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Y-shaped carbon nanotubes can switch

Posted: 18 Aug 2005 ?? ?Print Version ?Bookmark and Share

Keywords:carbon nanotube? transistor? computer?

Researchers at the University of California San Diego (UCSD) and Clemson University have discovered that specially synthesized carbon nanotube structures exhibit electronic properties that are improved over conventional transistors used in computers, according to UCSD.

UCSD engineering professors Prabhakar Bandaru and Sungho Jin, graduate student Chiara Daraio, and Clemson physicist Apparao Rao have reported in the September issue of Nature Materials that Y-shaped nanotubes can be made to behave as three-terminal electronic switches similar to conventional transistors.

"This is the first time that a transistor-like structure has been fabricated using a branched carbon nanotube," said Bandaru, in a statement. "This discovery represents a new way of thinking about nano-electronic devices, and I think people interested in creating functionality at the nanoscale will be inspired to explore the ramifications of these Y-junction elements in greater detail."

The Y-shaped nanotubes discussed in the Nature Materials paper are only a few tens of nanometers thick and can be made as thin as a few nanometers.

"The small size and dramatic switching behavior of these nanotubes makes them candidates for a new class of transistor," said Bandaru.

The Y-shaped carbon nanotube transistors were initially grown as straight elements. Titanium-modified iron catalyst particles added to the synthesis mixture are then attached to the straight nanotubes, to nucleate additional growth, which continued like branches growing from a tree trunk.

Experiments conducted in Bandaru's lab at UCSD's Jacobs School of Engineering showed that the movement of electrons through the Y-junction can be controlled, or gated, by applying a voltage to the stem.

Bandaru said the gating phenomenon makes Y-shaped nanotubes the smallest ready-made transistors yet devised, with rapid switching speeds and possible three-way gating capability. In earlier attempts to make carbon nanotube-based transistors, separate gates were added rather than grown in.

- Peter Clarke

EE Times

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