Thinking Small

By Barry Pangrle
“But I am not afraid to consider the final question as to whether, ultimately—in the great future—we can arrange the atoms the way we want; the very atoms, all the way down! What would happen if we could arrange the atoms one by one the way we want them (within reason, of course; you can’t put them so that they are chemically unstable, for example). — Richard Feynman, Dec. 29, 1959

Nobel Laureate Richard Feynman was certainly well ahead of his time with his vision into the great future. Researchers continue to push devices smaller. In 2010 a team of researchers at the University of New South Wales, Australia and the University of Wisconsin published their work on what was at the time the smallest transistor ever built, with only 7 atoms.

Figure 1. 7-Atom “Quantum Dot” Transistor (Source: UNSW)

In an article published on the UNSW Web site, co-author Professor Michelle Simmons, director of the CQCT, an Australian Research Council Centre of Excellence says, “The significance of this achievement is that we are not just moving atoms around or looking at them through a microscope. We are manipulating individual atoms and placing them with atomic precision, in order to make a working electronic device.” Sounds very similar to Richard Feynman’s description, doesn’t it?

Michelle Simmons’ team at UNSW isn’t resting on its laurels and is continuing to forge ahead. Earlier this year her team published work on a Single-atom Transistor in Nature Nanotechnology in collaboration with a team of researchers at Purdue University.

Figure 2. Single Atom Transistor Donor Potential within the Device Architecture (Source: Purdue University)

“To me, this is the physical limit of Moore’s Law,” says Gerhard Klimeck, who directed the Purdue team that ran the simulations. “We can’t make it smaller than this.”

On the upside, the devices are still being built on largely silicon structures, even though the “single-atom” is phosphorus. On the downside? It currently needs to be at liquid nitrogen temperatures (minus 196 degrees Celsius) to operate properly. However, it does provide a first look at how such a device could operate.

Of course, smaller devices promise higher levels of integration and better energy efficiency, providing manufacturers can find ways to economically bring these devices to market one day. To stay on the path of Moore’s law, the single-atom transistor shouldn’t be needed until post 2020, so researchers still have some time to find ways to make these devices economical.

There’s a nice USNW video that presents some of the concepts behind their single-atom device that interested readers should take a look at, and you can also find a copy of Richard Feynman’s talk here.

Best wishes for a happy, healthy and prosperous 2013.

—Barry Pangrle is a senior power methodology engineer at Nvidia.