Direct observation of conducting filaments on resistive switching of NiO thin films

Abstract

The $\mathrm{Hg}∕\mathrm{Ni}\mathrm{O}∕\mathrm{Pt}$ capacitor with a Hg top electrode diameter of about $35\mu \mathrm{m}$ showed the typical bistable resistive switching characteristic. After the removal of the Hg top electrode, we directly observed the formation and removal of filaments for a high resistive state $\left(R_{\text{off}}\right)$ and a low resistive state $\left(R_{\text{on}}\right)$ by conducting atomic force microscope (CAFM). CAFM images for $R_{\text{off}}$ and $R_{\text{on}}$ states directly exhibit evidence of the formation and removal of filaments on the surface, which supports well the filament model as a switching mechanism of resistive random access memory.