Carbon nanotubes: they can be far stronger than steel, lighter than aluminum, and more conductive than copper. Their potential applications range from ultrathin, breathable, waterproof fabrics to bright, rugged flat-panel displays for televisions and computer monitors.

Carbon nanotubes will undoubtedly be the wonder material of the 21st century. And though their list of potential applications is long and dazzling, none are more important than those envisioned in electronics. Already, researchers have built a variety of carbon-nanotube electronic and optoelectronic devices: transistors, diodes, light emitters, and detectors. Most remarkable, you can get all those different functions with a single device, merely by altering the voltages you apply to it.

In fact, so attractive are carbon nanotubes' electrical properties that researchers are already eyeing them as replacements for silicon circuits. Since individual nanotubes can be created to be metallic conductors or semiconductors, you can use some of them as transistors and others as the connections between transistors—the two main ingredients of an integrated circuit. And that's very good news to electronics researchers who are approaching fundamental physical limits as they strive to scale conventional CMOS silicon circuits down into a realm in which certain transistor parts are only tens of atoms wide.

The steady reduction in the dimensions of transistors on ICs has been the main force behind the regular leaps in the level of performance of silicon ICs over the past four decades. However, no one expects those leaps to go on forever. In fact, technologists expect that those physical limits will become a serious problem within a decade. Of course, huge industries have grown accustomed to regular increases in computing power and memory-chip density, and they are already preparing for their long-term future by investigating potential successors to ordinary CMOS ICs.

Carbon nanotubes are one of the most promising of the technologies that might someday pick up where conventional CMOS devices leave off. An electronics industry based on nanotubes could preserve a lot of what's good about existing silicon technology—the logic circuits and much of the manufacturing process—but base it on new materials that get around the majority of problems that would probably doom any attempts to make extremely small CMOS devices. So groups all over the world are making and investigating nanotube devices. My group, at the IBM Thomas J. Watson Research Center in Yorktown Heights, N.Y., is evaluating the potential of carbon nanotubes to augment and maybe ultimately replace today's ubiquitous silicon CMOS.