Designing Phase-Change Superlattices via Selectively Modulating Stochasticity and Covalency to Efficiently Implement Stable Multi-Level Memory

Interfacial phase-change materials (iPCMs), composed of superlattice architecture with GeTe and Sb 2 Te 3, show outstanding advancements in phase-change characteristics over alloy-based PCMs. Owing to their strongly aligned anisotropic structures, iPCMs reduce unnecessary entropic loss during phase-change operation. By conducting meticulous structural analysis, this study elucidates the structural and atomic behaviors of the phase-change process within different memory states in iPCM. Moreover, the overall phase-change properties of iPCMs are enhanced with doping Ti by selectively modulating the covalency of interatomic bonds. In addition to the improvements of the conventional phase-change characteristics, suppressed resistance drift and confined multi-level states present the potential of Ti-doped iPCM as a neuromorphic memristor. The bonding characteristics of iPCMs can be precisely tuned by selectively incorporating transition metals into either the even or odd layers of the superlattice, thereby engineering anisotropic covalency at the atomic scale. This study lays the foundation for designing frameworks for phase-change superlattices, which facilitate the development of next-generation neuromorphic memories.