University of Illinois researchers have developed a way to heal gaps in wires too small for even the world's tiniest soldering iron.
Carbon nanotubes themselves are high-quality conductors, but creating single tubes suitable to serve as transistors is very difficult. Arrays of nanotubes are much easier to make, but the current has to hop through junctions from one nanotube to the next, slowing it down. In standard electrical wires, such junctions would be soldered, but how could the gaps be bridged on such a small scale?
"It occurred to me that these nanotube junctions will get hot when you pass current through them," said Lyding, "kind of like faulty wiring in a home can create hot spots. In our case, we use these hot spots to trigger a local chemical reaction that deposits metal that nano-solders the junctions."
The nano-soldering process is simple and self-regulating. A carbon nanotube array is placed in a chamber pumped full of the metal-containing gas molecules. When a current passes through the transistor, the junctions heat because of resistance as electrons flow from one nanotube to the next. The molecules react to the heat, depositing the metal at the hot spots and effectively "soldering" the junctions. Then the resistance drops, as well as the temperature, so the reaction stops.
The nano-soldering takes only seconds and improves the device performance by an order of magnitude -- almost to the level of devices made from single nanotubes, but much easier to manufacture on a large scale. [emphasis mine]
That was informative - thank you