Phase change memory (PCM) is a type of nonvolatile memory that utilizes a phase change material (PCM) capable of transitioning between an amorphous state (disorganized atoms) and a crystalline state (atoms tightly packed together). This reversible phase change produces an electrical property that can be engineered to store and retrieve data.
PCM has the potential to revolutionize data storage due to its high storage density and faster read and write capabilities. However, challenges in mass production arise from the complex switching mechanism and intricate fabrication methods associated with these materials.
In recent years, researchers from Tohoku University have explored the use of sputtering to fabricate large-area two-dimensional (2D) van der Waals (vdW) tetra-chalcogenides as promising PCMs for phase change memory. Through this technique, they successfully fabricated and identified niobium telluride (NbTe4) as an exceptionally promising material. NbTe4 stands out from other transition metal dichalcogenides (TMDs) due to its ultra-low melting point of approximately 447 ºC (onset temperature). These findings were published in the journal Advanced Materials.
Sputtering is a widely used technique for depositing thin films of materials onto a substrate, enabling precise control over film thickness and composition. In this case, the researchers deposited amorphous NbTe4 films, which could be crystallized into a 2D layered crystalline phase through annealing at temperatures above 272 ºC.
Unlike conventional amorphous-crystalline PCMs like Ge2Sb2Te5 (GST), NbTe4 offers a unique combination of a low melting point and a high crystallization temperature. This combination provides reduced reset energies and improved thermal stability at the amorphous phase.
Following the fabrication of NbTe4, the researchers proceeded to evaluate its switching performance, which proved to be superior to conventional phase-change memory compounds. The operation energy required for switching was significantly reduced in NbTe4.
Moreover, the estimated 10-year data retention temperature for NbTe4 was found to be 135 ºC, surpassing the 85 ºC of GST. This indicates excellent thermal stability and suggests that NbTe4 could be utilized in high-temperature environments like the automotive industry. Furthermore, NbTe4 exhibited a fast-switching speed of approximately 30 nanoseconds, further emphasizing its potential as a next-generation phase-change memory material.
Shuang commented, “Our research has opened up exciting possibilities for the development of high-performance phase-change memories. With its low melting point, high crystallization temperature, and exceptional switching performances, NbTe4 emerges as the ideal material to tackle the current challenges faced by existing PCMs.”
Source: Tohoku University