ReRAM is highly expected to replace conventional flash memory due to its low power consumption, small bit cell size, and fast switching speed. The underlying mechanism of the resistance switching behavior is still poorly
understood, although there have been various proposed models of the resistance BAY 11-7082 in vivo switching mechanism such as formation and rupture of conductive filament paths [3, 4], field-induced electrochemical migration such as oxygen vacancy creation/diffusion [5, 6], alteration of the width and/or height of a Schottky-like barrier by trapped charge carriers in the interface states , trap-controlled space-charge-limited current [8–12], injecting electrons into and extracting electrons from the interface , and oxidation/reduction reaction at the interface [14–20]. It was also reported that the resistance switching is significantly dependent on electrode materials in the ReRAM devices [14, 18, 21–26]. The precise identity of the switching location where resistance change mainly occurs has not been revealed. The comprehensive understanding for the origin of the resistance switching is required to meet the requirement for the next-generation nonvolatile memory application. Impedance spectroscopy
is a useful technique for characterizing the resistance switching in metal oxide films, which indicates whether the overall resistance of the device is dominated MI-503 by a bulk, grain CAL-101 nmr boundary, or interface component [30–39]. In this work, the resistance switching mechanism in PCMO-based Cediranib (AZD2171) devices was investigated by impedance spectroscopy. In order to study the resistance switching mechanism in the PCMO-based
devices, the frequency response of complex impedance was measured in the PCMO-based devices with various metal electrodes. Based on impedance spectral data, the electrode material dependence of the resistance switching in the PCMO-based devices was discussed by correlating with the standard Gibbs free energy of the formation of metal oxides and the work function of each electrode metal. Methods Polycrystalline PCMO films were deposited on prefabricated Pt/SiO2/Si substrates by radio-frequency (rf) magnetron sputtering with a Pr0.7Ca0.3MnO3−δ target. The base pressure was 1 × 10−6 Torr. Before the deposition, the target was presputtered for 30 min to obtain a clean target surface. A mixture of Ar and O2 gases with 25% oxygen content was used for the sputter deposition. The process pressure was controlled at 20 mTorr. The rf power was 80 W. The substrate temperature was 450°C. The film thickness was obtained by cross-sectional scanning electron microscopy. All films were about 100 nm thick. In order to measure the electrical properties of the deposited films, we prepared layered structures composed of PCMO sandwiched between a Pt bottom electrode and top electrodes.