Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Penn Researchers Take a Big Step Forward in Making Smaller Circuits

01.08.2005


Physicists at the University of Pennsylvania have overcome a major hurdle in the race to create nanotube-based electronics. In an article in the August issue of the journal Nature Materials, available online now, the researchers describe their method of using nanotubes tiny tubes entirely composed of carbon atoms -- to create a functional electronic circuit. Their method creates circuits by dipping semiconductor chips into liquid suspensions of carbon nanotubes, rather than growing the nanotubes directly on the circuit.



"Given their amazing electric properties, nanotubes have been a subject of keen interest for creating such things as chemical sensors, flexible electronics and high-speed, high-device-density microprocessors for computing," said Alan T. Johnson, associate professor in Penn’s Department of Physics and Astronomy. "The problem is that the properties we like best about nanotubes their size and physical properties also make them very difficult to manipulate."

Instead of growing nanotubes in a pattern on a silicon chip, as is conventionally done, the Penn researchers devised a means of "sprinkling" nanotubes onto chips.


"We dip the chips into nanotubes much like dipping an ice cream cone into candy," said Danvers Johnston, a graduate student in Johnson’s laboratory and lead author of the study. "Ultimately we can make it so that the nanotubes only stick where want them to in order to form a circuit."

Single-walled nanotubes are formed by turning a single sheet of carbon atoms into a seamless cylinder approximately one nanometer a billionth of a meter in diameter.

Nanotubes can be either semiconducting or "metallic" the latter is highly conductive to electricity depending on the exact geometry of the carbon atoms. Semiconducting nanotubes make for exceptional transistors, which is why so much attention has been devoted to finding a way to use them in electronics.

Previously, most nanotube circuits have been made by growing each nanotube on the surface of a chip, using a process known as chemical vapor deposition. Unfortunately, this method often results in a circuit comprised of both types of nanotubes, metallic and semiconducting. Furthermore, the growth direction of the nanotube is arbitrary, and their diameters are large. Small diameter carbon nanotubes are more useful for switches.

"Fortunately, other researchers have made it possible to grow small diameter nanotubes and to separate metallic from semiconducting nanotubes in solution," said Arjun Yodh, a professor in Penn’s Department of Physics and Astronomy. "Ultimately our process can create a large batch of small diameter nanotubes in solution, can separate out the semiconducting nanotubes and then can place them in proper position on a patterned silicon chip."

The researchers, along with post-doctoral associate Mohammed F. Islam, found their biggest challenge in purifying the mass-produced nanotubes. The process they used to create nanotubes in bulk frequently adds impurities usually stray bits of carbon and leftover catalysts that ultimately detract from the quality of the nanotubes.

The Penn researchers found a purification scheme for the nanotubes by heating them in moist air with a gentle acid treatment and then using magnetic fields to separate the nanotubes from the impurities. They deposit the nanotubes by dipping a chip covered with a glue-like substance into the nanotube solution, and then they wash off the excess glue and whatever solvents that remain.

The resulting circuits take advantage of unique electrical properties of nanotubes and can be produced in bulk. Since the researchers can create nanotubes via processes separate from the chips, this process allows for a better control of the quality and diameter. The Penn researchers believe there is a definite role for nanotechnology in the future of electronics.

"The only way to make faster processors is to cram more transistors together," Johnson said. "Nanotubes are just about the smallest transistors that exist right now. So the more densely they can be packed on a chip, the faster the chips can become."

Funding for this research was provided by grants from the National Science Foundation and NASA.

Greg Lester | EurekAlert!
Further information:
http://www.upenn.edu

More articles from Physics and Astronomy:

nachricht Significantly more productivity in USP lasers
06.12.2016 | Fraunhofer-Institut für Lasertechnik ILT

nachricht Shape matters when light meets atom
05.12.2016 | Centre for Quantum Technologies at the National University of Singapore

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: 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...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

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

NTU scientists build new ultrasound device using 3-D printing technology

07.12.2016 | Health and Medicine

The balancing act: An enzyme that links endocytosis to membrane recycling

07.12.2016 | Life Sciences

How to turn white fat brown

07.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>