Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A little logic goes a long way

09.11.2001


Nano-circuits promise powerful palmtops.
© Y. Huang, X. Duan and C.M. Lieber, Harvard University


Ultra-minaturized electrical components could shrink supercomputers.

Researchers in the Netherlands and the United States have constructed simple computer circuits with electrical components many times smaller than those on commercial silicon chips1,2. These ultra-minaturized logic circuits hold out the prospect of hand-held computers as powerful as today’s state-of-the-art supercomputers.

Cees Dekker and co-workers at the Delft University of Technology in the Netherlands have used single molecules to produce logic circuits capable of basic arithmetical calculations1. The molecules are carbon nanotubes, tiny tubes of pure carbon just a few millionths of a millimetre (nanometres) wide.



A second team at Harvard University in Cambridge, Massachusetts, led by Charles Lieber, have produced similar circuits from wires of similar size to carbon nanotubes, but made from the semiconducting materials silicon and gallium nitride2. Lieber’s group previously perfected methods for growing these ’nanowires’ to specified dimensions and chemical composition.

Conventional diodes and transistors are etched out of flat sandwiches of silicon and other materials using acids. This approach struggles to make components smaller than about 200 nanometres across. Dekker and Lieber assemble their devices atom by atom. It is the difference between an artist chiselling away at a block of wood or gluing together matchsticks.

Carbon-nanotube transistors and even logic circuits have been made before. In 1998, Dekker’s group was the first to build a nanotube transistor; and last June, a team from IBM’s research laboratories in Yorktown Heights, New York, created logic circuits, called NOT gates, from nanotube transistors3. Dekker and colleagues have now wired up groups of nanotubes to make a variety of logic circuits, including a memory cell that could form part of a random-access memory.

One of the difficulties in making nanotube circuits on a large scale, Lieber points out, is that it is very hard to control the way the tubes conduct electricity. Some nanotubes are like metal wires, others act like semiconductors such as silicon. To make a nanotube transistor requires semiconducting rather than metallic conduction. But which kind of tube you get using existing synthesis methods is largely a matter of chance.

Lieber has much more control over the electrical properties of his nanowires. Transistors and other elements of logic circuits typically require two kinds of semiconductor, called p-type and n-type. The electrical currents are carried in these by positively and negatively charged particles, respectively. Lieber can grow both p- and n-type semiconducting nanowires.

Lieber crosses p-type silicon nanowires at right angles to n-type gallium-nitride nanowires. Devices form at the crossing points. By wiring several different devices together, the researchers produce all the major logic gates of computer circuitry.

References

  1. Bachtold, A. Hadley, P. Nakanishi, T. Dekker, C. Logic circuits with carbon nanotube transistors. Science, 294, 1317 , (2001).

  2. Huang, Y. et al. Logic gates and computation from assembled nanowire building blocks. Science, 294, 1313 - 1317, (2001).

  3. Derycke, V. Martel, R. Appenzeller, J. & Avouris, Ph.Carbon nanotube inter- and intramolecular logic gates. Nano Letters, 9, 453 - 456 , (2001).

PHILIP BALL | © Nature News Service
Further information:
http://www.nature.com/nsu/011115/011115-1.html

More articles from Information Technology:

nachricht Cloud technology: Dynamic certificates make cloud service providers more secure
15.01.2018 | Technische Universität München

nachricht New discovery could improve brain-like memory and computing
10.01.2018 | University of Minnesota

All articles from Information Technology >>>

The most recent press releases about innovation >>>

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

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Morbid Obesity: Gastric Bypass and Sleeve Gastrectomy Are Comparable

17.01.2018 | Health and Medicine

Researchers identify new way to unmask melanoma cells to the immune system

17.01.2018 | Health and Medicine

Genetic discovery may help better identify children at risk for type 1 diabetes

17.01.2018 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>