Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Customized Y-shaped carbon nanotubes can compute

15.08.2005



Researchers at UCSD and Clemson University have discovered that specially synthesized carbon nanotube structures exhibit electronic properties that are improved over conventional transistors used in computers. In a paper published* in the September issue of Nature Materials and released online on August 14, UCSD Mechanical and Aerospace Engineering professors Prabhakar Bandaru and Sungho Jin, graduate student Chiara Daraio, and Clemson physicist Apparao M. Rao reported that Y-shaped nanotubes behave as electronic switches similar to conventional MOS (metal oxide semiconductor) transistors, the workhorses of modern microprocessors, digital memory, and application-specific integrated circuits.

“This is the first time that a transistor-like structure has been fabricated using a branched carbon nanotube,” said Bandaru. “This discovery represents a new way of thinking about nano-electronic devices, and I think people interested in creating functionality at the nanoscale will be inspired to explore the ramifications of these Y-junction elements in greater detail.”

The stunning increase in the speed and power efficiency of electronics over the past two decades was primarily due to the steady shrinkage in size of conventional transistors. Chip makers have reduced the minimum feature size of transistors to about 100 nanometers, and that dimension is expected to shrink by the end of this decade. However, industry experts predict that fundamental technological and financial limits will prevent the makers of conventional MOS transistors to reduce their size much further. The Y-shaped nanotubes discussed in the Nature Materials paper are only a few tens of nanometers thick and can be made as thin as a few nanometers.



“The small size and dramatic switching behavior of these nanotubes makes them candidates for a new class of transistor,” said Bandaru.

The new transistors were initially grown as straight nanotube elements. Titanium-modified iron catalyst particles added to the synthesis mixture were then attached to the straight nanotubes, nucleating additional growth, which continued like branches growing from a tree trunk. Consequently, the nascent nanotubes assumed a Y-shape with the catalyst particle gradually becoming absorbed at the junction of the stem and two branches.

When electrical contacts are attached to the nanotube structures, electrons travel into one arm of the Y, hop onto the catalyst particle, and then hop to the other arm and flow outward. Experiments conducted in Bandaru’s lab at UCSD’s Jacobs School of Engineering showed that the movement of electrons through the Y-junction can be finely controlled, or gated, by applying a voltage to the stem. Bandaru hypothesized that positive charge applied to the stem enhances the flow of electrons through the two arms, producing a strong “on” signal. Then, when the polarity of the charge is reversed, the movement of electrons through the arms essentially stops, creating an “off” signal. Such binary logic is the basis of nearly all transistors.

“Among electrical device engineers, this phenomenon is called gating,” said Bandaru. He said the phenomenon effectively makes Y-shaped nanotubes the smallest ready-made transistor yet, with rapid switching speeds and possible three-way gating capability. In earlier attempts to make carbon nanotube-based transistors, separate gates were added rather than built in.

“We think this discovery extends the paradigm of nanotechnology beyond just making things small,” said Bandaru. “We can synthesize functionality at the nanoscale, in this case to include the three elements of a circuit – the gate, source, and drain – and we don’t have to go to the trouble of making them separately and assembling them.”

The researchers plan to experiment with various other catalyst particles in order to tailor the three-way gating properties of the Y-junctions. “If we can easily fabricate, manipulate, and assemble these nano-devices on a large scale they could become the basis of a new kind of transistor and nanotechnology,” said Bandaru.

* "Novel electrical switching behaviour and logic in carbon nanotube Y-junctions," P.R. Bandaru, C. Daraio, S. Jin and A.M. Rao, Nature Materials, September 2005

Rex Graham | EurekAlert!
Further information:
http://www.ucsd.edu

More articles from Physics and Astronomy:

nachricht Taking a spin on plasma space tornadoes with NASA observations
20.11.2017 | NASA/Goddard Space Flight Center

nachricht NASA detects solar flare pulses at Sun and Earth
17.11.2017 | NASA/Goddard Space Flight Center

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: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Antarctic landscape insights keep ice loss forecasts on the radar

20.11.2017 | Earth Sciences

Filling the gap: High-latitude volcanic eruptions also have global impact

20.11.2017 | Earth Sciences

Water world

20.11.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>