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Scientists Invent Transistor Made of a Single Molecule

Thursday, November 08, 2001

WASHINGTON — Scientists have invented the tiniest transistor that may ever be possible — using only a single molecule.

Bell Labs' organic nanotransistor, about 10 million of which can fit on the head of a pin, could be used to fit lightning-fast computers on clothes and paper and otherwise revolutionize technology as we know it.

"It may become the cornerstone of a new era," Bell Labs vice president Federico Capasso said.

The breakthrough was created by physicist Hendrik Schon and chemists Zhenan Bao and Hong Meng and published Thursday on the Web site of the journal Science.

Experts say the minuscule, molecular transistor may make traditional silicon transistors obsolete.

"You might think about flexible electronics, some things in which silicon cannot do," Schon said.

Stanford University professor David Goldhaber-Gordon called the invention "really remarkable."

"It really looks for all the world like a standard silicon transistor, and in some ways even has better parameters," Goldhaber-Gordon said

Schon's team used "conjugated molecules" made out of a broth of carbon, hydrogen and sulfur. The solution is poured from a beaker onto gold electrodes, and the transistors form by themselves.

And the ease of its manufacture will probably please the computer industry. The molecular transistor is cheap to make and can be produced in an ordinary lab rather than the ultra-sanitary "clean room" now used by chipmakers.

Transistors are the most critical component of computers, setting the physical limit for how quickly they can process electronic signals. As a rule of thumb, smaller transistors are more efficiently designed, and thus faster. Silicon transistors, the current standard, were invented in 1947, and depend on conductive material implanted on a silicon chip. Chipmakers like Intel squeeze millions of transistors into a single microprocessor to power the computers, a process that is extremely expensive.

They are expected to become as small as physically possible within the next 20 years.

The molecular transistor would bypass that barrier, setting what Schon called the "ultimate limit for miniaturization."

Don't expect computerized shoes or toupees anytime soon, though. The microscopic transistor faces several years of testing and improvements before it can be used in products.

Also, Schon and his team also need to figure out how it works.

"There were some pleasant surprises in the observed experimental results," Schon said. "Now we have to work on getting a better understanding of what's going on this scale."

And then there's the usual inertia from established industries. Researchers may have too much invested in silicon to see it replaced by molecular cousins anytime soon, Goldhaber-Gordon said.

"Forty to 50 years of development plus the GNP of a decent sized country will get you quite a lot," Goldhaber-Gordon said of silicon research.

But the new transistors might pop up in the medical fields — the device's small size would be useful for biological sensors, he said.

Schon's team has already blazed the trail in miniaturization — just a month ago, when they created a transistor out of a cluster of molecules.

In August, IBM researchers created a simple logic circuit on a carbon nanotube, a single-molecule strand of carbon.

The molecular transistor may not be the final say in tiny technology. No one's entirely ruled out atomic or even subatomic transistors.

"Some people have ideas about making chains of atoms and then maybe moving the atoms to change the conductance. But I don't see how you can amplify signals with that," Schon said. "I don't know, maybe some people will come up with clever ideas."

-- Anonymous, November 08, 2001