相变异质结（PCH）存储材料相变行为的原位观测

相变异质结（PCH）存储材料相变行为的原位观测

董自麒，丁科元，王  旭，饶  峰，田  鹤^*，张  泽

（1. 浙江大学电子显微镜中心，硅材料国家重点实验室，材料科学与工程学院，浙江 杭州310027；2. 深圳大学，材料科学与工程学院，广东 深圳 518060；3.深圳大学光电子器件与系统教育部/广东省重点实验室，光电工程学院，广东 深圳 518060）

摘  要 相变存储器（PCM）具有速度快、寿命长等一系列优点。传统的相变存储器在相变过程中会产生蘑菇状的相变层，导致沿电流方向的元素迁移，使器件在多次循环之后失效。相变异质结（phase-change heterostructure, PCH）存储材料通过在相变材料Sb₂Te₃（ST）中嵌入约束层TiTe₂（TT），能够有效降低其在相变过程中元素迁移和结构变异的可能性，使性能获得巨大提升。为了从微观结构上深层次地解释这一原因，本文采用原位透射电镜技术，综合利用多种表征手段，通过施加电脉冲的方法，实现了相变层由晶态到非晶态的纳秒级快速转变。约束层在整个过程中结构保持不变，具有良好的稳定性，从而能够将相变层限制在纳米尺度区域，阻止元素的扩散和迁移，保持整个结构的稳定。该结果为材料的进一步优化设计提供了支持，同时为相变存储材料的研究提供了一种新的思路。

关键词 原位透射电子显微镜；相变异质结存储材料；电脉冲

中图分类号：TG115.21⁺5.3

文献标识码：Adoi:10.3969/j.issn.1000-6281.2021.01.001

In situ observation of dynamic behavior of phase-change heterostructure (PCH) memory materials

DONG Zi-qi¹，DING Ke-yuan ^2，3，WANG Xu ¹，RAO Feng^2，3，TIAN He ^1*，ZHANG Ze ¹

(1. Center of Electron Microscope, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou Zhejiang 310027；2. College of Materials Science and Engineering, Shenzhen University, Shenzhen Guangdong 518060；3.Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen Guangdong 518060, China)

Abstract  Phase-change memory（PCM）materials have a series of advantages, such as high speed and long cycle endurance. Atomic diffusion occurs in typical mushroom-type PCM devices, which results in the failure of devices after extensive cycles. The phase-change heterostructure (PCH) memory material, fabricated by alternately depositing nanolayers of a confinement material (TiTe₂) and a PCM(Sb₂Te₃), can effectively reduce the possibility of atomic diffusion and structural variation during the switching process, which greatly improves the performance. In order to explain the reason from the microstructure, electrical pulse was used to realize the rapid transition of ST layers from crystalline state to amorphous state in in-situ transmission electron microscopy. The structure of TT layers can keep stable, so that ST layers can be confined to the nanoscale region, which can suppress the atomic diffusion and migration and maintain the stability of the PCH film. The results support the further optimization of this kind of materials and provide a new idea for the research of phase change memory materials.

Keywords   in-situ TEM；phase-change heterostructure memory materials；electrical pulse

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