We show the electronic roles in vacancy-filamentary-type switching of binary oxide-based resistive random access memories using ab initio modeling. We show that charge injection and removal determine the thermodynamic stability of the filament and the diffusion in the devices. The vacancy cohesion-isolation phase transition upon charge injection and removal is thus one of the main factors that govern resistive switching. Based on the physics, we propose desirable three-layer stack structures for further improvement of the memory characteristics, where spatial differences in the oxygen chemical potential in the device cell lead to an asymmetrical vacancy filament shape that can be used to improve the memory characteristics, such as ON/OFF ratio.
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