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 No more traffic blues for information transfer: decongesting wireless channels
11.11.2019 | Tokyo University of Science

nachricht A new quantum data classification protocol brings us nearer to a future 'quantum internet'
11.11.2019 | Universitat Autonoma de Barcelona

All articles from Information Technology >>>

The most recent press releases about innovation >>>

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

Im Focus: Magnets for the second dimension

If you've ever tried to put several really strong, small cube magnets right next to each other on a magnetic board, you'll know that you just can't do it. What happens is that the magnets always arrange themselves in a column sticking out vertically from the magnetic board. Moreover, it's almost impossible to join several rows of these magnets together to form a flat surface. That's because magnets are dipolar. Equal poles repel each other, with the north pole of one magnet always attaching itself to the south pole of another and vice versa. This explains why they form a column with all the magnets aligned the same way.

Now, scientists at ETH Zurich have managed to create magnetic building blocks in the shape of cubes that - for the first time ever - can be joined together to...

Im Focus: A new quantum data classification protocol brings us nearer to a future 'quantum internet'

The algorithm represents a first step in the automated learning of quantum information networks

Quantum-based communication and computation technologies promise unprecedented applications, such as unconditionally secure communications, ultra-precise...

Im Focus: Distorted Atoms

In two experiments performed at the free-electron laser FLASH in Hamburg a cooperation led by physicists from the Heidelberg Max Planck Institute for Nuclear physics (MPIK) demonstrated strongly-driven nonlinear interaction of ultrashort extreme-ultraviolet (XUV) laser pulses with atoms and ions. The powerful excitation of an electron pair in helium was found to compete with the ultrafast decay, which temporarily may even lead to population inversion. Resonant transitions in doubly charged neon ions were shifted in energy, and observed by XUV-XUV pump-probe transient absorption spectroscopy.

An international team led by physicists from the MPIK reports on new results for efficient two-electron excitations in helium driven by strong and ultrashort...

Im Focus: A Memory Effect at Single-Atom Level

An international research group has observed new quantum properties on an artificial giant atom and has now published its results in the high-ranking journal Nature Physics. The quantum system under investigation apparently has a memory - a new finding that could be used to build a quantum computer.

The research group, consisting of German, Swedish and Indian scientists, has investigated an artificial quantum system and found new properties.

Im Focus: Shedding new light on the charging of lithium-ion batteries

Exposing cathodes to light decreases charge time by a factor of two in lithium-ion batteries.

Researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory have reported a new mechanism to speed up the charging of lithium-ion...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

High entropy alloys for hot turbines and tireless metal-forming presses

05.11.2019 | Event News

Smart lasers open up new applications and are the “tool of choice” in digitalization

30.10.2019 | Event News

International Symposium on Functional Materials for Electrolysis, Fuel Cells and Metal-Air Batteries

02.10.2019 | Event News

 
Latest News

Magnets for the second dimension

12.11.2019 | Machine Engineering

New efficiency world record for organic solar modules

12.11.2019 | Power and Electrical Engineering

Non-volatile control of magnetic anisotropy through change of electric polarization

12.11.2019 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>