Stanford scientists discover a possible successor to silicon
By Lisa M. Krieger


Mercury News

Posted: 06/15/2009 06:44:59 PM PDT


Physicists at Stanford University have identified an important new trait of a
chemical compound that could become an heir to silicon, perhaps transforming the
computing industry.

The researchers found that electrons in a chemical compound called bismuth
telluride have a unique property: They can travel without resistance, losing no
energy. This suggests that there might be a new way to carry more information
than silicon-based chips can handle.

It is one of many competing ideas in the search for new tools that could
accelerate the development of even smaller, cheaper and more powerful computers.

"We're at the very beginning of understanding this new class of materials," said
lead investigator Yulin Chen of Stanford Institute for Materials & Energy
Science. "The next step is to apply what we've learned â€" to see if it can
fabricated, and made functional."

Engineers have been doubling the number of components that fit on a piece of
silicon, called a chip, every two years. This miniaturization trend, dubbed
"Moore's Law," has produced modern computers that are enormously more powerful
than their predecessors.

But soon the industry may hit a wall, because there are limits to what silicon
can do.

Scientists are exploring several different possible successors. One is optical
computing, which relies on photons rather than electrons. Another is
nanochemistry using tiny chemical processes.

SLAC's new discovery uses


electronic spin to carry information, part of a new field called spintronics.

Spintronics takes electronics down to the quantum level. Because electrons don't
just carry charge â€" they also carry an "up" or "down" spin, which can be read
as a binary pattern, they can be used to store information.

When voltage is put on top of Stanford's new material, electronics flow without
resistance. This approach to energy flow means lower power use, and make it
possible for smaller devices to process information.

Stanford scientists had speculated the bismuth telluride that this unique
characteristic. But its unique property, called topological insulation, was
finally revealed by using X-rays from the Stanford Synchroton Radiation Light
Source at SLAC and the Advanced Light Source at Lawrence Berkeley National
Laboratory.Their findings are published online in the June 11 issue of the
journal Science Express.

However, the material â€" shiny, reflective and black, grown in special campus
furnaces â€" can only carry small currents so is not yet applicable.

But it could pave the way for a paradigm shift in microchip development,
according to team member Xiaoliang Qi.

"This could lead to new applications of spintronics, or using the electron spin
to carry information," Qi said. "I'm optimistic it can lead to new devices,
transistors, and spintronics devices."

But Dag Spicer, senior curator of the Computer History Museum in Mountain View,
was cautious in interpreting the significance of the finding.

"It's exciting to think about potential applications for a new discovery â€" but
such ruminations are often devoid of common-sense factors like economics,
training, consumer desire, manufacturability and so on," said Spicer. "Silicon
has had its death knell sounded for the last two decades."

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Contact Lisa M. Krieger at lkrieger@... or 408-920-5565.