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.
John Cumings
The researchers found that the passage of the electric current heated up a substrate beneath the carbon nanotube and melted metal nanoparticles on the surface of the substrate but 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 the design of 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 cool.
Baloch informed that electrons of the nanotube vibrated but not its atoms. However, the atoms of the silicon nitride substrate vibrated and became hot instead. The researchers believed that the vibration of the atoms of the substrate occurred due to electrical fields.
Cumings explained that the atoms of the substrate respond directly to the electrical fields formed by the electrons of the nanotube due to the passage of the current. These electric fields transfer the energy not due to the vibration of the substrate’s atoms caused by the electrons of the nanotube.
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 nanoelectronics with built-in thermal management, Cumings concluded.