Topological Materials Could Shrink Chip Interconnects and replace copper

Amazing stuff!

"... However, as electronics continue to shrink, copper becomes a dramatically worse conductor. Now scientists find that a new class of materials containing exotic quasiparticles might one day help enable next-generation interconnects that become better conductors the thinner they get. ...

Once copper wires shrink beneath this limit—in copper’s case, 40 nanometers—their electrical conductivity drops dramatically because their electrons start experiencing more collisions. ...

Researchers are investigating other metals that show better conductivity at nanometer scales for use in interconnects. For instance, cobalt and ruthenium have electron mean free paths of 10 nm and 6 nm, respectively. This means interconnects made from these metals can get smaller than copper wires before running into the same conductivity problem. However, if they shrink far enough, they will have to deal with the same challenge. ...

In a new study, scientists instead investigated topological materials, which possess extraordinary properties based on the topology of their structures. The researchers synthesized nanowires made of one such material as a proof of concept. ...

In the new study, ... synthesized nanowires of the Weyl semimetal niobium arsenide using a method known as thermomechanical nanomolding. This method allowed the researchers to make a single-crystal nanowire 2 to 3 micrometers long and as thin as 40 nm.

The scientists found the resistivity of niobium arsenide nanowires dropped with decreasing diameter. At room temperature, a 40-nm-wide nanowire displayed a resistivity about 70 percent lower than that of bulk single crystals. Their analyses suggest this improvement was due to surface conduction. ..."

From the editor's summary and abstract:

"Editor’s summary

Nanowires of the topological Weyl semimetal niobium arsenide (NbAs) are three to four times as conductive as the bulk material. Cheon et al. used thermomechanical nanomolding to grow single-crystalline nanowires with diameters as small as 40 nanometers. These stable nanowires also have favorable breakdown current density and thermal conductivity that could enable application as interconnects in electronics. ...

Abstract

Ongoing demands for smaller and more energy-efficient electronic devices necessitate alternative interconnect materials with lower electrical resistivity at reduced dimensions.

We report the synthesis of Weyl semimetal niobium arsenide (NbAs) nanowires through thermomechanical nanomolding with single crystallinity and controlled diameters down to 40 nanometers.

The resistivity of NbAs nanowires decreases with decreasing diameter, and 40-nanometer-diameter nanowires exhibited a room-temperature resistivity of 10.5 ± 1.9 microhm·centimeters, which is ~70% lower than their bulk counterpart.

Calculations attribute this resistivity reduction to surface-dominant conduction with a long carrier lifetime at finite temperatures. Further characterization of nanowires and bulk crystals revealed high breakdown current density, stability, and thermal conductivity.

These properties highlight the potential of NbAs nanowires as next-generation interconnects that could surpass the limitations of current copper-based interconnects."

Topological Materials Could Shrink Chip Interconnects - IEEE Spectrum "New materials grow more conductive as they get smaller, not less"

Surface-dominant transport in Weyl semimetal NbAs nanowires for next-generation interconnects (no public access)

Surface-dominant transport in Weyl semimetal NbAs nanowires for next-generation interconnects (preprint, open access)

The nanowires seen in this electron microscope image were molded from a bulk feedstock of niobium arsenide crystals.