|Customized Y-shaped Carbon Nanotubes Can Compute. UCSD Jacobs School of Engineering professor Sungho Jin (left), professor Prabhakar Bandaru, and postdoctoral fellow Chiara Daraio.|
Bandaru and colleagues at UCSD and Clemson University investigate nanotube electronics and reported in Nature Materials in 2005 that Y-shaped nanotubes can behave like transistors. Microscopic switches made with such nanotubes could offer a way to shrink the size of transistors beyond that possible with conventional silicon microelectronics, and offer new types of functionality.
UCSD researchers explain in this video how they analyzed the properties of Y-shaped nanotubes.
Scientific American announced its list on Nov. 13 and the list is available at the magazine’s Website and will be published in the magazine’s December 2006 issue, which is expected at newsstands Nov. 21.
Bandaru has focused his research on the underlying physics and chemistry of modern materials, focusing primarily on the electrical, magnetic, and optical properties at the nanoscale. “I feel very honored to be included in this list, and this recognition is also a credit to many people who have helped me, including my collaborators and colleagues at UCSD and fellow researchers at other institutions who also study nanotubes,” said Bandaru. “It’s interesting that the Scientific American editors call the graphitic structures we work with ‘chicken wire.’ I wish they were as easy to handle as chicken wire.”
|Schematic drawing of a single-walled carbon nanotube showing the chicken-wire molecular architecture. Credit: NASA Glenn Research Center|
The Y-shaped nanotube transistors were initially grown as straight elements. Titanium-modified iron catalyst particles added to the synthesis mixture were then attached to the straight nanotubes, nucleating additional growth, which continued like branches growing from a tree trunk. Consequently, the nascent nanotubes assumed a Y-shape with the catalyst particle gradually becoming absorbed at the junction of the stem and two branches.
Experiments conducted in Bandaru’s lab showed that the movement of electrons through the Y-junction can be finely controlled, or gated, by applying a voltage to the stem. Bandaru hypothesized that positive charge applied to the stem enhances the flow of electrons through the two arms, producing a strong “on” signal. Then, when the polarity of the charge is reversed, the movement of electrons through the arms essentially stops, creating an “off” signal. Such binary logic is the basis of nearly all transistors.
Bandaru is continuing to study new categories of Y-shaped nanotubes that have geometry-dependent electrical effects. “Large-scale assembly of hundreds, thousands, or even millions of these tubes is still an unsolved technical issue,” he said. “In addition to the use of nanotubes for electronics, we’re also looking into using nanotubes as fluid-flow sensors.”
Founded in 1845, Scientific American is the oldest continuously published magazine in the U.S. Editorial contributors to the magazine have included more than 100 Nobel laureates.