Circuit designers are always on the lookout for ways to make gadgets smaller, faster, and more efficient. But as cellphones and tablets get thinner and quicker, a major problem presents itself: overheating.
That’s where IEEE Senior Member Alexander Balandin, a nanotechnology researcher, and his team at the University of California at Riverside come in. A professor of electrical engineering and chair of materials science and engineering at the university, Balandin has been working with graphene, a one-atom-thick sheet of graphite, to remove heat—a circuit’s worst enemy—from electronic devices and computer chips. Discovered in 2004 by Andre Geim and Konstantin Novoselov at the University of Manchester, United Kingdom, graphene conducts electricity 100 times better than silicon. Balandin and his team have proven graphene to be a great conductor of heat as well, because it is two-dimensional, so phonons—the vibrations of molecules that lead to the transport of energy, or heat—have fewer places to go and are forced to travel within one plane. Nanotechnology researchers became greatly interested in graphene because it could be used as a conducting electrode and a heat-management material in small devices.
It was Balandin’s work with graphene, in part, that led him to win this year’s Pioneer Award in Nanotechnology from the IEEE Nanotechnology Council. He was cited for “pioneering contributions to nanoscale phonon transport with applications in nanodevices, graphene devices, thermoelectric and thermal management of advanced electronics.”
When graphene was discovered, Balandin was working on thermal management—methods of removing heat from nanoelectronic devices—at UC Riverside. He set out to discover how to apply graphene to his research. If the material demonstrated high thermal conductivity, it could be placed on top of a component to absorb and disperse its heat. But he faced a roadblock. “At first, I could not figure out how to measure graphene’s thermal conductivity using conventional techniques on a film that was just one atom thick,” he says.
Two years later, Balandin and his team made a breakthrough. By using a Raman spectrometer—a tool used to study vibrational, rotational, and other low-frequency modes in a system—they could measure graphene’s ability to conduct heat. They found that at room temperature graphene’s thermal conductivity was extremely high. “In terms of heat conduction, graphene performs even better than diamond—the best bulk heat conductor. As a conductor of electricity it is just as good as copper, but it does not suffer from the electromigration problems of copper and other metals,” Balandin says.
Balandin and his team began developing graphene thermal interface materials, used in computers to carry heat away from computer chips. Graphene is also thinner than a similar layer of silicon, so it can be used to remove heat in tiny devices. The team is currently working on producing graphene transistors, which are faster than silicon transistors.
Balandin predicts that graphene components will be used in devices that use touch screens, like cellphones, tablet computers, and flexible displays—thin, sturdy screens that can be bent or rolled up—in as little as a year. Further along, graphene will someday be found in sensors, battery electrodes, and high-frequency communication devices, “but not for another five to 10 years,” he says.
Graphene may never replace silicon because it does not have an energy band gap for electrons. This is a serious drawback “because it means that you cannot switch a graphene transistor entirely off,” Balandin says. “This leads to power leakage.”
He says graphene and silicon can be used together to create faster and more efficient computer chips and circuits.
A FORK IN THE ROAD
Balandin earned a master’s degree in 1991 in applied physics from the Moscow Institute of Physics and Technology. When he arrived in Indiana two years later to attend the University of Notre Dame, he found himself at a crossroads. He could continue studying electromagnetic theory—his main focus in Moscow—or try something different.
“I decided it would be exciting to study something entirely new, like semiconductor nanostructures,” Balandin says. “My background in solid-state physics allowed me to make a rather smooth transition.”
He earned master’s and doctoral degrees in electrical engineering, with a focus on semiconductor nanostructures, from Notre Dame in 1995 and 1996. He then worked as a researcher at the University of California at Los Angeles before leaving in 1999 to become an electrical engineering professor at UC Riverside. The following year he helped establish the university’s Nano-Device Laboratory where he and his team investigate the properties of nanomaterials. The U.S. Office of Naval Research is funding his team’s current work with graphene-based heat spreaders, which are layers of thermally conductive materials that help manage the temperature of high-power gallium-nitride devices such as the violet laser diodes used to read Blu-ray discs.
Long before working on the cutting edge of materials science, Balandin’s nose was buried in books about space travel. “I read too much science fiction during my school days in Russia,” he says, “and I also had fun following the space race between Russia and the United States.” He attributes his interest in physics and engineering to his early passion for space exploration.
“Hopefully my work on graphene materials and devices will lead to some space applications, among other things,” he says.