Shen Xueyang, Zhou Yuxing, Zhang Hanyi, Deringer Volker L, Mazzarello Riccardo, Zhang Wei
Center for Alloy Innovation and Design (CAID), State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an, 710049, China.
Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, Oxford, OX1 3QR, UK.
Nanoscale. 2023 Sep 29;15(37):15259-15267. doi: 10.1039/d3nr03536k.
Elemental antimony (Sb) is regarded as a promising candidate to improve the programming consistency and cycling endurance of phase-change memory and neuro-inspired computing devices. Although bulk amorphous Sb crystallizes spontaneously, the stability of the amorphous form can be greatly increased by reducing the thickness of thin films down to several nanometers, either with or without capping layers. Computational and experimental studies have explained the depressed crystallization kinetics caused by capping and interfacial confinement; however, it is unclear why amorphous Sb thin films remain stable even in the absence of capping layers. In this work, we carry out thorough molecular dynamics (AIMD) simulations to investigate the effects of free surfaces on the crystallization kinetics of amorphous Sb. We reveal a stark contrast in the crystallization behavior between bulk and surface models at 450 K, which stems from deviations from the bulk structural features in the regions approaching the surfaces. The presence of free surfaces intrinsically tends to create a sub-nanometer region where crystallization is suppressed, which impedes the incubation process and thus constrains the nucleation in two dimensions, stabilizing the amorphous phase in thin-film Sb-based memory devices.
元素锑（Sb）被认为是一种有潜力的材料，可用于提高相变存储器和神经形态计算设备的编程一致性和循环耐久性。尽管块状非晶态锑会自发结晶，但通过将薄膜厚度减小至几纳米，无论有无覆盖层，非晶态的稳定性都能大大提高。计算和实验研究已经解释了由覆盖层和界面限制引起的结晶动力学抑制现象；然而，尚不清楚为什么即使没有覆盖层，非晶态锑薄膜仍能保持稳定。在这项工作中，我们进行了全面的从头算分子动力学（AIMD）模拟，以研究自由表面对非晶态锑结晶动力学的影响。我们揭示了在450 K时块状模型和表面模型之间结晶行为的鲜明对比，这源于靠近表面区域与块状结构特征的偏差。自由表面的存在本质上倾向于形成一个抑制结晶的亚纳米区域，这阻碍了孕育过程，从而在二维上限制了成核，稳定了基于锑薄膜的存储器件中的非晶相。
