Scientists Manipulate Atoms in Real Time

The paper describing the research was published Friday as the cover story in the journal Science.

To observe the behavior of individual copper and iron atoms billionths of a meter in size, the scientists had to use a “scanning tunneling microscope,” a device invented by IBM researchers in 1981.

It isn’t your typical microscope.

IBM Postdoctoral Researcher Sebastian Loth next to the scanning tunneling microscope. (Credit: IBM Almaden-Research Center)

“The cool thing about the scanning tunneling microscope is that you can not only see these atoms, you can move them around,” said Sebastian Loth, a postdoctoral researcher at the IBM Almaden-Research Center, and the lead author of the paper.

The device uses a metallic-pointed tip mounted on a robotic arm to move with atomic-scale precision next to iron and copper atoms. Iron was chosen because it’s magnetically active, even at the scale of individual atoms. While the individual copper atoms aren’t magnetically active, they influence the duration the iron atoms stay magnetically active when they’re placed next to them.

Loth and his four other team members sent a current from the tip of the microscope to the iron atoms, which are like tiny bar magnets. The current causes the iron atom to become polarized, or to change its magnetic orientation, so instead of pointing north, it points south.

This is the information, or data, that the scientists observed and measured on the order of nanoseconds, or billionths of a second. The difference between one nanosecond and one second is equal to the difference between one second and 30 years.

It’s similar to the way a computer reads the bits of data stored on a computer chip. But here, instead of the typical sequence of ones and zeroes to indicate information, the scientists looked at magnetic information -- the direction the iron atom pointed in and for how long it kept its magnetic orientation.

The scientists experimented with the number and placement of iron atoms next to copper atoms to find the right configuration that would yield the longest time frame an iron atom would hold its magnetic position.

“The particular structure that we studied is this combination of one iron and one copper atom right next to it, snuggling it. With this configuration, the iron atom it holds the magnetic information for 200 nanoseconds”, said Loth.

Closeup view of the IBM scanning tunneling microscope. (Credit: IBM Almaden-Research Center)

At the moment, the research team is exploring other configurations of iron and copper atoms to increase this length of time, which although extremely brief, is still long enough for meaningful activity to take place in today’s computers. For example, a laptop with a fast processor refreshes data constantly, every nanosecond. So in 200 nanoseconds, the computer has already performed a few hundred operations while its user is typing a document, surfing the web or checking email.

Today’s hard drives, as compact as they are, still require about 10,000 atoms to store one bit of data. Each bit is a magnet pointing up or down, referring to a one or a zero, which a sensor on the hard drive reads when it retrieves data. Since the IBM researchers showed that magnetic information can be stored and read out on just one iron atom, the real estate needed to store data could shrink enormously.

“If you could do atomic-scale data storage in a real device, you would have another 40 years in the development of Moore’s Law”, said Andreas Heinrich, a co-author of the paper and the research team leader.

Moore’s Law, coined in 1965 by Intel co-founder Gordon Moore, states that the number of transistors on a computer chip doubles every 18 months, allowing for an exponential increase in computing power and storage. At a certain point, which is fast approaching, the physical limitation of engineering such small silicon transistors will prevent this exponential progress in computer chip technology.

Nanotechnology, the science of manipulating particles billionths of a meter in size, is widely seen as the answer to leapfrog over the limitations of traditional silicon chip manufacturing.

“We want to get away from transistors, to come up with new schemes on single atoms that allow you to do computation and data storage differently, more efficiently with less power”, said Heinrich.

A key challenge the IBM scientists had to overcome was to somehow visualize the individual atoms’ magnetic behavior in real time, on the order of a few nanoseconds. The computer attached to their microscope generated a map of the location of the atoms but it was missing the crucial time component.

“We see these images of the atoms and they all look static,” said Loth. “The reason for that is that the scanning tunneling microscope is a slow technique. It takes minutes to get one of these images.”

But thanks to inspiration from a Sci-Fi blockbuster, the researchers were able to actually capture movies that show the evolution of magnetically active individual iron atoms, a million times faster than was previously possible.

“This was a true feat of five people sticking their heads together for days on end. We were all in the lab talking about this and I was thinking of these cool bullet shots from The Matrix, when the villain shoots at the good guy and you see the bullets stop in the air,” Loth said. “This is what we wanted to do. We wanted to freeze the motion so that we can inspect it and the way The Matrix movie guys did it, they just took a bunch of still pictures. So we took a bunch of still pictures too.”

Think of it as time-lapse photography, shot at the nano-scale. But since neither the microscope nor its attached computer have lenses, the “pictures” they generated were individual points of action, recorded every few nanoseconds, while manipulating the iron atoms.

The research team connected to their microscope a machine, a pulse pattern generator, to deliver extremely fast pulses of electricity from the metallic tip of the microscope to the iron atoms. After an iron atom was given a tiny electric current to initially polarize it and change its magnetic orientation from north to south, for example, a second, smaller current was then given to measure how strongly the atom held its magnetic orientation.

The process was repeated over and over again, generating individual frames of action every 2 or 3 nanoseconds to capture in real time the magnetic behavior of the iron atom.

“You have a defined delay between the initiating pulse and the reading pulse and this is what sets our time,” said Loth. “Instead of having to watch really closely and hope you catch this information in time, you predefine it by these pulses.”

The frames were then sequentially played back as a movie, with the various data the computer was collecting to refer to the location of the atom and its magnetic orientation, for example, converted into a map showing the dynamic activity of the iron atom over time. The six movies the team has generated today are about a minute long but they show action that was recorded over the space of one millionth of a second.

3D map illustration of iron atoms, with the strength of their magnetic polarization represented as yellow bars. (Credit: IBM Almaden-Research Center)

“Science is often close to an art. And one aspect of this is how you visualize your data in a way that looks most efficient and cool,” said Heinrich.

The ability to capture atomic activity in real time represents a major milestone.

“This is our effort to speed up nanoscience and put high-speed time into the nanoscience,” said Heinrich. “People were able to study nano-sized objects since the invention of the scanning tunneling microscope, and people were able to study fast phenomena using lasers, but they weren’t able to combine these two worlds.”

“This work is beautiful,” said Kathryn Moler, a professor of applied physics at Stanford University. “For information technology, it could mean a new generation of devices with better storage capabilities and lower power consumption,” she added.

The IBM researchers said they are confident that their breakthrough will spur innovation in other fields as well.

Heinrich said the microscope set-up could be “tuned to a different channel of information.” So instead of looking at the magnetic characteristics of an atom, scientists working on solar cells could track at the level of nanoseconds when a photon of light is converted into energy. Such work could yield better-designed solar cells that are more efficient at capturing light and converting it into electricity.

“As a scientist, sometimes you make a development or discovery that is truly great and this was one of those moments when I knew this was a great development and something to be really proud of,” he added.

Movie of iron atoms placed alongside copper atoms as they change their magnetic polarization over time. Red indicates high polarization and white indicates low polarization.(Credit: IBM Almaden-Research Center)