Femtosecond x-ray diffraction reveals a liquid-liquid phase transition in phase-change materials
Femtosecond x-ray diffraction reveals a liquid-liquid phase transition in phase-change materials
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DOI：
10.1126/science.aaw1773
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发表时间：
2019-06-14
期刊：
影响因子：
56.9
通讯作者：
Sokolowski-Tinten, Klaus
中科院分区：
文献类型：
--
作者：
Zalden, Peter;Quirin, Florian;Sokolowski-Tinten, Klaus
在相变存储器装置中，材料在玻璃态和结晶态之间循环。其结晶过程的高度温度依赖性动力学使其能够应用于存储器技术，但过渡尚未在原子尺度上解决。利用飞秒x射线衍射和从头算计算机模拟，我们确定了相变材料在整个熔融淬火和结晶过程中的时间相关的对关联函数。我们发现，在相变材料Ag_4 In_3Sb_（67）Te_（26）和Ge_（15）Sb_（85）中，分别在660和610开尔文下发生液-液相变。该过渡主要是由佩尔斯扭曲的发病，其幅度与扩散的表观活化能的增加。这揭示了原子结构和动力学之间的关系，使系统优化的记忆开关动力学。
In phase-change memory devices, a material is cycled between glassy and crystalline states. The highly temperature-dependent kinetics of its crystallization process enables application in memory technology, but the transition has not been resolved on an atomic scale. Using femtosecond x-ray diffraction and ab initio computer simulations, we determined the time-dependent pair-correlation function of phase-change materials throughout the melt-quenching and crystallization process. We found a liquid-liquid phase transition in the phase-change materials Ag4In3Sb67Te26 and Ge15Sb85 at 660 and 610 kelvin, respectively. The transition is predominantly caused by the onset of Peierls distortions, the amplitude of which correlates with an increase of the apparent activation energy of diffusivity. This reveals a relationship between atomic structure and kinetics, enabling a systematic optimization of the memory-switching kinetics.