- Updated September 25, 2013, 5:17 p.m. ET
Scientists Build First Nanotube Computer
Device Is a Milestone on Path Toward Faster, More Powerful Electronics
wsj
In an advance toward a future of smaller, faster and
more powerful electronics, researchers at Stanford University on
Wednesday unveiled the first working computer built entirely from carbon
nanotube transistors.
These seamless cylinders of ultrapure carbon are among many exotic
materials researchers are investigating—including the quantum particles
inside every atom and the DNA inside every cell—as electronics
developers near the limits of conventional silicon transistors.
Norbert von der Groeben
Max Shulaker, doctoral student
in electrical engineering at Stanford, holds a wafer filled with carbon
nanotube computers. To his left, a basic CNT computer using this
technology is sandwiched beneath a probe card.
Scientists unveil the first working computer
built entirely from carbon nanotube transistors in a significant step
toward finding the future of electronics beyond silicon. Lee Hotz joins
the News Hub with details. Photo: AP
While primitive, the invention proves
that transistors made with these unusual carbon fibers, among the
strongest materials yet discovered, can be assembled into a general
purpose computer. It can run a basic operating system, perform
calculations and switch between different processes running at the same
time, the scientists said.
"It really is a computer in every sense of the word," said Stanford
University electrical engineer Max Shulaker, who led construction of the
device. "This shows that you can build working, useful circuits out of
carbon nanotubes and they can be manufactured reliably."
Their research was published Wednesday in Nature.
"They have tamed nanotubes," said carbon electronics expert Franz
Kreupl at the Technical Institute of Munich in Germany, who wasn't
involved in the project.
Mihail Roco, senior adviser for nanotechnology at the
National Science Foundation, which helped fund the work, called the
nanotube computer "an important scientific step." If perfected, he said,
"this would allow a computer to work faster, and with smaller
components and with about one-tenth the energy."
Researchers are tantalized by the digital potential of carbon
nanotubes, which are exceptional at conducting electricity and heat, and
at absorbing or emitting light. Long a laboratory curiosity, they are
made from sheets of carbon just one atom thick and rolled into tubes
about 10,000 times thinner than a human hair.
"Of all the candidates that have been considered as a successor to
silicon, carbon nanotubes remain the most promising," said Supratik
Guha, director of physical sciences at
International Business Machines Corp.'s
IBM -0.26%
Thomas J. Watson Research Center in Yorktown Heights, N.Y.
The
first nanotube transistor—a version of the digital on-and-off switch at
the heart of almost every commercial electronics device—was invented in
1998. Until recently, though, researchers found it all but impossible to
manufacture batches of the infinitesimally small tubes with the perfect
alignment, regularity and purity required for a computer's complex
integrated circuits.
Nanotubes are grown, like crystals. They fall into place randomly,
like a shower of pick-up sticks, which can cause cross-connections.
About 30% develop unpredictable metallic impurities. Any imperfection
can cause a short-circuit.
"People said you would never be able to manufacture this stuff," said
Stanford electrical engineer Subhasish Mitra, who was part of the
project. The researchers developed a special circuit design and a
powerful debugging technique to overcome the impurities.
Driven by the commercial possibilities, researchers have been racing to harness the material's promising electrical properties.
Last year, IBM researchers showed off carbon nanotube transistors
that run three times as fast as conventional silicon transistors, while
using a third of the power. And last October, scientists at the IBM's
Watson Research Center reported a way to create batches of 10,000 or
more carbon nanotube transistors arrayed on a single computer wafer.
They have yet to connect them into a working circuit.
Last week, at Cambridge University in the U.K., scientists said they
had devised a simple way to grow the densest array of carbon nanotubes
to date—about five times as compact as previous methods, while
researchers at the University of Southern California recently found a
way to custom-tailor their atomic structure.
At Stanford, the experimental nanotube computer contains 178
transistors formed from "several tens of thousands of carbon nanotubes,"
Dr. Shulaker said. A conventional silicon chip today can pack two
billion transistors in an area the size of thumbnail. The Stanford
system contains as many transistors as in the earliest transistor-based
computers made in the 1950s. The researchers used a logic design on a
par with computers made in the 1960s.
The Stanford scientists assembled 985 of the nanotube computers—each
with 178 carbon nanotube transistors—on a single chip wafer, using
standard chip-fabrication techniques and design tools.
"What we have demonstrated is a very simple computer," said Stanford
engineering professor Philip Wong, who worked on the device. "There is a
vast distance between what we accomplished and an eventual product."
