Niobium phosphide can conduct electricity better than copper in films that are only a few atoms thick; moreover, these films can be created and deposited at sufficiently low temperatures to be compatible with modern computer chip fabrication, according to a team of scientists led by Stanford University.
A film a few atoms thick of non-crystalline niobium phosphide conducts better through the surface to make the material, as a whole, a better conductor. Image credit: Il-Kwon Oh / Asir Khan.
“We are breaking a fundamental bottleneck of traditional materials like copper,” said Stanford University’s Dr. Asir Intisar Khan.
“Our niobium phosphide conductors show that it’s possible to send faster, more efficient signals through ultrathin wires.”
“This could improve the energy efficiency of future chips, and even small gains add up when many chips are used, such as in the massive data centers that store and process information today.”
Niobium phosphide is what researchers call a topological semimetal, which means that the whole material can conduct electricity, but its outer surfaces are more conductive than the middle.
As a film of niobium phosphide gets thinner, the middle region shrinks but its surfaces stay the same, allowing the surfaces to contribute a greater share to the flow of electricity and the material as a whole to become a better conductor.
Traditional metals like copper, on the other hand, become worse at conducting electricity once they are thinner than about 50 nm.
The researchers found that niobium phosphide became a better conductor than copper at film thicknesses below 5 nm, even when operating at room temperature.
At this size, copper wires struggle to keep up with rapid-fire electrical signals and lose a lot more energy to heat.
“Really high-density electronics need very thin metal connections, and if those metals are not conducting well, they are losing a lot of power and energy,” said Stanford University’s Professor Eric Pop.
“Better materials could help us spend less energy in small wires and more energy actually doing computation.”
Many researchers have been working to find better conductors for nanoscale electronics, but so far the best candidates have had extremely precise crystalline structures, which need to be formed at very high temperatures.
The niobium phosphide films made by the team are the first examples of non-crystalline materials that become better conductors as they get thinner.
“It has been thought that if we want to leverage these topological surfaces, we need nice single-crystalline films that are really hard to deposit,” said Akash Ramdas, a doctoral student at Stanford University.
“Now we have another class of materials — these topological semimetals — that could potentially act as a way to reduce energy usage in electronics.”
Because the niobium phosphide films don’t need to be single crystals, they can be created at lower temperatures.
The scientists deposited the films at 400 degrees Celsius (752 degrees Fahrenheit), a temperature that is low enough to avoid damaging or destroying existing silicon computer chips.
“If you have to make perfect crystalline wires, that’s not going to work for nanoelectronics,” said Stanford University’s Professor Yuri Suzuki.
“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.”
The authors are also working on turning their niobium phosphide films into narrow wires for additional testing.
They want to determine how reliable and effective the material could be in real-world applications.
“We’ve taken some really cool physics and ported it into the applied electronics world,” Professor Pop said.
“This kind of breakthrough in non-crystalline materials could help address power and energy challenges in both current and future electronics.”
The work was published in the journal Science.
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Asir Intisar Khan et al. 2025. Surface conduction and reduced electrical resistivity in ultrathin noncrystalline NbP semimetal. Science 387 (6729): 62-67; doi: 10.1126/science.adq7096
This article is a version of a press-release provided by Stanford University.
