Npj Comput. Mater.: 稳定相变存储材料的非晶结构：巧用维度变化

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相变存储材料在室温下具有稳定的晶体相和非晶相两种结构。通过利用材料在这两相间的电阻率差异和快速可逆的相变过程，相变存储器件可以实现数据“0”和“1”的信息存储。进一步地，通过调控器件中相变材料晶体相与非晶相两相间的比例，可以实现数据的多级存储，为人工智能以及类脑计算提供硬件支持。但传统相变存储材料（例如锗锑碲三元合金）的非晶相热稳定性较差，在 150℃左右会发生自发的结晶化过程，难以满足车载芯片等嵌入式应用场景的工况温度需求。

Fig. 1 | Materials screening for ABCh ₃ alloys.

a The trilayer slab of CrGT with Crcentered octahedrons and Ge-centered tetrahedrons being highlighted. The Cr, Ge, and Te atoms are rendered with red, blue, and green spheres, respectively. b The high-throughput materials screening scheme employed in this work. c–e The three typical crystal structures that are comprised of trilayer slabs in different stacking order.

通过在相变材料中进行元素掺杂，可以有效的提升材料的非晶热稳定性，但这又会增加相变材料在读写循环过程中发生材料偏析以及分相的趋势。因此，有必要寻找非晶相具有本征高热稳定性的相变存储材料。

Fig. 2 | The calculated band structures.

a rhombohedral CrGeTe ₃ , b rhombohedral CrSiTe ₃ , crhombohedral ScSiTe _3, d rhombohedral BiSiTe ₃ , e rhombohedral InGeTe ₃ , fhexagonal InSiTe ₃ , and g hexagonal AlSiTe ₃ . The bands are plotted in black for non-magnetic compounds, and the bands are plotted in red (spin up) and blue (spin down) for magnetic compounds.

来自西安交通大学材料创新设计中心的张伟教授团队，以新近发现的铬锗碲（CrGeTe ₃ ）层状相变材料（具有本征高热稳定性）为蓝本，通过基于晶体学数据库的高通量材料筛选、以及计算模拟结合实验验证的方法，发现了一类具有本征非晶热稳定性的二维层状相变存储材料。

Fig. 3 | Local structure analyses of amorphous models.

a The amorphous models generated by the melt-quench simulation scheme for the tellurides CrSiTe ₃ , ScSiTe ₃ , BiSiTe ₃ , InGeTe ₃ , InSiTe ₃ , and AlSiTe ₃ . The representing colors for different atoms are marked in the figure. b The radial distribution function (RDF), c angular distribution function (ADF), and d coordination number distribution for the respective compounds. The data are collected from the annealing trajectories at 300 K for 30 ps.

他们模拟预测并实验验证了铟锗碲合金（InGeTe ₃ ）具有显著高于传统锗锑碲合金的结晶化温度，同时具有高达五个数量级的两相电阻率差异，有望应用于嵌入式相变存储器件中。除此以外，该研究还发现铬硅碲（CrSiTe ₃ ）合金的结晶化温度高达~300℃，而且在相变过程中表现出与铬锗碲合金相似的反向电阻率变化特征。

Fig. 4 | Electronic structure calculations of ABTe ₃ alloys.

The density of states (DOS) in both crystalline (c−) and amorphous (a−) phases for a CrSiTe3, b ScSiTe ₃ , c BiSiTe ₃ , d InGeTe ₃ , e InSiTe ₃ , and f AlSiTe ₃ . The spin-up and spin-down electronic states of magnetic CrSiTe ₃ are rendered in red and blue, respectively.

该研究发现良好的非晶相热稳定性是此类二维层状相变材料的共同特征，这主要归功于此类材料较为复杂的层状原子结构增加了结晶化过程中的形核能垒。

Fig. 5 | Experimental characterizations of CrSiTe ₃ , InGeTe ₃ , and AlSiTe ₃ thin films.

The sheet resistance as a function of temperature and the corresponding X-ray diffraction (XRD) pattern of preannealed a CrSiTe ₃ , b InGeTe ₃ , and c AlSiTe ₃ thin films.

Fig. 6 | Transmission electron microscopy (TEM) images.

TEM experiments on crystallized a CrSiTe3 and bInGeTe3 thin films. The dark field images, the SAED patterns, and the HR-TEM images viewed along [100] and [001] are shown.

该研究团队在二维层状相变存储材料方向的发现，启发了利用低维材料开发面向嵌入式应用场景的相变存储器件的全新思路。 该文近期发表于 npj Computational Materials 10 , 189(2024)。

论文链接：

https://www.nature.com/articles/s41524-024-01387-3

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