New Nanoscale Phenomenon Helps Develop Faster Computer Processors

John Cumings and Kamal Baloch, researchers from the University of Maryland, have discovered a new phenomenon at the nanoscale when they allowed an electric current to traverse a carbon nanotube.

The researchers found that the passage of the electric current tends to heat up a substrate beneath the carbon nanotube and melts the metal nanoparticles on the surface of the substrate. However, the carbon nanotube as well as the metal contacts bonded to it remained cool. The new phenomenon, termed as ‘remote Joule heating’ by the researchers, paves the way to design faster computer processers that avoid overheating by dissipating heat to another place.

The scientists conducted the experiment at an electron microscopy facility at the University of Maryland’s A. James Clark School of Engineering. They utilized electron thermal microscopy, a method developed at the lab of Cumings, to map heat generation spots in nanoscale electrical devices in order to study the impact of current on the carbon nanotube. They observed that the silicon nitride substrate below the nanotube became hot, but the nanomaterial stayed relatively cold.

Baloch informed that electrons in the nanotube were vibrated, while its atoms remained unaffected. However, the atoms of the silicon nitride substrate vibrated and became hot instead. The researchers believed that the vibration of the substrate’s atoms might be induced by electrical fields.

Cumings explained that the atoms of the substrate respond directly to the electrical fields formed by the nanotube’s electrons due to the passage of the current. This energy transfer occurs via these intermediaries, and not due to the vibration of the substrate’s atoms caused by the nanotube’s electrons.

According to Baloch, the remote Joule heating effect paves the way to design electrical conductor and thermal conductor separately by selecting optimal properties for each, thus eliminating the need to create the two from the same material that occupy the same space region.

Hitherto the researchers found the new effect only in carbon materials, and at the nanoscale. The researchers’ next step is to identify whether other materials can demonstrate this phenomenon, and if so, what properties they might have. Understanding the working principle of this effect will open the door to engineer new generation of nanoelectronics with built-in thermal management, Cumings concluded.