Abstract
Although the presence of an oxygen reservoir (OR) is assumed in many models that explain resistive switching of resistive random access memory (ReRAM) with electrode/metal oxide (MO)/electrode structures, the location of OR is not clear. We have previously reported a method, which involved the use of an AFM cantilever, for preparing an extremely small ReRAM cell that has a removable bottom electrode (BE). In this study, we used this cell structure to specify the location of OR. Because an anode is often assumed to work as OR, we investigated the effect of changing anodes without changing the MO layer and the cathode on the occurrence of reset. It was found that the reset occurred independently of the catalytic ability and Gibbs free energy (ΔG) of the anode. Our proposed structure enabled to determine that the reset was caused by repairing oxygen vacancies of which a filament consists due to the migration of oxygen ions from the surrounding area when high ΔG anode metal is used, whereas by oxidizing the anode due to the migration of oxygen ions from the MO layer when low ΔG anode metal is used, suggesting the location of OR depends on ΔG of the anode.
Highlights
We reported a method, which involved the use of an AFM cantilever, for preparing an extremely small resistive random access memory (ReRAM) cell that has a removable bottom electrode (BE)[14]
A Pt-top electrode (TE)/NiO/X-BE (X = Pt, Au, Ni, or TiN) structure was formed by contacting the X-BE with the cantilever and the area of the structure was estimated to be less than 10 nm in diameter[14]
These four BEs were used for reset, and will be denoted hereafter as X-BE(R) (X = Pt, Au, Ni, or TiN)
Summary
The presence of an oxygen reservoir (OR) is assumed in many models that explain resistive switching of resistive random access memory (ReRAM) with electrode/metal oxide (MO)/electrode structures, the location of OR is not clear. Our proposed structure enabled to determine that the reset was caused by repairing oxygen vacancies of which a filament consists due to the migration of oxygen ions from the surrounding area when high ΔG anode metal is used, whereas by oxidizing the anode due to the migration of oxygen ions from the MO layer when low ΔG anode metal is used, suggesting the location of OR depends on ΔG of the anode. Models in which resistive switching of an electrode/metal oxide (MO)/electrode structure is caused by the thermally activated migration of oxygen ions are being widely accepted In these models, a conductive filament (CF) that is formed in the MO layer consists of oxygen vacancies, and resistive switching is caused by the generation and repair of oxygen vacancies (VO’s)[1,2,3,4,5,6,7,8,9]. The MO layer is suggested to be the OR when a metal with a high Gibbs energy of formation reaction is used as the anode, whereas to be the anode itself when a metal with a low Gibbs energy is used as the anode
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