacuum tubes were bulky and unreliable, and they consumed too much power. Silicon transistors addressed those problems and ushered in an era of compact, portable electronics.

Now molecular transistors could escalate the next step of developing nanomachines that would take just a few atoms to perform complex calculations, enabling massive parallel computers to be built.

The team, which includes researchers from Yale University and the Gwangju Institute of Science and Technology in South Korea, published their findings in the Dec. 24 issue of the journal Nature.

For about two decades – since Mark Reed, a professor of engineering and applied science at Yale, showed that individual molecules could be trapped between electrical contacts – researchers have been trying to create a functional molecular transistor.

Some of the challenges they have faced include being able to fabricate the electrical contacts on such small scales, identifying the molecules to use, and figuring out where to place them and how to connect them to the contacts.

"There were a lot of technological advances and understanding we built up over many years to make this happen," says Reed.

Despite the significance of the latest breakthrough, practical applications such as smaller and faster molecular computers could be decades away, says Reed.

"We're not about to create the next generation of integrated circuits," he says. "But after many years of work gearing up to this, we have fulfilled a decade-long quest and shown that molecules can act as transistors."

Photo: A benzene molecule can be manipulated to act as a traditional transistor

Courtesy: Hyunwook Song and Takhee Lee

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