Bumpy surfaces with a layer of graphene in between them could help carry heat away from electronic gadgets.
No matter the size, electronic devices need to disperse the heat they produce, says Rouzbeh Shahsavari, a materials scientist at Rice University.
“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 says.
Shahsavari and colleagues used computer models to enhance the interface between gallium nitride semiconductors and diamond heat sinks. They replaced the flat interface with patterned ones. Then they added a layer of graphene—an atom-thick form of carbon.
“Oftentimes, the individual materials in hybrid nano- and microelectronic devices function well but the interface of different materials is the bottleneck for heat diffusion,” Shahsavari says.
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 says. Diamond is an excellent heat sink, but its atomic interface with gallium nitride is hard for phonons—quasiparticles of sound that also carry heat—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, says Lei Tao, a graduate student and lead author of the study published in ACS Applied Materials and Interfaces.
“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 says.
Source: Rice University
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