Researchers are working toward the day when carbon nanotubes will help create computing and other electronic systems thousands of times faster than those in use today.
One challenge in making nanotubes work for electronic applications is controlling their growth patterns.
Ganapathiraman Ramanath and Pulickel Ajayan, faculty of Rensselaer Polytechnic Institute's Department of Materials Science and Engineering, already are making headway in this area.
The two RPI faculty members are the first to grow nanotubes into any set of predetermined directions on silicon-based substrates. Their work paves the way for making nanoscale devices that depend on the connection of tiny wires in many directions.
Preliminary results of their work were published last year in Applied Physics Letters.
To allow the nanotubes to grow in different directions, the researchers place pieces of silica on a silicon substrate. A catalyst, called ferrocene, is introduced along with xylene, the hydrocarbon that is the source of carbon.
Carbon nanotubes grow selectively on the silica, leaving the spaces of the silicon layer bare.
The tubes grow in different directions depending on the topography of the silica, Ramanath explains. For example, if a piece of silica is carved into a one-micrometer-thick cylindrical disc, the nanotubes will grow vertically on the silica’s top surface while growing horizontally on its side.
“We can control nanotube growth with fine detail by manipulating the topography and harnessing the way we deliver the catalyst,” Ramanath says. “This is the first time several key strategies have been combined to grow nanotubes vertically and horizontally at the same time.”
[Contact: Pulickel Ajayan, Ganapathiraman Ramanath]