The crystallization mechanism of zirconium-doped Sb₂Te₃ material for phase-change random-access memory application

Sb₂Te₃ (ST) as phase-change material has the advantage of high speed, but very poor thermal stability, which cannot be directly used for phase-change random-access memory (PCRAM). In this study, Zr_1.5(Sb₂Te₃)_98.5 (ZST) material was investigated for PCRAM application. Zr dopant can efficiently improve the thermal stability of ST alloy, stabilizing its amorphous state at room temperature. During annealing process, amorphous ZST film firstly transfers to face-centered cubic structure with small grain size, and following the second switching to hexagonal phase, it is delayed to 225 °C, which is more than 100 °C higher than ST alloy, confirming by in situ heating transmission electron microscopy. Furthermore, ZST-based PCRAM cell has good endurance up to 1.5 × 10⁴ electrical cycles, a high amorphous resistance larger than 10⁶ Ω and a resistance ratio of about 1.5 orders of magnitude. The reversible phase transition can be realized by a pulse of 100 ns.