Copper wires in electronic chips conduct electricity less well when they become very thin. Researchers at Cornell propose a different approach.
Their niobium arsenide nanowires, on the contrary, become more conductive at the nanoscale, which could be of interest for future generations of components.
A scanning electron microscope image shows niobium arsenide nanowires still attached to a bulk raw material.
Niobium arsenide, or NbAs, belongs to the family of Weyl semimetals. These materials have electrons that circulate on their surface. These electrons move quickly and experience fewer disturbances than those present in the bulk of the material.
This characteristic becomes important when the diameter of a wire decreases. In a copper wire, electrons encounter more internal surfaces. These interactions increase electrical resistance and limit the miniaturization of connections between transistors.
The researchers fabricated single-crystal nanowires using a process called thermomechanical nanomolding. The material is pressed at high temperature into a porous mold. After removing the mold, the resulting wire is deposited on a silicon wafer.
This method allows controlling the diameter of the wires down to about 10 nanometers. The scientists were thus able to precisely compare their behavior as their size decreased. The result confirms an unusual property, absent from conventional metallic conductors.
At this scale, niobium arsenide nanowires conduct better than copper. Their behavior also remains robust at room temperature.
The result does not mean, however, that niobium arsenide will soon replace copper in all chips. The arsenic from which niobium arsenide is derived is toxic, which greatly complicates the manufacturing and handling of components. Compatibility with industrial processes will also need to be studied.
The main interest therefore lies in the demonstration of a principle. Other materials will also have to be examined to find, if they exist, safer and industry-compatible candidates.