When IBM researcher Don Eigler picked up and moved the first individual atom 20 years ago today, he paved the way for what arguably was the smallest publicity stunt ever: IBM’s logo made from a precise arrangement of 35 Xenon atoms.
But moving tiny atoms had big consequences by making the idea of assembling devices atom by atom very real. And the company has built on that nanotechnology foundation, storing information on specific gold atoms, collecting carbon monoxide molecules into computer logic circuits, and pursuing a vision for vastly more compact computing technology.
Despite the progress, Eigler is cautious about when or even if his ideas for computing will bear fruit.
“We did the introduction, and we’re in chapter 1,” Eigler said. “This is way off in the future, if it ever comes about. I cannot conceive, under the best circumstances, this is going to happen in 10 or 15 years.”
Don Eigler moved the first individual atom 20 years ago, and shortly afterwards wrote ‘IBM’ with 35 Xenon atoms
Eigler, now an IBM fellow, said he was “boggled” that day he moved his first atom with an IBM device called a scanning tunnelling microscope. He programmed the system to make the move, then held his breath while his screen went blank during the actual operation.
“You can’t see it while you actually move it. Then you see the picture come in and say, ‘Yes, it’s there’,” Eigler said. He moved the atom back and forth three times to make sure it really worked: “For us, that’s [a] sort of sacred thing. The key thing and most important thing about science is reproducibility. If you can’t reproduce your own result, you might as well forget it. It’s as if you’d never done it.”
Shortly after that, in November 1989, Eigler arranged the 35 atoms to spell IBM. There was, of course, publicity in it for the company, but Eigler had no complaints. For one thing, it demonstrated that IBM really could control atoms with atomic-scale precision and that its work was not just a fluke. For another, Eigler was grateful that IBM let him pursue his work.
“It was more than a publicity stunt. Emotionally, for me, it was much more important. This is going to sound hokey, but it’s the truth. IBM picked me up off the scrap heap of science and gave me every opportunity a scientist could hope for to be successful,” Eigler said. “As far as I was concerned, it was payback time.”
No mass manufacturing
Eigler and colleagues have been working on the technology since but, so far, the benefits have been indirect. That is because moving and studying atoms with a scanning tunnelling microscope and its offshoot, the atomic-force microscope, is a far cry from assembling computing devices that operate at much larger scales.
“Being able to put atoms together with atomic-scale precision at a level that allows you to deliver a marketable product is something that is largely hope and vision for our future,” Eigler said. “We are not there yet.”
There are other directions of nanotechnology research: Eigler gave graphene and topological insulators as possibilities. Eigler, however, remains excited to pursue his own long-term vision for computers that process information without today’s reliance on the movement of electrons.
Specifically, he is interested in using the quantum mechanical property called spin for computing. The conventional conception for this general idea, called spintronics, uses spin to control the flow of electric current, but Eigler wants to use spin alone.
“My goal is to do everything we need to do for computation — logic, storage, information transport — but without moving electrons around at all,” Eigler said.
One advantage of the approach is that it avoids electrical current that produces the waste heat that is a major limiting factor in today’s computers. Another is that it can enable three-dimensional computing designs much more densely packed with processing power than today’s two-dimensional circuitry etched onto silicon wafers.
Spin engineering
The spin of one atom can affect that of its neighbour. The hard part is arranging atoms in order to harness that effect and perform useful computing operations.
“We have to learn how to engineer things so they work the way we want them to work. If you have two atoms, each has spin, and those spins are coupled together in usually two, three, or even four different ways,” he said. “You have to place them in the appropriate relationship with one another.”
One milestone towards this goal was work by Gerhard Meyer of IBM’s Zurich Research Laboratory and others to store data in the form of electrical charges on individual atoms of gold, Eigler said.
In another, IBM’s Christopher Lutz found he could trigger a ‘molecule cascade’, in which a series of carbon monoxide molecules could transmit information. The metastable molecules could store energy, then release it from one neighbour to another, similar to a chain of balanced dominoes falling.
Lutz then found a way to arrange those molecules into basic logical processing units of computers, ‘and gates’ and ‘or gates’, which are foundations of today’s computers. It did not use spin, but it is a step in that direction, Eigler said.
Building blocks
One possible intermediate step between moving single atoms and mass manufacturing is what Eigler calls nano plug-ins.
If physicists and engineers could figure out how to construct individual logic gates out of a complicated molecule, IBM chemists might be able to work out a way to synthesise such units in quantity. Next would come the assembly process of snapping these units together appropriately.
“That strategy for building things that work on a very small scale may well be what we see in the future,” Eigler said.
And it may arrive, even if his spin-based computation does not. “It may be [used with] regular conventional electronics, [or] with carbon nanotubes or graphene,” he said. This brings him to the point about why IBM Research invests in such distantly useful technologies.
“The knowledge we’re generating in the process of getting there,” Eigler said, “is likely to feed into the industry much sooner than the actual outcome — if we ever get to that outcome”.
Ciprian Muntean 