Developmental Mechanism for the Memory Effect in Perovskite Oxide-Based ReRAM Consisting of Bi2Sr2CaCu2O8+δ Bulk Single Crystal

Abstract

Resistive random access memory (ReRAM) structures of M-TE/Bi2Sr2CaCu2O8+δ (Bi-2212) bulk single crystal/Pt-BE (M = Al, Pt) were prepared and their memory characteristics and superconducting properties were evaluated, here TE and BE represent top and bottom electrodes. The resistance switching effect developed only in the Al-TE/Bi-2212/Pt-BE structure and was enhanced with decreasing critical temperature by annealing in Ar atmosphere. This suggests that reduction of Bi-2212 single crystal is required for the resistance switching effect. Additionally, due to the large resistance anisotropy (ρc/ρab > 103) of bulk Bi-2212 single crystals, the resistance switching effect was confirmed to occur at the interface between the Al electrode and the Bi-2212 single crystal. These results indicate that introduction of an oxygen-depleted Bi-2212 layer to the surface of the Bi-2212 single crystal at the vicinity of the Al electrode is required to develop the resistance switching effect, which could be achieved by the deposition of electrodes with small Gibbs free energy and raising the temperature to exceed the activation energy for oxygen ions to move from the Bi-2212 single crystal to the electrode. A model which explains the resistance switching of perovskite oxide-based ReRAM by generation/recovery of the oxygen-depleted Bi-2212 layer. The most direct way to prove the validity of the proposed resistance switching model is to show the development of the resistance switching effect simply by inserting the oxygen-depleted Bi-2212 layer at the interface between a large Gibbs free energy electrode such as Pt and Bi-2212 single crystal. Utilizing the catalytic effect of Pt that drastically enhances the reduction reaction of hydrogen, we introduced the oxygen-depleted Bi-2212 layer into the surface of the Bi-2212 single crystal at the vicinity of the Pt electrode by annealing a Pt-TE/Bi-2212/Au-BE structure in H2 atmosphere. The resistance switching effect developed also in a Pt-TE/Bi-2212/Au-BE structure annealed in hydrogen gas, proving the validity of the resistance switching model.