We noted a few weeks ago a new nanotech method to make structurally pure metallic single-walled carbon nanotubes (SWNTs) and, the following week, a way to prepare semiconducting SWNTs from mixtures by eliminating the metallic ones. Maintaining the momentum of rapid progress, now comes a method to prepare high-density arrays of perfectly aligned, 95%-pure semiconducting SWNTs. From Duke University, via AAAS EurekAlert “Semiconducting nanotubes produced in quantity at Duke“:

After announcing last April a method for growing exceptionally long, straight, numerous and well-aligned carbon cylinders only a few atoms thick, a Duke University-led team of chemists has now modified that process to create exclusively semiconducting versions of these single-walled carbon nanotubes.

The achievement paves the way for manufacturing reliable electronic nanocircuits at the ultra-small billionths of a meter scale, said Jie Liu, Duke’s Jerry G. and Patricia Crawford Hubbard Professor of Chemistry, who headed the effort.

“I think it’s the holy grail for the field,” Liu said. “Every piece is now there, including the control of location, orientation and electronic properties all together. We are positioned to make large numbers of electronic devices such as high-current field-effect transistors and sensors.”

A report on their achievement, co-authored by Liu and a team of collaborators from his Duke laboratory and Peking University in China, was published Jan 20, 2009 in the research journal Nano Letters [abstract]. Their work was funded by the United States Naval Research Laboratory, the National Science Foundation of China, carbon nanotube manufacturer Unidym Inc., Duke University and the Ministry of Science and Technology of the People’s Republic of China.

Compared to their earlier method, the new method that gives essentially only semiconducting SWNTs also improved the atomic alignment of the SWNTs with the substrate on which they were grown. The researchers are investigating whether further refinement of their method might produce all metallic SWNTs.
—Jim