5 × 10−9 and 7 × 10−9 learn more F as the best-fit parameters, respectively. Knowing the interface capacitance C, the thickness of the Al oxide interfacial layer, d = ε 0 εS / C, can be estimated, where ε 0, ε, and S are the vacuum permittivity, the dielectric constant of aluminum oxide, and the electrode area, respectively [33]. With ε 0 = 8.85 × 10−14 F/cm, ε = 10, and S = 2 × 10−3 cm2, d is obtained to be 7 and 2.5 nm in the high and low resistance states, respectively. The thickness of the Al oxide interfacial layer obtained by click here impedance spectroscopy in this work was in good agreement with that estimated by HRTEM

and XPS [18–20]. The oxidation of the Al electrode plays a dominant role TPX-0005 nmr in the bipolar resistance switching in the PCMO-based

devices. On the contrary, the resistance change at the interface might not give a dominant contribution to the overall resistance change of Ni/PCMO/Pt and Ag/PCMO/Pt devices because with Ni and Ag, it is difficult to form the oxide interface layer as compared with Al. As a result, the resistance change ratio of Ni/PCMO/Pt and Ag/PCMO/Pt devices is smaller than that of the Al/PCMO/Pt device. It is rather difficult to categorize Ni and Ag into the group of top electrode materials that cause the ReRAM effect. Conclusions The electric-pulse-induced resistance switching in manganite film-based devices with various metal electrodes of Al, Ni, Ag, and Au was studied by dc current–voltage measurements and ac impedance spectroscopy. The hysteretic I-V characteristics and resistance switching were observed in the PCMO-based devices with top electrode of Al, Ni, and Ag. The Al/PCMO/Pt device showed larger resistance switching than other PCMO-based old devices with top electrode of Ni and Ag. The electrode material dependence of the

resistance switching in polycrystalline manganite films was investigated in more detail by impedance spectroscopy. Two semicircular arcs were observed in the impedance spectra of the Al/PCMO/Pt device, while the Cole-Cole plots in the devices with Ni, Ag, and Au showed only one semicircular arc. These two distinctive features of the Al/PCMO/Pt device could be assigned to the PCMO bulk and to the interface between the PCMO film and the Al electrode, respectively. By comparing the impedance spectra between the high and low resistance states in the Al/PCMO/Pt device, we suggested that the resistance switching in the PCMO-based devices was mainly due to the resistance change in the interface between the film and the electrode. According to the theoretical simulation of impedance spectra, the interface component observed by impedance spectroscopy in the Al/PCMO/Pt device might be due to Al oxide layer formed by oxidation of Al top electrode. The interfacial transition layer of Al oxides is possibly responsible for the large resistance change in the Al/PCMO/Pt device.