Jiuxiang Dai

The direct growth of Bi₂O₂Se nanoflakes on Si substrates is reported using an oxygen-assisted chemical vapor deposition (CVD) technique, achieving a record room temperature carrier mobility exceeding 2000 cm² V⁻¹ s⁻¹. This value surpasses all previously reported mobilities for Bi₂O₂Se and represents a significant advancement in high-performance 2D semiconductors.

Abstract

Bi₂O₂Se has recently attracted immense interest in nanoelectronics and optoelectronics for its superior mobility, ferroelectric order, tunable bandgap, and exceptional air stability. However, until now, the direct growth of Bi₂O₂Se is limited to mica, or perovskite oxide substrates [SrTiO₃, LaAlO₃, (La, Sr)(Al, Ta)O₃], incompatible with mainstream semiconductor processes, and the room temperature mobility is limited to ≈800 cm² V⁻¹ s⁻¹. Here, the controllable growth of Bi₂O₂Se nanoflakes on SiO₂/Si substrates is reported and with room temperature electron mobility higher than 2000 cm² V⁻¹ s⁻¹, exceeding all previous reports. The unpreceded in-plane electron mobility is found to strongly correlate with the out-of-plane ferroelectric order, which is stabilized by the expanded c-lattice in oxygen-deficient Bi₂O₂Se. The stabilized ferroelectric phase is confirmed by piezoresponse force microscopy (PFM) and anisotropic transport property measurements, which generally possess a high dielectric constant, thus reducing the impurity scattering. The silicon-compatible ultrahigh mobility Bi₂O₂Se sheds light to high-performance electronic devices.

This review summarizes recent strategies for field-free switching of perpendicular magnetization through low-crystal-symmetry and low-magnetic-symmetry materials, including non-collinear antiferromagnets and altermagnets. It also highlights recent advances in out-of-plane anti-damping magnon torques. Moreover, it discusses the challenges and perspectives for developing all-electric spin-orbit torque devices, emphasizing the exploration of physical mechanisms and the identification of novel low-symmetry materials.

Abstract

Spin-orbit torque (SOT), which relies on the generation of spin currents from charge currents in materials with strong spin-orbit coupling, provides a fast and energy-efficient approach for magnetization manipulation in magnetic memory devices. A critical challenge for SOT-based devices lies in generating out-of-plane spin polarization to eliminate the need for an external magnetic field, enabling all-electric switching of perpendicular magnetization. In this review, recent advances in generating out-of-plane spin currents and achieving field-free switching of perpendicular magnetization by utilizing materials that break lateral surface crystal symmetries and magnetic symmetries are summarized. Moreover, the observation of out-of-plane anti-damping magnon torques and the realization of all-electric magnon devices are reported. It is emphasized that, although key components of spintronics devices based on low-symmetry materials are demonstrated, many promising materials and critical questions remain to be explored. Thus, this area represents a dynamic and promising frontier in spintronics, with substantial potential for advancing future memory and computational technologies.

A new class of transparent metal–organic complex glasses has been synthesized through a bottom-up self-assembly process that enables facile doping of lanthanide ions. By leveraging the room-temperature phosphorescence (RTP) sensitized lanthanide strategy, these glasses exhibit high photoluminescence quantum yield and efficient optical waveguiding in the NIR region, thus offering potential advanced NIR-II photonic applications.

Abstract

The increasing demands for modern information communication and storage necessitate the development of near-infrared (NIR) active optical waveguides. However, achieving efficient NIR emission with minimal optical loss remains a critical challenge. Herein, we present a new class of rare earth single-atomic hybrid glasses, synthesized via bottom-up self-assembly, as a solution to these limitations. By harnessing the ultralong phosphorescence of Nd³⁺-doped complex glasses, these materials achieve NIR-II emission extending to 1.32 µm with a photoluminescence quantum yield (PLQY) of ∼5.7%, setting a new record among state-of-the-art rare-earth-based complexes in the NIR-II region. This exceptional performance stems from the efficient sensitization of Nd³⁺ ions in hybrid glass, with a phosphorescence energy transfer efficiency of 93.55%. Furthermore, these transparent and flexible hybrid glasses trigger optical waveguiding in Eu³⁺- and Nd³⁺-doped microstructures, enabling ultralow-loss coefficients of 0.978 dB mm⁻¹ at 819 nm and 5.1 dB mm⁻¹ at 1048 nm, respectively. Therefore, this work not only demonstrates that metal–organic complex glasses with ultralong phosphorescence can effectively serve as sensitizer matrices for boosting NIR-II emission, but also supports the fabrication of 1D and 2D glassy microstructures with ultralow-loss optical waveguiding for advanced NIR-II photonic applications.

A review: geometric design and electronic engineering of transition metal phosphides for key electrochemical energy technologies: nanoarchitectonics and application.

Abstract

Transition Metal Phosphides (TMPs) are highly focused on as electrode materials for their potential applications in electrochemical energy storage and conversion (EESC) devices due to their high theoretical capacity, carrier mobility, and excellent chemical and mechanical stability. However, pristine TMPs typically suffer from low device stability and safety concerns due to sluggish electronic/ionic kinetics and volumetric variation after prolonged cycling. The precise morphological design and synthesis of TMPs with good dispersity, novel assembling techniques, and mitigation approaches, emphasizing nanoarchitectonics engineering, opens up new frontiers to overcome these challenges. This paper comprehensively reviews state-of-the-art advances in TMP-based key materials, focusing on geometric design engineering, electronic structure modulation, and their applications in EESC, including rechargeable batteries, supercapacitors, and electrocatalysis. In the end, current technical concerns and potential future research prospects of TMP-based nanostructured materials have also been presented for EESC applications.

The multiheterostructure of high-quality graphene, h-BN, and Mo₂C ternary systems are precisely assembled through conditioning of CVD precursors, enabling the observation of crystal orientation mobilization and Moiré fringes, as well as Mo₂C with superconducting transitions.

Abstract

2D van der Waals multiheterostructures serve as an extensively studied material due to their unique physical properties. However, the multicomponent heterostructure is difficult to obtain on a large scale and is limited by the conventional method of mechanical stacking, which hinders their potential applications. Here a precursor-modulated chemical vapor deposition strategy is reported for selectively growing vertical multiheterostructures, lateral multiheterostructures, and their combinate stackings. The composition within the heterostructure can be precisely controlled by modulating the concentration of precursors. As a result, four types of heterostructure are resoundingly achieved including graphene/h-BN, graphene/Mo₂C, h-BN/Mo₂C, and graphene/h-BN/Mo₂C superposition multiheterostructure. Morphological, spectroscopic, and atomic-scale structural characterizations are conducted to suggest the high quality of the heterostructures, demonstrating the precise controllability of the strategy. Moreover, both the crystal orientation miss-alignment and Moiré fringes within graphene/Mo₂C vertical heterostructures are also successfully observed benefiting from the fluidity of the liquid copper catalyst under high temperatures. The obtained Mo₂C shows 2D characteristics of superconducting transitions (at 0 T, 6.9 K) as well as a strong anisotropy with magnetic field orientation. The replication of the multiheterostructure customization process in other 2D materials is anticipated, potentially expediting the design of next-generation functional devices.

This review article aims to provide an overview of recent progress in the field of topological magnetism, focusing on topological magnetic materials and device design. The study delves into the design of new structures, such as lattice or composition asymmetry engineering, to expand the family of topological magnetic materials, as well as the manipulation of various topological magnetic structures.

Abstract

The emerging interest in topological magnetism has ignited exciting vitality in the field of spintronics, thereby offering a promising route for breaking Moore's law constraints and establishing an efficient information storage model. Unlike the conventional 2D storage cell based on macroscopic magnetization, magnetic skyrmions—the representative of topological magnetism—are considered candidates for realizing 3D memory, such as “racetrack memory,” facilitating the development of topological spintronics. Since the discovery of skyrmion-hosting materials, extensive studies on topological magnetic materials are conducted, although challenges have arisen with rapid research progress. Herein, the recent progress in topological spintronics, including material and device design, is reviewed. Beyond bulk magnets, research on topological magnetism is focused on low-dimensional materials, including magnetic films and 2D magnetic materials, which are promising candidates for magnetic storage devices. Furthermore, the design of new structures, such as in lattice or composition asymmetry engineering, to expand the family of topological magnetic materials is essential. In addition to skyrmions, various topological magnetic structures such as antiskyrmions, merons, and 3D complex structures are detailed. Furthermore, topological magnetism manipulation and related principal devices are discussed. This review provides an opportunity to generate more interest and deepen the discussion of topological magnetism.

A machine-learning approach is presented to characterize ferromagnetic LSMO thin films by featurizing their surface morphology. Through an ensemble model, the non-linear correlations between surface morphology and the electric/magnetic properties of LSMO thin films are successfully captured. This result demonstrates that surface morphology can effectively reveal essential information about the correlated physical properties of ferromagnetic oxide materials.

Abstract

Ferromagnetic perovskite oxides, particularly La_0.7​Sr_0.3MnO₃ (LSMO), show significant promise for spintronics and electromagnetic applications due to their unique half-metallicity and colossal magnetoresistance properties. These properties are known to arise from Mn-O-Mn double-exchange interactions, which are directly related to microscopic lattice structures. However, since the microscopic structure in LSMO is highly sensitive to various material parameters, such as thickness, lattice strain, oxygen deficiency, and cation stoichiometry, understanding the intricate relationship between the microscopic structures and the resulting physical properties of LSMO remains challenging. Herein, a machine learning approach is introduced to characterize ferromagnetic LSMO thin films by featurization of their surface morphology. Using an ensemble machine learning method, the non-linear correlations between surface morphology and the electronic, magnetic properties of LSMO thin films are captured and modeled. Based on these estimated correlations, LSMO thin films are classified into five representative types, each characterized by distinctive properties and surface morphologies. These results imply that surface morphology can reveal hidden information about the strongly correlated properties of ferromagnetic LSMO thin films. Consequently, the machine learning-based approach provides an efficient method for understanding the correlated material properties of ferromagnetic oxides and related materials through surface morphology analysis.

This work demonstrates the control of crystal phases in rare-earth titanates containing multiple rare-earth elements. By combining atomic-level structure characterization techniques, the atomic structures are elucidated, and entropy of mixing for each phase is quantitatively estimated. A crystal-phase map as a function of temperature and average ionic radius is reproduced and predicted using a machine learning approach.

Abstract

Multi-cation oxides have been extensively studied over the past decade for various solid-state applications. The source of their functionality lies in a wide compositional search space derived from countless cation combinations and diverse crystal structures formed in metal oxides. However, due to the vast space and complexity of structure control, material exploration has been limited to dispersed compositions under different synthesis conditions, hindering their systematic understanding and rational design. Here, a crystalline-phase map of multi-cation rare-earth titanates is reported, where three types of crystals, i.e., cubic and hexagonal, and orthorhombic phases, emerge depending on the composition and temperature and exhibit systematic changes. The crystal structures of each phase are thoroughly characterized with X-ray diffraction, electron microscopy, and first-principles calculations. The configurational entropies calculated from the crystallographic information support the phase-boundary shift between hexagonal and orthorhombic phases observed in the phase map. Further, a machine learning procedure is proposed for constructing the map from sparse experimental data, allowing predictive exploration for stable crystalline phases across a large compositional space. These findings may facilitate the design of multi-cation oxides with a desired structure dispersed in a large search space.

We apply thermomechanical epitaxy (TME), a pressure-driven diffusion process, to achieve wafer-scale growth of single-crystalline, one-dimensional (1D) topological nanomaterials. Alongside this fabrication approach, we develop a theoretical framework that predicts material compatibility with TME by correlating phase stability with pressure-induced chemical potential. Together, these advancements expand the range of accessible 1D topological nanomaterials and provide a systematic route for their scalable synthesis, offering new opportunities for fundamental research and device applications.

Light: Science & Applications, Published online: 25 April 2025; doi:10.1038/s41377-025-01821-1

Wafer-level InP-LiNbO₃ heterogeneous integration platform enables large-scale, multifunctional, and high-performance lithium niobate photonic integrated circuits for Pbit/s hyperscale data center interconnects and mmwave/THz photonics.

Independently modulating the transmittance of solar spectra, specifically within the visible and near-infrared light ranges, presents a significant prospect for windows to effectively manage lighting and energy consumption in both buildings and electrical-vehicles. Electrochromic devices, capable of regulating the transmittance of visible and near-infrared light in response to external electrical stimuli, are considered as one of ideal candidates for smart windows. However, electrochromic devices typically suffer from single-mode control (i.e., simultaneously varying the visible and near-infrared light), slow response and inadequate long-term durability. In this paper, we demonstrate that TT-Nb₂O₅ enables independent modulation of visible and near-infrared light and possesses rapid switching kinetics and exceptional cycling stability, i.e., no observed degradation of optical modulation after more than 10,000 cycles. The dual band modulation is attributed to a combination of progressive splitting and downward shift of Nb 3d conduction bands and rise of Fermi level as ion insertion proceeds. The open framework of the crystal structures accounts for the exceptional cycling stability. Simulation results based on assembled smart windows indicate a potential cooling energy saving of 160 GJ without compromising the outdoor view, or 225 GJ for a complete blocking of visible and near-infrared light, can be achieved in hot climate zones.

Temperature and stress sensing based on flexible optical fibers may be the key to future artificial intelligence's perception of the world, here an optical fiber sensor capable of realizing such dual mode sensing is preliminary confirmed based on CaZnOS:Nd³⁺,Er³⁺.

Abstract

Mechanoluminescence (ML) and upconversion luminescence (UCL) materials exhibit significant potential in advanced optical sensing applications. However, single-function luminescent materials often fail to meet the increased complexity and precision demands of modern application scenarios. Here, flexible optical fiber based on ML and UCL dual-mode luminescence is demonstrated in Ca/SrZnOS: Nd³⁺, Er³⁺, which can be integrated into potential dual-mode stress and temperature sensing devices. After 4200 cycles of 2 N load, the ML intensity remaines at ≈67% of its initial value. Additionally, such device has a temperature sensitivity of 1.423% K⁻¹ at 273.15 K, with a detection accuracy of 1.1990 °C. The device maintained excellent cycling stability over a broad temperature range (0–80 °C), as evidenced by the unchanged FIR values after 10 cycles. The device demonstrates potential applications in remote stress and temperature monitoring, particularly in high-temperature, high-pressure, or hazardous environments, where optical fiber transmission ensures both safety and accuracy.

Thermal transport serves as an ultra-sensitive probe for detecting the magnetic order in 2D materials. Using the suspended thermal bridge method enhanced by Wheatstone bridges, it is, for the first time, observed anomalous critical behavior in few-layer CrOCl near its Néel temperature. Meanwhile, the first experimental confirmation is provided that magnon can enhance interfacial thermal conduction in metal-insulator interface.

Abstract

Few-layer van der Waals magnets are exceptional candidates for investigating the fundamental spin behaviors and advancing the development of next-generation ultra-compact spintronic devices. While the intrinsic long-range magnetic order is well-established in the monolayer limit, the thermal transport behavior involving magnons, phonons, and magnetophonon polarons near the phase transition remains largely unexplored. In this work, the thermal transport behavior is probed near the phase transitions from bulk to the monolayer limit by using a differential suspended thermal bridge method, which provides an ultra-sensitive temperature and thermal conductance measurement enhanced by the double Wheatstone bridge. In the few-layer CrOCl flake, a stronger magnon-phonon coupling is observed compared to the bulk, resulting in a shift in the thermal transport behavior from a dip to a peak shape around the Néel temperature. Additionally, below the Néel temperature, the few-layer CrOCl significantly enhances the interfacial thermal conductance between the metal electrode and insulator substrate, potentially leading to the substantial improvements in the heat dissipation in Si-based semiconductor devices. This study introduces a novel method and strategy for probing the fundamental magnetic phase transition behavior and lays a solid foundation for the potential application of van der Waals magnets in the electronic devices.

Controlling motion paths in soft active material-based robots is challenging due to their inherently high degrees of freedom. Inspired by aerial trams, a new class of autonomous, track-guided soft robots composed of twisted liquid crystal elastomer rings are reported. Under constant infrared light, these robots can self-navigate along predefined 3D tracks without spatiotemporal control of light sources.

Abstract

Navigating in three-dimensional (3D) environments with precise motion control is challenging for soft robots due to their inherent flexibility. Inspired by aerial trams, here, an autonomous soft twisted ring robot is reported capable of navigating pre-defined tracks in 3D space under constant photothermal actuation, without requiring spatiotemporal control of actuation sources. Made of liquid crystal elastomers, the ring robot, suspended on thread-based tracks, self-flips around its centerline when exposed to constant infrared light. Curling the twisted ring around tracks converts its self-rotary motion into autonomous linear movement via screw theory. This mechanism enables the autonomous robot to adapt to tracks of various materials and micron-to-millimeter sizes, overcome obstacles like knots on tracks, transport loads over 12 times its weight, ascend and descend steep slopes up to 80°, and navigate complex paths, including circular, polygonal, and 3D spiral tracks, as well as loose threads with dynamically changing shapes.

The growth of monolayer 2D Bi₂TeO₅ is achieved by introducing a buffer layer between the substrate and nanosheets, which relieves strain and stabilizes in-plane ferroelectricity. This method enhances the synthesis of monolayer nanosheets, establishes a stable approach for ultrathin ferroelectric materials, and has the potential to serve as a universal technique for synthesizing 2D ternary oxides.

Abstract

Miniaturizing van der Waals (vdW) ferroelectric materials to atomic scales is essential for modern devices like nonvolatile memory and sensors. To unlock their full potential, their growth mechanisms, interface effects, and stabilization are preferably investigated, particularly for ultrathin 2D nanosheets with single-unit cell thickness. This study focuses on Bi₂TeO₅ (BTO) and utilizes precise control over growth kinetics at the nucleation temperature to create specific interfacial reconfiguration layers. Ultrathin BTO nanosheets with planar ferroelectricity at a single-unit cell thickness are successfully grown. Atomic-scale characterization reveals a disordered distribution of elements in the interfacial layer, which buffers strain from lattice mismatch. The theoretical calculations support these observations. Furthermore, this strategy also can be extended to the growth of a variety of 2D ternary oxide nanosheets. This work contributes to a better understanding of growth and stability mechanisms in 2D ultrathin nanosheets.

Annealing gold nanofilm is an effortless way to prepare gold nanostructures. In this study, the utilization of sacrificial 2D transition metal dichalcogenides promotes such a process allowing the formation of target gold nanostructures provided in reduced thickness and shows potential in plasmonic application.

Abstract

The synthesis of gold nanostructures (AuNS) is a classical topic, celebrated for the exceptional capabilities these structures exhibit across a spectrum of applications. Controlling the morphology and location of gold nanostructures on a large scale is typically a complex task. For example, the thermal annealing method necessitates precise management of the wetting behavior between the gold nanofilm and the substrate during heating to facilitate the transformation of the gold nanofilm into gold nanostructures. Here, the study innovatively applies 2D monolayer MoS₂ as the sacrificial substrate for gold nanostructure growth, leveraging the epitaxy between MoS₂ and gold. This relationship leads to the patterning of larger and more uniform gold nanostructures when contrasted with those grown on original SiO₂/Si substrates. Moreover, the gold nanostructures prepared under this method present four times enhancement in photoluminescence signal of AuNS/TMDC heterostructure, demonstrating the potential application on optoelectronics.

Carbon allotropes have been extensively studied due to their unique structures and properties. On-surface synthesis methods offer a promising approach for the generation and characterization of sp-hybridized carbon allotropes particularly challenging to synthesize due to high reactivity. In this review, recent experimental efforts are summarized in the synthesis of sp-hybridized carbon allotropes, including linear carbon chains and cyclo[n]carbons on surfaces.

Abstract

Carbon allotropes have been extensively studied due to their unique structures and properties. Carbon exists in three hybridization states, among which sp-hybridized carbon allotropes are particularly challenging to synthesize due to their high reactivity. On-surface synthesis methods have emerged as a promising approach for the generation and characterization of such carbon allotropes. In this review, recent experimental efforts are summarized in the synthesis of sp-hybridized carbon allotropes, including linear carbon chains and cyclo[n]carbons on surfaces.

Light: Science & Applications, Published online: 22 April 2025; doi:10.1038/s41377-025-01849-3

Optical second harmonic generation technology quantitatively characterized the enhancement of antiferromagnetic order and Néel temperature in epitaxially strained BiFeO3, providing a quantitative detection and manipulation for the antiferromagnetism.

This work investigates the Nernst effect in the Kagome magnet ErMn₆Sn₆ which exhibits both topological and anomalous Nernst effects with the anomalous Nernst coefficient reaching 1.71 µV K⁻¹ at 300 K. This value surpasses that of most canted antiferromagnetic materials, making ErMn₆Sn₆ a promising candidate for advancing thermoelectric devices based on the Nernst effect.

Abstract

The Nernst effect, the generation of a tranverse electric voltage in the presence of longitudinal thermal gradient, has garnered significant attention in the realm of magnetic topological materials due to its superior potential for thermoelectric applications. In this work, the electronic and thermoelectric transport properties of a Kagome magnet ErMn₆Sn₆ are investigated, a compound showing an incommensurate antiferromagnetic phase followed by a ferrimagnetic phase transition upon cooling. It is shown that in the antiferromagnetic phase ErMn₆Sn₆ exhibits both topological Nernst effect and anomalous Nernst effect, analogous to the electric Hall effects, with the Nernst coefficient reaching 1.71 µV K⁻¹ at 300 K and 3 T. This value surpasses that of most of previously reported state-of-the-art canted antiferromagnetic materials and is comparable to recently reported other members of RMn₆Sn₆ (R = rare-earth, Y, Lu, Sc) compounds, which makes ErMn₆Sn₆ a promising candidate for advancing the development of Nernst effect-based thermoelectric devices.

This review significantly concentrates on state-of-the-art progress in preparations, properties, and applications of 2D TMD-based LHSs, which can generate significant interest in recent processes of 2D TMD-based LHSs as well as inspire further future exploration of LHSs.

Abstract

Two-dimensional transition metal dichalcogenides (2D-TMDs) have attracted considerable attention from academic and industrial fields due to their atomical thin thickness and unique and tunable physical and chemical properties. Especially, 2D TMD-based lateral heterostructures (LHSs), formed by one-to-one covalent bonding of 2D TMDs with similar lattice structure and constant, provide a new freedom and exciting material platforms for exploring exotic physical and chemical properties at micro–nano–pico scales and show great potential applications in high density integrated electric and photoelectric devices. However, progress in this field has been largely limited by the availability of high-quality LHSs, which cannot be obtained by simple stacking but only by precise synthesis. Firstly, this review summarizes the latest research on LHSs, covering synthesis strategies like chemical vapor deposition (CVD) to molecular beam epitaxy (MBE), and analyzing growth mechanisms. Secondly, it explores interface properties (such as bandgap tuning, strain engineering, and interfacial exciton effects), linking them to device performance. Additionally, it also highlights applications in high-speed electronics, optoelectronics, and catalysis, highlighting their cross-disciplinary potential. Finally, it addresses challenges like large-scale fabrication and defect control, and proposes future directions in material design and multifunctional integration. This provides a key reference for the development of 2D-TMDs-based LHSs.

Nature Communications, Published online: 18 April 2025; doi:10.1038/s41467-025-58643-3

In most van der Waals ferromagnets, reducing the number of layers reduces the Curie temperature. Here, Chuang et al., find that Cr2Se3 has an increased Curie temperature for thinner samples, and through angle-resolved photoemission spectroscopy they attribute this to differences in the valley carrier density in different thickness samples.