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

Abstract

SrFeOx 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 SrTiO3 was used as the bottom electrode. We studied a SrFeOx/Nb-doped SrTiO3 (111) device with a high on/off ratio, and used in-situ transmission electron microscopy to examine the crystalline structures of the SrFeOx layer in the high and low resistance states. We employed electron energy-loss spectroscopy to determine oxygen redistribution near the interface between the SrFeOx structure and Nb-doped SrTiO3. The resistance increased when oxygen vacancies accumulated at the interface between Nb-doped SrTiO3 and perovskite SrFeO3-delta, and decreased when oxygen ions filled the interface. In contrast, we observed little change in the oxygen concentration at the interface between Nb-doped SrTiO3 and brownmillerite SrFeO3-delta. We show that the resistance of the SrFeOx/Nb-doped SrTiO3 (111) device is mostly concentrated at the interface between the perovskite SrFeO3-delta and Nb-doped SrTiO3, which changes the barrier height.