Graphene Takes the Heat

Feb 20, 2008 By Laura Mgrdichian feature
Graphene Takes the Heat
A schematic of a graphene sheet placed over a trench in a substrate.

Carbon nanotubes are being touted by many scientists and engineers as the material of the future, with the potential to revolutionize electronic technologies. But a new study shows that nanotubes may not be the only form of carbon with the promise of great things to come.

Researchers from the University of California – Riverside (UCR) discovered that a single layer of carbon atoms arranged in a honeycomb pattern, known as graphene, exhibits far better thermal conductivity than carbon nanotubes. Their results open a new window to graphene applications in electronics, where materials that can manage heat are vital.

The group's results are described in a paper appearing in the February 20, 2008, online edition of Nano Letters.

“With the continuously decreasing size of electronic devices, materials that can conduct heat efficiently are rapidly growing in importance,” said the paper's lead author, UCR electrical engineering professor Alexander Balandin, to PhysOrg.com. “Our work increases the range of graphene applications as the thermal management material in optoelectronics, photonics, and bioengineering.”

A material's thermal conductivity is measured in the units W/m•K, read as “watts per meter per degree Kelvin.” A watt is a unit of power equal to a joule per second and a degree Kelvin is a unit of temperature. The meter is, of course, a unit of distance, since thermal conductivity is normalized to the material's thickness. Thermal conductivity defines how well a given material conducts heat. For example, the value of thermal conductivity of silicon, the most important electronic material, is around 145 W/m•K if measured at room temperature.

Carbon nanotubes have a typical thermal conductivity range of 3000 to 3500 W/m•K. Diamond, another form of carbon, comes in between 1000 and 2200 W/m•K. The single-layer graphene studied by the UCR researchers displayed a thermal conductivity as high as 5300 W/m•K near room temperature.

“Graphene is particularly promising as a thermal management material because its superior thermal conductivity is supplemented by plane geometry and good integration with silicon,” added Balandin.

The interdisciplinary UCR team, which included research groups of electrical engineering professor Balandin and physics assistant professor Chun Ning Lau, measured the graphene's thermal conductivity in an unconventional way. The usual contact-based methods for measuring thermal conduction are not appropriate for graphene because it is only a single atom thick. Instead, the group used a noncontact approach: They placed a sheet of graphene onto a substrate with a trench carved out of it, such that part of the graphene sheet was suspended over the trench. They then scattered laser light off the suspended portion and measured the graphene’s vibrational response with a technique called Raman spectroscopy (one of several light-based methods used to learn about material properties).

By carefully analyzing the graphene's Raman spectra – its unique response to the light – and the spectra's dependence on the laser power, the group was able to extract thermal conductivity data. The entire experimental setup is tiny, with the trench just three micrometers (millionths of a meter) in width.

Citation: Nano Lett. ASAP Article, 10.1021/nl0731872

Copyright 2008 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

Explore further: A nanosized hydrogen generator

add to favorites email to friend print save as pdf

Related Stories

'Small' transformation yields big changes

Sep 15, 2014

An interdisciplinary team of researchers led by Northeastern University has developed a novel method for controllably constructing precise inter-nanotube junctions and a variety of nanocarbon structures in ...

Aligned carbon nanotube / graphene sandwiches

Sep 12, 2014

By in situ nitrogen doping and structural hybridization of carbon nanotubes (CNTs) and graphene via a two-step chemical vapor deposition (CVD), scientists have fabricated nitrogen-doped aligned carbon nanotu ...

Tough foam from tiny sheets

Jul 29, 2014

Tough, ultralight foam of atom-thick sheets can be made to any size and shape through a chemical process invented at Rice University.

Recommended for you

A nanosized hydrogen generator

Sep 20, 2014

(Phys.org) —Researchers at the US Department of Energy's (DOE) Argonne National Laboratory have created a small scale "hydrogen generator" that uses light and a two-dimensional graphene platform to boost ...

For electronics beyond silicon, a new contender emerges

Sep 16, 2014

Silicon has few serious competitors as the material of choice in the electronics industry. Yet transistors, the switchable valves that control the flow of electrons in a circuit, cannot simply keep shrinking ...

Making quantum dots glow brighter

Sep 16, 2014

Researchers from the University of Alabama in Huntsville and the University of Oklahoma have found a new way to control the properties of quantum dots, those tiny chunks of semiconductor material that glow ...

The future face of molecular electronics

Sep 16, 2014

The emerging field of molecular electronics could take our definition of portable to the next level, enabling the construction of tiny circuits from molecular components. In these highly efficient devices, ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

NeilFarbstein
1 / 5 (3) Feb 24, 2008
Vulvox plans to conduct research on graphene platelet materials in the near future.
http://vulvox.tripod.com
Our breakthrough carbon nanotube adhesive is described on our website.
NOM
not rated yet Apr 16, 2009
Our breakthrough carbon nanotube adhesive is described on our website.
Hey, that's your famous butt-glue, right?