Scientists identify compound with memory: ScienceAlert

It is not alive and has no structures approaching the complexity of the brain, but a compound called vanadium dioxide is capable of ‘remembering’ previous external stimuli, researchers have found.

This is the first time this ability has been identified in a material; but it may not be the last. The discovery has some very intriguing implications for the development of electronic devices, in particular data processing and storage.

“Here we report long-lived electronically accessible structural states in vanadium dioxide that can provide a scheme for data storage and processing,” a team of researchers led by electrical engineer Mohammad Samizadeh Nikoo of the École Polytechnique Fédérale de Lausanne in Switzerland wrote in the paper Theirs.

“These glass-like functional devices can outperform conventional metal-oxide-semiconductor electronics in terms of speed, power consumption and miniaturization, and provide a path to neuromorphic computing and multi-level memories.”

Vanadium dioxide (VO2) is a material that has recently been floated as an alternative or complement to silicon as a base for electronic devices, due to its potential to outperform the latter material as a semiconductor.

One of the most intriguing properties of VO2 is that, below 68 degrees Celsius (154.4 degrees Fahrenheit), it behaves like an insulator – but above that critical temperature, it suddenly changes to a metal, with good conductivity, a change known as the metal-insulator transition.

Only recently, in 2018, did scientists discover the reason: as the temperature rises, the way atoms arrange themselves in their lattice pattern changes.

When the temperature drops again, the material returns to its original state of insulation. Samizadeh Nikoo first set out to investigate how long VO2 switches from insulator to metal and vice versa, taking measurements when he turns on the switch.

It was these measurements that revealed something very special. Although returned to the same initial state, VO2 acted like he remembered Last activity.

The experiments involved injecting an electric current into the material, which took a precise path from one side to the other. This current ignited the VO2, causing it to change its state – the aforementioned rearrangement of the atomic structure. When the current was removed, the atomic structure relaxed again.

When the power was reapplied, things got interesting.

“The voice2 it seemed to ‘remember’ the first phase transition and predict the next,” explains electrical engineer Alison Matioli of EPFL. “We didn’t expect to see this kind of memory effect, and it’s not about the electronic states, but rather the physical structure of the material . It’s a new discovery: no other material behaves in this way.”

The team’s work revealed that VO2 stored some type of information in the most recently applied stream for at least three hours. In fact, it could be significantly longer — “but we don’t currently have the instruments to measure it,” says Matioli.

The switch remembers the behavior of neurons in the brain, which serve as both a memory unit and a processor. Described as neuromorphic technology, computing based on such a system could have a real advantage over classic chips and circuit boards.

Because this dual property is inherent to the material, VO2 seems to tick all the wish list boxes for memory devices: potential for high capacity, high speed and scalability. In addition, its properties give it an advantage in memory devices that encode data in a binary format controlled by electrical states.

“We have reported glass-like dynamics in VO2 that can be excited on sub-nanosecond time scales and monitored over several orders of magnitude in time, from microseconds to hours,” the researchers write.

“Thus, our functional devices can potentially meet the ongoing demands of electronics in terms of downscaling, fast operation, and low supply voltage.”

The research was published in Nature Electronics.

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