This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A Husker research team's latest research could open the door to broader use of a class of materials whose electrical properties may someday power next-generation electronics, high-density energy storage, improved computer memory and new strategies for cooling. In a new paper published in Science, University of Nebraska–Lincoln researchers Xiaoshan Xu, Alexei Gruverman and Evgeny Tsymbal demonstrate that hafnium oxide—a tough, heat-resistant chemical compound used widely in modern electronics—is inherently antiferroelectric, a rare quality found in very few materials.
Unlike hafnium oxide, also known as hafnia, many intrinsically antiferroelectric materials contain the toxin lead, which limits their widespread use. The trio said the discovery will help settle a longstanding debate about hafnia's properties. Though scientists have long observed the material's antiferroelectric behavior, they have disagreed on whether it results from "true" antiferroelectricity or from an artificial effect stemming from the entrapment or redistribution of electrical charges.
"The paper is very exciting," said lead author Xu, Susan J. Rosowski Professor of physics and astronomy. "Not only have we discovered this new material with inherent antiferroelectricity, but the material is already compatible with the modern electronics we already have, including our cellphones and computers.
That sets it apart from all the other materials that have ferroelectricity." The paper goes a step further, suggesting that hafnia might serve as a prototype antiferroelectric, meaning it could represent the class of materials for teaching and research purposes. Its composition aligns with the classical definition of antiferroelectricity: The material's positive and negative atoms are separated by neutral atoms. An antiferroelectric material has tiny electrical polarizations, positive and negative, that naturally point in opposite directions, largely canceling each other out.
When an external voltage is applied, it acts as a switch, changing the material from electrically neutral to polarized until the charge is removed. This "switchability" is valuable because it enables the material to take in and release energy, change temperature and store information. Future applications could include high-performance capacitors that help shrink the size of electronic components and devices; solid-state cooling systems that are more compact and less reliant on environmentally harmful refrigerants; and computers with better memory due to energy-efficient storage and access to data.
Demonstrating hafnia's inherent antiferroelectricity was an interdisciplinary effort. Xu, an expert in growing thin films, used pulsed laser deposition at the Nebraska Center for Materials and Nanoscience to create an extremely thin layer of hafnium oxide on an underlying crystal. The crystal compressed the hafnia, stabilizing the atomic arrangement that confers antiferroelectricity.
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