Friday, September 02, 2022

First material found to "remember" its own history

Amazing stuff!

"... The material in question is vanadium dioxide (VO2), and it’s already known to have some intriguing properties. It’s normally an insulator, but when heated to 68 °C (154.4 °F) its lattice structure changes, meaning it acts like a metal instead. This can make it a great coating for windows or roofs that either block heat from the Sun or let it pass through, depending on the weather. Previous studies have even found that it can conduct electricity without conducting heat. ..."

"... made a chance discovery during his research on phase transitions in Vanadium Dioxide (VO2). VO2 has an insulating phase when relaxed at room temperature, and undergoes a steep insulator-to-metal transition at 68 °C, where its lattice structure changes. Classically, VO2 exhibits a volatile memory: “the material reverts back to the insulating state right after removing the excitation” ...
In his experiments ... applied an electric current to a sample of VO2. “The current moved across the material, following a path until it exited on the other side,” ... As the current heated up the sample, it caused the VO2 to change state. And once the current had passed, the material returned to its initial state. ... then applied a second current pulse to the material, and 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.” ..."

From the abstract:
"Metal–oxide–semiconductor junctions are the building blocks of modern electronics and can provide a variety of functionalities, from memory to computing. ... Manipulation of structural—rather than electronic—states could provide a path to ultrascaled low-power functional devices, but the electrical control of such states is challenging. Here we report electronically accessible long-lived structural states in vanadium dioxide that can provide a scheme for data storage and processing. The states can be arbitrarily manipulated on short timescales and tracked beyond 10,000 s after excitation, exhibiting features similar to glasses. In two-terminal devices with channel lengths down to 50 nm, sub-nanosecond electrical excitation can occur with an energy consumption as small as 100 fJ. 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."

First material found to "remember" its own history

Researchers discover a material that can learn like the brain EPFL researchers have discovered that Vanadium Dioxide (VO2), a compound used in electronics, is capable of “remembering” the entire history of previous external stimuli. This is the first material to be identified as possessing this property, although there could be others.

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