An electrical domain with an area smaller than 1 nm² could offer a clue to fitting more memory onto a chip. Researchers working with Washington University in St. Louis observed domains that small in zirconia, a material chemically similar to an insulator already used in silicon transistors.

In a separate study, they identified a way to switch the electrical structure of thin films made from that insulator, known as hafnia.

The studies involved Washington University materials scientist Rohan Mishra and collaborators at the University of Nebraska–Lincoln, Georgia Tech and South Korea’s UNIST, among others.

The teams combined atomic-scale simulations with electron microscopy and experiments to see how changes in the two materials could help meet growing demand for denser data storage as AI use expands.

Hafnia forms a thin insulating layer in silicon transistors. Its appeal for memory lies in a property called ferroelectricity.

An electric field can flip the direction of a ferroelectric material’s polarization, and the material holds that orientation after the field is removed. Those two orientations could encode digital information.

Most ferroelectric materials lose that behavior when thinned below about 10 nanometers. Earlier work by researchers in Germany showed that hafnia behaves differently. It can become ferroelectric in extremely thin films, even though the bulk material typically lacks that property.

To understand what drives the change, Mishra’s team worked with researchers at the University of Nebraska–Lincoln to grow single-crystal films of lanthanum-doped hafnia.

Guodong Ren, then a doctoral student in Mishra’s group, used electron microscopy to resolve individual columns of atoms.

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