Vanadium Dioxide Has Memory Of Phases

By Wesley Roberts •  Updated: 08/22/22 •  3 min read

Vanadium Dioxide is a compound used in electronics which has distinct properties, making it an ideal silicon replacement for the next generation of low-power electronic devices.

The compound can be used, for example, to make programmable radio frequency electronic functions for aerospace communication systems. Other Vanadium dioxide applications like artificial intelligence, micro-robots, or neuromorphic computing are on the horizon.

Now, researchers at Ecole Polytechnique Fédérale de Lausanne have revealed that Vanadium Dioxide (VO2) can “remember” the complete history of previous external stimuli. It is the first material ever to be identified as having this property,

While researching phase transitions in VO2, EPFL Ph.D. student Mohammad Samizadeh Nikoo made an accidental discovery.

Vanadium Dioxide Phase Transition

Vanadium Dioxide

Credit: POWERlab / 2022 EPFL

Vanadium dioxide has an insulating phase when at room temperature, but goes through a steep insulator-to-metal transition at 68 °C (154.4°F) , where its lattice structure changes. VO2 is known to show a volatile memory.

“The material reverts back to the insulating state right after removing the excitation,”

explained Samizadeh Nikoo. For his thesis, he set out to establish how long it takes for VO2 to change from one state to another.

But his research took him in a different direction. After hundreds of measurements, he discerned a memory effect in the material’s structure.

Samizadeh Nikoo applied an electric current to a VO2 sample in an experiment.

“The current moved across the material, following a path until it exited on the other side,”

he said. As the electrical current warmed the sample, it resulted in the VO2 changing state. Once the current had passed, the material returned to its initial state.

Unforeseen Memory

When Samizadeh Nikoo applied a second current pulse to the material, he saw that the time it took to change state was directly linked to the history of the material.

“The VO2 seemed to ‘remember’ the first phase transition and anticipate the next. We didn’t expect to see this kind of memory effect, and it has nothing to do with electronic states but rather with the physical structure of the material. It’s a novel discovery: no other material behaves in this way,”

explained Prof. Elison Matioli, EPFL POWERlab head.

Vanadium Dioxide Uses

The researchers eventually found that vanadium dioxide can remember its most recent external stimulus for up to three hours. The external memory effect could remain for several days in theory, but we don’t currently have the instruments needed to measure that, according to Matioli.

The importance of the discovery is in the fact that the memory effect they observed is an intrinsic property of the material itself.

Engineers rely on memory to perform calculations of all kinds, and materials that could enhance the calculation process by offering greater capacity, speed and miniaturization are in high demand. VO2 ticks all three of these boxes.

Additionally, vanadium dioxide’s continuous, structural memory sets it apart from conventional materials that store data as binary information dependent on the manipulation of electronic states.

Original Study: Mohammad Samizadeh Nikoo, et al. Electrical Control of Glass-like Dynamics in Vanadium Dioxide for Data Storage and Processing. Nature Electronics