Taking another step toward post-silicon semiconductors, IBM scientists on Sunday presented a computer circuit made from a carbon nanotube, a tube-shaped molecule of carbon atoms 100,000 times thinner than a human hair.
The IBM eggheads have created a voltage inverter out of a single strand of carbon. A voltage inverter is one of three logic circuits that form the basis of current microprocessors. An inverter in a chip changes ones into zeros and vice versa. The circuit was presented on Sunday at the National Meeting of the American Chemical Society in Chicago, IBM said.
Scientists at IBM say they discovered a way to allocate two different ways of carrying electrical current on a single nanotube, making it suitable to function as a voltage inverter. All previous carbon nanotube transistors could only carry electrical current in one way, according to IBM.
Carbon nanotubes, tiny cylinders of carbon atoms, are the top candidate to replace silicon when current chip features just can't be made any smaller, IBM said. The company expects that barrier to occur in within 15 years. The beyond-silicon technology promises not only smaller, but also more powerful computers as chipmakers will be able to fit more transistors onto a chip.
The single-molecule computer circuit is IBM's second achievement using carbon this year. In April the same IBM team presented a technique to produce arrays of carbon nanotube transistors. The smaller size of carbon nanotube semiconductors allows more transistors to be placed on a chip than is possible using silicon.
The IBM team, led by Phaedon Avouris, is now working to create more complex circuits, which it sees as the next step to molecular computers. In addition the IBM scientists are working to improve the performance of individual nanotube transistors and to further integrate them into more complex circuits.