Self-Assembled Nanotube Networks

In the brownstone neighborhoods of New York City the view out the back window is often one of myriad telephone wires hanging from a forest of poles. Now the same thing has been achieved on the nanometer scale.

Scientists at the Nippon Telegraph and Telephone Corporation (NTT) have created an arbor of nm-wide silicon pillars (with standard lithography techniques) and then, in a follow-up step, grown a
cobweb of carbon nanotubes, most of which are strung bridgelike between neighboring silicon pillars (see figure).

The NTT researchers (contact Yoshikazu Homma, 81-46-240-3462,
homma@will.brl.ntt.co.jp) are able to send currents through the suspended nanotubes, and the goal is to establish interconnection between nanodevices, and also some kind of nanotube transistor network or even a self-learning neural network.

Carbon nanotubes have versatile electrical properties. They can, for example, be made as either n-type or p-type semiconductors through doping. But the metallic nanotubes are of greater interest right now since electrons can move ballistically through the tubes (that is, moving in straight line trajectories, with few disruptive scatterings), even at room temperatures. Photonic interactions in the suspended nanotube arrays might also be an attractive possibility. (Homma et al., Applied Physics Letters, 16 September 2002)