Recipe for ultrafast and persistent phase-change memory materials

The contradictory nature of increasing the crystallization speed while extending the amorphous stability for phase-change materials (PCMs) has long been the bottleneck in pursuing ultrafast yet persistent phase-change random-access memory. Scandium antimony telluride alloy (ScxSb2Te3) represents a feasible route to resolve this issue, as it allows a subnanosecond SET speed but years of reliable retention of the RESET state. To achieve the best device performances, the optimal composition and its underlying working mechanism need to be unraveled. Here, by tuning the doping dose of Sc, we demonstrate that Sc0.3Sb2Te3 has the fastest crystallization speed and fairly improved data nonvolatility. The simultaneous improvement in such ‘conflicting’ features stems from reconciling two dynamics factors. First, promoting heterogeneous nucleation at elevated temperatures requires a higher Sc dose to stabilize more precursors, which also helps suppress atomic diffusion near ambient temperatures to ensure a rather stable amorphous phase. Second, however, enlarging the kinetic contrast through a fragile-to-strong crossover in the supercooled liquid regime should require a moderate Sc content; otherwise, the atomic mobility for crystal growth at elevated temperatures will be considerably suppressed. Our work thus reveals the recipe by tailoring the crystallization kinetics to design superior PCMs for the development of high-performance phase-change working memory technology. Optimizing the composition of an alloy provides a route to ultrafast and stable non-magnetic electronic memories according to research from China. The atoms in many materials can stably exist in either an organized crystalline or a disorganized amorphous arrangement. Phase-change materials, which quickly and reversibly switch between the two states, are being developed as digital memories: small regions of the material are encoded in crystalline or amorphous states just as ones and zeros are stored in a magnetic memory. Feng Rao from Shenzhen University and co-workers developed an approach for creating phase-change memory materials that change phase quickly and retain a phase for a long time. The team identified the optimum scandium content in the alloy scandium antimony telluride and showed that this led to faster crystallization and improved data stability. In this work, we reveal the recipe for the design of superior phase-change materials to enable ultrafast and persistent memory application.