The observation of "conduction spot" on NiO resistance random access memory

We succeeded in observing the "conduction spot" (CS) in the capacitor structure resistance random access memory (ReRAM), which includes a conductive filament. In this study, we used NiO prepared by thermal oxidation at a high temperature as 800°C. It requires a forming process using an extra high voltage, which partly removes the top electrode from the resistance switched area. These experiments enabled us to observe the conductive filament directly in CS on NiO ReRAM by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). From SEM images, CSs seem to be produced by some kind of breakdown, but we confirmed the reproducible resistance switching at least 50 cycles after the CS generation. By energy dispersive X-ray spectroscopy (EDX) with TEM observations, drastic oxygen reduction was observed in a local area within CS of NiO films. Moreover, the CS area depended on the injection power for forming. These experimental data suggest that the miniaturization of ReRAM will be achieved by reducing the injection power for forming.