Department of Mechanical Engineering , National University of Singapore , 9 Engineering Drive 1 , Singapore 117576.
Institute of Materials Research and Engineering (IMRE) , Agency for Science, Technology and Research (A*STAR) , Fusionopolis Way , Innovis #08-03, Singapore 138634.
ACS Appl Mater Interfaces. 2018 Mar 7;10(9):8092-8101. doi: 10.1021/acsami.7b16188. Epub 2018 Feb 23.
Ionic transport and electrochemical reactions underpin the functionality of the memory devices. NiO, as a promising transition metal oxide for developing resistive switching random access memory, has been extensively explored in the terms of the resistive switching. However, there is limited experimental evidence to visualize the ionic processes of the NiO under the external electrical field. In addition, the correlation between the ionic processes and the resistive switching has not been established. To close this gap and also to determine the role of the ionic processes in resistive switching of the NiO, in this study, a series of scanning probe microscopy techniques, including electrochemical strain microscopy (ESM), conductive atomic force microscopy, Kelvin probe force microscopy, and a newly developed first-order reversal curve-IV, are employed to measure the ESM response, the resistive switching performance, the work function, and the ionic dynamics of NiO, respectively. The results in this work have clearly visualized the ionic transport and electrochemical reactions of NiO when subjected to the electrical field. It has been found that the ionic processes and the resistive switching accompanied each other. Furthermore, it is found that the electrochemical reactions play a determinative role in the resistive switching of the NiO, and this electrochemically induced resistive switching performance can be explained by an integrated mechanism that has combined the filamentary and the interfacial effects underlying resistive switching. In addition to providing a better understanding of the resistive switching of NiO, this work also provides effective methods to probe the ionic processes and to correlate these ionic processes to the performance of functional materials.
离子输运和电化学反应是记忆器件功能的基础。NiO 作为一种有前途的用于开发电阻式随机存取存储器的过渡金属氧化物，在电阻式开关方面已经得到了广泛的研究。然而，对于外电场下 NiO 的离子过程，目前仅有有限的实验证据可以证实。此外，离子过程与电阻式开关之间的相关性尚未建立。为了弥补这一空白，并确定离子过程在 NiO 电阻式开关中的作用，在这项研究中，我们采用了一系列扫描探针显微镜技术，包括电化学应变显微镜（ESM）、导电原子力显微镜、Kelvin 探针力显微镜以及新开发的一阶反转曲线-IV，分别测量 ESM 响应、电阻式开关性能、功函数和 NiO 的离子动力学。这项工作的结果清楚地显示了 NiO 在电场作用下的离子输运和电化学反应。研究发现，离子过程和电阻式开关相互伴随。此外，还发现电化学反应在 NiO 的电阻式开关中起着决定性的作用，这种电诱导的电阻式开关性能可以通过一个综合机制来解释，该机制结合了电阻式开关底层的丝状和界面效应。除了提供对 NiO 电阻式开关的更好理解之外，这项工作还提供了探测离子过程的有效方法，并将这些离子过程与功能材料的性能联系起来。
