Conductive atomic chains inside insulating nanotubes create true nanowires

Wearable tech and electronic cloth may be the way of the future, but getting there requires wiring that is strong, flexible and efficient. Such wiring may now have been developed by physicists at Michigan Technological University by threading conductive tellurium atomic chains through insulating boron nitride nanotubes (BNNT). In collaboration with colleagues at Purdue University, Washington University and the University of Texas at Dallas, the physicists report their work in a paper in Nature Electronics.

As demand for smaller and faster devices grows, scientists and engineers are turning to materials with properties that can deliver when existing ones lose their punch or can't shrink enough. For wearable tech, electronic cloth or extremely thin devices that can be laid over the surface of cups, tables, space suits and other materials, researchers have begun to tune the atomic structures of nanomaterials.

These nanomaterials need to bend as a person moves, but not go all noodly or snap. They also need to hold up under different temperatures and still provide enough juice to run the software functions users expect out of their desktops and phones.

BNNTs are hollow in the middle, highly insulating, and as strong and bendy as an Olympic gymnast. That made them a good candidate to pair with another material with great electrical promise: tellurium. Strung into atom-thick chains and threaded through the hollow center of BNNTs, the tellurium forms a tiny wire with immense current-carrying capacity.

"Without this insulating jacket, we wouldn't be able to isolate the signals from the atomic chains. Now we have the chance to review their quantum behavior," Yap said. "The is the first time anyone has created a so-called encapsulated atomic chain where you can actually measure them. Our next challenge is to make the boron nitride nanotubes even smaller."

A bare nanowire is kind of a loose cannon. Controlling its electronic behavior – or even just understanding it – is very difficult when it's in rampant contact with flyaway electrons. Nanowires of tellurium, which is a metalloid similar to selenium and sulfur, are expected to possess different physical and electronic properties than bulk tellurium. Researchers just needed a way to isolate it, which BNNTs now provide.

"This tellurium material is really unique. It builds a functional transistor with the potential to be the smallest in the world," said Peide Ye from Purdue University, who led the research.

Using transmission electron microscopy at the University of Texas at Dallas, the team was surprised to find that the atoms in these one-dimensional chains wiggle. "Silicon atoms look straight, but these tellurium atoms are like a snake. This is a very original kind of structure," Ye said.

The tellurium-BNNT nanowires allowed the creation of field-effect transistors only 2nm wide; current silicon transistors on the market are 10–20nm wide. The new nanowires current-carrying capacity reached 1.5×10⁸ A cm^-2, which beats most other semiconducting nanowires. Once encapsulated, the team assessed the number of tellurium atomic chains held within the nanotube, finding single and triple bundles arranged in a hexagonal pattern.

Additionally, the tellurium-filled nanowires are sensitive to light and pressure, another promising aspect for future electronics. The team also tried encasing the tellurium nanowires in carbon nanotubes, but their properties are not measurable due to the conducting or semiconducting nature of carbon.

While tellurium nanowires have been captured within BNNTs, like a firefly in a jar, much of the mystery remains. Before people begin sporting tellurium T-shirts and BNNT-laced boots, the nature of these atomic chains needs characterizing so that their full potential for wearable tech and electronic cloth can be realized.

This story is adapted from material from Michigan Technological University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.