Scientists Harness Electric Fields to Direct Nanowire Growth

The ultra‑high‑vacuum electron microscope tucked away in a lab on the ground floor of the IBM Thomas J. Watson Research Center in Westchester County, NY, is a powerful tool for uncovering the physics that govern materials at the nanoscale. By visualizing how structures behave under extreme conditions, researchers can design the next generation of electronic devices.

In the lab, scientists grow nanowires—tiny, one‑micrometer‑wide crystals made from semiconducting materials—using a vapor‑liquid‑solid approach. Tiny catalytic metal droplets serve as “seeds” on a flat silicon substrate. When heated and exposed to a carefully chosen gas mixture, each seed nucleates a nanowire that extends straight upward from the droplet tip.

In a breakthrough study, IBM researchers led by Dr. Frances Ross, in collaboration with the University of Cambridge, the University of Pennsylvania, and the Technical University of Denmark, demonstrated that applying an electric field during growth can deform the catalyst droplet. This deformation steers the nanowire, causing it to bend or stretch in response to the field. The findings were published in Nature Communications (DOI: 10.1038/ncomms12271).

“We wanted to add a new control knob to our growth process,” said Ross. “By turning an electric field on and off, we could observe the droplet deform and the nanowire follow its motion.” The team experimented with temperature, pressure, gas composition, and catalyst material, but the electric field offered a novel way to dictate growth direction.

Observing the process in real time required the microscope’s 50,000‑× magnification and 30 frames per second recording capability. This setup allowed researchers to capture the dynamic response of the droplet and the nanowire as the field was applied.

“Metals respond predictably to electric fields,” Ross explained. “When we saw the droplet shift, we also saw the nanowire grow along the new trajectory, revealing a direct link between droplet mechanics and crystal growth.”

The experiments also yielded a precise measurement of the catalyst droplet’s surface tension—a key parameter for computational models that predict nanowire behavior. Accurate surface‑tension values help scientists design growth protocols that reliably produce desired shapes.

“Temperature and pressure adjustments give us vertical growth,” Ross noted. “With an electric field, we can now force wires to grow sideways or at arbitrary angles, opening the door to three‑dimensional nanostructures.”

Applications for “dancing” Nanowires

Nanowires that can be steered into specific geometries have broad implications for next‑generation electronics. Angled or kinked wires could serve as interconnects in densely packed circuits, enable novel IoT sensors, or act as probes that interface directly with living cells to monitor electrical activity. Additionally, wire geometries shaped like letters “T” or “X” can be used in magnetic fields to study quantum excitations—an essential step toward robust quantum‑information storage.

The Ultra‑High‑Vacuum Electron Microscope in 360°

Beyond growth experiments, the microscope’s 360‑degree imaging capability allows researchers to inspect nanostructures from all angles, ensuring that subtle morphological changes are not missed. This comprehensive view is critical for validating the reliability of electrically driven nanowire fabrication.