Toward the Speed Limit of Phase-Change Memory.

Phase-change memory (PCM) is one of the most promising candidates for next-generation data-storage technology, the programming speed of which has enhanced within a timescale from milliseconds to sub-nanosecond (≈500 ps) through decades of effort. As the potential applications of PCM strongly depend on the switching speed, namely, the time required for the recrystallization of amorphous chalcogenide media, the finding of the ultimate crystallization speed is of great importance both theoretically and practically. In this work, through systematic analysis of discovered phase-change materials and ab initio molecular dynamics simulations, elemental Sb-based PCM is predicted to have a superfast crystallization speed. Indeed, such cells experimentally present extremely fast crystallization speeds within 360 ps. Remarkably, the recrystallization process is further sped up as the device shrinks, and a record-fast crystallization speed of only 242 ps is achieved in 60 nm-size devices. These findings open opportunities for dynamic random-access memory (DRAM)-like and even cache-like PCM using appropriate storage materials.

Y-Doped Sb2Te3 Phase-Change Materials: Toward a Universal Memory.

The disadvantages of high power consumption and slow operating speed hinder the application of phase-change materials (PCMs) for a universal memory. In this work, based on a rigorous experimental scheme, we synthesized a series of YxSb2-xTe3 (0 ≤ x ≤ 0.333) PCMs and demonstrated that Y0.25Sb1.75Te3 (YST) is an excellent candidate material for the universal phase-change memory. This YST PCM, even being integrated into a conventional T-shaped device, exhibits an ultralow reset power consumption of 1.3 pJ and a competitive fast set speed of 6 ns. The ultralow power consumption is attributed to the Y-reduced thermal and electrical conductivity, while the maintained crystal structure of Sb2Te3 and the grain refinement provide the competitive fast crystallization speed. This work highlights a novel way to obtain new PCMs with lower power consumption and competitive fast speed toward a universal memory.