A rudimentary nanocomputer built from an array of tiny wires could point the way to skirting the limits of Moore’s Law and lead to new kinds of biosensors or microcontrollers for robots.
The wires are laid out in parallel on a surface of silicon coated with silicon dioxide, with layers of dielectric material on top and chromium and gold contacts laid perpendicularly across the nanowires.
Each point where the contacts cross the nanowires is a programmable transistor node, which can be switched between an active and an inactive state by applying voltage so that the structure forms a “Crossbar array.”
Researchers concerned with the eventual end of Moore’s Law have been experimenting with nanowires as an alternative to CMOS technology, at least for some applications. Nanowires can easily be grown from a solution on a substrate, using a variety of techniques.
Lieber and his team overcame those problems with a technique they call “Deterministic nanocombing.” After they’d already grown nanowires on one substrate, they coat another substrate that will form the base of their array with a thin layer of resist, then use electron-beam lithography to remove narrow slots in the resist layer where they want the wires to go.
After using a chemical treatment on the wires that makes them more likely to stick to the exposed silicon oxide surface, the researchers take the substrate on which they grew their nanowires and scrape it across the slotted surface of the other substrate.