Nanoscale observations of resistive switching high and low conductivity states on TiN/HfO2/Pt structures

Resistive Switching (RS) phenomenon in Metal-Insulator-Metal (MIM) structures with polycrystalline HfO2 layers as dielectric has been studied at the nanoscale using Conductive Atomic Force Microscope (CAFM). The CAFM measurements reveal that (i) the conductive filaments (CFs) created at very small areas are the origin of the RS phenomenon observed at device level and (ii) RS conductive filaments are primarily formed at the grain boundaries, which exhibit especially low breakdown voltage. CAFM images obtained on MIM structures at the Low and High Resistive states also show that, although the current in the Low Resistive State is mainly driven by a completely formed single CF, the cell area dependence of the conductivity in the High Resistive State could be explained by considering the presence of multiple partially formed CFs.