Researchers have discovered that creating a graphene-copper-graphene “sandwich” enhances copper’s heat conducting properties, which could help in shrinking electronics. Engineers at the University of California, Riverside, and the University of Manchester, UK, in collaboration, found that adding a layer of graphene, a one-atom thick material on each side of a copper film increased heat conducting properties by up to 24 percent.
Whether the heat conducting properties of copper would improve by layering it with graphene is an important question because copper is the material used for semiconductor interconnects in modern computer chips. Copper replaced aluminum because of its better electrical conductivity.
Downscaling the size of transistors and interconnects and increasing the number of transistors on computer chips has put an enormous strain on copper’s interconnect performance.
In their experiments, the researchers were surprised that the improvement of thermal properties of graphene coated copper films was significant despite graphene’s thickness being only one atom. They realized that the improvement is the result of changes in copper’s nano- and microstructure, not from graphene’s action as an additional heat conducting channel.
After examining the grain sizes in copper before and after adding graphene, the researchers found that chemical vapor deposition of graphene conducted at high temperature stimulates grain size growth in copper films. The larger grain sizes in copper coated with graphene results in better heat conduction.
Additionally, the researchers found that the heat conduction improvement by adding graphene was more pronounced in thinner copper films. This is significant because the enhancement should further improve as future copper interconnects scale down to the nanometer-range.