Aus unis achieve perfect single-atom transistor

Seeking to keep Moore's Law on pace, researchers have developed a repeatable technique for assembling a single-atom version of the transistor — the building block of semiconductors and computers.

Single-atom transistor

Researchers were able to make a single-atom transistor with a scanning tunnelling microscope that includes the single red phosphorous atom and electrical leads for control gates and electrodes.
(Credit: UNSW)

Researchers are getting down to the atomic level in the pursuit of smaller and more powerful computers.

The University of New South Wales in Australia has announced it has made a single-atom transistor using a repeatable method, a development that could lead to computing devices that use these tiny building blocks.

About two years ago, a team of researchers from the Helsinki University of Technology, the University of New South Wales (UNSW) and the University of Melbourne in Australia announced the creation of a single-atom transistor designed around a single phosphorus atom in silicon.

Now a new paper published in the journal Nature Nanotechnology describes a technique for making this type of transistor with very precise control. That opens up the possibility that the method can be automated and single-atom transistors could be manufactured, according to the group at the UNSW.

"The thing that's unique about the work that we've done is that we have, with atomic precision, positioned this single atom within our device," said Martin Fuechsle from the lab. That level of control is important in order to fabricate the other components, including control gates and electrodes, needed for a working transistor, the building block of microprocessors and computers.

The lab members used a scanning tunnelling microscope to manipulate atoms at the surface of a silicon crystal. Then with a lithographic process, they laid phosphorous atoms onto the silicon substrate.

"Our group has proved that it is really possible to position one phosphorus atom in a silicon environment — exactly as we need it — with near-atomic precision, and at the same time register gates," Fuechsle said in a statement.

Group leader Professor Michelle Simmons from the UNSW said that until now single-atom transistors had been realised only by chance.

"But this device is perfect," she said in a statement.

"This is the first time anyone has shown control of a single atom in a substrate with this level of precise accuracy."

Work on alternatives to traditional microprocessor designs has been going on for years to maintain the pace of Moore's Law, which predicts that the number of transistors on a semiconductor doubles every 18 months. Intel last year announced it would start using three-dimensional transistors for its 22-nanometre process, a move designed to avoid the leakage of current that occurs at this very small scale. Other groups have pursued carbon nanotubes or graphene rather than silicon in the pursuit of miniaturisation.

The UNSW team hopes that its method of manipulating at the atomic scale can form the basis for quantum computers, machines that use the effects of quantum mechanics, specifically the spin of electrons around an atom, to represent digital information.

"This individual position (of a phosphorus atom in silicon) is really important ... because it turns out that if you want to have precise control at this level, you need to position individual atoms with atomic precision with respect to control gates and electrodes," Fuechsle said.

AAP contributed to this article.


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