Mines Physicist Assists in Nanotech Computer Memory Material Breakthrough

Dr. Tula Paudel (left), who assisted in the creation of a ultra-thin memristor that could change how computer memory is stored, stands with his graduate students, Paul White, Bhubnesh Lama, and Khimananda Acharya.

Tula R. Paudel, Ph.D., assistant professor of physics at South Dakota Mines is among the researchers who helped discover new active materials for computer memory. The discovery could lead to increased memory storage in a smaller space at increased computer speeds.

Paudel and the team are working with multiferroic materials that can be electrically and magnetically polarized. Magnets inside a compass are one example of material that can be magnetically polarized; one side of the magnet will always point toward the magnetic north pole. In the 1920s, researchers found that certain materials can change their polarization when an electric current is applied. These materials are called ferroelectric. Both electrical and magnetic polarization co-exists in multiferroic materials.

Ferroelectric materials like magnets contain polarized regions called domains separated by thin walls. An electric field can switch the polarization of these regions and, like a switch, record a direction as one or a zero.

In recent years researchers have begun to study ferroelectricity on smaller and smaller scales. This has led to a focus on the thin boundaries, or domain walls, that separate domains. Paudel and his team found that when they applied electric current to a very thin layer of a ferroelectric Bismuth ferrite, they could move these walls.

The team showed that unlike a RAM on a magnetic disk, which needs continued zaps of electricity to keep polarized directional memory intact, this ultra-thin layer of bismuth ferrite will hold its polarization even after the power shuts off. Paudel says that at these small scales, the presence of oxygen vacancy within the crystalline structure of the material helped balance the charge in the domain walls, thus, locking them in place until a current is again applied. The potential of this discovery is that computers using this technology would have intact memory even when shut down without allowing for storing memory in magnetic storage. Furthermore, the team found they could store more memory than just using 1's and 0's with these methods.

"This material allows us to expand from binary memory to multiple memory. This could also allow a computer that could be computing and storing memory at the same time," says Paudel.

Paudel says this property is called a memristive behavior—or a type of device that memorizes the polarization state through it. This discovery could have great value in the creation of next-generation computing technology.

"We know how to create these domains; we know how to control these domains. We understand the fundamental science behind the process," he says. "There is a lot more work that needs to be done to convert this fundamental knowledge to devices."

Paudel began work with this team during his tenure as a post-doc at the University of Nebraska Lincoln. You can read more about this research in this article. The scientific paper on this subject, published in the journal Nature, is titled, In-plane charged domain walls with memristive behavior in a ferroelectric film. Paudel is continuing the research as a faculty member in the physics department at South Dakota Mines. His separate work on ultrathin ferroelectric films Prominent Size Effects Without a Depolarization Field Observed in Ultrathin Ferroelectric Oxide Membranes has recently been published in the journal Physical Review Letters.

"This is a very collaborative effort, it's a multi-national and multi-institutional effort. I am excited about the future of this work," he says. He's currently working with three graduate students on this research and other projects in this field. He is seeking more students to work with.  

Last edited 8/16/2023 6:43:13 PM

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