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Politics : Formerly About Applied Materials -- Ignore unavailable to you. Want to Upgrade?

To: Proud_Infidel who wrote (53834)	10/4/2001 9:27:19 PM
From: Proud_Infidel	Read Replies (1) \| Respond to of 70976

Researchers develop nanotube SRAM By Paul Kallender EE Times (10/04/01 13:17 p.m. EST) TSUKUBA, Japan — A team of researchers at the Delft University of Technology (Delft, Netherlands) claim to have developed the world's first SRAM with carbon-nanotube-laced transistors. The university's department of applied physics has scored two firsts, said Cees Dekker, who designed the transistor. First-generation carbon nanotube (CNT) transistors, which use CNTs as the channel, use a back-gate design that employs between 150 to 200 nanometers of silicon dioxide. That severely stifles the gain so that it is usually well under 1. By developing a well-insulating local-gate design, Dekker said he has managed to get the oxide layer down to 2 nm and boosted gain enough to make digital logic circuits possible. "It's really exciting. With this design we get a gain of between 10 and 20. The main thing is that this transistor makes it possible . . . to make things like ANDs and ORs and standard flip-flops, the basic memory element," Dekker said. So far Dekker's lab has also made NOR and three-transistor ring oscillator circuits with the well transistors, and researchers can quickly improve performance parameters, he said. "Molecular logic has been one of the holy grails of nanotube research. Now we have done it. Intrinsically, these circuits will run anywhere from megahertz to terahertz speeds," he said. Dekker spoke at a symposium that gathered over 500 of the world's leading nanotechnology researchers to celebrate the 10th anniversary of the carbon nanotube. His upbeat presentation, which forayed into the possibility of splicing CNT transistors and other circuits with DNA — to combine nano- and biotechnology — reflected a common mood that carbon nanotubes are finally on the cusp of becoming the raw material for new industries. "In all my years of experience I have never seen such a keen interest in basic research, I'd call it an explosion," said Hiroshi Kamimura, professor emeritus of physics at the Science University of Tokyo. "There are so many technologists here, the gradient is so high, I think the practical applications of CNT will be realized within five years," he said. Dekker's transistors were the second breakthrough to developing high-gain nanotube circuits that are potentially vast improvements over today's common but still clumsy nanotube transistors. At present, researchers using back-gate transistors with large nanotube and metal contacts consider themselves lucky if they can make circuits with gains of a fraction of one. Dekker has found a way to cut down oxide thickness and boost gain by sandwiching it between the nanotube and the silicon dioxide substrate. In another development, Phaedon Avouris, manager of nanometer-scale science and technology at IBM, announced a different improvement when he revealed to EE Times that he has made top-gate carbon nanotube field-effect transistors. These, also capable of powerful — but as yet undisclosed — gains will also enable large-scale integration. Employing a 100-nm nanotube and running at 5 Hz, Dekker's transistor is still a long way from the THz-speed single-electron transistors researchers want to develop, said Hisatsune Watanabe, associate senior vice president of NEC Laboratories. "It is a key breakthrough, but it is just the first breakthrough," said Watanabe. "The important thing is to push integration density and application speed. These transistors will be very small, but the huge contact areas and high capacitance means their speed is very slow. These things are static and laid down one by one. First they have to improve the speed, then show manufacturability and then show large-scale integration." Watanabe said NEC Labs, like many other research institutions, has made its own transistors with nanotubes. The next stage, following breakthroughs such as those by IBM and Delft University, is to shrink the nanotubes one order and replace the clumsy metal electrodes with other nanotubes such as boron nitride nanotubes. "His [Dekker's] device is a 100-nm device. Now we need to shrink to 10 nm and then make a pure nanotube device. Now that is very attractive, and we should be able to do that within five years," Watanabe said. Decker said he was less interested in improving the performance of the transistor than attacking a bigger challenge — developing self-assembly CNT circuits hooked to DNA.