Researchers at the University of Illinois have developed a low-temperature, catalyst-free technique for growing copper nanowires. These copper nanowires could serve as interconnects in electronic device fabrication and as electron emitters in a television-like, very thin flat-panel display known as a field-emission display.

Hyungsoo Choi, a research professor in the Micro and Nanotechnology Laboratory at The University of Illinois, explained: “The copper nanowires are grown on a variety of surfaces, including glass, metal and plastic by chemical vapour deposition from a precursor.

“The patented growth process is compatible with contemporary silicon-processing protocols.”

Typically, the nanowires of 70 to 250 nanometers in diameter are grown on a silicon substrate at temperatures of 200 to 300°C and require no seed or catalyst. The size of the nanowires is controlled by the processing conditions, such as substrate, substrate temperature, deposition time and precursor feeding rate. The columnar, five-sided nanowires terminate in sharp, pentagonal tips that facilitate electron emission.

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

Kyekyoon Kim, a professor of electrical and computer engineering, explained: “The emission characteristics of the copper nanowires in our proof-of-principle field-emission display were very good. Our experimental results suggest bundled nanowires could lead to longer lasting field-emission displays.”

In addition to working on flexible displays made from copper nanowires grown on bendable plastic, the researchers are also working on silver nanowires.