Researchers discover new material to help power electronics

The team published its findings on March 18 in the newspaper Nature Materials.

"We basically found a dual-personality material," said Joseph Heremans, co-author of the study, professor of mechanical and aerospace engineering and a prominent nanotechnology researcher from Ohio to Ohio State. . "It's a concept that did not exist before."

Their findings could mean a redesign of how engineers create all types of electronic devices. This includes everything from solar cells to your TV's light-emitting diodes, to your laptop's transistors and to the camera's light sensors on your smartphone.

These devices are the building blocks of electricity: each electron has a negative charge and can radiate or absorb energy depending on how it is handled. The holes – essentially the absence of the electron – have a positive charge. Electronic devices work by moving electrons and holes – essentially while driving electricity.

But historically, every part of the electronic device could only act as an electron holder or holder of holes, not both. This meant that the electronics needed multiple layers and several materials to work.

But Ohio State researchers have found a material: NaSn.₂As₂, a crystal that can be both a carrier for electrons and for a hole – potentially eliminating the need for multiple layers.

"It's this dogma of science, that you have electrons or holes, but you do not have both, but our findings turn it all upside down," said professor Wolfgang Windl. of materials science and engineering at Ohio State, and co-author of the study. "And it's not that an electron becomes a hole, because it's the same assemblage of particles." Here, if you look at the material in a sense, it looks like an electron, but if you look on the other side, it looks like a hole. "

This discovery could simplify our electronic components, perhaps creating more efficient systems, operating faster and breaking down less often.

Imagine it as a Rube Goldberg machine or the 1960s Mouse Trap board game: the more parts are in play and more moving parts, the less energy flows in the system – and the more it is likely that a failure will occur.

"We now have this new family of layered crystals in which the carriers behave like electrons when they travel in each layer and holes as they move through the layers. … You can imagine that there are unique electronic devices that you could create, "said Joshua Goldberger, an associate professor of chemistry and biochemistry at Ohio State.

Researchers have named this double capacity phenomenon "goniopolarity". They believe that the material works this way because of its unique electronic structure and say that it is likely that other laminate materials could present this property.

"We have not found them yet," said Heremans. "But now we know how to look for them."

The researchers made the discovery almost by accident. Bin He, a researcher with a degree from the Heremans laboratory, measured the properties of the crystal when he noticed that the material sometimes behaved like an electron carrier and sometimes as a hole-holder – which at the time , was considered by science impossible. He thought that he might have made a mistake, conducted the experiment again and again and achieved the same result.

"It's that thing he paid attention to and he did not assume anything," Heremans said.

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More information:
The geometric origin of the Fermi surface of axis-dependent conduction polarity in layered materials, Nature Materials (2019). DOI: 10.1038 / s41563-019-0309-4, https://www.nature.com/articles/s41563-019-0309-4