In 1956 Bell Labs scientists Shockley, Bardeen, and Brattain won the acclaimed Nobel Prize for Physics for the invention of the transistor. Now, some fifty years later, it looks like Bell Labs has done it again: This time its scientists have fabricated the first molecular-scale transistor (see Bell Labs Gets Molecular).

By "molecular scale," it means that the critical dimension of the transistor -- the length of what's called the channel -- is determined by the length of a molecule. The new Bell Labs transistor, the details of which were reported in the journal Nature today, has a channel length of 1 nanometer, which is approximately 100 times smaller than in today's transistors.

"This really does represent the ultimate in small," says John Rogers, the director of nanotechnology research at Bell Labs.

This has a couple of potential benefits. First, the channel length influences the speed of the transistor, shorter channels being faster because electrons can traverse them more quickly. Second, it will allow more transistors to be squeezed onto a chip -- if anyone can work out how to connect them all.

"The primary reason we believe it will have an impact on electronics is because of Moore's Law," notes Rogers. Moore's Law is an empirical observation that the number of transistors on a chip doubles every 18 months. The simple consequence of keeping up with Moore's Law is that transistors must keep getting smaller.

All this is very futuristic, however. Chip makers like Intel Corp. (Nasdaq: INTC) reckon that standard silicon processing will keep going until 2010, so molecular electronics would most likely wait until after that (see Intel Shows Tiny Transistor).

Bell Labs is not alone in its interest in things molecular. A bunch of research labs around the world have made molecular-scale electronic widgets, such as switches, memory elements, and even units that perform logic functions. Where Bell Labs can claim to have advanced the cause is by making the first molecular-scale transistor.

"Switching on its own is not enough for preparing a logic circuit," says Hendrick Schon, a member of Bell Labs' technical staff. Every logic manipulation that's carried out introduces loss, so in order to make complicated, cascaded computations, the logic element needs also to amplify the signal. In other words, it needs to be a transistor because transistors have gain.

It's worth mentioning that IBM Corp. (NYSE: IBM) recently made a transistor based on a carbon nanotube, which is a single molecule. But the molecule did not actually define the size of the device: That was still fixed by standard lithography techniques.

Bell Labs scientists used a self-assembly technique to make the transistors, relying on the chemistry of the molecules to adhere them to a gold electrode. In contrast to lithography, which uses expensive equipment and a sophisticated cleanroom, the self-assembly process happens in a beaker on a benchtop, so it could prove to be a highly cost effective method in the long run, says Schon.

— Pauline Rigby, Senior Editor, Light Reading
http://www.lightreading.com