According to the researchers, gallium nitride has become a strong candidate for use in high power, high temperature applications such as uninterruptible power supplies, motors, solar converters and hybrid vehicles. Diamond is said to be an excellent heat sink, but its atomic interface with gallium nitride is supposedly hard for phonons to traverse.
In computer models, the team replaced the flat interface between the materials with a nanostructured pattern and added a layer of graphene as a way to improve heat transfer.
“Often, the individual materials in hybrid nano- and microelectronic devices function well but the interface of different materials is the bottleneck for heat diffusion," said materials scientist Rouzbeh Shahsavari.
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%. A layer of graphene between the materials further reduced resistance by 33%.
"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 concluded. "Our strategy is amenable to several other hybrid materials and provides novel insights to overcome the thermal boundary resistance bottleneck."