Navigation Links
Carbon nanotube avalanche process nearly doubles current

CHAMPAIGN, Ill. By pushing carbon nanotubes close to their breaking point, researchers at the University of Illinois have demonstrated a remarkable increase in the current-carrying capacity of the nanotubes, well beyond what was previously thought possible.

The researchers drove semiconducting carbon nanotubes into an avalanche process that carries more electrons down more paths, similar to the way a multilane highway carries more traffic than a one-lane road.

"Single-wall carbon nanotubes are already known to carry current densities up to 100 times higher than the best metals like copper," said Eric Pop, a professor of electrical and computer engineering at the U. of I. "We now show that semiconducting nanotubes can carry nearly twice as much current as previously thought."

As reported in the journal Physical Review Letters, the researchers found that at high electric fields (10 volts per micron), energetic electrons and holes can create additional electron-hole pairs, leading to an avalanche effect where the free carriers multiply and the current rapidly increases until the nanotube breaks down.

The sharp increase in current, Pop said, is due to the onset of avalanche impact ionization, a phenomenon observed in certain semiconductor diodes and transistors at high electric fields, but not previously seen in nanotubes.

While the maximum current carrying capacity for metallic nanotubes has been measured at about 25 microamps, the maximum current carrying capacity for semiconducting nanotubes is less established. Previous theoretical predictions suggested a similar limit for single-band conduction in semiconducting nanotubes.

To study current behavior, Pop, graduate student Albert Liao and undergraduate student Yang Zhao first grew single-wall carbon nanotubes by chemical vapor deposition from a patterned iron catalyst. Palladium contacts were used for measurement purposes. The researchers then pushed the nanotubes close to their breaking point in an oxygen-free environment.

"We found that the current first plateaus near 25 microamps, and then sharply increases at higher electric fields," said Pop, who also is affiliated with the Beckman Institute and the Micro and Nanotechnology Laboratory at the U. of I. "We performed repeated measurements, obtaining currents of up to 40 microamps, nearly twice those of previous reports."

By inducing very high electric fields in the nanotubes, the researchers drove some of the charge carriers into nearby subbands, as part of the avalanche process. Instead of being in just one "lane," the electrons and holes could occupy several available lanes, resulting in much greater current.

The avalanche process (which cannot be observed in metallic carbon nanotubes because an energy gap is required for electron-hole multiplication) offers additional functionality to semiconducting nanotubes, Pop said. "Our results suggest that avalanche-driven devices with highly nonlinear turn-on characteristics can be fashioned from semiconducting single wall nanotubes."


Contact: James E. Kloeppel, Physical Sciences Editor
University of Illinois at Urbana-Champaign

Related biology technology :

1. Sheet of carbon atoms acts like a billiard table, physicists find
2. Sheet of carbon atoms acts like a billiard table, physicists find
3. Researchers measure carbon nanotube interaction
4. The sensitive side of carbon nanotubes: Creating powerful pressure sensors
5. NASA Goddard Space Flight Centers carbon nanotube manufacturing technology wins Nano 50 Award
6. Understanding of actuator properties of carbon nanotubes bring micro machines closer
7. Improved wettability of carbon nanotubes opens the door to new possibilities
8. Growing tiny carbon nanotube wires to connect computer chips of the future
9. Carbon nanotubes to be replaced by MoSIx nanowires in high-tech devices says new study
10. FED-TVs with carbon nanotube technology could supersede plasma and LCD flat screens
11. Clemson researcher studies carbon fibers for nuclear reactor safety
Post Your Comments:
(Date:12/1/2015)... ... December 01, 2015 , ... Matthew “Tex” VerMilyea, PhD, HCLD, ... VerMilyea will oversee all IVF lab procedures as well as continue his research ... “We traveled 7,305 miles to Auckland, New Zealand to bring home a High Complexity ...
(Date:11/30/2015)... ... 2015 , ... Global Stem Cells Group today ... Santiago Marriott. The Global Stem Cells Group GMP facility is equipped with the ... medical researchers and practitioners, experienced in administering stem cell protocols using highly manipulated ...
(Date:11/30/2015)... , December 1, 2015 Partnership includes ... for the u niversity , ... support treatment s cale - up ... (ARVs)   Africa , where licensees based anywhere in ... based on SDN technology. --> Africa , where licensees based ...
(Date:11/30/2015)... , Nov. 30, 2015 Spherix ... company committed to the fostering and monetization of ... current and prospective initiatives designed to create shareholder ... Executive Officer of Spherix. "Based on published reports, ... licensees exceeds $50 billion and Spherix will seek ...
Breaking Biology Technology:
(Date:10/29/2015)... , Oct. 29, 2015 Daon, a global ... it has released a new version of its ... North America have already installed ... also includes a FIDO UAF certified server component ... preparing to activate FIDO features. These customers include some ...
(Date:10/29/2015)... YORK , Oct. 29, 2015 ... technology, announced a partnership with 2XU, a global ... to deliver a smart hat with advanced bio-sensing ... and other athletes to monitor key biometrics to ... the strategic partnership, the two companies will bring together ...
(Date:10/26/2015)... 26, 2015 ... adds Biometrics Market Shares, Strategies ... well as Emerging Biometrics Technologies: Global ... its collection of IT and Telecommunications ... --> . ...
Breaking Biology News(10 mins):