Kinetics Features Conducive to Cache-Type Nonvolatile Phase-Change Memory

Cache-type phase-change random-access memory is a remaining challenge on the path to universal memory. The recently designed Sc0.2Sb2Te3 (SST) alloy is one of the most promising phase-change materials (PCMs) to overcome this challenge, as it allows subnanosecond crystallization speed to reach the crystalline ("1") state at elevated temperatures (e.g., 600 K) but years of reliable retention of the amorphous ("0") state for data storage at room temperature. This contrast in kinetics behavior, upon a relatively small temperature excursion, is more dramatic than that in other PCMs. From the temperature dependence of the crystallization kinetics uncovered via ultrafast differential scanning calorimetry, here, we report an apparent fragile-to-strong crossover in the SST supercooled liquid. We illustrate that two factors are at work simultaneously. First, Sc-stabilized precursors serve as heterogeneous sites to catalyze nucleation, reducing the stochasticity and thereby accelerating the nucleation rate. Second, the SST exhibits an enlarged kinetic contrast between elevated and ambient temperatures. Together they constitute a recipe for the design of PCMs that meets the needs of cache-type nonvolatile memory.