Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Future Electronics Based on Carbon Nanotubes

08.04.2015

A team at the University of Illinois at Urbana-Champaign finds way to purify arrays of single-walled carbon nanotubes (SWCNTs), possibly providing a step toward post-silicon circuits and devices

The exceptional properties of tiny molecular cylinders known as carbon nanotubes have tantalized researchers for years because of the possibility they could serve as a successors to silicon in laying the logic for smaller, faster and cheaper electronic devices.


J.Rogers/UIUC

Thermal gradients associated with mild heating of a metallic carbon nanotube induces thermocapillary flows in a thin organic overcoat. The result is an open trench with the tube at the base.

First of all they are tiny -- on the atomic scale and perhaps near the physical limit of how small you can shrink a single electronic switch. Like silicon, they can be semiconducting in nature, a fact that is essential for circuit boards, and they can undergo fast and highly controllable electrical switching.

But a big barrier to building useful electronics with carbon nanotubes has always been the fact that when they're arrayed into films, a certain portion of them will act more like metals than semiconductors -- an unforgiving flaw that fouls the film, shorts the circuit and throws a wrench into the gears of any potential electronic device.

In fact, according to University of Illinois-Urbana Champaign professor John Rogers, the purity needs to exceed 99.999 percent -- meaning even one bad tube in 100,000 is enough to kill an electronic device. "If you have lower purity than that," he said, "that class of materials will not work for semiconducting circuits."

Now Rogers and a team of researchers have shown how to strip out the metallic carbon nanotubes from arrays using a relatively simple, scalable procedure that does not require expensive equipment. Their work is described this week in the Journal of Applied Physics, from AIP Publishing.

The Road to Purification

Though it has been a persistent problem for the last 10-15 years, the challenge of making uniform, aligned arrays of carbon nanotubes packed with good densities on thin films has largely been solved by several different groups of scientists in recent years, Rogers said.

That just left the second problem, which was to find a way to purify the material to make sure that none of the tubes were metallic in character -- a thorny problem that had remained unsolved. There were some methods of purification that were easy to do but fell far short of the level of purification necessary to make useful electronic components. Very recent approaches offer the right level of purification but rely on expensive equipment, putting the process out of reach of most researchers.

As the team reports this week, they were able to deposit a thin coating of organic material directly on top of a sheet of arrayed nanotubes in contact with a sheet of metal. They then applied current across the sheet, which allowed the current to flow through the nanotubes that were metal conductors -- but not the bulk of the tubes, which were semiconducting.

The current heated up the metal nanotubes a tiny amount -- just enough to create a "thermal capillary flow" that opened up a trench in the organic topcoat above them. Unprotected, the metallic tubes could then be etched away using a standard benchtop instrument, and then the organic topcoat could be washed away. This left an electronic wafer coated with semiconducting nanotubes free of metallic contaminants, Rogers said. They tested it by building arrays of transistors, he said.

"You end up with a device that can switch on and off as expected, based on purely semiconducting character," Rogers said.

The article, “Direct current injection and thermocapillarity flow for purification of aligned arrays of single-walled carbon nanotubes,” is authored by Xu Xie, Muhammad A. Wahab, Yuhang Li, Ahmad E. Islam, Bojan Tomic, Jiyuan Huang, Branden Burns, Eric Seabron, Simon N. Dunham, Frank Du, Jonathan Lin, William L. Wilson, Jizhou Song, Yonggang Huang, Muhammad A. Alam and John A. Rogers. It appears in the Journal of Applied Physics on April 7, 2015 (DOI: 10.1063/1.4916537). After that date, it can be accessed at: http://scitation.aip.org/content/aip/journal/jap/117/13/10.1063/1.4916537

The researchers on this paper are affiliated with the University of Illinois at Urbana-Champaign; Purdue University in West Lafayette, Indiana; Beihang University in Beijing, China; Zhejiang University in Hangzhou, China; and Northwestern University in Evanston, Illinois.

ABOUT THE JOURNAL

Journal of Applied Physics is an influential international journal publishing significant new experimental and theoretical results of applied physics research. See: http://jap.aip.org

Contact Information
Jason Socrates Bardi
+1 240-535-4954
jbardi@aip.org
@jasonbardi

Jason Socrates Bardi | newswise

Further reports about: AIP Applied Physics Nanotubes carbon nanotubes circuit expensive metallic purification semiconducting tiny tubes

More articles from Physics and Astronomy:

nachricht Further Improvement of Qubit Lifetime for Quantum Computers
09.12.2016 | Forschungszentrum Jülich

nachricht Electron highway inside crystal
09.12.2016 | Julius-Maximilians-Universität Würzburg

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>