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 When AI and optoelectronics meet: Researchers take control of light properties
20.11.2018 | Institut national de la recherche scientifique - INRS

nachricht How to melt gold at room temperature
20.11.2018 | Chalmers University of Technology

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: Nonstop Tranport of Cargo in Nanomachines

Max Planck researchers revel the nano-structure of molecular trains and the reason for smooth transport in cellular antennas.

Moving around, sensing the extracellular environment, and signaling to other cells are important for a cell to function properly. Responsible for those tasks...

Im Focus: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Optical Coherence Tomography: German-Japanese Research Alliance hosted Medical Imaging Conference

19.11.2018 | Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

 
Latest News

Nonstop Tranport of Cargo in Nanomachines

20.11.2018 | Life Sciences

Researchers find social cultures in chimpanzees

20.11.2018 | Life Sciences

When AI and optoelectronics meet: Researchers take control of light properties

20.11.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>