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Carbon-nanotube-based transistors can outperform transistors made from silicon, according to a new study. The finding strengthens the position of carbon nanotubes as the leading contender to replace silicon in electronic devices when the size of silicon-based circuits can no longer be reduced. Advances in microelectronics, lithography, and related fields have helped shrink electronic circuits at a fast rate for the past two decades. But experts contend that such reductions cannot continue much longer due to limitations imposed by fundamental materials properties. So researchers are investigating new materials and methods for making circuits with nanometer-scale dimensions. "Carbon nanotubes are already the top candidate to replace silicon when current chip features just can't be made any smaller--a barrier expected to be reached in 10 to 15 years. Yet even with carbon-nanotube-based electronics poised to make a big splash, silicon circuitry has maintained a comfortable, if shrinking, lead over the competition. But now carbon nanotubes have pulled ahead in the performance race. The latest Co.'s carbon-nanotube field-effect transistors (FETs) outperform transistors found in today's commercially available devices and even score higher than prototype advanced silicon-based transistors. Authors report that their new carbon-nanotube FETs work better in terms of the switching rate and the amount of current they can carry per width of conductor. The new devices differ from carbon-nanotube FETs demonstrated previously in several important ways, Avouris explains. The latest round of FETs do not use a silicon wafer that supports the device as one of the electrodes. Instead, the FETs are designed with a top gate--an electrode situated above the nanotube that controls the flow of electricity through the device. The design enables all FETs in contact with the silicon wafer to be switched individually--an advantage that opens the door to increasing device complexity. In addition, the switching voltage has been decreased by roughly one order of magnitude relative to older designs. And both p-type (positive-charge carrying) and n-type devices were demonstrated by the group further increasing the usefulness of the new circuit building blocks. "The work shows that carbon- nanotube transistors can be very competitive with silicon, and therefore the effort in nanotube research is certainly worthwhile. PERFORMANCE Carbon-nanotube field-effect transistors (FETs), with a design that places a gate (electrode) above a carbon nanotube and includes very thin insulating layers, outperform FETs made from silicon |
| UPDATE | 06.02 |
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