New Theory by Rice Scientists Enhance Heat Sinks in Future Microelectronics

Rice simulations show that graphene between patterned gallium nitride and diamond would offer excellent heat transfer in next-generation hybrids of nano- and microelectronics. Graphic by Lei Tao

Rice University scientists suggest that bumpy surfaces with graphene between would help to dissipate heat in next-generation microelectronic devices.

Theoretical studies conducted by the scientists show that improving the interface between gallium nitride semiconductors and diamond heat sinks would permit phonons, quasiparticles of sound that also carry heat, to disperse in a more efficient manner. Heat is carried away from electronic devices by heat sinks.

Rouzbeh Shahsavari, Rice materials scientist, stated that Rice computer models replaced the flat interface existing between the materials with a nanostructured pattern and then added a graphene layer, the atom-thick form of carbon, in order to dramatically enhance heat transfer.

The new research by Shahsavari, Rice graduate student and lead author Lei Tao and postdoctoral researcher Sreeprasad Sreenivasan was published this month in the American Chemical Society journal ACS Applied Materials and Interfaces.

Despite the size, electronic devices will have to disperse the heat they generate, Shahsavari said.

With the current trend of constant increases in power and device miniaturization, efficient heat management has become a serious issue for reliability and performance,” he said. “Oftentimes, the individual materials in hybrid nano- and microelectronic devices function well but the interface of different materials is the bottleneck for heat diffusion.

Rouzbeh Shahsvari, Materials Scientist, Rice University

Gallium nitride is currently considered to be a strong candidate ideal for use in high-temperature, high-power applications like uninterruptible power supplies, hybrid vehicles, solar converters and motors, he said. Even though diamond is an exceptional heat sink, its atomic interface with gallium nitride is difficult for phonons to traverse.

The team simulated 48 distinct grid patterns with round or square graphene pillars and then tuned them to match phonon vibration frequencies existing between the materials. A major decrease was observed in thermal boundary resistance of up to 80% when a dense pattern of small squares was sunk into the diamond. The resistance was even more reduced by 33% by a layer of graphene between the materials.

Lei highlighted the need for fine-tuning the pillar length, density, hierarchy, shape, size and order.

With current and emerging advancements in nanofabrication like nanolithography, it is now possible to go beyond the conventional planer interfaces and create strategically patterned interfaces coated with nanomaterials to significantly boost heat transport. Our strategy is amenable to several other hybrid materials and provides novel insights to overcome the thermal boundary resistance bottleneck.

Rouzbeh Shahsvari, Materials Scientist, Rice University

Shahsavari is an assistant professor of civil and environmental engineering and of materials science and nanoengineering.

The National Science Foundation-supported DAVinCI supercomputer and the Blue Gene supercomputer were used by the researchers. Both these computers are administered by Rice’s Center for Research Computing and were procured in partnership with Rice’s Ken Kennedy Institute for Information Technology.

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