Improved cycling stability and ON/OFF ratio of SrFeOx topological phase transition memristors using a La0.7Sr0.3MnO3 bottom electrode

Abstract

The resistive functional layer in SrFeO_x (SFO) topological phase transition (TPT) memristors is typically epitaxially grown on a perovskite bottom electrode and thus the bottom electrode plays an important role in the microstructure and resistive switching performance of the SFO functional layer. Unfortunately, the excessive diffusion of oxygen in the bottom electrode to SrFeO_x causes uncontrollable distortion of the microstructure of the resistive functional layer, thereby compromising the overall device properties. In this study, SFO films were epitaxially grown on two different bottom electrodes of La_0.7Sr_0.3MnO₃ (LSMO) and SrRuO₃ (SRO) using pulsed laser deposition (PLD). The SFO memristor with a LSMO electrode exhibits excellent cycling stability, ON/OFF ratio, data retention, and endurance performance. In addition, the phase constituents, superlattice-like stripes and elemental valence states of SFO/LSMO and SFO/SRO hetero-structures were characterized by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. Furthermore, the oxygen migration free energy barriers of the bottom electrodes in the two devices were calculated by first-principles. All the above research results indicate that the LSMO electrode, being less prone to diffuse oxygen ions, significantly contributes to the superior structural stability and enhanced performance of the SFO/LSMO heterostructure. Finally, the energy band structures and Schottky barriers between BM-SFO and the top electrode of Au and the bottom electrode of LSMO were analyzed by ultraviolet photoelectron spectroscopy and ultraviolet-visible spectroscopy, which provide experimental insights into explaining its conductive mechanism.