I-V measurement of NiO nanoregion during observation by transmission electron microscopy

Conduction measurements with simultaneous observations by transmission electron microscopy (TEM) were performed on a thin NiO film, which is a candidate material for resistance random access memories (ReRAMs). To conduct nanoscale experiments, a piezo-controlled TEM holder was used, where a fixed NiO sample and a movable Pt-Ir counter electrode were placed. After the counter electrode was moved to make contact with NiO, I-V measurements were carried out from any selected nanoregions. By applying a voltage of 2 V, the insulating NiO film was converted to a low resistance film. This phenomenon may be the forming process required to initialize ReRAMs. The corresponding TEM image indicated a structural change in the NiO layer generating a conductive bridge with a width of 30-40 nm. This finding supports the breakdown type forming in the so-called filament model of operation by ReRAMs. The inhomogeneity of resistance in the NiO film was also investigated.