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Electric Findings

Discovery could revolutionize electronic devices

Levy’s diagram of “stretched” ferroelectric material

Jeremy Levy, an associate professor in Pitt’s Department of Physics and Astronomy, can hear the excitement in the voice of his friend and fellow researcher, Darrell Schlom. Schlom, professor of materials science and engineering at Penn State University, is sharing with Levy research findings about a new material created from strontium titanate.

It could have some interesting properties, Schlom says. I’m very excited about the characteristics.

Now, it’s up to Levy to find out what all that means.

Normal strontium titanate is a crystalline material made from oxygen and the metals strontium and titanium. The new material was created by taking strontium titanate and stretching it, atom by atom. This produced a ferroelectric version—a form with natural electric properties. All ferroelectric materials respond to an electrical charge by absorbing some electricity, but incompletely. This imperfect absorption makes it more difficult for these materials to be used and manipulated in a controlled way.

Levy, who specializes in imaging, has a lab in Old Engineering Hall that is full of lasers, microscopes, and electronic equipment. Using imaging techniques, he wants to learn more about the new version of strontium titanate and whether it differs from other ferroelectric materials.

When Levy gets the “stretched” strontium titanate in his lab, he uses very short lasers, like a ministrobe light, to probe the new material. The beam takes a snapshot of the action, allowing Levy to figure out what is happening in the material. The results, converted into movies and replayed at one-billionth normal speed, tell a surprising story.

Before this snapshot of the new strontium titanate, most readings of ferroelectric material had many different colors on the printout, indicating that the material was buckled and uneven, making the ferroelectricity volatile. But the new material was almost one color, meaning that it was smooth. The smoother the ferroelectric material is, the easier it is to control, and the less electricity it absorbs, explains Levy.

Based on the results, the researchers believe they have created a novel form of strontium titanate that promises to outperform all other known materials for use in high-frequency devices.

“The technological implications are staggering,” says Levy. He and his research colleagues—as part of a collab-orative effort led by Pitt and Penn State scientists—described their successful transformation of the normal properties of strontium titanate in a report pub-lished last August in the journal Nature.

The process is akin to stretching a bed sheet beyond its normal limits, said Schlom from Penn State, where the stretched material was synthesized. In this case, the “bed sheet” is strontium
titanate and the “bed” is a newly synthesized crystalline material, dysprosium scandate. “What we are doing is stitching, atom by atom, the ‘bed sheet’ of strontium titanate to the ‘bed’ of dysprosium scandate,” he explained. “In doing so, we can prevent the strontium titanate from wrinkling or tearing, and we can transform the properties of this sheet of material in ways that are impossible to do otherwise.”

The distances between adjacent atoms in strontium titanate and dysprosium scandate agree to within 1 percent, close enough to make the stitching possible. The atomic separation for the film of strontium titanate, however, is slightly smaller than for the substrate of dysprosium scandate, so the film is forced to stretch in order to grow properly. In doing so, the properties are significantly altered, allowing the material to become ferroelectric at room temperature.

“Ordinarily, strontium titanate is not ferroelectric even at absolute zero, the lowest temperature attainable,” notes Pitt’s Levy. “The quality of this material has been found to be so high that its performance in high-frequency devices exceeds that of all other known materials.”

The new material could have a variety of commercial applications. A material that wouldn’t absorb electricity could be used, for example, in cell phones. Cell phones work on a range of frequencies, and this ferroelectric material could be used to make the change between these frequencies close to seamless, or it could help cell phones use less power. The new ferroelectric material could also be used to improve computer operations, such as storage capacity and effectiveness. For instance, it could supplement computer random access memory (RAM). Now, when a person turns off her computer, the RAM disappears. If RAM were ferroelectric, this information would stay in the computer when it was turned off.

Further research on the new material needs to be done, but Levy believes the discovery might one day lead to the next gen-eration of high-speed electronic devices.

No wonder Schlom was excited.
—Meghan Holohan

Breakthroughs in the Making

Walking from his Shadyside apartment to his office in Oakland, Oliver Board does his best thinking. Although he is recently married, he doesn’t think about his bride or their honeymoon in southern France. Instead, he thinks about economics. He is a man immersed in his work. The heart of his work can be seen wherever there are businesses.

Board, an assistant professor of economics at Pitt, is considered a pioneer in game theory and its application to economics; to the rest of us, that means how businesses deal with competitors. Board’s work could alter the way that everything from electronics to produce is sold.

Take Wal-Mart, for instance. If that company decides to skyrocket the price of a bushel of apples by, say, $5, mom and pop stores would probably consider that a foolish move but would most likely raise their own prices by $3 to profit from Wal-Mart’s irrational action. Then, Wal-Mart could drop the price $1 lower than the locals’ new prices, ensuring a “guaranteed low price” that is still $2 higher than the initial price.

Wal-Mart, by making a seemingly irrational decision, actually controlled its competitors’ actions. This is the core of Board’s logic. He doesn’t project businesses always making rational decisions.

Board—who earned undergraduate and graduate degrees from the University of Oxford—has proven that established concepts of game theory, based on rationality, are invalid, because they don’t acknowl-edge ongoing changes in beliefs and rationality. He has demonstrated that businesses using his logic can better predict the outcome of business strategies, which he believes will change the way businesses compete on a global scale.
—Eric Brennan

 

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