IBM scientists have made carbon nanotube transistors smaller and faster silicon transistors. Carbon nanotube transistors have long had the potential to be better than silicon, but this is the first time when that promise has been realized. Now IBM and others will have to scale up superior carbon nanotube devices.
IBM scientists have been experimenting with carbon nanotubes, rolled-up sheets of carbon atoms just 1 nanometer, or a billionth of a meter, in diameter. But difficulties working with the material have meant that, for optimal performance, nanotube transistors have to be even larger than current silicon transistors, which are about 100 nanometers across. To cut that number down, a team of scientists used a new technique to build the contacts that draw current into and out of the carbon nanotube transistor. They constructed the contacts out of molybdenum, which can bond directly to the ends of the nanotubes, making them smaller. They also added cobalt so the bonding could take place at a lower temperature, allowing them to shrink the gap between the contacts. Another advance allowed for practical transistors. Carrying enough electrical current from one contact to another requires several nanotube “wires.
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