IBM發明納米碳管效能測量法

IBM Scientists Create Method to Measure Performance of Carbon Nanotubes as Building Blocks for Ultra Tiny Computer Chips of the Future

Petaling Jaya, October 16, 2007 – IBM scientists today announced they have measured the electrical charges directly inside tubes of carbon that measure just 1-2 nanometers in diameter, 50,000 times thinner than a strand of a human hair. This novel technique, which leverages the interactions between electrons and phonons, provides a detailed understanding of the electrical behavior of carbon nanotubes, a material that shows promise as a building block for vastly smaller, faster and lower power computer chips compared to today’s conventional silicon transistors.

A phonon is a description of the atomic vibrations that occur inside material, and can determine the material’s thermal and electrical conductivity. An electron is a subatomic particle that carries the electrical charge and produces the current. Both are important features of materials that can be used to carry electrical signals and perform computations.

The interaction between electrons and phonons can release thermal energy and impede electrical conductance inside computer chips. By understanding the interaction of electrons and phonons in carbon nanotubes, the researchers have developed a way to measure their suitability as wires and semiconductors inside of future computer chips.

In order to make carbon nanotubes useful in building logic circuitry, scientists are pushing to demonstrate their high speed, high packing density and low power consumption capabilities as well as the ability to make them viable for potential mass production. “The success of nanoelectronics will largely depend on the ability to build reliable carbon nanotube transistors,” said Dr. Phaedon Avouris, IBM Fellow and lead researcher for IBM’s carbon nanotube efforts.

“Using this technique, we will now be able to locally test the performance of nano-circuits to perfect the reproducibility of carbon nanotube transistors.” To date, researchers have been able to build carbon nanotube transistors with superior performance, but have been challenged with reproducibility issues. Carbon nanotubes are sensitive to environmental influences.

For example, their properties can be altered by foreign substances, affecting the flow of electrical current and changing device performance. These interactions are typically local and change the density of electrons in the various devices of an integrated circuit, and even along a single nanotube. A better understanding of how local environment affects the electrical charge of a carbon nanotube is needed to allow the manufacture of more reliable transistors, making them viable for mass production.

Therefore, the ability to measure local electron density changes in a nanotube is essential. A team of researchers from the IBM’s T.J. Watson Research Center in Yorktown Heights have just solved this problem. This achievement was published online October 14, 2007 in the journal Nature Nanotechnology. The team monitored changes in the color of the scattered light or Raman effect from the nanotube to probe these electron density changes.

The technique takes advantage of the interaction between the motion of the atomic nuclei and the motion of the electrons so that electron density changes can be reflected in changes of the frequency of the vibrational motion of the nuclei of the nanotube atoms. In March 2006, IBM announced that its researchers built the first complete electronic integrated circuit around a single carbon nanotube molecule.