SEOUL, September 02 (AJP) - Researchers at the Korea Advanced Institute of Science and Technology (KAIST) have successfully visualized, for the first time, how tiny particles inside memory devices move and interact when data is written and erased. The discovery could help make future memory chips faster, smaller, and more reliable — a major breakthrough for next-generation computing and artificial intelligence.
On September 2, 2025, KAIST announced that two research teams, led by Professor Hong Seung-beom and Professor Park Sang-hee of the Department of Materials Science and Engineering, have figured out exactly how electrons and oxygen ions behave inside a new kind of memory called ReRAM. Their study shows that these particles move together in complex ways and that this movement directly affects how memory stores and deletes information.
ReRAM stands for Resistive Random Access Memory. It is considered one of the most promising alternatives to current memory technologies because it can store data even when the power is off, has a simple structure, and operates at high speed. Unlike traditional memory chips, ReRAM uses special materials that can change their electrical resistance when a small voltage is applied. This change in resistance is what turns memory "on" and "off."
Until now, scientists knew that ReRAM worked because of tiny defects called oxygen vacancies, but they did not fully understand how those defects actually caused the resistance to change. That knowledge gap made it harder to design ReRAM chips that are fast, stable, and energy-efficient.
To solve this mystery, the KAIST team built a custom research tool called a “multi-modal scanning probe microscope.” This instrument combines several advanced types of microscopes into one machine. Each type looks at something different: one sees how electric current flows (C-AFM), another tracks the movement of oxygen ions (ESM), and a third detects changes in surface voltage (KPFM). Using this tool, the researchers could watch what was happening inside the memory chip in real time.
They tested a thin film made of titanium dioxide (TiO2), a common material used in ReRAM, and applied tiny electrical signals to simulate how memory gets written and erased. What they saw was that electrons need open “paths” to flow through the material, and those paths depend on where the oxygen vacancies are. When more vacancies are bunched together, the paths open up and current flows easily. When the vacancies are spread out, the paths disappear and current is blocked. This directly explained how the memory turns on and off.
The researchers also found something new: electrons and oxygen ions don’t just act separately. They interact in complex ways, and their movement is closely linked. This means that both types of particles must be controlled carefully to make ReRAM more stable and efficient.
One important discovery was related to how memory can be “erased.” During this process, oxygen ions are pushed into the material, helping the memory stay in the "off" state longer. This insight could be key to making future ReRAM devices more reliable.
"This is the first time anyone has been able to directly observe the spatial relationship between oxygen defects, ions, and electrons inside a working memory device," said Professor Hong. "Our approach can be used to study many other materials used in next-generation semiconductors, and could help open up entirely new areas of research."
The first author of the paper is PhD candidate Kong Chae-won of KAIST’s Department of Materials Science and Engineering. The study was published on July 20, 2025, in ACS Applied Materials and Interfaces, a leading journal published by the American Chemical Society.
The research was supported by the Ministry of Science and ICT and the National Research Foundation of Korea.
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Park Sae-jin
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