Analysis on Resistance Change Mechanism of NiO-ReRAM Using Visualization Technique of Data Storage Area with Secondary E
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1250-G12-03
Analysis on Resistance Change Mechanism of NiO-ReRAM Using Visualization Technique of Data Storage Area with Secondary Electron Image K. Kinoshita1,2, T. Makino1, T. Yoda1, K. Dobashi1, and S. Kishida1,2 1
Department of Information and Electronics, Graduate School of Engineering, Tottori University, 4-101 Koyama-Minami, Tottori 680-8552, Japan. 2 Tottori University Electronic Display Research Center, 522-2 Koyama-Kita, Tottori 680-0941, Japan. ABSTRACT Both a low and a high resistance states which were written by voltage application in a local region of NiO/Pt films by using conducting atomic force microscopy (C-AFM) were observed by using scanning electron microscope (SEM) and electron probe micro analysis (EPMA). The writing regions are distinguishable as dark areas in a secondary electron image and thus can be specified without using complicated sample fabrication process to narrow down the writing regions such as the photolithography technique. In addition, the writing regions were analyzed by using energy dispersive X-ray spectroscopy (EDS) mapping. No difference between the inside and outside of the writing regions is observed for all the mapped elements including C and Rh. Here, C and Rh are the most probable candidates for contamination which affect the secondary electron image. Therefore, our results suggested that the observed change in the contrast of the secondary electron image is related to the intrinsic change in the electronic state of the NiO film and the secondary electron yield is correlated to the physical properties of the film. INTRODUCTION Recent years, research and development of resistive random access memory (ReRAM) which utilizes voltage induced resistive change in transition metal oxides (TMOs) as memory media is advancing. ReRAM is a candidate for a substitution for the Flash memory, which is facing a micro-fabrication limit in the near future. Furthermore, a development of a nonvolatile and high-density universal memory with fast switching and high switching endurance is expected in the future. However, the optimization of the performance and the establishment of reliability have been prevented by the facts that switching mechanism of ReRAM has not yet been clarified. Therefore, the elucidation of switching mechanism is urgently required. ReRAM has a simple structure of a top electrode (TE)/TMO/a bottom electrode (BE). Memory effect develops after a forming process, and it becomes possible to cause a set, which is a resistive switching from a high resistance state (HRS) to a low resistance state (LRS), and a reset, which is a resistive switching from the LRS to the HRS, alternately. Here, the forming is a phenomenon, which is similar to a soft breakdown, and a conductive path called a filament is formed after it. Resistive switching is thought to take place in the filament [1-4]. The reason why the elucidation of the resistive switching mechanism is hindered is attributed to the difficulty in applying conventional analytical methods to the resistance switching region due t
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