August 1, 2005 11:45 AM PDT

In building nanotube chips, see what sticks?

Related Stories

U.S. leads in nanotech investment

June 29, 2005

Group aims to play nanotech nanny

June 21, 2005

Carbon nanotechnologies companies merge

December 22, 2004

The stuff of dreams

October 20, 2003
Researchers at the University of Pennsylvania have borrowed a technique from Dairy Queen that could someday help scientists resolve two problems in making nanotube chips.

Carbon nanotubes, thin tubes of pure carbon, conduct electricity faster than most other materials and do not lose electrons, a property called ballistic conductivity. Unfortunately, not all nanotubes are equal: Some act like metals and conduct electricity spontaneously, while others conduct electricity only with a jump start. To build a chip out of nanotube transistors, manufacturers have to filter out the metallic ones.

The second problem comes in placing the nanotube transistor onto a silicon chip. NEC and Intel have developed experimental methods to grow nanotubes onto the surface of a silicon wafer. The metallic nanotubes are then singed off, leaving only those that act like a semiconductor.

Under the technique devised at Penn, nanotubes are made in a chemical foundry, the current method for manufacturing, and then placed in moist, slightly acidic air. A magnetic field is applied that separates the metallic products from the semiconductor nanotubes.

The harvested semiconducting nanotubes are then poured into a solution. A silicon wafer with dots of a gluelike substance is then dipped in. Nanotubes stick to the glue and create connections between two points on the silicon water. Excess glue, and stray nanotubes, are subsequently washed off.

Using this or a similar process to produce chips remains years away, and several technical hurdles remain. Still, in theory the technique could be used to create intricate circuit patterns.

"We dip the chips into nanotubes much like dipping an ice cream cone into candy," Danvers Johnston, a graduate student in Johnson's laboratory and lead author of the study, said in a statement. "Ultimately we can make it so that the nanotubes only stick where want them to in order to form a circuit."

 

Join the conversation

Add your comment

The posting of advertisements, profanity, or personal attacks is prohibited. Click here to review our Terms of Use.

What's Hot

Discussions

Shared

RSS Feeds

Add headlines from CNET News to your homepage or feedreader.