Life In The Nano-Fast Lane

It was only two issues ago when we found that Bell Labs scientists had constructed working transistors 100 times smaller than those in today's chips, out of clusters of molecules. Imagine -- we were talking about man-made things built from "Clusters of molecules!"

But today, just one month later, readers Victor Panlilio and others steer us to the truly startling news that these same scientists have now created working transistors -- no longer out of "clusters of molecules" -- but out of "one-single-organic-molecule!"

(The entire "active channel" of the transistor is composed of only one molecule.

Small, And Cheap. And Not "Built."

Not only does this redefine "small," since ten million of these transistors will fit onto the head of that proverbial pin, but these transistors are also "cheap to make" and can be "built" in ordinary laboratories, without the hugely-expensive clean room facilities necessary to make today's chips.

Note that the word "built" is in quotes, because these transistors aren't "built" in the traditional sense -- when Hendrik Schon and his team dip a specially-prepared wafer into a solution of "conjugated molecules," the single-molecule transistor forms itself! According to Schon,

"Our experiment shows that it is possible to realize transistor action in a single molecule without sophisticated fabrication procedures."

Connections.

But once we have such tiny, single-molecule transistors, how do we "connect" them together, and to the outside world? Can we simply "wire them up" in the same way that components on today's integrated circuits are "wired up?" Bell Labs' Zhenan Bao explains,

"It is virtually impossible to attach three electrodes to a microscopically small molecule. We overcame this problem by letting the molecule find these contacts, and attach itself to them; a process called 'self-assembly.' "

In the Nov. 8 SiliconValley.com, Bell Labs VP Federico Capasso suggests that this may "become the cornerstone of a new era," because aside from packing FAR more computing power into tiny packages, these single-molecule transistors may give rise to completely new types of "smart material."

It's worthwhile noting that these single-molecule transistors are not simply laboratory curiosities: to prove that single-molecule transistors can actually work together to perform more complex tasks, Schon's team has already demonstrated them working in "inverter circuits, with gain," according to the Nov. 8 Science magazine (http://www.sciencemag.org/cgi/content/abstract/1066171).

Not A Single, Tiny, "Flash In The Pan."

By the way, just in case we might be tempted to think that this is an interesting advance, but one that might not pan out (and so allow us to remain comfortable with "merely" Moore's Law performance increases), it's important to realize that this is just one of many diverse paths that researchers are taking to change all the rules. For example, readers John Hock and Victor Panlilio point us to other work, by Charles Lieber at Harvard, that self-assembles tiny transistors in a very different manner (http://www.nytimes.com/2001/11/09/technology/09NANO.html and
http://www.harvard-magazine.com/on-line/110157.html):

"Instead of carving [transistors out of silicon], they build them up from individual atoms. Out of a droplet of solvent saturated with silicon or another semiconductor like gallium nitride, they grow perfect, rod-shaped crystals less than a millionth of an inch wide and several thousandths of an inch long.

A solution containing the nanowires is squirted onto a silicon oxide wafer. A chemical on the wafer guides the wires to the right place.

Each intersection, where one nanowire crosses another, acts like a transistor, not much different from the tens of millions of transistors in current computer chips -- just much smaller...

The researchers have shown that the nanowire transistors can be wired together to perform all of the basic logic operations needed for computer computations. To build dense circuitry, the researchers would move the nanowires closer together. "Voilà," Dr. Liber said. "You have a billion devices."

Similarly, Cees Dekker, at Delft University, has created complex circuits out of transistors made of carbon nanotubes. He says,

"Molecular logic has been one of the holy grails of nanotube research. Now we have done it.

Intrinsically, these circuits will run anywhere from megahertz to terahertz speeds."

"[These nanomachines will be] the raw material for new industries."

The point, of course, is that while one or more of these nano-techniques might prove resistant to commercialization, there are other approaches just waiting in the wings to take us far, far beyond the course charted by Mr. Moore!

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