Forming-free resistive random access memory (ReRAM) devices having low switching voltages are a prerequisite for their commercial applications. In this study, the forming-free resistive switching characteristics of graphene oxide (GO) films embedded with gold nanoparticles (Au Nps), having an enhanced on/off ratio at very low switching voltages, were investigated for non-volatile memories. The GOAu films were deposited by the electrophoresis method and as-grown films were found to be in the low resistance state; therefore no forming voltage was required to activate the devices for switching. The devices having an enlarged on/off ratio window of ∼10(6) between two resistance states at low voltages (<1 V) for repetitive dc voltage sweeps showed excellent properties of endurance and retention. In these films Au Nps were uniformly dispersed over a large area that provided charge traps, which resulted in improved switching characteristics. Capacitance was also found to increase by a factor of ∼10, when comparing high and low resistance states in GOAu and pristine GO devices. Charge trapping and de-trapping by Au Nps was the mechanism responsible for the improved switching characteristics in the films.

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Monoclinic pyrochlore ceramic Bi 2 Zn 2/3Àx/3 Nb 4/3À2x/3 Ti x O 7 (M-BZN) with x 5 0-0.4 is synthesized and the structure and microwave cryogenic properties are scrutinized. The dielectric constant (e 0 ) and loss tangent (tand) of these ceramics are measured at a frequency of 3 GHz and temperature range of 15-300 K. With an increase in x value from 0 to 0.4, the dielectric constant and dielectric loss tangent of the investigated materials increase from 70 to 114 and 0.009 to 0.061, respectively. The Tisubstituted ceramics show an increase in dielectric constant with temperature, and the loss tangent shows a peak around 200 K. The peak in the dielectric loss tangent becomes more prominent with an increase of Ti content. The temperature where the dielectric loss tangent peak appears is found to be decreasing slightly with an increase of titanium doping. The observed dielectric characteristics of the titanium-doped M-BZN ceramics are attributed to the presence of the relaxation in these materials, originating from the disorder caused by the Ti 41 substitution. C. A. Randall-contributing editorThis work was financially supported by UGC, DST, and DST Nanocenter Project.

We report unipolar resistive switching suitable for nonvolatile memory applications in polycrystalline BiFeO 3 thin films in planar electrode configuration with nonoverlapping Set and Reset voltages, On/Off resistance ratio of ∼10 4 and good data retention (verified for up to 3,000 s). We have also observed photovoltaic response in both high and low resistance states, where the photocurrent density was about three orders of magnitude higher in the low resistance state as compared to the high resistance state at an illumination power density of ∼100 mW/cm 2 . Resistive switching mechanisms in both resistance states of the planar device can be explained by using the conduction filament (thermo-chemical) model. C

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