How important is the {103} plane of stable Ge2Sb2Te5 for phase-change memory?

Closely correlating with {200} plane of cubic phase, {103} plane of hexagonal phase of Ge2Sb2Te5 plays a crucial role in achieving fast phase change process as well as formation of modulation structures, dislocations and twins in Ge2Sb2Te5. The behaviors of {103} plane of hexagonal phase render the phase-change memory process as a nanoscale shape memory. Lay description Exploring the phase-change mechanism, structures and properties of chalcogenides has been currently one of the hot topics. Ge-Sb-Te chalcogenides are of tremendous technological importance ranging from optical data storage to PRAM. Exhibiting the best performance for DVD-RAM in terms of speed and stability, Ge2Sb2Te5 is currently the most important phase-change alloy. There exist three solid phases in Ge2Sb2Te5: amorphous, metastable rocksalt (FCC) and stable hexagonal (Hex) phases. The whole switching operation in optical data storage and electronic memories is based on the following rapid cycling processes by either laser or electric heating: amorphousFCC (Erase/SET process)Hexliquidamorphous (Write/RESET process). The stable Hex is an indispensable concern to bridge the aforementioned whole cycling framework. In this work, structural correlations between the two crystalline phases were analyzed and the rich structural phenomena were unraveled. Closely correlated with {200} plane of FCC phase, {103} plane of Hex phase of Ge2Sb2Te5 plays a crucial role in achieving fast phase change process as well as formation of modulation structures, dislocations and twins in Ge2Sb2Te5. We propose that from a point view of maintaining the ultra-high transition speed, (103) of Hex phase can effectively facilitate phase-change memory. This leads to a novel concept that phase-change process can be treated as a nanoscale shape-memory, towards essential understanding of the relevant structural features of Ge-Sb-Te chalcogenides.