Role of Anode on Resistance Switching Phenomenon of Metal Oxide Resistive Random Access Memory
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Role of Anode on Resistance Switching Phenomenon of Metal Oxide Resistive Random Access Memory Kentaro Kinoshita1, 2, Sang-Gyu Koh1, Takumi Moriyama1, and Satoru Kishida1, 2 1 Department of Information and Electronics, Graduate School of Engineering, Tottori University, 4-101 Koyama-Minami, Tottori 680-8552, Japan. 2 Tottori Univ. Electronic Display Research Center, 522-2 Koyama-Kita, Tottori 680-0941, Japan. ABSTRACT Although the presence of oxygen reservoir is assumed in many theoretical models which explain resistive switching of ReRAM with an electrode/metal oxide (MO)/electrode structure, the location of oxygen reservoir is not clear. We have previously reported a method for preparing an extremely small ReRAM cell which has removable bottom electrode (BE), by using AFM cantilever. In this study, we used this cell structure to specify the location of oxygen reservoir. Since an anode is assumed to work as an oxygen reservoir in most models, we investigated the effect of changing anodes for the same filament on the presence or absence of the occurrence of reset switching. It was revealed that reset occurred independently of catalytic ability and Gibbs free energy (ΔG) of anode material. However, reset was caused by repairing oxygen vacancies of which filament consists when metals with high ΔG is used as an anode, whereas by oxidizing an anode when metals with low ΔG is used as an anode. This result suggests that the MO film works as an oxygen reservoir for anode with high ΔG, whereas an anode works as an oxygen reservoir for anode with low ΔG. INTRODUCTION Models in which resistive switching is caused by the thermally activated migration of oxygen ions are being widely accepted. In these models, a conductive filament (CF) consists of oxygen vacancies and resistive switching is caused by generation and repair of oxygen vacancies (VO's).1-3) This means that resistive switching is caused by exchanging oxygen ions between the filament and oxygen reservoir. However, the details about the oxygen reservoir are still not clear. We don’t even know the location of an oxygen reservoir; does that exist in electrode or in TMO? The location of an oxygen reservoir should be elucidated, to design cell structure including electrodes and TMO materials for optimizing memory performance. Since many papers claim that an anode works as an oxygen reservoir,4-6) it is advantageous in identifying the location of an oxygen reservoir if anode is replaceable for the same filament. Recently, we have reported a method for preparing an extremely small ReRAM cell which has removable bottom electrode (BE), by using an AFM cantilever.7) First, a metal oxide film is deposited on the surface of a Pt-coated cantilever which works as top electrode. Then, by contacting a bottom electrode with the cantilever, tiny ReRAM cell structure is formed at the contact area. This method enables replacing anodes at any time simply by moving the cantilever from one BE to another BE. In this paper, the influence of changing anode material for the same filament on th
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