Wang Dong, Yan Shaoan, Chen Qilai, He Qiming, Xiao Yongguang, Tang Minghua, Zheng Xuejun
School of Mechanical Engineering, Xiangtan University, Xiangtan 411105, China.
Key Laboratory of Welding Robot and Application Technology of Hunan Province, School of Mechanical Engineering, Xiangtan University, Xiangtan 411105, China.
Nanomaterials (Basel). 2019 Sep 21;9(10):1355. doi: 10.3390/nano9101355.
Oxygen ions' migration is the fundamental resistive switching (RS) mechanism of the binary metal oxides-based memristive devices, and recent studies have found that the RS performance can be enhanced through appropriate oxygen plasma treatment (OPT). However, the lack of experimental evidence observed directly from the microscopic level of materials and applicable understanding of how OPT improves the RS properties will cause significant difficulties in its further application. In this work, we apply scanning probe microscope (SPM)-based techniques to study the OPT-enhanced RS performance in prototypical HfO based memristive devices through in situ morphology and electrical measurements. It is first found that the structural deformations in HfO nanofilm induced by migration of oxygen ions and interfacial electrochemical reactions can be recovered by OPT effectively. More importantly, such structural deformations no longer occur after OPT due to the strengthening in lattice structure, which directly illustrates the enhanced quantity of HfO nanofilm and the nature of enhanced RS properties after OPT. Finally, the underlying mechanisms of OPT-enhanced RS performance are analyzed by the results of X-ray photoelectron spectroscopic (XPS) surface analysis. In the OPT-enhanced HfO nanofilm, oxygen vacancies in crystalline regions can be remarkably reduced by active oxygen ions' implantation. The oxygen ions transport will depend considerably on the grain boundaries and OPT-enhanced lattice structure will further guarantee the stability of conductive filaments, both of which ensure the uniformity and repeatability in RS processes. This study could provide a scientific basis for improving RS performance of oxides-based memristive devices by utilizing OPT.
氧离子迁移是二元金属氧化物基忆阻器件的基本电阻开关（RS）机制，最近的研究发现，通过适当的氧等离子体处理（OPT）可以提高RS性能。然而，缺乏从材料微观层面直接观察到的实验证据以及对OPT如何改善RS特性的适用理解，将给其进一步应用带来重大困难。在这项工作中，我们应用基于扫描探针显微镜（SPM）的技术，通过原位形貌和电学测量来研究典型的基于HfO的忆阻器件中OPT增强的RS性能。首先发现，由氧离子迁移和界面电化学反应引起的HfO纳米薄膜中的结构变形可以通过OPT有效地恢复。更重要的是，由于晶格结构强化，OPT后不再发生这种结构变形，这直接说明了OPT后HfO纳米薄膜数量的增加以及RS性能增强的本质。最后，通过X射线光电子能谱（XPS）表面分析结果分析了OPT增强RS性能的潜在机制。在OPT增强的HfO纳米薄膜中，活性氧离子注入可显著减少晶体区域中的氧空位。氧离子传输将很大程度上取决于晶界，OPT增强的晶格结构将进一步保证导电细丝的稳定性，这两者都确保了RS过程中的均匀性和可重复性。本研究可为利用OPT提高氧化物基忆阻器件的RS性能提供科学依据。
