Multilevel resistance state of Cu/La.sub.2O.sub.3/Pt forming-free switching devices

An improved temperature dependent uniformity and reliability is investigated in La.sub.2O.sub.3/Pt-based memory devices with Cu top electrode. The microstructural investigation suggested the formation of polycrystalline La.sub.2O.sub.3 layer with stoichiometric chemical composition confirmed by X-ray photoelectron spectroscopy. Besides showing a forming-free resistive switching (RS) behaviour, the device also exhibited excellent multilevel capability with low switching voltage. A uniformity in the SET/RESET process was observed indicating enhanced switching stability. In addition, endurance with a high ON/OFF ratio of the order 10.sup.3 and satisfactory data retention time over 10.sup.4 s at 85 °C temperature confirmed the reliability of memory cells. Intrinsic tailoring of switching mechanism has been discussed in the framework of electric field-induced creation and annihilation of the reproducible Cu filaments in switching layer. The metallic nature of conducting filament has further been confirmed by temperature-dependent RS characterization.