Extremely small resistive random access memory test cell structure with removable and movable bottom electrode

We established a method of preparing an extremely small memory cell by fabricating a resistive random access memory (ReRAM) structure on the tip of a cantilever of an atomic force microscope (AFM). This structure has the high robustness against the drift of the cantilever, and the effective cell size was estimated to be less than 10 nm in diameter due to the electric field concentration at the tip of the cantilever, which was confirmed using electric field simulation. This method does not require complicated sample fabrication processes such as a photolithography and etching, and enables long-time measurement of the same filament that is confined in a tiny ReRAM structure. The proposed structure, which has a removable bottom electrode, enables the performance of unique experiments such as changing electrodes for the same filament. The proposed method is shown to be effective in finding the location of oxygen reservoir, which plays an important role in causing resistive switching by exchanging oxygen ions with the filament.