By Josh Perry, Editor
[email protected]

Scientists at Ohio State University (Columbus, Ohio) discovered a crystal material, NaSn₂AS₂, that acts as both an electron-holder or a hole-holder, performing the multiple roles that form the foundation of electronic devices and removing the need for multiple layers in electronics.

Researchers discovered a new material that could change the way electronic devices are formed. (Wikimedia Commons)

This research, according to a report from the university, could alter the way that engineers approach the design of everyday electronics from computers to LED to solar cells.

“Each electron has a negative charge and can radiate or absorb energy depending on how it is manipulated,” the article explained. “Holes—essentially, the absence of an electron—have a positive charge. Electronic devices work by moving electrons and holes—essentially conducting electricity.”

Prior to this research, each part of the electronic device had to be one or the other, but NaSn₂AS₂ acts like electrons when traveling within a layer and holes when moving between the layers. The scientists named this goniopolarity. They believe that other, as yet undiscovered, materials could also feature this dual-purpose.

“The researchers made the discovery almost by accident,” the article noted. A grad student “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, science thought was impossible. He thought perhaps he had made an error, ran the experiment again and again, and got the same result.”

The research was recently published in Nature Materials. The abstract stated:

“Electronic materials generally exhibit a single isotropic majority carrier type, electrons or holes. Some superlattice and hexagonal materials exhibit opposite conduction polarities along in-plane and cross-plane directions due to multiple electron and hole bands.

“Here, we uncover a material genus with this behaviour that originates from the Fermi surface geometry of a single band. NaSn₂As₂, a layered metal, has such a Fermi surface. It displays in-plane electron and cross-plane hole conduction in thermopower and exactly the opposite polarity in the Hall effect. The small Nernst coefficient and magnetoresistance preclude multi-band transport.

“We label this direction-dependent carrier polarity in single-band systems ‘goniopolarity’. We expect to find goniopolarity and the Fermi surface geometry that produces it in many metals and semiconductors whose electronic structure is at the boundary between two and three dimensions.

“Goniopolarity may enable future explorations of complex transport phenomena that lead to unprecedented device concepts.”