According to EPFL researchers, vanadium dioxide (VO2), a chemical used in electronics, is capable of “remembering” the full history of past external shocks. This is the first substance identified as having this feature, although others may exist.
Mohammad Samizadeh Nikoo, a doctoral student at EPFL’s Power and Wide-band-gap Electronics Research Laboratory (POWERlab), made an accidental finding while studying phase transitions in vanadium dioxide (VO2). At room temperature, VO2 has an insulating phase, and its lattice structure transitions abruptly from insulator to metal at around 68 °C.Traditionally, VO2 has a volatile memory: “the material immediately returns to its insulating condition after the excitation is removed,” explains Samizadeh Nikoo. For his thesis, he set out to determine how long it takes for VO2 to move from one state to another. But his research took him in a different direction. After taking a lot of measurements, he found that the structure of the material had a memory effect.
A surprising revelation
In his studies, Samizadeh Nikoo administered an electric current to a sample of vanadium dioxide. “The stream followed a course across the material until it emerged on the other side,” he explains. As the current heated the sample, the condition of the vanadium dioxide changed. And as the current passes, the substance is restored to its original state. Samizadeh Nikoo then applied a second current pulse to the material and observed that the time required for the material to change state was precisely proportional to its history. “The vanadium dioxide appeared to’remember’ the first phase transition and predict the next,” reveals POWERlab director Professor Elison Matioli. “This type of memory effect was not anticipated, and it has nothing to do with electronic states but rather the physical structure of the material. This is a remarkable discovery, as no other substance behaves in this manner. ”
A memory that can hold up to three hours
In addition, the researchers discovered that vanadium dioxide can remember its most recent external input for up to three hours. Matioli states, “The memory impact could in fact endure for several days, but we lack the necessary technology to measure this at this time.”
The significance of the team’s discovery lies in the fact that the memory effect they observed is an inherent property of the material. Engineers rely on memory to complete a variety of calculations, and there is a considerable need for materials that could improve the calculation process by providing more capacity, speed, and downsizing. Vanadium dioxide meets all three of these requirements. It also has a continuous structural memory, which makes it different from most materials, which store information as binary data that depends on how the electronic states change.
Numerous measures were performed by the researchers in order to arrive at their conclusions. They further validated their findings by using the novel technique on several materials in laboratories throughout the world. This discovery is an exact copy of what happens in the brain because vanadium dioxide switches work the same way as neurons.
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