It isn’t living and lacks the brain’s components, but researchers have discovered that a molecule called vanadium dioxide can’ remember’ previous external stimuli.
This is the first time this feature has been discovered in a material, but it may not be the last. In addition, the discovery has several interesting implications for the evolution of electronic devices, specifically data processing and storage.
“Here we present electronically accessible long-lived structural states in vanadium dioxide that can provide a scheme for data storage and processing,” wrote researchers headed by electrical engineer Mohammad Samizadeh Nikoo of Switzerland’s École Polytechnique Fédérale de Lausanne in their work.
“These glass-like functional devices could outperform conventional metal-oxide-semiconductor electronics in terms of speed, energy consumption and miniaturization, as well as provide a route to neuromorphic computation and multilevel memories.”
Known for its ability to outperform silicon as a semiconductor, vanadium dioxide (VO2) has lately been floated as an alternative to silicon as a base for electronic devices.
Moreover, VO2 also functions as an insulator below 68 degrees Celsius (154.4 degrees Fahrenheit). Still, above that threshold temperature, it quickly transforms into a metal with strong conductivity, a transformation known as the metal-insulator transition.
Scientists only recently found why: as temperature rises, the way the atoms arrange themselves in their lattice pattern changes. Then, when the temperature returns to normal, the material reverts to its insulator state.
Samizadeh Nikoo’s initial goal was to determine how long VO2 takes to move from insulator to metal and, conversely, take measurements while he flipped the switch. The data indicated despite returning to its initial state; the VO2 acted as if it remembered recent activities.
The investigations carried an electrical current through the material, specifically from one side to the other. This current heated the VO2, causing it to shift state – the aforementioned atomic structure rearrangement. The atomic structure unfolded to its original state when the current was released. Later, the current was applied again.
“The VO2 seemed to ‘remember’ the first phase transition and anticipate the next,” explains electrical engineer Elison Matioli of EPFL.
“We didn’t expect to see this kind of memory effect, and it has nothing to do with electronic states but rather with the material’s physical structure. It’s a novel discovery: no other material behaves in this way.”
The team’s studies have found that VO2 preserved information about the most recently applied current for at least three hours. It could be much longer, but “we don’t currently have the instruments needed to measure that,” Matioli says.
The switch mimics the function of neurons in the brain, which serve as both a memory unit and a processor. As a result, computing built on a similar concept, dubbed neuromorphic technology, could offer a significant edge over traditional chips and circuit boards.
VO2 appears to check all the boxes on the wishlist for memory devices: potential for great capacity, high speed, and scalability, considering this dual characteristic is inherent to the material. Furthermore, compared to memory devices that encode data in a binary format controlled by electrical states, its features provide it with an advantage.
“We have reported glass-like dynamics in VO2 that can be excited in sub-nanosecond timescales and monitored for several orders of magnitudes in time, from microseconds to hours,” the researchers wrote.
“Our functional devices can, thus, potentially meet the continuous demands of electronics in terms of downscaling, fast operation and decreasing the voltage-supply level.”
The research has been published in Nature Electronics.