Observation of the Ni 2 O 3 phase in a NiO thin‐film resistive switching system

We propose that the Ni 2 O 3 phase is the conducting filament in a unipolar NiO resistive switching system. The NiO film was grown by pulsed laser deposition using platinum top and bottom electrodes. Electron diffraction and high‐resolution transmission electron microscopy were used to explore the microstructure. This system had forming‐free properties, which suggested that the filaments were introduced in the pristine state. The Ni 2 O 3 ‐phase nanostructures were connected and disconnected in the pristine‐ and OFF‐state samples, respectively, which implied that the phase acted as the conducting channel. X‐ray photoemission spectroscopy results showing Ni 3+ bonding in the pristine‐state film support the importance of the Ni 2 O 3 phase in the switching. Observed Ni 2 O 3 phase (indicated by the red line) in the low resistance state of a pristine sample.