Jiuxiang Dai

Nature Materials, Published online: 21 June 2024; doi:10.1038/s41563-024-01931-y

Current transfer printing technologies enable versatile flexible devices but challenges remain. Here the authors report a facile, versatile and damage-free dry transfer printing strategy based on stress control of the deposited thin films.

Nature Communications, Published online: 22 June 2024; doi:10.1038/s41467-024-49518-0

The Mermin-Wagner theorem states that for short-range isotropic interactions, magnetic order in two dimensions is destroyed by magnetic fluctuations at finite temperatures. Observing this situation is challenging due to the finite size of typical laboratory samples. Here, Kiaba et al observe the suppression of magnetic order in oxide superlattices, at the thickness of the superlattice layers are reduced to one monolayer.

This review examines advancements in integrated photonic neuromorphic systems, focusing on materials and device engineering breakthroughs needed to advance the field. We analyze various technologies in neuromorphic photonic AI accelerators, evaluating energy efficiency and compute density. Highlighting components like PCSEL lasers and optical interconnects, we discuss recent breakthroughs and recognize obstacles to achieving peta-level performance. Potential innovations in devices, materials, and integration are explored to overcome these challenges and transform AI and scientific computing in the near future.

Abstract

In the dynamic landscape of Artificial Intelligence (AI), two notable phenomena are becoming predominant: the exponential growth of large AI model sizes and the explosion of massive amount of data. Meanwhile, scientific research such as quantum computing and protein synthesis increasingly demand higher computing capacities. As the Moore's Law approaches its terminus, there is an urgent need for alternative computing paradigms that satisfy this growing computing demand and break through the barrier of the von Neumann model. Neuromorphic computing, inspired by the mechanism and functionality of human brains, uses physical artificial neurons to do computations and is drawing widespread attention. This review studies the expansion of optoelectronic devices on photonic integration platforms that has led to significant growth in photonic computing, where photonic integrated circuits (PICs) have enabled ultrafast artificial neural networks (ANN) with sub-nanosecond latencies, low heat dissipation, and high parallelism. In particular, various technologies and devices employed in neuromorphic photonic AI accelerators, spanning from traditional optics to PCSEL lasers are examined. Lastly, it is recognized that existing neuromorphic technologies encounter obstacles in meeting the peta-level computing speed and energy efficiency threshold, and potential approaches in new devices, fabrication, materials, and integration to drive innovation are also explored. As the current challenges and barriers in cost, scalability, footprint, and computing capacity are resolved one-by-one, photonic neuromorphic systems are bound to co-exist with, if not replace, conventional electronic computers and transform the landscape of AI and scientific computing in the foreseeable future.

A schematic representation of conventional (spin-FET and 3D spin-valve based on bulk transport) and a topological spintronic logic device (2D spin-valve) where topological switching of edge state conductance in a topological Rashba type spin gapless quantum material is implemented via bulk-boundary correspondence.

Abstract

Quantum materials, with nontrivial quantum phenomena and mechanisms, promise efficient quantum technologies with enhanced functionalities. Quantum technology is held back because a gap between fundamental science and its implementation is not fully understood yet. In order to capitalize the quantum advantage, a new perspective is required to figure out and close this gap. In this review, spin gapless quantum materials, featured by fully spin-polarized bands and the electron/hole transport, are discussed from the perspective of fundamental understanding and device applications. Spin gapless quantum materials can be simulated by minimal two-band models and could help to understand band structure engineering in various topological quantum materials discovered so far. It is explicitly highlighted that various types of spin gapless band dispersion are fundamental ingredients to understand quantum anomalous Hall effect. Based on conventional transport in the bulk and topological transport on the boundaries, various spintronic device aspects of spin gapless quantum materials as well as their advantages in different models for topological field effect transistors are reviewed.

This article overviews the progress in studies on 2D artificial microstructure devices (2D AMs), encompassing electronic devices, photonic devices, optoelectronic devices and device integrations. This article also discusses typical strategies to enhance light-matter interactions and analyzes the influences of external stimuli on optoelectronic properties. Furthermore, it summarizes the challenges and future perspectives to stimulate research and development of 2D AMs for future photonics and optoelectronics.

Abstract

By modulating subwavelength structures and integrating functional materials, 2D artificial microstructures (2D AMs), including heterostructures, superlattices, metasurfaces and microcavities, offer a powerful platform for significant manipulation of light fields and functions. These structures hold great promise in high-performance and highly integrated optoelectronic devices. However, a comprehensive summary of 2D AMs remains elusive for photonics and optoelectronics. This review focuses on the latest breakthroughs in 2D AM devices, categorized into electronic devices, photonic devices, and optoelectronic devices. The control of electronic and optical properties through tuning twisted angles is discussed. Some typical strategies that enhance light-matter interactions are introduced, covering the integration of 2D materials with external photonic structures and intrinsic polaritonic resonances. Additionally, the influences of external stimuli, such as vertical electric fields, enhanced optical fields and plasmonic confinements, on optoelectronic properties is analysed. The integrations of these devices are also thoroughly addressed. Challenges and future perspectives are summarized to stimulate research and development of 2D AMs for future photonics and optoelectronics.

An organic photoelectrochemical transistor biosensor with a stable transconductance is devised using a metal–organic framework derived indium sulfide photogate to modulate a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) polymeric channel. The as-developed biosensor achieves high-performance detection of carcinoma embryonic antigen in terms of a wide linear range from 10 fg mL⁻¹ to 1 ng mL⁻¹ and a low detection limit of 5 fg mL⁻¹.

Abstract

Transconductance (g _m) is one important figure of merit for benchmarking organic electrochemical transistor (OECT) biosensors, which nevertheless experiences undesired fluctuation instead of keep constant during the target detection of varied concentrations. Light-matter interplay is recently shown as a potential way to regulate the OECT characteristics, e.g. maximum g _m at zero gate bias is achieved. In this work, the challenge of unstable g _m is addressed by using a unique metal-organic framework (MOF)-derived hollow tube indium sulfide (m-In₂S₃) as the photogate. Interestingly, the light irradiation on m-In₂S₃ generate a straight transfer curve, leading to a stable g _m that is desirable for biological application. Exemplifying by an aptasening, such a device is then tested for protein quantification with a stable sensitivity during the detection. This work features the feasibility of light-matter interplay to achieve a stable g _m in organic electronics.

This study presents a novel approach to stabilizing oxidation-prone nitride semiconductors. By depositing a thin amorphous GaN layer on Zn₃N₂, it is demonstrated that the typically fast-oxidizing Zn₃N₂ resists oxidation and maintains stability for over 3 years in ambient conditions. This method provides a robust solution for stabilizing Zn₃N₂, facilitating its application in high-performance electronic devices and energy conversion systems.

Abstract

Zinc nitride (Zn₃N₂) is a promising semiconductor for a range of optoelectronic and energy conversion applications, offering a direct bandgap of 1.0 eV, large carrier mobilities, and abundant constituent elements. However, the material is prone to bulk oxidation in ambient environments, which has thus far impeded its practical deployment. While previous approaches have focused on stabilizing the material via integration of ZnO surface layers, these strategies introduce additional challenges regarding elevated processing temperatures and limited control of interface properties. In this study, it is shown that amorphous GaN thin films can serve as highly stable protection layers on Zn₃N₂ surfaces and can be deposited at the same growth temperature and in the same deposition system as the underlying semiconductor. The GaN-capped Zn₃N₂ structures exhibit long-term stability, surviving over 3 years of exposure to ambient conditions with no discernible alterations in composition, structure, or electrical properties. Notably, the amorphous GaN coatings can even impede Zn₃N₂ oxidation under prolonged aqueous exposure. Thus, this study offers a solution to stabilize Zn₃N₂ in ambient conditions, providing a viable pathway to its utilization in robust and high-performance electronic devices, such as thin film transistors and solar energy conversion systems.

Abstract

Spin chiral anisotropy (SChA) refers to the occurrence of different spin polarization in antipodal chiral structures. Herein, we report the SChA in diamagnetic chiral mesostructured In₂O₃ films (CMIFs) with manifestation of chirality-dependent magnetic circular dichroism (MCD) signals. CMIFs were grown on fluorine-doped tin dioxide conductive glass (FTO) substrates, which were synthesized via a hydrothermal route, with malic acid used as the symmetry-breaking agent. Two levels of chirality have been identified in CMIFs: primary nanoflakes with atomically twisted crystal lattices and secondary helical stacking of the nanoflakes. CMIFs exhibit chirality-dependent asymmetric MCD signals due to the different interactions of chirality-induced effective magnetic field and external magnetic field, which distinguish from the commonly observed external magnetic fielddependent symmetric MCD signals. These findings provide insights into spin manipulation of spin-paired diamagnets.

Nature Communications, Published online: 22 June 2024; doi:10.1038/s41467-024-49518-0

The Mermin-Wagner theorem states that for short-range isotropic interactions, magnetic order in two dimensions is destroyed by magnetic fluctuations at finite temperatures. Observing this situation is challenging due to the finite size of typical laboratory samples. Here, Kiaba et al observe the suppression of magnetic order in oxide superlattices, at the thickness of the superlattice layers are reduced to one monolayer.

Nature, Published online: 19 June 2024; doi:10.1038/s41586-024-07560-4

By using a chiral halide perovskite material, spin injection at room temperature into a conventional III–V semiconductor multiple quantum well light-emitting diode is demonstrated, resulting in a semiconductor platform that can also control spin.

High dynamic strength is of fundamental importance for fibrous materials that are used in high–strain rate environments. Carbon nanotube fibers are one of the most promising candidates. Using a strategy to optimize hierarchical structures, we fabricated ...

The field-effect transistor (FET) is a cornerstone of modern electronics, pivotal in the development of compact and efficient integrated microprocessors and memory storage devices capable of low-power operation. At the heart of a FET is a semiconductor ...

A single photon detector for communication wavelength (1550 nm) is demonstrated using van der Waals heterojunction. The detector exhibits an external quantum efficiency of >20% and a dark count rate less than 1 kHz while operating at room temperature. The results are important for quantum communication, sensing, and computing applications.

Abstract

Single-photon detectors (SPDs) are crucial in applications ranging from space, biological imaging to quantum communication and information processing. The SPDs that operate at room temperature are of particular interest to broader application space as the energy overhead introduced by cryogenic cooling can be avoided. Although silicon-based single photon avalanche diodes (SPADs) are well-matured and operate at room temperature, the bandgap limitation restricts their operation at telecommunication wavelength (1550 nm) and beyond. InGaAs-based SPADs, on the other hand, are sensitive to 1550 nm photons but suffer from relatively lower efficiency, high dark count rate, afterpulsing probability, and pose hazards to the environment from the fabrication process. In this work, the properties of nanomaterials that can be leveraged to address these challenges are demonstrated and a room-temperature single-photon detector capable of operating at 1550 nm is realized. This is achieved by coupling a low bandgap (≈ 350 meV) absorber (black phosphorus) to a sensitive van der Waals probe that is capable of detecting discrete electron fluctuation. The device is optimized for operation at 1550 nm and demonstrates an overall quantum efficiency of 21.4% (estimated as 42.8% for polarized light), and a minimum dark count of ≈ 720 Hz at room temperature.

This review summarizes cutting-edge research on emerging ferroelectric control of spin-orbitronics (FECSO) in various material systems by means of spontaneous polarization, reversible ferroelectric switching, and multiferroic coupling. Two fascinating topics of topological spin texture and spin-charge interconversion are carefully discussed. It aptly classifies the primary control mechanisms of FECSO and also provides clear future perspectives.

Abstract

Spin-orbit coupling refers to the relativistic interaction between the spin and orbital motions of electrons. This interaction leads to numerous intriguing phenomena, including spin-orbit torques, spin–momentum locking, topological spin textures, etc., that have recently gained prominence in the field of spin-orbitronics. In particular, the emerging ferroelectric control is recognized and validated as an effective means to enhance energy efficiency across a broad spectrum of spin-orbitronic devices. Here, cutting-edge research on ferroelectric control of spin-orbitronics (FECSO) by means of spontaneous polarization, reversible ferroelectric switching, and multiferroic coupling, are comprehensively reviewed. Two fascinating topics are mainly discussed: topological spin texture and spin-charge interconversion. The classification of control mechanisms for different interactions in FECSO is summarized first. Then, from the perspective of material classification, the ferroelectric-controlled spin-orbit coupling with tunable topological spin texture in oxide systems, magnetic metal multilayers, and 2D van der Waals materials is reviewed. Subsequently, the ferroelectric-tunable spin-charge interconversion on heavy metal layers, oxide interfaces, and ferroelectric Rashba semiconductors is highlighted. In the end, the challenges and forthcoming prospects of FECSO are discussed. This work may provide pertinent and forward-thinking guidance to accelerate the ongoing advancement of this field.

The current work proposes a simple approach of using empirical formulas and existing thermodynamic data to discover eutectic high-entropy alloys for rapid solidification processes, such as metal additive manufacturing. The exemplarily devised material containing face-center-cubic and Laves phases demonstrates high hardness in its as-built state.

Abstract

Excellent castability, significantly refined microstructure, and good mechanical properties make eutectic high-entropy alloys (EHEAs) a natural fit for rapid solidification processes, e.g., additive manufacturing. Previous investigations have focused on developing EHEAs through trial and error and mixing known binary eutectic materials. However, eutectic compositions obtained from near-equilibrium conditions do not guarantee a fully eutectic microstructure under rapid solidifications. In this work, a thermodynamically guided high-throughput framework is proposed to design EHEAs for rapid solidification. Empirical formulas derived from past experimental observations and thermodynamic computations are applied and considered phase growth kinetics under rapid solidification (skewed phase diagram). The designed alloy candidate, Co_25.6Fe_17.9Ni_22.4Cr_19.1Ta_8.9Al_6.1 (wt.%), contains nanostructured eutectic lamellar and shows a high Vickers hardness of 675 Hv. In addition to this specific composition, the alloy design toolbox enables the development of new EHEAs for rapid solidification without the limitation of previous knowledge.

This work demonstrates thermal, electrical, and all-optical tuning of the nonlinear optical response of hBN encapsulated monolayer graphene, considering the interplay between electronic temperature, Pauli blocking, and electron dephasing. The device displays electrostatic third-harmonic (TH) modulation for both electrons and holes, and ultrafast all-optical TH modulation with close to 90% modulation depth.

Abstract

Graphene is a unique platform for tunable opto-electronic applications thanks to its linear band dispersion, which allows electrical control of resonant light-matter interactions. Tuning the nonlinear optical response of graphene is possible both electrically and in an all-optical fashion, but each approach involves a trade-off between speed and modulation depth. Here, lattice temperature, electron doping, and all-optical tuning of third-harmonic generation are combined in a hexagonal boron nitride-encapsulated graphene opto-electronic device and demonstrate up to 85% modulation depth along with gate-tunable ultrafast dynamics. These results arise from the dynamic changes in the transient electronic temperature combined with Pauli blocking induced by the out-of-equilibrium chemical potential. The work provides a detailed description of the transient nonlinear optical and electronic response of graphene, which is crucial for the design of nanoscale and ultrafast optical modulators, detectors, and frequency converters.

An organic coating layer, direct, low-temperature and vacuum-free strategy to improve the remanent polarization (P _r) of perovskite oxide films is employed. The P _r is significantly increased from 36 to 56 µC cm⁻². This organic coating layer strategy may open a new way for exciting and transformative developments of perovskite materials, further improving its prospective for application in the electron devices field.

Abstract

Perovskite oxides and organic–inorganic halide perovskite materials, with numerous fascinating features, have been subjected to extensive studies. Most of the properties of perovskite materials are dependence on their ferroelectricity that denoted by remanent polarization (P _r). Thus, the increase of P _r in perovskite films is mainly an effort in material physics. At present, commonplace improvement schemes, i.e., controlling material crystallinity, and post-annealing by using a high-temperature process, are normally used. However, a simpler and temporal strategy for P _r improvement is always unavailable to perovskite material researchers. In this study, an organic coating layer, low-temperature, and vacuum-free strategy is proposed to improve the P _r, directly increasing the P _r from 36 to 56 µC cm⁻². Further study finds that the increased P _r originates from the suppression of the oxygen defects and Ti defects. This organic coating layer strategy for passivating the defects may open a new way for the preparation of higher-performance and cost-effective perovskite products, further improving its prospective for application in the electron devices field.

Defect-rich metastable MoS₂ nanozymes (1T2H-MoS₂) are designed via reduction and phase transformation in molten sodium. The clinical feasibility of 1T2H-MoS₂ via ex vivo therapeutic responses is demonstrated as a guide treatment for human breast cancer. The 1T2H-MoS₂ can function as an extracellular hydroxyl radical generator, efficiently repolarizing TAMs to the M1-like phenotype and directly killing cancer cells.

Abstract

Tumor-associated macrophages (TAMs) play a crucial function in solid tumor antigen clearance and immune suppression. Notably, 2D transitional metal dichalcogenides (i.e., molybdenum disulfide (MoS₂) nanozymes) with enzyme-like activity are demonstrated in animal models for cancer immunotherapy. However, in situ engineering of TAMs polarization through sufficient accumulation of free radical reactive oxygen species for immunotherapy in clinical samples remains a significant challenge. In this study, defect-rich metastable MoS₂ nanozymes, i.e., 1T2H-MoS₂, are designed via reduction and phase transformation in molten sodium as a guided treatment for human breast cancer. The as-prepared 1T2H-MoS₂ exhibited enhanced peroxidase-like activity (≈12-fold enhancement) than that of commercial MoS₂, which is attributed to the charge redistribution and electronic state induced by the abundance of S vacancies. The 1T2H-MoS₂ nanozyme can function as an extracellular hydroxyl radical generator, efficiently repolarizing TAMs into the M1-like phenotype and directly killing cancer cells. Moreover, the clinical feasibility of 1T2H-MoS₂ is demonstrated via ex vivo therapeutic responses in human breast cancer samples. The apoptosis rate of cancer cells is 3.4 times greater than that of cells treated with chemotherapeutic drugs (i.e., doxorubicin).

The MoS₂/Ba_0.6Sr_0.4TiO₃-FETs exhibited remarkable non-volatile memory properties and memristive behavior, which can be switched by gate voltage. As a non-volatile memory, it delivers low operating energy at ≈0.3 pJ per spike. Using the historic memory behaviors, a cryptosystem is developed with auto-generated reading log which is tamper-resistant at hardware level. Moreover, the synaptic functions are also realized on the device such as the short-term potentiation/depression and gating-depending synaptic plasticity.

Abstract

To overcome the von Neumann bottleneck between memory and computing, the novel architectures with computing in-memory are paid much attention and expected to be compatible with digital logic computing and/or analog brain-inspired neuromorphic computing. Herein, by combining the Ba_0.6Sr_0.4TiO₃ (BST) ferroelectric film and MoS₂ layered semiconductor, a non-volatile memory is constructed, which deliver the gate-switchable function between the digital and analog functionality modes. The on/off ratio, subthreshold swing, and carrier mobility of MoS₂/BST ferroelectric field-effect transistor (FeFET) are 4.95×10⁶, 68 mV dec⁻¹, and 16.7 cm² V⁻¹ s⁻¹, respectively. By a small electrical stimulation, the device demonstrates remarkable non-volatile memory properties, including robust long-term retention of ≈3000 s, superior endurance over 34 000 cycles, low operating energy at ≈0.3 pJ per spike. By a large electrical stress, it exhibits well memristive behavior and gating history dependent accumulation/diminution effect, which is attributed to the charge dynamic trapping/de-trapping activation at the MoS₂/BST interface. Following the historic memory behaviors, a cryptosystem is developed with auto-generated reading log which is tamper-resistant at hardware level. Moreover, the synaptic functions are realized on the device such as the short-term potentiation/depression and gating-depending synaptic plasticity. This study shows the opportunities of multi-functionalities integration in a single FeFET device.

Nature Electronics, Published online: 19 June 2024; doi:10.1038/s41928-024-01204-1

3D integration proceeds tier-by-tier