Resistance switching of the nonstoichiometric zirconium oxide for nonvolatile memory applications

The resistance switching behavior and switching mechanism of nonstoichiometric zirconium oxide thin films were investigated for nonvolatile memory application. The Pt/ZrO_x/p⁺-Si sandwich structure fabricated by reactive sputtering shows two stable resistance states. By applying proper bias, resistance switching from one to another state can be obtained. The composition in ZrO_x thin films were confirmed from X-ray photoelectron spectroscope (XPS) analysis, which showed three layers such as top stoichiometric ZrO₂ layer with high resistance, transition region with medium resistance, and conducting ZrO_x bulk layer. The resistance switching can be explained by electron trapping and detrapping of excess Zr⁺ ions in transition layer which control the distribution of electric field inside the oxide, and, hence the current flow.