Understanding the Behavior of Oxygen Vacancies in an SrFeOx/Nb:SrTiO3 Memristor

SrFeO x resistive switching memory devices based on brownmillerite with an oxygen vacancy channel exhibit high durability and fast performance. In particular, a high on/off ratio of > 10 4 was observed when Nb-doped SrTiO 3 was used as the bottom electrode. We studied a SrFeO x /Nb-doped SrTiO 3 (111) device with a high on/off ratio, and used in-situ transmission electron microscopy to examine the crystalline structures of the SrFeO x layer in the high and low resistance states. We employed electron energy-loss spectroscopy to determine oxygen redistribution near the interface between the SrFeO x structure and Nb-doped SrTiO 3. The resistance increased when oxygen vacancies accumulated at the interface between Nb-doped SrTiO 3 and perovskite SrFeO 3− δ , and decreased when oxygen ions filled the interface. In contrast, we observed little change in the oxygen concentration at the interface between Nb-doped SrTiO 3 and brownmillerite SrFeO 3− δ . We show that the resistance of the SrFeO x /Nb-doped SrTiO 3 (111) device is mostly concentrated at the interface between the perovskite SrFeO 3− δ and Nb-doped SrTiO 3 , which changes the barrier height. Graphical Abstract