According to Slava Rotkin, an assistant professor of physics at the Lehigh University, modern-day laptops are able to generate heat much faster than a dedicated hotplate, and also at levels comparable to a very small nuclear reactor. This happens because of the ever-increasing numbers of semiconductor electronic circuits, which are placed in greater numbers of boards and chips as technology progresses. Together with an international team of experts, Rotkin believes that they may have found a solution – use “near-field” radiation to cool carbon-nanotube electronics in the future, by acting at the substrate level, near the surface on which the carbon nanotubes lie.
 

“Other methods of heat dissipation do not succeed at discharging heat from within the channel of the nanotube or nanowire. Our method enables the heat to leave the channel and move to the substrate, while also scattering the hot electrons. This constitutes a novel cooling mechanism without any moving parts or cooling agents,” Rotkin said. Details of the research, which the professor conducted with colleagues from the T.J. Watson Research Center, at IBM, and the Ioffe Institute in St. Petersburg, the Russian Federation, appear in the latest issue of the journal Nano Letters.
 

Rotkin, who is also a primary faculty member at the Lehigh University Center for Advanced Materials and Nanotechnology, said that, in average computers, the rate of thermal coupling, or heat release, is comparable to that of dry wood, as in very low and ineffective. The team believes that, by using a technique known as surface phonon-polariton (SPP) thermal coupling, they could make better use of the way in which electrons move in carbon nanotubes, allowing for a much higher heat release.
 

“If you put a graphene monolayer, or layer of carbon nanotubes, in a near field zone, this enables the hot electrons to be scattered by the surface polariton and to give out energy to the substrate. Heat is dissipated into the substrate as radiation tunnels from the nanotube through the near field zone to the substrate. If you move the nanotube away from the substrate, the near field tunneling ceases and the mechanism is absent. We achieve all of our coupling through surface polariton scattering because of a large enhancement of the electrical field of the polariton in the near field zone,” the expert said.
 

“Most semiconductor devices fabricated now have the nanotube or nanowire placed directly on a silica substrate, which is polar. With this mechanism, if the substrate is polar and if there's a small van der Waals gap, our new near-field channel totally dominates thermal coupling. We have shown that SPP thermal coupling increases the effective thermal conductance over the interface between nanotube and [polar substrate] by an order of magnitude,” he concluded.