In situ TEM revealing pretreatment and interface effects in Ge₂Sb₂Te₅

Random access memory devices that rely on phase changes are primarily limited by the speed of crystallization. However, imaging structural dynamics in working devices with nanoscale resolution remains elusive. Using an ultrafast liquid-quenching system in transmission electron microscope, we obtain a melt-quenched amorphous phase-change material Ge₂Sb₂Te₅ nanosheet. We find that the applied incubation field (pretreatment) leads to nonuniform nucleus formation and growth in the amorphous Ge₂Sb₂Te5, accompanied by a slight change in electric properties. Moreover, the phase-change mechanism changes from the material inherent crystallization mechanism (nucleation-dominated) to the heterocrystallization mechanism, indicating the incubation period of nucleation might be bypassed.