Creating amorphous materials, which lack an organized atomic structure, usually requires a lot of energy.
This process, known as amorphization, typically involves heating materials until they melt and then cooling them quickly to lock atoms in a random arrangement.
However, researchers from the University of Pennsylvania, the Indian Institute of Science, and MIT have developed a breakthrough technique that uses far less energy to amorphize a material called indium selenide (In₂Se₃), opening up exciting possibilities for data storage technology.
In phase-change memory (PCM), data is stored by switching materials between crystalline (ordered) and amorphous (disordered) states, similar to an on/off switch.
However, PCM’s potential has been limited by the high energy needed to create these changes. Ritesh Agarwal, a materials science professor at Penn Engineering, explains that this energy demand is one reason why PCM hasn’t seen widespread use yet.
This new method, detailed in the journal Nature, uses only a tiny fraction of the energy required by traditional techniques.
The researchers found that an electrical current could amorphize In₂Se₃ without melting it. This discovery could pave the way for more energy-efficient data storage devices.
The breakthrough was made by accident. Gaurav Modi, a doctoral student at Penn Engineering, noticed that when he ran a current through thin In₂Se₃ wires, they suddenly stopped conducting electricity.
When he looked closer, he realized that sections of the wires had become amorphous. This was surprising, as amorphization normally requires pulsed electricity, not a continuous current. Suspecting he might have damaged the wires, Modi continued to investigate.
To understand this unusual effect, Modi and Agarwal sent samples of the wires to Pavan Nukala, a former student of Agarwal’s and now a professor at the Indian Institute of Science. Nukala and his team used advanced microscopy techniques to study the wires in detail.
They discovered that several unique properties of In₂Se₃—a 2D structure, ferroelectricity (the ability to polarize), and piezoelectricity (generating an electric charge under stress)—combine to create an energy-efficient path to amorphization.
The process works like an avalanche or earthquake: tiny sections of the In₂Se₃ wires begin to amorphize as the electric current deforms them. The piezoelectric properties cause parts of the wire to shift slightly, reaching a critical point where the movement spreads rapidly, creating an “acoustic jerk,” or sound wave, that deforms the entire wire.
This spreads the amorphous structure throughout the material, similar to how an avalanche gathers momentum or how seismic waves move through the earth during an earthquake.
The discovery could revolutionize data storage by providing an ultra-low-energy pathway for PCM. Agarwal and his team are excited about the potential of these findings.
“This opens up a new field in structural transformations, with great possibilities for low-power memory devices,” says Agarwal. By lowering the energy needed for PCM, this technique could lead to more efficient and powerful data storage solutions for future technologies.
