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A micrograph shows carbon nanotubes attached to a thin metal wire. |
Up to now, connecting nanotubes to metal created high-resistance interfaces between the tubes and substrate, making the small tubes useless for electronics. The new techniques, which were developed with funding from the National Science Foundation and Intel Corp., open the way for engineers and researchers to begin exploiting nanotubes' electrical properties in ICs, displays, sensors, and other electronic devices.
One connection method, called floating-catalyst chemical-vapor deposition, first heats a carbon-rich compound until it vaporizes. As it cools, arrays of carbon nanotubes deposit on a metal surface. The attachment between tubes and metal is strong, regardless of the metal substrate shape or size, and electrical connection is good. The downside of this method is that it involves high temperatures, which make it incompatible with some sensitive electronics.
The second method, however, uses much lower temperatures. In this process, technicians grow nanotubes on silicon using chemical deposition. They transfer the tubes from the silicon to a metal surface coated with solder where the tubes maintain their original arrangement. Solder, which is inherently electrically conductive, melts at a much lower temperature, so this method works better for heat-sensitive components.