SerpApi.Org
Researchers in the US have developed nanowires made from niobium arsenide, a quantum material that can replace copper because it becomes a better electrical conductor as it gets thinner.
Electrical interconnects are tiny wires and connectors that link electronic systems and transistors, and allow them to communicate. They are critical to modern chip performance and are typically made of copper due to its high conductivity.
However, copper begins to lose its performance as chips shrink to the nanoscale. This increases electrical resistance and limits further miniaturization. To address the issue, researchers at New York’s Cornell University developed single-crystal nanowires from niobium arsenide, a topological quantum material.
Unlike copper, the quantum material becomes a better electrical conductor as its dimensions shrink. The researchers believe this could boost the performance and energy efficiency of future microchips.
Reinventing copper wires
Copper is widely used for microscopic processor wires (interconnects) because of its high electrical conductivity. In fact, the semiconductor industry switched from aluminum to copper in the late 1990s, with IBM pioneering the transition in 1997.
The change became necessary as transistors continued to shrink. It allowed more features to be packed onto chips. But while copper is an excellent conductor at larger sizes, its performance declines when those wires shrink to the nanoscale.
This is because as copper wires become thinner, electrons collide more frequently with their surfaces, increasing electrical resistance and reducing efficiency.
To overcome this challenge, the Cornell team turned to niobium arsenide (NbAs), a topological semimetal whose surface electrons behave differently from those in conventional metals. “Electrons that are flowing on the surface of the material travel really fast, and they do not scatter off as easily as electrons in the bulk,” Judy Cha, PhD, the paper’s senior author and a materials science professor, said.
Cha said that as copper wires become smaller, electrons increasingly collide with their surfaces, scattering in different directions and reducing conductivity. “That’s why it becomes electrically very resistive.”
In contrast to copper, which relies on electrons traveling through its interior, NbA benefits from fast-moving surface electrons. As it gets thinner, the surface effects become even stronger, improving electrical performance.
A better material
To create the ultrathin wires, the researchers used a fabrication technique known as thermomechanical nanomolding. The process begins with a bulk sample of the material that is pressed into a porous aluminum oxide mold at high temperatures.
Once the mold is removed, the scientists are left with high-quality, single-crystal nanowires that can be transferred onto silicon wafers. This approach allowed the team to precisely control wire diameters down to 10 nanometers (nm).
Cha compared the process to making pasta. “If you swap the front plate of your pasta maker, you can make fettuccine or angel hair,” she stressed. “We just take the bulk feedstock as our ‘dough’ and use different molds with different pore diameters.”
Beyond producing highly uniform nanowires, the technique speeds up materials research. The lab previously studied only one or two material systems each year. With thermomechanical nanomolding, it can now investigate one new material every month.
The team also discovered the material remained stable at room temperature. This is an important advantage because many quantum materials are fragile or prone to oxidation outside carefully controlled laboratory conditions.
“I feel like that is the real significance of the work, that one may not need the highest-quality pristine sample, and you don’t need to go to the lowest-temperature, noise-free environment to see these types of quantum mechanical effects,” Cha concluded in a press release.
The study has been published in the journal Science.
