A Stanford-led team has devised a method of storing data that depends on the sliding of ultra-thin layers of metal. The new memory technique cannot only store more data in a given area than would be possible with any technology based on silicon but also do so using less energy.

The research, which has been led by Aaron Lindenberg, an associate professor of materials science and engineering at Stanford and the SLAC National Accelerator Laboratory, could give rise to a new type of nonvolatile memory storage representing a major upgrade to today’s silicon-based technologies, such as flash chips.

The research was detailed in the journal Nature Physics. The staring roll in this breakthrough is held by a new class of metals that form amazingly thin layers. In these experiments, the metal employed was tungsten ditelluride, and the layers themselves were each a mere three atoms thick.

Shifting Layers of Ultra-Thin Metal

The experimental procedure involved stacking these ultra-thin layers as though they were part of an atomic-scale deck of cards. Then, a minute amount of electricity is injected into the stack, which caused the odd-numbered layers to shift by a minute amount in relation to the even-numbered layers above and below it. 

As noted by Lindenberg, “The arrangement of the layers becomes a method for encoding information,” creating the on-off, 1s-and-0s that store binary data. Of great significance was that the offset was permanent, in the manner of nonvolatile memory, and reprogrammable nonvolatile. A subsequent jolt of electricity caused the skewed even and odd layers to realign. 

As illustrated below, the three separate three-atom thick layers of metal are depicted as being composed of gold balls. When electricity is applied, the tiny shift of the middle layer sets off electrons’ motion as depicted by the red swirls, encoding digital 1’s and 0’s.

Illustration of how experimental memory technology stores data.

An illustration of how experimental memory technology stores data by shifting the relative position of three atomically thin layers of metal, depicted as gold balls. The swirling colors reveal how a shift in the middle layer affects the motion of electrons in a way that encodes digital ones and zeros. Image credited to Ella Maru Studios


Accessing Stored Digital Data

A phenomenon known as the Berry curvature was employed to read the data stored between the ultra-thin layers. This quantum property serves as a magnetic field, manipulating the electrons in the device, understanding the arrangement of the layers while not disturbing the stack. 

Jun Xiao, the first author of the paper, published Nature Physics and a postdoctoral scholar in Lindenberg’s lab; it takes very little energy to cause the layers to shift back and forth. Consequently, it would take far less energy to write a one or a zero to the new device compared to extant nonvolatile memory technologies. 

A Hundred Times Faster Than Today’s Nonvolatile Memories

Even more noteworthy is that the sliding process occurs so blazingly fast that data storage could be accomplished more than a hundred times faster than with current technologies. The next step for the team will be to explore other ultra-thin 2D materials that might perform even better than the contemporary medium of tungsten ditelluride.

“The scientific bottom line here,” Lindenberg adds, “Is that very slight adjustments to these ultrathin layers have a large influence on its functional properties. We can use that knowledge to engineer new and energy-efficient devices towards a sustainable and smart future.” 

Source: All About Circuits