US researchers have patented a "breakthrough" low-temperature, catalyst-free technique for growing copper nanowires.

Scientists at the University of Illinois claim that copper nanowires made using the technique could serve as interconnects in electronic device fabrication, and as electron emitters in very thin field-emission displays.

"We can grow forests of freestanding copper nanowires of controlled diameter and length, suitable for integration into electronic devices," said Kyekyoon Kim, a professor of electrical and computer engineering at the University of Illinois.

The copper nanowires are grown on a variety of surfaces, including glass, metal and plastic, by chemical vapour deposition from a precursor.

Hyungsoo Choi, a research professor in the Micro and Nanotechnology Laboratory at the University, explained that the growth process is "compatible with contemporary silicon-processing protocols".

To demonstrate the practicability of the low-temperature growth process, the researchers first grew an array of copper nanowires on a patterned silicon substrate.

They then fashioned a field-emission display based on the array's bundles of nanowires.

In a field-emission display, electrons emitted from the nanowire tips strike a phosphor coating to produce an image.

Because the researchers used a bundle of nanowires for each pixel in their display, the failure of a few nanowires will not ruin the device.

"The emission characteristics of the copper nanowires in our proof-of-principle field-emission display were very good," said Kim.

"Our experimental results suggest that bundled nanowires could lead to longer lasting field-emission displays."