In the world of electronics, thinner is often better. But as wires shrink to just a tiny fraction of the width of a human hair, traditional materials like copper falter, struggling to conduct electricity efficiently. Now, scientists at Stanford University have unveiled an unexpected champion: niobium phosphide, a topological semimetal that defies the odds. They found that this material can conduct electricity more efficiently than copper when reduced to ultrathin films — something that could have a major impact on nanoelectronics.
A New Champion in Thin Conductors
“As today’s electronic devices and chips become smaller and more complex, the ultrathin metallic wires that carry electrical signals within these chips can become a bottleneck when they are scaled down,” said Dr. Asir Intisar Khan, a visiting postdoctoral scholar at Stanford and lead author of the study.
Conventional metals like copper lose conductivity dramatically when reduced to thicknesses below 50 nanometers, making them inefficient for the dense circuitry of modern chips.
But Niobium phosphide kicks this trend. As a topological semimetal, its outer surfaces are inherently more conductive than its interior. “Our niobium phosphide conductors show that it’s possible to send faster, more efficient signals through ultrathin wires,” Khan explained. Remarkably, the material’s resistivity decreases as its thickness shrinks. So, it outperforms copper in films thinner than 5 nanometers —even at room temperature.
This ability to maintain conductivity at such scales could have profound implications for the energy efficiency of data centers, which rely on millions of chips to store and process information. “Even small gains add up when many chips are used,” Khan noted.
From Physics to Application
This discovery didn’t come easily. Niobium phosphide has been studied in bulk for years. But fabricating it as a non-crystalline film thin enough for nanoelectronics posed unique challenges. The Stanford team had to optimize everything from substrate choice to deposition temperature, which they kept at 400°C to ensure compatibility with existing silicon-based chip manufacturing.
“If you have to make perfect crystalline wires, that’s not going to work for nanoelectronics,” said Professor Yuri Suzuki, a co-author of the study. “But if you can make them amorphous or slightly disordered and they still give you the properties you need, that opens the door to potential real-world applications.”
Crucially, niobium phosphide films are not just thinner. They also require lower temperatures to fabricate than traditional crystalline materials, which often require extreme heat. So, they are easier to integrate into state-of-the-art chip designs.
Next Steps
The researchers are now exploring ways to turn their thin films into wires and testing their reliability under real-world conditions. They’re also investigating other topological semimetals to find materials with even better conductivity.
“For this class of materials to be adopted in future electronics, we need them to be even better conductors,” said Xiangjin Wu, a doctoral student at Stanford and a co-author of the study. Early results suggest that niobium phosphide is just the tip of the iceberg.
“We’ve taken some really cool physics and ported it into the applied electronics world. This kind of breakthrough in non-crystalline materials could help address power and energy challenges in both current and future electronics,” added Eric Pop, the study’s senior author.
As devices demand more power in smaller packages, the discovery of such unconventional conductors could usher in a new era of high-efficiency electronics — one ultrathin wire at a time.
The results appeared in the journal Science.
