-- Eugen* Leitl <a href="http://www.lrz.de/~ui22204/">leitl</a>
ICBMTO : N48 10'07'' E011 33'53'' http://www.lrz.de/~ui22204
57F9CFD3: ED90 0433 EB74 E4A9 537F CFF5 86E7 629B 57F9 CFD3
---------- Forwarded message ----------
Date: Mon, 27 Aug 2001 09:53:12 -0500
From: Udhay Shankar N <firstname.lastname@example.org>
Subject: [silk] Computronium at last?
Sunday August 26, 8:01 am Eastern Time
IBM Researchers Build World's First
Single-Molecule Computer Circuit
Carbon nanotube transistors transformed into
logic-performing integrated circuits; major step toward molecular
YORKTOWN HEIGHTS, N.Y.--(BUSINESS WIRE)--Aug. 26, 2001-- IBM researchers
today announced they have created and demonstrated the world's first
logic-performing computer circuit within a single molecule, which may
someday lead to a new class of smaller and faster computers that consume
less power than today's machines.
The IBM team made a `` voltage inverter '' -- one of the three fundamental
logic circuits that are the basis for all of today's computers -- from a
carbon nanotube, a tube-shaped molecule of carbon atoms that is 100,000
times thinner than a human hair. IBM scientists will present the
achievement today at the 222nd National Meeting of the American Chemical
Society being held in Chicago and it appears in the web edition of the
ACS' journal Nano Letters.
This is the second major research breakthrough this year by IBM scientists
using carbon nanotubes to make tiny electronic devices. In April, the same
IBM team became the first to develop a ground breaking technique (Science,
Vol. 292, Issue 5517, April 27, 2001) to produce arrays of carbon nanotube
transistors, bypassing the need to meticulously separate metallic and
semiconducting nanotubes. The team used these nanotube transistors to make
the circuit revealed today.
``Carbon nanotubes are now the top candidate to replace silicon when
current chip features just can't be made any smaller, a physical barrier
expected to occur in about 10 to 15 years,'' said Dr. Phaedon Avouris,
lead scientist on the project and manager of nanoscale science, IBM
Research. `` ;Such 'beyond silicon' nanotube electronics may then lead to
unimagined progress in computing miniaturization and power.''
Building a Computer Circuit ``Inverter'' Out of Carbon Nanotubes
The IBM scientists used nanotubes to make a ``voltage inverter'' circuit,
also known as a ``NOT'' gate . They encoded the entire inverter logic
function along the length of a single carbon nanotube , forming the
world's first intra-molecular -- or single-molecule -- logic circuit. In
the binary digital world of zeros and ones, a voltage inverter changes a
'1' into a '0', and a ' 0' into a '1' inside computer chips. The
processors at the heart of today' s computers are basically vast and
intricate combinations of the NOT gate, with two other basic functions,
``AND'' and ``OR'' gates, which perform other computations.
Voltage inverters typically comprise two types of transistors with
different electronic properties ? ``n-type'' (in which electrons carry the
electrical current) and ``p-type'' (in which electron-deficient regions
called ``holes'' carry the electrical current). All previous carbon
nanotube transistors have been p-type only. These transistors, while fine
for scientific studies, are not sufficient to build logic-performing
computer circuits. Scientists at IBM and elsewhere have been able to alter
the properties of nanotube transistors by adding atoms of another element,
such as potassium, to the carbon nanotube. However, Avouris' team recently
discovered a new, simpler way to convert p-type nanotube transistors into
n-type transistors. They found that they could simply heat p-type
transistors in a vacuum, which turns them into n-type transistors and that
they could reverse this process by exposing the transistors to air.
The team also discovered that in addition to converting an entire nanotube
from p-type to n-type, they could also selectively convert part of a
single nanotube to n-type, leaving the remaining part of the single
nanotube p-type. The researchers used this process to build the world's
first single-molecule logic circuit.
More importantly, the output signal from IBM's new nanotube circuit is
stronger than the input. This phenomenon, called ``gain,'' is essential
for assembling gates and other circuit elements into useful
microprocessors. Circuits with a gain less than one are ultimately useless
-- the electrical signal becomes so faint that it cannot be detected.
Since IBM's nanotube circuit has a gain of 1.6, Avouris is hopeful that
even more complex circuits could be made along single nanotubes.
The IBM team is now working to create these more complex circuits, which
is the next step toward molecular computers. In addition, the team is
working to further improve the performance of individual nanotube
transistors, and further integrate them into more complex circuits.
The report on this work ``Carbon nanotube inter- and intra-molecular logic
gates'' by Vincent Derycke, Richard Martel, Joerg Appenzeller and Phaedon
Avouris of IBM's T.J. Watson Research Center in Yorktown Heights, N.Y.
will be published in the August 26 Web edition of Nano Letters, a peer
reviewed journal of the American Chemical Society, the world's largest
scientific society. The online version is available at
http://pubs.acs.org/nano. The work will also be presented in Chicago at
the 222nd national meeting of the American Chemical Society at 2:20 p.m.,
Sunday, August 26 during a symposium on ``Molecular Electronics.''
For more information on IBM Research, go to:
To download images related to this announcement, go to:
IBM is a registered trademark of International Business Machines Corp.
Matthew McMahon, 914/945-3499
Copyright © 2001 Yahoo! Inc. All rights reserved.
Udhay Shankar N Iponics India Pvt Ltd
This archive was generated by hypermail 2b30 : Fri Oct 12 2001 - 14:40:18 MDT