Unbelievable New Memory Technology: Crystal-to-Glass Conversion with Billions of Times Less Energy Amorphization in Indium Selenide Driven by Electricity Electrically driven amorphization in the layered semiconducting ferroelectric material In2Se3 is depicted by the artist. The carrier-wind force slips the middle layer, and the lightning bolts show electrical spikes from mechanical shocks caused by piezoelectricity that amorphize the material. Credit: Jain Akanksha A new discovery in indium selenide that allows for low-energy crystalline-to-glass transitions has the potential to completely transform memory storage technology.
Bypassing the energy-intensive melting and quenching process, researchers discovered that this transformation can be accomplished by mechanical shocks generated by continuous electric current. A billion times less energy is used with this new method, which could lead to more effective data storage devices.
Groundbreaking Finding in Memory Storage Substances Indium selenide is a special material that can “shock” itself into changing from a crystalline to a glassy phase with very little power, according to a ground-breaking study published on November 6 in Nature. Compared to the traditional melt-quench method of turning crystals into glass, this transformation process uses a billion times less energy and is crucial for memory storage in devices like CDs and computer RAM.
Scientists from the Massachusetts Institute of Technology (MIT), the University of Pennsylvania School of Engineering and Applied Science (Penn Engineering), and the Indian Institute of Science (IISc) worked together on the study.
Comprehending Memory Devices’ Glass Transition Although they don’t have the usual periodic arrangement of atoms, glasses behave like solids. To keep the glass from becoming overly ordered, a crystal is liquefied (melted) and then abruptly cooled (quenched) during the glassmaking process. In order to write data, laser pulses rapidly heat and quench a crystalline material to the glassy phase; reversing the process can erase data. This melt-quench process is also utilized in CDs, DVDs, and Blu-ray discs. Computers employ comparable materials known as phase-change RAMs, where data is stored according to the resistance type—high versus low—provided by the crystalline and glassy states.
However, the issue is that these gadgets consume a lot of power, particularly when writing. The crystals must be heated to temperatures higher than 800 degrees Celsius and then abruptly cooled. The power needed for memory storage can be greatly decreased if it is possible to convert the crystal straight to glass without the need for an intermediate liquid phase.
Pradeep Kumar and Pavan Nukala Pradeep Kumar (left), who oversees the electron microscope facility at CeNSE, is pictured with Pavan Nukala (right). The screen displays images of biased nanowires. Thanks to Manjunath NS Finding of Indium Selenide’s Low-Energy Amorphization The researchers found that long stretches of indium selenide, a 2D ferroelectric material, abruptly amorphized into glass when electric current was applied to the wires. One of the original authors, Gaurav Modi, a former PhD candidate at Penn Engineering, says, “This was very unusual.” In fact, I was afraid I might have ruined the material. Any amorphization would normally require electrical pulses, but in this case, a constant current had broken the crystalline structure, which shouldn’t have
Together with Pavan Nukala, an assistant professor at the Centre for Nano Science and Engineering (CeNSE), IISc, and his PhD student Shubham Parate, Modi and Ritesh Agarwal, Srinivasa Ramanujan Distinguished Scholar in Materials Science and Engineering (MSE) at Penn Engineering, closely monitored this process under an electron microscope at length scales ranging from atoms to micrometers.
“Here at IISc, we have developed a suite of in situ microscopy tools over the past few years,” says Nukala. “We decided it was time to test these tools after Ritesh informed me of this odd observation.”
Domain Formation and Sliding Layers: The Earthquake Effect The team discovered that the 2D layers of the material slide against one another in different directions when a constant current is applied parallel to them. As a result, numerous domains—tiny pockets with distinct dipole moments—are created, each of which is separated by a defective region. The structural integrity of the crystal collapses to form glass locally when several defects meet in a small nanoscopic area, such as too many holes punched in a wall.
Tectonic plates are analogous to these domain boundaries. When they collide, mechanical (and electrical) shocks similar to an earthquake are produced. They move with the electric field. By causing disruptions far from the epicenter, this earthquake sets off an avalanche effect that results in additional domain boundaries and glassy regions, which in turn give rise to more earthquakes. When the material completely transforms into glass (long-range amorphization), the avalanche stops.
One of the original authors, Parate, says, “Seeing all of these factors come to life and play together, at different length scales in an electron microscope is just goosebumps stuff.”
Nukala points out that this ultralow energy pathway for amorphization through shocks is made possible by a number of special characteristics of indium selenide, including its 2D structure, ferroelectricity, and piezoelectricity. He continues, “To integrate these devices on CMOS platforms, we are going to push this to the next level.”
Future Phase-Change Memory Device Implications According to Agarwal, “the energy required is one of the reasons phase-change memory (PCM) devices haven’t reached widespread use.” A greater variety of PCM applications could be made possible by this development, revolutionizing data storage in gadgets like computers and smartphones.