Nanotech breakthrough promises faster CPUs

US scientists have developed a breakthrough technique for creating functional electronic circuits using microscopic nanotubes.

The physicists at the University of Pennsylvania unveiled a revolutionary process which centes on dipping semiconductor chips into liquid suspensions of carbon nanotubes.

Single-walled nanotubes are formed by turning a single sheet of carbon atoms into a seamless cylinder approximately one nanometer a billionth of a meter in diameter.     

"The only way to make faster processors is to cram more transistors together, " Alan Johnson, associate professor in Penn's Department of Physics and Astronomy said.

"Nanotubes are just about the smallest transistors that exist right now.  So the more densely they can be packed on a chip, the faster the chips can become. "

Instead of growing nanotubes in a pattern on a silicon chip, as is conventionally done, the Penn researchers devised a means of "sprinkling" nanotubes onto chips.

"We dip the chips into nanotubes much like dipping an ice cream cone into candy," said Danvers Johnston, a graduate student in Johnson's laboratory and lead author of the study.  

"Ultimately we can make it so that the nanotubes only stick where want them to in order to form a circuit."

The resulting circuits take advantage of unique electrical properties of nanotubes and can be produced in bulk.  Since the process allows the creation of nanotubes via processes separate from the chips, this process allows for a better control of the quality and diameter, the Penn researchers said.

Previously, most nanotube circuits have been made by growing each nanotube on the surface of a chip, using a process known as chemical vapor deposition. Unfortunately, this method often results in quality variations, arbitary growth direction and large diameters in the resultant nanotubes, the researchers explained.