Here we report enhanced power generation, faster transient response and longer durability of HT-PEMFC by employing a composite membrane of PBI with reduced graphene oxide (rGO) at an optimum loading ...of 1%. Easy and low cost synthesis of the composite membranes at different loading of rGO is achieved using methane sulfonic acid (MSA) as solvent that resolves the long-standing issue of poor solubility of PBI in the conventional solvents. Property and performance mapping with respect to rGO loading not only leads to attain the optimum but also identifies the window of feasible operating zone. It is observed that with very low (1%) rGO content, composite PBI membrane (rGO-PBI-1) offers the maximum enhancement of all properties viz water uptake, acid uptake, proton conductivity, ion exchange capacity, acid retention capacity, chemical stability, yield strength, while beyond a threshold/critical loading (~4%) deterioration of electrochemical and mechanical properties occur. Steady state performance analysis reveals almost two times peak power enhancement of HT-PEMFC using rGO-PBI-1 electrolyte membrane at an operating temperature of 170 °C; insitu impedance analysis during fuel cell operation reveals sharp decay in charge transfer resistance. Multiple step response analysis confirms (~2 times) faster transient response of fuel cell using rGO-PBI-1 while compared to that with pristine PBI membrane. Fuel cell stability analysis ensures longer durability of operation with negligible decay in voltage.
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•Low cost easy synthesis of rGO-PBI composite electrolyte using MSA as solvent.•Optimum (1%) and critical (4%) rGO loading from property-performance mapping.•2 times power generation at 170 °C using optimum rGO loading.•Enhancement of proton conductivity from Insitu Impedance analysis.•Faster transient step response of fuel cell using 1% rGO.
Abstract Low‐power nonvolatile memories operating down to deep cryogenic temperatures are important for a large spectrum of applications from high‐performance computing, electronics interfacing ...quantum computing hardware to space‐based electronics. Despite the potential of Hf 0.5 Zr 0.5 O 2 (HZO), thanks to its compatibility with complementary metal‐oxide‐semiconductor (CMOS) back‐end‐of‐line processing, only few studies of HZO‐based memory devices down to cryogenic operation temperatures exist. Here, analog ferroelectric memory stack fabrication with 10 nm HZO and their detailed characterization under wide range of pulse amplitudes and frequencies down to 4 K are reported. When operated at temperatures below 100 K, HZO devices can support high amplitude voltage pulses, yielding record high P r of up to 75µC cm −2 at ±7 V p (14 V pp ) pulse amplitudes accompanied with frequency‐dependent memory window between 6 and 8 V. Devices show excellent endurance exceeding 10 9 cycles of ±5 V p (10 V pp ) and P r of 30 µC cm −2 without significant degradation of coercive voltages or loss of polarization at cryogenic temperatures. At least 20 reproducible analog states for temperatures below 100 K with almost ideal linearity of intermediate polarization states in both pulse directions is observed, demonstrating the high potential of analog cryogenic ferroelectric memories, essential for on‐line training in in‐memory‐computing architecture.
The colossal magnetoresistive insulator to metal switching of almost nine orders of magnitude under the significantly reduced magnetic field is achieved by illumination for the low bandwidth ...manganite thin films. Similarly, by changing the measuring bias voltage through the sample the required magnetic field for insulator–metal transition can be further fine‐tuned. By applying a magnetic field of suitable strength, the samples can also be tuned to be extra sensitive to the illumination having colossal effect on the resistivity at low temperatures. This kind of utilizing of multiple external stimulants, which together change the properties of the material, could have significant impact on the new generation of phase‐change memories working under affordable conditions.
The colossal magnetoresistive insulator‐to‐metal switching of almost nine orders of magnitude under significantly reduced magnetic field is achieved by illumination for low bandwidth manganite thin films. The magnetic field biasing amplifies the samples response to illumination, having colossal effect on the resistivity, which could have significant impact on the new generation phase‐change memories working under affordable conditions.
Universal, giant and nonvolatile resistive switching is demonstrated for oxide tunnel junctions with ferroelectric PbZr0.2Ti0.8O3, ferroelectric BaTiO3, and paraelectric SrTiO3 tunnel barriers. The ...effects are caused by reversible migration of oxygen vacancies between the tunnel barrier and bottom La2/3Sr1/3MnO3 electrode. The switching process, which is driven by large electric fields, is efficient down to a temperature of 5 K.
Materials engineering on the nanoscale by precise control of growth parameters can lead to many unusual and fascinating physical properties. The development of pulsed laser deposition (PLD) 25 years ...ago has enabled atomistic control of thin films and interfaces and as such it has contributed significantly to advances in fundamental material science. One application area is the research field of spintronics, which requires optimized nanomaterials for the generation and transport of spin-polarized carriers. The mixed-valence manganite La sub(1-x)Sr sub(x)MnO sub(3) (LSMO) is an interesting material for spintronics due to its intrinsic magnetoresistance properties, electric-field tunable metal-insulator transitions, and half-metallic band structure. Studies on LSMO thin-film growth by PLD show that the deposition temperature, oxygen pressure, laser fluence, strain due to substrate-film lattice mismatch and post-deposition annealing conditions significantly influence the magnetic and electrical transport properties of LSMO. For spintronic structures, robust ferromagnetic exchange interactions and metallic conductivity are desirable properties. In this paper, we review the physics of LSMO thin films and the important role that PLD played in advancing the field of LSMO-based spintronics. Some specific application areas including magnetic tunnel junctions, multiferroic tunnel junctions and organic spintronic devices are highlighted, and the advantages, drawbacks and opportunities of PLD-grown LSMO for next-generation spintronic devices are discussed.
Quantum Conductance
In article number 2201248, Gianluca Milano, Ilia Valov, and co‐workers review the state‐of‐the‐art of quantum conductance effects in memristive devices. Besides analyzing ...fundamental physicochemical phenomena and electronic ballistic transport in nanofilaments, recent developments in experimental observation of quantum effects in memristive devices and related challenges are discussed. Representing suitable platforms for investigating quantum phenomena at room temperature, future perspectives of memristive devices in quantum and neuromorphic systems are envisioned.
•Photoinduced colossal magnetoresistance response of 109% has been reported in Pr0.6Ca0.4MnO3 thin films.•Depending on film thickness, the structural property changes significantly.•Improved ...crystallinity results in higher ferromagnetic interaction.•Insulator-metal transition under substantially lower magnetic field can be obtained under photoexcitation in films of different thicknesses.•Lowest transition field and most sharp transition are achieved in film with best crystalline property.
We report photo-induced colossal magnetoresistive insulator-metal transition (IMT) in Pr0.6Ca0.4MnO3 thin films under much reduced applied magnetic field. The colossal effect was studied as a function of film thickness and thus with variable structural properties. Thorough structural, magnetic and magnetotransport characterization under light shows that the highest effect on the transition field can be obtained in the thinnest film (38nm). However, due to the substrate induced strain of this film the required magnetic field for IMT is quite high. The best crystalline properties of the 110nm film lead to the lowest IMT field under light and 109% change in resistance at 10K. With increasing thickness, the film properties start to move more toward the bulk material and, hence, IMT is no more observed under the applied field of 9T. Our results indicate that for obtaining large photo-induced CMR, the best epitaxial quality of thin films is essential.
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