Maximum Micro Tech: Three New Technologies Explained

Posted 12/08/2011 at 12:50pm | by Zack Stern and Bill O'Brien

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Graphene

A recently isolated material could advance displays, batteries, solar cells, and computers beyond silicon

The tip of your pencil contains the future of computing, touch-screen displays, solar cells, gas detection, and the strongest, lightest physical materials ever. Each scribble leaves layers of this recently isolated super-substance.

It's called graphene, and it's a one-atom-thick hexagonal-grid pattern of carbon atoms. It looks a little bit like chicken-wire—or the Settlers of Catan board—only 100 million times smaller.

In its sheet form, it's the first two-dimensional, crystalline substance that's ever been isolated. It can be rolled into tubes—carbon nanotubes—that behave as a single-dimensional material, and can even be made into a zero-dimensional ball. These multidimensional properties allow for new research and experiments down to a quantum-physics level.

We'll explain the coming graphene boom, how the material is harvested, and why this space-age material could change everything from airplanes to mobile phones.

Harvesting Explosion

The 2010 Noble Prize in Physics was awarded to Andre Geim and Konstantin Novoselov for their research isolating graphene. Prior to their discovery and 2004 paper, scientists thought graphene couldn't be stable in a single, one-atom sheet.

In what Geim calls a "Friday night experiment"—a test on a whim at the end of the day—the scientists affixed cohesive tape to a chunk of carbon. Peeling it back, they tore off clusters of more than 100 layers of graphene. But by sticking the tape back to itself, they cleaved off smaller and smaller layers of graphene.

In the end, they discovered single layers of graphene flakes by viewing the substance on top of silicon oxide. A slightly pink halo revealed the location around the virtually clear substance; about 98 percent of light passed through the layer. In subsequent experiments, other scientists reproduced their technique, setting off a boom in graphene experimentation.

Graphene can be produced in many ways in addition to this low-tech method. In 2009, scientists devised a means of growing graphene suited to larger commercial applications. Researchers heat a silicon carbide wafer to 1,300 C, at which point the silicon layer bakes off, leaving the carbon atoms, which realign into graphene. This method can be used to pattern or cut into shapes for microelectronics.

Powerful Properties

Graphene's many unique properties lead to a wide range of potential applications. Two hundred times stronger than steel, it's possibly the lightest, strongest material ever discovered, suitable for airplane parts and other high-pressure, low-weight applications. It conducts electricity with an extremely low resistance—faster than silicon—making it suitable for many electronics applications.

Graphene is a 2D building material that, when isolated, can be wrapped into buckyballs, rolled into nanotubes, or stacked into graphite.

These traits, combined with graphene's transparency, could also make the material a key component in building more functional lightweight OLED, LCD, and touch-screen panels. And with its large surface-to-volume ratio, graphene in powder form could even improve batteries.

Graphene's electrical properties are leading to branching ideas about the future of computing. "You can try to do everything in a similar way but find a material that can maybe do it better [than silicon]," Dr. Roland Kawakami, an associate professor of physics and astronomy at the University of California, Riverside explains. "Maybe we can make a better transistor."

Following this logic, graphene could be built into tiny transistors that can move single electrons around with electromagnetic forces. An electron will come to an obstacle in its path—like a wedge—and have to move around it in one of two directions. This choice reproduces the binary basis for the rest of the computer. Theoretically, these transistors would be smaller, consume less power, and yield much higher speeds than current silicon. Heck, we might see 100GHz mobile phones based on the technology in coming decades.

The counter alternative to transistor replacement, according to Dr. Kawakami, is to "try to do computing in a different way. So…maybe you can have additional benefit since you're doing something fundamentally different," Kawakami says. His research relates to spin computing, and rethinking processing paradigms down to an atomic level.

Here's the logic: Electrons don't just have an atomic charge, they also have spin, behaving like tiny magnets with a north and south pole. Spin computers can take advantage of this polarity to process and store data; it's similar to the magnetic alignment of current hard disks. This spin can be oriented in many directions, easily accommodating the current binary concept as "up" or "down," while allowing for further expansion.

The problem is that when researchers try to inject spin into semiconductors, they have to cool them to cryogenic levels, such as 100 Kelvin. Even then, it works poorly. Graphene can maintain this spin much longer and do so at room temperatures. Kawakami has researched ways of extending the spin further by layering graphene with a thin insulator. Spin is injected through the insulator, and the extra material helps prevent it from leaking out immediately.

The spin can now last significantly longer than a nanosecond, with theoretical estimates of it lasting between a millisecond and microsecond. While these times don't sound long, consider a processor that runs at 1GHz—a graphene-based spin computer could retain information for up to a million cycles.

Commercial Graphene?

With so many uses and with the cost per yield continuously dropping, you can expect to see the first commercial uses of graphene in the next two to three years. More ambitious usage will, of course, take decades to develop. This said, some companies, such as Samsung, are already testing 30-inch graphene-based display prototypes.

Kawakami says, "There are certain things we can already do based on this last [research]." So, how long will it take until graphene computers make it to the market? "At the very optimistic end," Kawakami responded, "[it will take] at least 15 years."