Preparation and characterization of transparent Tm:YAG ceramics

The unusual unipolar resistive switching effect in Pr0.7Ca0.3MnO3 (PCMO) is investigated, which is a conventional bipolar switching material. The PCMO thin films are prepared with a broad resistivity range by tuning the growth oxygen pressure and substrate temperature. X-ray diffraction, Auger, and Raman spectra are used to identify the oxygen content and crystallinity in the films. The evolution of junction resistivity with growth condition is studied. It is found that only the junctions with moderate resistance values have low forming voltages and exhibit reproducible unipolar switching. The switching characteristics, including current transition mode and switching-voltage distribution, resemble those observed in insulating binary oxides, indicating a similar fuse-antifuse mechanism responsible for the unusual switching behavior in PCMO. The conversion of switching mode by increasing resistivity indicates that the unipolar switching may be a universal behavior for high-resistivity oxides. The materials which allow for unipolar switching may be far more abundant than those found presently.