Bumpy surfaces, graphene beat the heat in devices

November 29, 2016

HOUSTON - (Nov. 29, 2016) - Bumpy surfaces with graphene between would help dissipate heat in next-generation microelectronic devices, according to Rice University scientists.

Their theoretical studies show that enhancing the interface between gallium nitride semiconductors and diamond heat sinks would allow phonons - quasiparticles of sound that also carry heat - to disperse more efficiently. Heat sinks are used to carry heat away from electronic devices.

Rice computer models replaced the flat interface between the materials with a nanostructured pattern and added a layer of graphene, the atom-thick form of carbon, as a way to dramatically improve heat transfer, said Rice materials scientist Rouzbeh Shahsavari.

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

No matter the size, electronic devices need to disperse the heat they produce, 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."

Gallium nitride has become a strong candidate for use in high-power, high-temperature applications like uninterruptible power supplies, motors, solar converters and hybrid vehicles, he said. Diamond is an excellent heat sink, but its atomic interface with gallium nitride is hard for phonons to traverse.

The researchers simulated 48 distinct grid patterns with square or round graphene pillars and tuned them to match phonon vibration frequencies between the materials. Sinking a dense pattern of small squares into the diamond showed a dramatic decrease in thermal boundary resistance of up to 80 percent. A layer of graphene between the materials further reduced resistance by 33 percent.

Fine-tuning the pillar length, size, shape, hierarchy, density and order will be important, Lei said.

"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," Shahsavari said. "Our strategy is amenable to several other hybrid materials and provides novel insights to overcome the thermal boundary resistance bottleneck."

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

The researchers used the Blue Gene supercomputer and the National Science Foundation-supported DAVinCI supercomputer, which are both administered by Rice's Center for Research Computing and were procured in partnership with Rice's Ken Kennedy Institute for Information Technology.
-end-
Read the abstract at http://pubs.acs.org/doi/abs/10.1021/acsami.6b09482

This news release can be found online at http://news.rice.edu/2016/11/29/bumpy-surfaces-graphene-beat-the-heat-in-devices/

Follow Rice News and Media Relations via Twitter @RiceUNews

Related materials:

Multiscale Materials Laboratory home page: http://rouzbeh.rice.edu/

George R. Brown School of Engineering: http://engineering.rice.edu

Rice Department of Civil and Environmental Engineering: http://www.ceve.rice.edu

Rice Department of Materials Science and NanoEngineering: https://msne.rice.edu

Images for download:

http://news.rice.edu/files/2016/11/1121_GRAPHENE-1-WEB-2i47mpo.jpg

Rice University researchers used computer models to determine the best way to disperse heat produced by microelectronic devices using gallium nitride semiconductors and diamond. A patterned surface and a layer of atom-thick graphene helped transport phonons from the semiconductor to the heat sink. (Credit: Lei Tao/Rice University)

http://news.rice.edu/files/2016/11/1121_GRAPHENE-2-WEB-2bkz6vd.jpg

Rice University simulations show that graphene between patterned gallium nitride and diamond would offer excellent heat transfer in next-generation hybrids of nano- and microelectronics. (Credit: Lei Tao/Rice University)

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,910 undergraduates and 2,809 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for happiest students and for lots of race/class interaction by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl.com/RiceUniversityoverview.

Editor's note: Links to high-resolution images for download appear at the end of this release.

Jeff Falk
713-348-6775
jfalk@rice.edu

Mike Williams
713-348-6728
mikewilliams@rice.edu

Rice University

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