A large electric-pulse-induced reversible resistance change active at room temperature and under zero magnetic field has been discovered in colossal magnetoresistive (CMR) Pr0.7Ca0.3MnO3 thin films. Electric field-direction-dependent resistance changes of more than 1700% were observed under applied pulses of ∼100 ns duration and as low as ±5 V magnitude. The resistance changes were cumulative with pulse number, were reversible and nonvolatile. This electrically induced effect, observed in CMR materials at room temperature has both the benefit of a discovery in materials properties and the promise of applications for thin film manganites in the electronics arena including high-density nonvolatile memory.

Electric-pulse induced resistance hysteresis switching loops for Pr0.7Ca0.3MnO3 perovskite oxide films were found to exhibit an additional sharp "shuttle tail" peak around the negative pulse maximum for films deposited in an oxygen-deficient ambient. The resistance relaxation in time of this "shuttle tail" peak as well as resistance relaxation in the transition regions of the resistance hysteresis loop show evidence of oxygen diffusion under electric pulsing, and support a proposed oxygen diffusion model with oxygen vacancy pileup at the metal electrode interface region as the active process for the nonvolatile resistance switching effect in transition-metal oxides.

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A micro thin-film solid oxide fuel cell (TFSOFC) has been designed based on thin-film deposition and microlithographic processes. The TFSOFC is composed of a thin-film electrolyte grown on a nickel foil substrate and a thin-film cathode deposited on the electrolyte. The Ni foil substrate is then processed into a porous anode by photolithographic patterning and etching to develop pores for gas transport into the fuel cell. A La0.5Sr0.5CoO3 (LSCO) thin-film cathode is then deposited on the electrolyte, and a porous NiO–YSZ cermet layer is added to the anode to improve the electrode performance. The TFSOFC has stably operated in a temperature ranges as low as 480–570 °C, significantly lower than bulk SOFC’s, and has yielded a maximum output power density of ∼110 mW/cm2 in that temperature range.

We report the first direct measurements of the micro scale resistance profile between the terminals of a two terminal symmetric thin film Pr0.7Ca0.3MnO3 electrical pulse induced resistance change device composed of a Pr0.7Ca0.3MnO3 active layer. The symmetric device is one in which the electrode shape, size, composition, and deposition processing are identical. We show that under certain limitations of pulse switching voltage, such a symmetric electrical pulse induced resistance change device can exhibit either no net device resistance switching at room temperature, or bipolar switching with the resistance hysteresis curve exhibiting a "table leg" structure. The resistance measurements are made using surface scanning Kelvin probe microscopy, which allows for the measurement of the profile of resistance from one electrode, across the Pr0.7Ca0.3MnO3 material and into the second electrode, both before resistance switching and after switching. The results show that resistance switching in the symmetric device occurs primarily in the interface region within about 1 to 3 micron of the electrical contact surface. Resistance switching is also observed in the bulk Pr0.7Ca0.3MnO3 material although at a lower level. Symmetry considerations for a two terminal symmetric device that can switch resistance are discussed, and the data reported here is consistent with the symmetric model previously developed.[*]