Designing transparent flexible electronics with multi‐biological neuronal functions and superior flexibility is a key step to establish wearable artificial intelligence equipment. Here, a flexible ...ionic gel‐gated VO2 Mott transistor is developed to simulate the functions of the biological synapse. Short‐term and long‐term plasticity of the synapse are realized by the volatile electrostatic carrier accumulation and nonvolatile proton‐doping modulation, respectively. With the achievement of multi‐essential synaptic functions, an important sensory neuron, nociceptor, is perfectly simulated in our synaptic transistors with all key characteristics of threshold, relaxation, and sensitization. More importantly, this synaptic transistor exhibits high tolerance to the bending deformation, and the cycle‐to‐cycle variations of multi‐conductance states in potentiation and depression properties are maintained within 4%. This superior stability further indicates that our flexible device is suitable for neuromorphic computing. Simulation results demonstrate that high recognition accuracy of handwritten digits (>95%) can be achieved in a convolution neural network built from these synaptic transistors. The transparent and flexible Mott transistor based on electrically‐controlled VO2 metal‐insulator transition is believed to open up alternative approaches to developing highly stable synapses for future flexible neuromorphic systems.
A flexible Mott synaptic transistor is developed to simulate the functions of a biological synapse. A sensory neuron, nociceptor, is simulated based on multi‐essential synaptic functions. The high recognition accuracy of handwritten digits (>95%) can be achieved, demonstrating that the flexible ionic gel‐gated VO2 Mott transistor opens up alternative approaches to developing highly stable synapses for future flexible neuromorphic systems.
Valleytronics rooted in the valley degree of freedom is of both theoretical and technological importance as it offers additional opportunities for information storage, as well as electronic, magnetic ...and optical switches. In analogy to ferroelectric materials with spontaneous charge polarization, or ferromagnetic materials with spontaneous spin polarization, here we introduce a new member of ferroic family, that is, a ferrovalley material with spontaneous valley polarization. Combining a two-band k·p model with first-principles calculations, we show that 2H-VSe
monolayer, where the spin-orbit coupling coexists with the intrinsic exchange interaction of transition-metal d electrons, is such a room-temperature ferrovalley material. We further predict that such system could demonstrate many distinctive properties, for example, chirality-dependent optical band gap and, more interestingly, anomalous valley Hall effect. On account of the latter, functional devices based on ferrovalley materials, such as valley-based nonvolatile random access memory and valley filter, are contemplated for valleytronic applications.
Dielectric capacitors are widely studied for power supply systems because they can quickly store and release electrical energy. Among various kinds of dielectric materials, antiferroelectrics show ...promising features of high energy‐storage density and efficiency. In this study, epitaxial antiferroelectric PbHfO3 films with different orientations are fabricated, in which remarkable anisotropies of polarization and energy storage properties are discovered. With the optimization of film orientation, much‐improved energy density and excellent high‐temperature efficiency are achieved in the PbHfO3 films. Moreover, the PbHfO3 films are fabricated onto flexible mica substrates, which exhibit excellent property robustness against mechanical bending. This study provides a fundamental understanding of the anisotropic antiferroelectric behaviors of epitaxial PbHfO3 films and provides a generalizable pathway for flexible energy‐storage dielectric capacitors.
In this study, epitaxial antiferroelectric PbHfO3 films with different orientations are fabricated. With the optimization of film orientation, excellent high‐temperature efficiency is achieved in the PbHfO3 films. Moreover, the PbHfO3 films are fabricated onto flexible mica substrates, which exhibit excellent property robustness against mechanical bending. This study provides a fundamental understanding of the anisotropic antiferroelectric behaviors of epitaxial PbHfO3 films.
Black phosphorus (P) has been considered as a promising candidate for anodes due to its ability to absorb a large amount of Li atoms. Unfortunately, lithiation of bulk black P induces huge structural ...deformation, which limits its application. Here, on the basis of the density functional theory calculation, we predict that the newly found two-dimensional (2D) black and blue P are good electrodes for high-capacity lithium-ion batteries. Our theoretical calculations indicate that, in contrast to bulk black P, the monolayer and double-layer black and blue P can maintain their layered structures during lithiation and delithiation cycles. Moreover, it is found that Li diffusion on the surfaces of black and blue P has relatively low energy barriers (<0.4 eV), and the single-layer blue P and double-layer black and blue P possess high charge capacities.
Solid-liquid interface is a key concept of many research fields, enabling numerous physical phenomena and practical applications. For example, electrode-electrolyte interfaces with electric double ...layers have been widely used in energy storage and regulating physical properties of functional materials. Creating a specific interface allows emergent functionalities and effects. Here, we show the artificial control of ferroelectric-liquid interfacial structures to switch polarization states reversibly in a van der Waals layered ferroelectric CuInP
S
(CIPS). We discover that upward and downward polarization states can be induced by spontaneous physical adsorption of dodecylbenzenesulphonate anions and N,N-diethyl-N-methyl-N-(2-methoxyethyl)-ammonium cations, respectively, at the ferroelectric-liquid interface. This distinctive approach circumvents the structural damage of CIPS caused by Cu-ion conductivity during electrical switching process. Moreover, the polarized state features super-long retention time (>1 year). The interplay between ferroelectric dipoles and adsorbed organic ions has been studied systematically by comparative experiments and first-principles calculations. Such ion adsorption-induced reversible polarization switching in a van der Waals ferroelectric enriches the functionalities of solid-liquid interfaces, offering opportunities for liquid-controlled two-dimensional ferroelectric-based devices.
Multiferroics—materials that exhibit coupled ferroic orders—are considered to be one of the most promising candidate material systems for next‐generation spintronics, memory, low‐power ...nanoelectronics and so on. To advance potential applications, approaches that lead to persistent and extremely fast functional property changes are in demand. Herein, it is revealed that the phase transition and the correlated ferroic orders in multiferroic BiFeO3 (BFO) can be modulated via illumination of single short/ultrashort light pulses. Heat transport simulations and ultrafast optical pump‐probe spectroscopy reveal that the transient strain induced by light pulses plays a key role in determining the persistent final states. Having identified the diffusionless phase transformation features via scanning transmission electron microscopy, sequential laser pulse illumination is further demonstrated to perform large‐area phase and domain manipulation in a deterministic way. The work contributes to all‐optical and rapid nonvolatile control of multiferroicity, offering different routes while designing novel optoelectronics.
All‐optical manipulation of the complex phases and domain structures in multiferroic BiFeO3 thin films on ultrafast timescale is demonstrated by adoption of extremely short light pulses. The configuration of large‐area optically written domains can be controlled by tuning the competing elastic and electrostatic energies. These results offer a novel route for the development of all‐optical switchable devices and high‐speed multifunctional optoelectronics.
Two-dimensional (2D) van der Waals (vdW) materials provide the possibility of realizing heterostructures with coveted properties. Here, we report a theoretical investigation of the vdW magnetic ...tunnel junction (MTJ) based on VSe
/MoS
heterojunction, where the VSe
monolayer acts as a ferromagnet with room-temperature ferromagnetism. We propose the concept of spin-orbit torque (SOT) vdW MTJ with reliable reading and efficient writing operations. The nonequilibrium study reveals a large tunneling magnetoresistance of 846% at 300 K, identifying significantly its parallel and antiparallel states. Thanks to the strong spin Hall conductivity of MoS
, SOT is promising for the magnetization switching of VSe
free layer. Quantum-well states come into being and resonances appear in MTJ, suggesting that the voltage control can adjust transport properties effectively. The SOT vdW MTJ based on VSe
/MoS
provides desirable performance and experimental feasibility, offering new opportunities for 2D spintronics.
Epitaxial growth is of significant importance over the past decades, given it has been the key process of modern technology for delivering high-quality thin films. For conventional heteroepitaxy, the ...selection of proper single crystal substrates not only facilitates the integration of different materials but also fulfills interface and strain engineering upon a wide spectrum of functionalities. Nevertheless, the lattice structure, regularity and crystalline orientation are determined once a specific substrate is chosen. Here, we reveal the growth of twisted oxide lateral homostructure with controllable in-plane conjunctions. The twisted lateral homostructures with atomically sharp interfaces can be composed of epitaxial "blocks" with different crystalline orientations, ferroic orders and phases. We further demonstrate that this approach is universal for fabricating various complex systems, in which the unconventional physical properties can be artificially manipulated. Our results establish an efficient pathway towards twisted lateral homostructures, adding additional degrees of freedom to design epitaxial films.
Engineering the electronic band structure of material systems enables the unprecedented exploration of new physical properties that are absent in natural or as-synthetic materials. Half metallicity, ...an intriguing physical property arising from the metallic nature of electrons with singular spin polarization and insulating for oppositely polarized electrons, holds a great potential for a 100% spin-polarized current for high-efficiency spintronics. Conventionally synthesized thin films hardly sustain half metallicity inherited from their 3D counterparts. A fundamental challenge, in systems of reduced dimensions, is the almost inevitable spin-mixed edge or surface states in proximity to the Fermi level. Here, we predict electric field-induced half metallicity in bilayer A-type antiferromagnetic van der Waals crystals (i.e., intralayer ferromagnetism and interlayer antiferromagnetism), by employing density functional theory calculations on vanadium diselenide. Electric fields lift energy levels of the constituent layers in opposite directions, leading to the gradual closure of the gap of singular spin-polarized states and the opening of the gap of the others. We show that a vertical electrical field is a generic and effective way to achieve half metallicity in A-type antiferromagnetic bilayers and realize the spin field effect transistor. The electric field-induced half metallicity represents an appealing route to realize 2D half metals and opens opportunities for nanoscale highly efficient antiferromagnetic spintronics for information processing and storage.
2D polarization materials have emerged as promising candidates for meeting the demands of device miniaturization, attributed to their unique electronic configurations and transport characteristics. ...Although the existing inherent and sliding mechanisms are increasingly investigated in recent years, strategies for inducing 2D polarization with innovative mechanisms remain rare. This study introduces a novel 2D Janus state by modulating the puckered structure. Combining scanning probe microscopy, transmission electron microscopy, and density functional theory calculations, this work realizes force‐triggered out‐of‐plane and in‐plane dipoles with distorted smaller warping in GeSe. The Janus state is preserved after removing the external mechanical perturbation, which could be switched by modulating the sliding direction. This work offers a versatile method to break the space inversion symmetry in a 2D system to trigger polarization in the atomic scale, which may open an innovative insight into configuring novel 2D polarization materials.
2D polarization materials are promising for miniaturized devices due to their unique properties. However, strategies for creating 2D polarization through new mechanisms are rare. This work introduces a 2D Janus structure with both vertical and planar polarization, achieved by applying force with a nanoprobe. This technique breaks symmetry at the atomic level, inducing polarization and paving the way for new 2D polarization materials' development and design.
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