Switching of a single-atom channel

An Oct. 28, 2016 news item on phys.org announces a single-atom switch,

Robert Wolkow is no stranger to mastering the ultra-small and the ultra-fast. A pioneer in atomic-scale science with a Guinness World Record to boot (for a needle with a single atom at the point), Wolkow’s team, together with collaborators at the Max Plank Institute in Hamburg, have just released findings that detail how to create atomic switches for electricity, many times smaller than what is currently used.

What does it all mean? With applications for practical systems like silicon semi-conductor electronics, it means smaller, more efficient, more energy-conserving computers, as just one example of the technology revolution that is unfolding right before our very eyes (if you can squint that hard).

“This is the first time anyone’s seen a switching of a single-atom channel,” explains Wolkow, a physics professor at the University of Alberta and the Principal Research Officer at Canada’s National Institute for Nanotechnology. “You’ve heard of a transistor—a switch for electricity—well, our switches are almost a hundred times smaller than the smallest on the market today.”

An Oct. 28, 2016 University of Alberta news release by Jennifer Pascoe, which originated the news item, describes the research in more detail,

Today’s tiniest transistors operate at the 14 nanometer level, which still represents thousands of atoms. Wolkow’s and his team at the University of Alberta, NINT, and his spinoff QSi, have worked the technology down to just a few atoms. Since computers are simply a composition of many on/off switches, the findings point the way not only to ultra-efficient general purpose computing but also to a new path to quantum computing.

Green technology for the digital economy

“We’re using this technology to make ultra-green, energy-conserving general purpose computers but also to further the development of quantum computers. We are building the most energy conserving electronics ever, consuming about a thousand times less power than today’s electronics.”

While the new tech is small, the potential societal, economic, and environmental impact of Wolkow’s discovery is very large. Today, our electronics consume several percent of the world’s electricity.  As the size of the energy footprint of the digital economy increases, material and energy conservation is becoming increasingly important.

Wolkow says there are surprising benefits to being smaller, both for normal computers, and, for quantum computers too. “Quantum systems are characterized by their delicate hold on information. They’re ever so easily perturbed. Interestingly though, the smaller the system gets, the fewer upsets.” Therefore, Wolkow explains, you can create a system that is simultaneously amazingly small, using less material and churning through less energy, while holding onto information just right.

Smaller systems equal smaller environmental footprint

When the new technology is fully developed, it will lead to not only a smaller energy footprint but also more affordable systems for consumers. “It’s kind of amazing when everything comes together,” says Wolkow.

Wolkow is one of the few people in the world talking about atom-scale manufacturing and believes we are witnessing the beginning of the revolution to come. He and his team have been working with large-scale industry leader Lockheed Martin as the entry point to the market.

“It’s something you don’t even hear about yet, but atom-scale manufacturing is going to be world-changing. People think it’s not quite doable but, but we’re already making things out of atoms routinely. We aren’t doing it just because. We are doing it because the things we can make have ever more desirable properties. They’re not just smaller. They’re different and better. This is just the beginning of what will be at least a century of developments in atom-scale manufacturing, and it will be transformational.”

Bill Mah in a Nov. 1, 2016 article for the Edmonton Journal delves a little further into issues around making transistors smaller and the implications of a single-atom switch,

Current computers use transistors, which are essentially valves for flowing streams of electrons around a circuit. In recent years, engineers have found ways to make these devices smaller, but pushing electrons through narrow spaces raises the danger of the machines overheating and failing.

“The transistors get too hot so you have to run them slower and more gently, so we’re getting more power in modern computers because there are more transistors, but we can’t run them very quickly because they make a lot of heat and they actually just shut down and fail.”

The smallest transistors are currently about 14 nanometres. A nanometre is one-billionth of a metre and contains groupings of 1,000 or more atoms. The switches detailed by Wolkow and his colleagues will shrink them down to just a few atoms.

Potential benefits from the advance could lead to much more energy-efficient and smaller computers, an increasingly important consideration as the power consumption of digital devices keeps growing.

“The world is using about three per cent of our energy today on digital communications and computers,” Wolkow said. “Various reports I’ve seen say that it could easily go up to 10 or 15 per cent in a couple of decades, so it’s crucial that we get that under control.”

Wolkow’s team has received funding from companies such as Lockheed Martin and local investors.

The advances could also open a path to quantum computing. “It turns out these same building blocks … enable a quantum computer, so we’re kind of feverishly working on that at the same time.”

There is an animation illustrating a single-atom switch,

This animation represents an electrical current being switched on and off. Remarkably, the current is confined to a channel that is just one atom wide. Also, the switch is made of just one atom. When the atom in the centre feels an electric field tugging at it, it loses its electron. Once that electron is lost, the many electrons in the body of the silicon (to the left) have a clear passage to flow through. When the electric field is removed, an electron gets trapped in the central atom, switching the current off.  Courtesy: University of Alberta

Here’s a link to and a citation for the research paper,

Time-resolved single dopant charge dynamics in silicon by Mohammad Rashidi, Jacob A. J. Burgess, Marco Taucer, Roshan Achal, Jason L. Pitters, Sebastian Loth, & Robert A. Wolkow. Nature Communications 7, Article number: 13258 (2016)  doi:10.1038/ncomms13258 Published online: 26 October 2016

This paper is open access.

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