Nallagatla Venkata Raveendra, Jo Janghyun, Acharya Susant Kumar, Kim Miyoung, Jung Chang Uk
Department of Physics and Oxide Research Center, Hankuk University of Foreign Studies, Yongin, 449-791, Korea.
Department of Material Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul, 151-747, Korea.
Sci Rep. 2019 Feb 4;9(1):1188. doi: 10.1038/s41598-018-37986-6.
We had discovered novel resistance switching phenomena in SrCoO epitaxial thin films. We have interpreted the results in terms of the topotactic phase transformation between their insulating brownmillerite phase and the conducting perovskite phase and the existence of a rather vertical conducting filament due to its inherent layered structure. However, the rough interface observed between the SrCoO and the Au top electrode (area ~10000 μm) was assumed to result in the observed fluctuation in key switching parameters. In order to verify the effect of rough interface on the switching performance in the SrCoO device, in this work, we studied the resistive switching properties of a SrCoO device by placing a Au-coated tip (end area ~0.5 μm) directly on the film surface as the top electrode. The resulting device displayed much improved endurance and showed high uniformity in key switching parameters as compared to the device having a large top electrode area. A simulation result confirmed that the Au-coated tip provides a local confinement of the electrical field, resulting in confinement of oxygen ion distribution and therefore localization of the conducting filament. By minimizing other free and uncontrollable parameters, the designed experiment here provides the most direct and isolated evidence that the rough interface between electrode and ReRAM matrix is detrimental for the reproducibility of resistivity switching phenomena.
我们在SrCoO外延薄膜中发现了新型电阻开关现象。我们已根据其绝缘的钙钛矿褐锰矿相和导电的钙钛矿相之间的拓扑相变以及由于其固有层状结构而存在的相当垂直的导电细丝来解释这些结果。然而，SrCoO与Au顶电极之间观察到的粗糙界面（面积约10000μm）被认为是导致关键开关参数出现波动的原因。为了验证粗糙界面对SrCoO器件开关性能的影响，在本工作中，我们通过将涂有Au的尖端（端部面积约0.5μm）直接放置在薄膜表面作为顶电极，研究了SrCoO器件的电阻开关特性。与具有大顶电极面积的器件相比，所得器件的耐久性有了很大提高，并且在关键开关参数方面表现出高度均匀性。模拟结果证实，涂有Au的尖端提供了电场的局部限制，从而导致氧离子分布的限制，进而使导电细丝局部化。通过最小化其他自由且不可控的参数，此处设计的实验提供了最直接且孤立的证据，表明电极与电阻式随机存取存储器（ReRAM）基质之间的粗糙界面不利于电阻率开关现象的可重复性。
