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 Magnetic Quantum Objects in a "Nano Egg-Box"
25.07.2017 | Universität Wien

nachricht 3-D scanning with water
24.07.2017 | Association for Computing Machinery

All articles from Information Technology >>>

The most recent press releases about innovation >>>

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

Im Focus: Physicists Design Ultrafocused Pulses

Physicists working with researcher Oriol Romero-Isart devised a new simple scheme to theoretically generate arbitrarily short and focused electromagnetic fields. This new tool could be used for precise sensing and in microscopy.

Microwaves, heat radiation, light and X-radiation are examples for electromagnetic waves. Many applications require to focus the electromagnetic fields to...

Im Focus: Carbon Nanotubes Turn Electrical Current into Light-emitting Quasi-particles

Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers

Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...

Im Focus: Flexible proximity sensor creates smart surfaces

Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.

At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...

Im Focus: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

 
Latest News

Programming cells with computer-like logic

27.07.2017 | Life Sciences

Identified the component that allows a lethal bacteria to spread resistance to antibiotics

27.07.2017 | Life Sciences

Malaria Already Endemic in the Mediterranean by the Roman Period

27.07.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>