Towards forming-free resistive switching in oxygen engineered HfO2−x

We have investigated the resistive switching behavior in stoichiometric HfO2 and oxygen-deficient HfO2− x thin films grown on TiN electrodes using reactive molecular beam epitaxy. Oxygen defect states were controlled by the flow of oxygen radicals during thin film growth. Hard X-ray photoelectron spectroscopy confirmed the presence of sub-stoichiometric hafnium oxide and defect states near the Fermi level. The oxygen deficient HfO2− x thin films show bipolar switching with an electroforming occurring at low voltages and low operating currents, paving the way for almost forming-free devices for low-power applications.