Technique readies carbon nanotubes for flexible electronics

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Carbon nanotubes hold a great deal of promise for use in low cost flexible electronics and displays, thanks to their high conductivity.

However, their use has so far been restricted because creating single tubes suitable to serve transistors is very difficult. Now, researchers from the University of Illinois have found away to heal gaps in wires too small for even the smallest soldering iron. The nano-soldering process is described as simple and self-regulating. A carbon nanotube array is placed in a chamber pumped full of 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 is said to improve 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. "It would be easy to insert the chemical vapour deposition (CVD) process in existing process flows," said lead researcher Professor Joseph Lyding. "CVD technology is commercially available off the shelf. "People can fabricate these transistors with the ability to turn them on so that this process can be done. Then when it's finished they can finish the wiring and connect them into the circuits. Ultimately it would be a low cost procedure." Now, the group is working to refine the process. "We think we can make it even better," Lyding noted. "This is the prelude, we hope, but it's actually quite significant."