Carbon Nanotubes Could Revolutionise Processors With ‘Remote Heating’ Property

Scientists at the University of Maryland (UMD) have discovered a counter-intuitive property of carbon nanotubes (CNTs) which has the potential to significantly increase processor speeds without overheating.

The team found that when an electrical current was passed through a CNT, a surrounding substrate heated up while the nanotubes remained cool, a phenomenon contrary to what is normally experienced with the Joule heating effect.

An unexpected result

Typically, electrons travelling through a conducting wire will clash into atoms, making them vibrate and release energy as heat. In tests run at the UMD however, both the CNT and attached metal contacts stayed relatively cold while the silicon nitride substrate beneath heated up.

Kamal Baloch and John Cumings, two of the study’s authors, have dubbed the effect “remote Joule heating”. The pair thinks that the occurrence may be due to electrical fields shifting energy from the nanotubes to the substrate.

“We believe that the nanotube’s electrons are creating electrical fields due to the current, and the substrate’s atoms are directly responding to those fields,” said Cumings. “The transfer of energy is taking place through these intermediaries, and not because the nanotube’s electrons are bouncing off of the substrate’s atoms.”

Cumings acknowledged that while the process in the CNT can be compared to a microwave oven (both conductors stay cool while heating up surrounding regions), the physics involved is very different as a microwave field was not being created intentionally in the tests.

While experiments on CNTs consistently yielded the same results, “remote Joule heating” has only been observed with carbon materials at a nanoscale. However, Baloch noted that the discovery may eventually and significantly impact the efficiency and power of future processors.

“What currently limits the performance of a computer’s processor is the speed at which it can run, and what limits the speed is the fact that it gets too hot,” Baloch said. “If you could find some way of getting rid of the waste heat more effectively, then it could run faster. A transistor that doesn’t dissipate energy within itself as heat, like the nanotubes in our experiment, could be a game-changer.

“This new mechanism of thermal transport would allow you to engineer your thermal conductor and electrical conductor separately, choosing the best properties for each without requiring the two to be the same material occupying the same region of space.”

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