Through oxygen profile engineering, we fabricated W/AlOx/Al2O3/Pt bilayer memristors with a 250-nm feature size. The AlOx fabricated by sputtering serves as an oxygen vacancy source, whereas the ...Al2O3 deposited by atomic layer deposition acts as a dominant resistive switching (RS) layer. Our devices show forming-free RS behaviors with high speed (28 ns), uniform resistance distribution, large on/off ratio (~103@100K, ~103@298K, and ~80@400K), and good retention. Besides, temperature stability with record high endurance from cryogenic to high-temperature (108@100K, 1010@298K, and 107@400K) is demonstrated, to the best of our knowledge.
A convenient interfacial engineering strategy is developed to the construction of worm-shaped palladium nanocrystals strongly coupled with polyelectrolyte-modified Ti3C2Tx MXene via direct ...electrostatic attraction, which express exceptional electrocatalytic ability toward methanol oxidation.
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•An interfacial engineering strategy is developed to construct Pd nanoworm/MXene catalyst.•The incorporation of PDDA ensures strong electrostatic attraction between Pd and MXene.•The resultant catalyst expresses superior catalytic performance for methanol oxidation.•DFT calculation discloses the enhanced antitoxic ability of Pd nanoworm/MXene toward CO.
The development of high-efficiency methanol oxidation electrocatalysts with acceptable costs is central to the practical use of direct methanol fuel cell. In this work, a convenient interfacial engineering strategy is developed to the design and construction of quasi-one-dimensional worm-shaped palladium nanocrystals strongly coupled with positively-charged polyelectrolyte-modified Ti3C2Tx MXene (Pd NWs/PDDA-MX) via the direct electrostatic attractions. Because of the intriguing structural features including ultrathin-sheet nature, homogeneous Pd dispersion, numerous grain boundaries, strong electronic interaction, and high metallic conductivity, the as-fabricated Pd NWs/PDDA-MX hybrid shows superior electrocatalytic performance with a large electrochemically active surface area of 105.3 m2 g−1, a high mass activity of 1526.5 mA mg−1, and reliable long-term durability towards alkaline methanol oxidation reaction, far outperforming the commercial Pd nanoparticle/carbon catalysts. Density functional theory calculation further demonstrate that there are strong electronic interactions in the Pd nanoworm/Ti3C2Tx model with a depressed CO adsorption energy, thereby guaranteeing a stable interfacial contact as well as strong antitoxic ability.
Magnetic multilayer devices that exploit magnetoresistance are the backbone of magnetic sensing and data storage technologies. Here, we report multiple-spin-filter magnetic tunnel junctions (sf-MTJs) ...based on van der Waals (vdW) heterostructures in which atomically thin chromium triiodide (CrI
) acts as a spin-filter tunnel barrier sandwiched between graphene contacts. We demonstrate tunneling magnetoresistance that is drastically enhanced with increasing CrI
layer thickness, reaching a record 19,000% for magnetic multilayer structures using four-layer sf-MTJs at low temperatures. Using magnetic circular dichroism measurements, we attribute these effects to the intrinsic layer-by-layer antiferromagnetic ordering of the atomically thin CrI
Our work reveals the possibility to push magnetic information storage to the atomically thin limit and highlights CrI
as a superlative magnetic tunnel barrier for vdW heterostructure spintronic devices.
Monolayer valley semiconductors, such as tungsten diselenide (WSe2), possess valley pseudospin degrees of freedom that are optically addressable but degenerate in energy. Lifting the energy ...degeneracy by breaking time-reversal symmetry is vital for valley manipulation. This has been realized by directly applying magnetic fields or via pseudomagnetic fields generated by intense circularly polarized optical pulses. However, sweeping large magnetic fields is impractical for devices, and the pseudomagnetic fields are only effective in the presence of ultrafast laser pulses. The recent rise of two-dimensional (2D) magnets unlocks new approaches to controlling valley physics via van der Waals heterostructure engineering. Here, we demonstrate the wide continuous tuning of the valley polarization and valley Zeeman splitting with small changes in the laser-excitation power in heterostructures formed by monolayer WSe2 and 2D magnetic chromium triiodide (CrI3). The valley manipulation is realized via the optical control of the CrI3 magnetization, which tunes the magnetic exchange field over a range of 20 T. Our results reveal a convenient new path toward the optical control of valley pseudospins and van der Waals magnetic heterostructures.
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