Formation of transition layers at metal/perovskite oxide interfaces showing resistive switching behaviors

The authors have investigated the chemical states at the interface of metal/perovskite oxides both with and without bipolar resistive switching (RS) behavior using photoemission spectroscopy and x-ray absorption spectroscopy. Al/Pr0.7Ca0.3MnO3 (PCMO), Al/La0.7Ca0.3MnO3 (LCMO), and Al/La0.33Sr0.67FeO3 interfaces were chosen as typical examples of interfaces for the perovskite-based resistance random access memory (ReRAM), while Pt/PCMO and Ag/LCMO were chosen as references for the metal/perovskite interface without RS behavior. Detailed analyses of spectroscopic data revealed that transition layers were formed at the interfaces showing RS behavior as a result of interfacial redox reactions between the Al electrodes and the transition metal ions in the oxides. On the other hand, for the interfaces that did not exhibit RS behavior, no chemical reaction occurred at the interface. The formation of the interfacial transition layer is naturally explained by considering the redox potential between the electrode materials and transition metal ions. These results suggest that a suitable combination of electrodes and oxides could be designed based on their redox potentials.