Springtime and Sparkling Films

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Cascading diamonds Shutterstock

Spring puts a sparkle in the air. That could be why diamond is April's birthstone.

Researchers at the Office of Science's Argonne National Laboratory recently devised a way to use that birthstone to brighten the performance of electronic devices, which could put a bit more sparkle in everyone's day.

Scientists at Argonne's Center for Nanoscale Materials, led by nanoscientist Anirudha Sumant, began to think differently about diamond. Instead of seeing it as a sparkling stone, they saw it as a formidable film, one that could take in a great deal of heat and still conduct electricity. Their work built on deposition techniques invented at Argonne to create films with exceptionally tiny grains of diamond; so tiny that a billion of the grains would fit into a single red blood cell. Those thin sheets of diamond have a world of uses, ranging from high-performance seals and ultra-low-friction wear coatings to biomedical implants and biosensors (for more information, see http://science.energy.gov/stories-of-discovery-and-innovation/127011/).

While diamond is incredibly hard, it also has an exceptional ability to take the heat. It is much better at absorbing, and moving heat (called thermal conductivity) than most materials, including many metals. That's why it feels cool to the touch, and could explain one of its nicknames, "ice."

Ice—or at least a good thermal conductor of some sort—is needed for modern electronics like computers, since they generate incredible of heat. Excess heat can cause inferior performance in integrated circuits, causing computers to slow down (and hopefully not smoke!). As their performance has improved, computers have hotted up, and so have had a harder time dissipating their heat. And recently, they've begun to hit a "thermal bottleneck," a point where it isn't possible to squeeze out more performance by adding in more power.

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Welding of an ultrananocrystalline diamond nanobelt (width: 1.5 um, thickness: 100 nm) at the two ends on the TEM grid by using focused ion beam. Image courtesy of Argonne National Laboratory

Welding of an ultrananocrystalline diamond nanobelt (width: 1.5 um, thickness: 100 nm) at the two ends on the TEM grid by using focused ion beam.

Diamond films had been considered as a possible solution to this thermal bottleneck, but they require such high deposition temperatures (about 1,500 degrees Fahrenheit) that other components already on the silicon chips would be damaged. However, Dr. Sumant's team discovered a way to deposit diamond films at about half that temperature, which makes them workable with a whole range of semiconductor materials and devices. They also found a way to "tune" the thermal properties of the diamond films, adjusting them for different temperatures and different applications.

The lower temperature process enabled Dr. Sumant's team to discover a way to combine diamond films with two other materials important for advanced devices, graphene and gallium nitride. Graphene is a rising star of the materials science world, with possibilities in everything from atomic antennas to high speed circuits. Gallium nitride is already used in a variety of high-powered light-emitting devices ranging from computer screens to traffic lights.

As a consequence, the two discoveries could put a great deal of sparkle into a whole range of electronics. By removing the thermal bottleneck, Argonne researchers could open the way to faster computers and more energy-efficient electronic devices.

That's the Office of Science at its best: Putting a sparkle in each day in an unexpected way.

The Department's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information about Argonne, please go to: http://www.anl.gov/.

Charles Rousseaux is a Senior Writer in the Office of Science.