Nanotubes form dense transistor array

The breakneck pace of microelectronics development in the last 3 decades has relied on squeezing more and more transistors onto silicon chips. Yet, within 10 to 15 years, silicon electronics will hit its miniaturization limit, experts say.

In background is an atomic-force-microscope image of a nanotube bundle lying across relatively large electrodes. Foreground diagram shows detail of metallic nanotubes (blue) and semiconducting nanotubes (pink) across electrodes (yellow). IBM

Now, researchers at IBM’s T.J. Watson Research Center in Yorktown Heights, N.Y., have urged carbon nanotubes, potential tools for keeping miniaturization going, over a major hurdle. In the April 27 Science, Phaedon Avouris and his colleagues report making transistor arrays of single-walled carbon nanotubes. Each tube is just atoms wide.

Researchers have made single transistors from carbon nanotubes before, but they haven’t been able to sort them and arrange them into the patterns necessary for commercial devices (SN: 5/9/98, p. 294). One reason for this is that nanotube production yields a tangle of metallic and semiconducting nanotubes. However, it’s only the semiconducting ones that can behave like transistors.

By sending a high current through electrodes into nanotube bundles, while using another electrode to remove semiconducting tubes’ electrons, Avouris’ team found that they could selectively destroy the metallic nanotubes, leaving the semiconducting ones intact. Remaining hurdles include integrating the semiconducting nanotubes into complex circuitry.

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