Our modern age has become accustomed to regular improvements in information technology, says Slava Rotkin, but these advances do not come without a cost.
Take the laptop, for example. Its components, especially its billions of semiconductor electronic circuits, are growing ever tinier while the instrument's power and capacity increase. But heat generated by electric current can cause the circuits to melt and the laptop hardware to fail.
Indeed, says Rotkin, an assistant professor of physics, a laptop in use can generate heat faster than an everyday hotplate and almost as fast as a small nuclear reactor.
Developing better methods to dissipate this heat has been listed as a "grand challenge" for modern electronics by the International Technology Roadmap for Semiconductors (ITRS) , a consortium of semiconductor manufacturers.
Rotkin and his colleagues at IBM's T.J. Watson Research Center and at the Ioffe Institute in St. Petersburg, Russia, have developed a heat-dissipation method that cools carbon nanotube electronics by utilizing nonconventional radiation in a "near-field zone" just above the substrate, or surface, on which the nanotubes rest.
The new cooling method requires that the nanotubes' substrate be composed of a polar material such as silicon-dioxide (SiO2), says Rotkin. The method channels excess heat from the nanotubes into the substrate which, being much larger, can be more effectively cooled by the vents that push cool air through laptops.
"Other methods of heat dissipation do not succeed at discharging heat from within the channel of the nanotube or nanowire," says Rotkin. "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 and his colleagues described the results of their research in an article published in March in Nano Letters, one of the premier international journals in the field of nanotechnology.
The article, titled "An Essential Mechanism of Heat Dissipation in Carbon Nanotube Electronics," was coauthored by Rotkin, who is a primary faculty member with Lehigh's Center for Advanced Materials and Nanotechnology; Vasilii Perebeinos and Phaedon Avouris of IBM's T.J. Watson Research Center; and Alexey G. Petrov of the Ioffe Institute.
Rotkin and his colleagues have been studying the heat-dissipation problems associated with carbon nanotube electronics for three years. Their current article is the fifth coauthored by Rotkin that Nano Letters has published in the past year.
Because the nanotubes and substrate are made of heterogeneous materials, says Rotkin, their rate of thermal coupling, or heat release, is relatively low, similar to that of dry wood. This makes it difficult to dissipate heat from the nanotubes to the substrate through classical thermal conduction.
Rotkin and his colleagues instead utilize what they call surface phonon-polariton (SPP) thermal coupling by exploiting the high level of electron scattering that occurs in non-suspended carbon nanotube transistors.
A wave called a surface polariton is caused by this electron scattering, says Rotkin. This polariton is particularly strong in the near field zone just above the substrate on which the carbon nanotubes rest.
"If you put a graphene monolayer, or layer of carbon nanotubes, in a near field zone," says Rotkin, "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.
"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."
A change advocated by ITRS – from a silica substrate to one made of dielectric materials with a higher dielectric constant – would give the substrate material an even stronger surface polariton, says Rotkin.
Rotkin's group used microscopic quantum models to calculate heat dissipation as a function of electric field, doping and temperature.
"Most of the energy losses are dissipated directly into the polar substrate and do not contribute to the field-effect transistor temperature rise," the group wrote in the most recent Nano Letters article.
"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."
Rotkin will summarize his research in an invited talk titled "Thermal Moore's law and near-field thermal conductance in carbon-based electronics" to be presented in August at SPIE's Optics + Photonics conference in San Diego, Calif. SPIE is an international organization devoted to light-based research.
Kurt Pfitzer | EurekAlert!
Further reports about: > Heat Blanket > ITRS > Nano > New 'near-field' radiation therapy > SPP > SiO2 > Substrate > carbon nanotube electronics > carbon nanotubes > cooling method > graphene monolayer > heterogeneous materials > nonconventional radiation > nuclear reactor > overheating laptops > semiconductor device > semiconductor electronic circuits > silicon-dioxide > thermal coupling
IHP technology ready for space flights
20.08.2018 | IHP - Leibniz-Institut für innovative Mikroelektronik
It’s All in the Mix: Jülich Researchers are Developing Fast-Charging Solid-State Batteries
20.08.2018 | Forschungszentrum Jülich
There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.
The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...
New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference
Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...
Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
17.08.2018 | Event News
08.08.2018 | Event News
27.07.2018 | Event News
20.08.2018 | Information Technology
20.08.2018 | Life Sciences
20.08.2018 | Information Technology