Sometimes genius looks like an elegant equation written in chalk on a blackboard. Sometimes it’s a hodgepodge of wires, canisters and aluminum-foil-wrapped hoses, all held together by shiny bolts.

Despite its homebrew appearance, this device, a scanning tunneling microscope, is one of the most extraordinary lab instruments of the last three decades. It can pick up individual atoms one by one and move them around to create supersmall structures, a fundamental requirement for nanotechnology.

Twenty years ago this week, on Sept. 28, 1989, an IBM physicist, Don Eigler, became the first person to manipulate and position individual atoms. Less than two months later, he arranged 35 Xenon atoms to spell out the letters IBM. Writing those three characters took about 22 hours. Today, the process would take about 15 minutes.

“We wanted to show we could position atoms in a way that’s very similar to how a child builds with Lego blocks,” says Eigler, who works at IBM’s Almaden Research Center. “You take the blocks where you want them to go.”

Eigler’s breakthrough has big implications for computer science. For instance, researchers are looking to build smaller and smaller electronic devices. They hope, someday, to engineer these devices from the ground up, on a nanometer scale.

“The ability to manipulate atoms, build structures of our own, design and explore their functionality has changed people’s outlook in many ways,” says Eigler. “It has been identified as one of the starting moments of nanotech because of the access it gave us to atoms, even though no product has comes out of it.”

On the 20th anniversary of Eigler’s achievement, we look at the science, art and implications of moving individual atoms.



Moving Atoms

Watching researchers move atoms can be an unsettling yet wonderful experience: It’s hard to conceive that humans can manipulate things so small that they can barely be called “things.”

But the work environment is quite a bit more prosaic. Today IBM researchers working on atomic science are housed in a cramped room noticeably lacking in flat-panel displays and personal supercomputers. Instead they hunch over a PC running Pentium processors that were popular in the late 1990s. The computer controls a multimillion dollar scanning tunneling microscope and moves its tip around.

Following the fuzzy, pixelized graphics on the monitor that shows the atoms, researchers can zero in on one individual atom, pick it up and drop it in a different location. It’s an experience that has what Eigler calls the “boggle factor.”

“What hits you is the enormity of what you are doing in terms of building at an atomic scale,” says Eigler in this video. “It’s so far from what we could have conceived many years ago.”

IBM spelled by positioning 35 Xenon Atoms.

Scanning Tunneling Microscope

At the heart of the atomic experiments is the scanning tunneling microscope that can not only take pictures of individual atoms but also build new structures using those atoms. Two IBM scientists at the company’s Zurich lab, Gerd Binnig and Heinrich Rohrer, created the first tunneling microscope in 1981. Six years later, the inventors won a Nobel Prize.

Here’s how it works. The microscope has a fine tip so sharp that it is just one of two atoms at the point. The tip is brought very near to the surface of a sample. An applied voltage will cause electrons to “tunnel” between the surface and the tip. That means the electrons move beyond the surface of the solid into a short region in space above it. Meanwhile, the tip slowly scans the surface of the sample at a distance equal to the diameter of a single atom. Through the scanning process, the tip maintains the same distance and helps draw a profile of the surface. A computer-generated contour map shows the atomic detail.

When the tip is brought close enough to the sample surface, a strong attractive force is present that can pick up an electron from the surface. To deposit it in another region of the sample, a repulsive force between the tip and the atom is generated.

Eigler built a specialized version of this microscope. His STM allows samples to be prepared and studied in an ultrahigh vacuum and at the temperature of liquid helium, which is just four degrees above absolute zero, or -459 degrees Fahrenheit. The low temperature keeps atoms from flying off the copper surface within the microscope.

“Physicists have to do experiments that require design and building of entirely new instrumentation, something that never exists before,” says Eigler. “It’s part of their training.”

Eigler built the first version of the microscope in about 14 months. “The actual microscope that moves the atoms is not very much larger; it can fit into the palm of the hand,” he says. “But it seems like a big machine because of everything else that was required to maintain very low vibration, high vacuum and excellent electronics to move the atoms.”

Nobel laureates Heinrich Rohrer (left) and Gerd Binnig (right) of IBM’s Zurich Research Laboratory are shown here in 1981 with a first-generation scanning tunneling microscope.

Fun With Single Atoms

Once IBM researchers had the ability to position individual atoms, they had some fun. In 1993, they spelled the Kanji characters for the word atom using iron atoms on a copper surface.

Researchers found it to be so much fun that they started leaving messages for their fellow scientists in the lab STM notebook. Mornings would bring a new figure drawn with manipulated atoms. In one case, a scientist manipulated carbon monoxide on a platinum surface, creating a carbon monoxide man who greeted his lab mates the next morning.

In 1996, The researchers also created the world’s smallest abacus with atoms. The abacus was created out of 10 carbon atoms and was seen as a milestone in nanoscale engineering. Moving the links of the abacus wouldn’t be easy and require the scanning tunneling microscope but with enough time and patience, it could be done.

The world’s smallest abacus with atoms (left), Kanji characters for the word ‘atom’ (center) and a carbon monoxide man were some of the pictures created by moving atoms.



Atomic Force Microscope

The successor to the STM is the atomic force microscope, which researchers use to measure the force needed to move individual atoms.

The atomic force microscope has a miniature “tuning fork” that measures the interaction between the tip of the microscope and the atoms on a surface. When the tip is positioned close to an atom on the surface, the frequency of the tuning fork changes slightly. This change in frequency is analyzed to determine the force exerted on the atom, which can be used for mapping the surface and moving atoms.

Eigler says the business of moving atoms around is fun and his work never gets boring.

“I have developed an unexpected affinity for some of the most common things in the world, like rocks,” he says. “The affinity comes from realizing that’s what I am — just a bunch of atoms. It’s a difficult thing to talk about and explain, but it’s a reaction that is deep, psychological and emotional.”

The atomic force microscope has a tuning fork used to measure the force required to move an atom.

Implications for Nanotechnology

In the last few years, Eigler’s group has built on his work and constructed custom molecules using the STM. They have also constructed and operated an electrical switch whose only moving part is a single atom.

In the “If you can read this, you are too close” image, the letters are just 1 nanometer wide and 1 nanometer tall.

A measure of the impact of this work is in the number of experiments and technical papers today that use atom manipulation as one of their primary scientific tools, says Eigler.

“If you think about it, this is not a manufacturing capability but a powerful technique in the laboratory,” he says. “It lets us do those experiments that give us the knowledge that we would not get otherwise.

“What’s really exciting to watch is that with every passing week, month or year we end up with new discoveries due to our abilities to work with very small structures,” says Eigler. “It’s fair to anticipate that these will have a technological impact on people’s lives very soon.”

These words were created by laying carbon monoxide molecules on a flat copper surface.

All photos courtesy IBM