Novel dual-personality material can hold both electrons and holes

"Now, we have this new family of layered crystals where the carriers behave like electrons when traveling within each layer, and holes when traveling through the layers. ... You can imagine there might be some unique electronic devices you could create."Joshua Goldberger, Ohio State University

A research team at The Ohio State University has discovered a way to simplify how electronic devices use electrons – with a material that can serve dual roles in electronics, where historically multiple materials have been necessary. The team reported its findings in a paper in Nature Materials.

"We have essentially found a dual-personality material," said Joseph Heremans, co-author of the paper and a professor of mechanical and aerospace engineering at Ohio State. "It is a concept that did not exist before."

The team’s findings could mean a revamp of the way engineers create electronic devices. This includes everything from solar cells, to the light-emitting diodes in televisions, to the transistors in laptops, to the light sensors in smartphone cameras.

Electronic devices work by moving electrons and holes to conduct electricity. Each electron has a negative charge and can radiate or absorb energy depending on how it is manipulated. Holes – essentially the absence of an electron – have a positive charge

Traditionally, each part of an electronic device could act as either an electron-holder or a hole-holder, not both. That meant that electronics needed multiple layers – and multiple materials – to work.

But the Ohio State researchers have now found a layered material made from sodium, tin and arsenic – NaSn₂As₂ – that can be both an electron-holder and a hole-holder, potentially eliminating the need for multiple layers.

"It is this dogma in science, that you have electrons or you have holes, but you don't have both. But our findings flip that upside down," said Wolfgang Windl, a professor of materials science and engineering at Ohio State, and co-author of the paper. "And it's not that an electron becomes a hole, because it's the same assembly of particles. Here, if you look at the material one way, it looks like an electron, but if you look another way, it looks like a hole."

The finding could simplify electronics, perhaps creating more efficient systems that operate more quickly and break down less often. This is because the more pieces at play and the more moving parts, the less efficiently energy travels throughout the system – and the greater the likelihood of failure.

"Now, we have this new family of layered crystals where the carriers behave like electrons when traveling within each layer, and holes when traveling through the layers. ... You can imagine there might be some unique electronic devices you could create," said Joshua Goldberger, associate professor of chemistry and biochemistry at Ohio State.

The researchers named this dual-ability phenomenon ‘goniopolarity’. They believe the material functions this way because of its unique electronic structure, and say it is probable that other layered materials could exhibit this property. "We just haven't found them yet," Heremans said. "But now we know to search for them."

The researchers made this discovery almost by accident. A graduate student researcher in Heremans' lab, Bin He, was measuring the properties of the crystal when he noticed that the material behaved sometimes like an electron-holder and sometimes like a hole-holder – something that, at that point, was thought to be impossible. He thought perhaps he had made an error, but when he ran the experiment again and again, he got the same result.

"It was this thing that he paid attention and he didn't assume anything," Heremans said.

This story is adapted from material from The Ohio State 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.