Jiuxiang Dai

Phononic devices offer unique advantages in RF applications due to their shorter wavelengths compared to photons. This perspective explores functional phononic devices that can enable integrated phononic circuits. These circuits promise to enable miniaturized communication systems with improved SWaP-C characteristics, while also finding applications in quantum information science, sensing, and biomedical engineering.

Abstract

The phonon wavelength, being much shorter than that of photons at the same frequency, offers phononic devices a unique niche in radio frequency (RF) applications. However, the current limitations of these devices, particularly their restricted functionality, hinder their broader integration and application. Currently, many functions are achieved using alternative signal forms like electric and photonic signals, requiring bulky converters to transform between phonon signals and other forms. The development of functional phononic devices paves the way for integrated phononic circuits, which aim to minimize the need for signal conversion while accomplishing all necessary functions. In this perspective, a brief overview of several types of functional phononic devices is provided that hold promise for integration, such as phononic modulators, amplifiers, lasers, nonreciprocal devices, and those inspired by topological physics. It is envisioned that through continued developments in materials, fabrication techniques, and designs, it's possible to realize integrated phononic circuits which will be applied in miniaturized communication devices with reduced size, weight, power consumption, and cost (SWaP-C), as well as in other fields including quantum information science, sensing, biomedical engineering, and beyond.

This work demonstrates high-quality, ultrathin AlN epilayers on sapphire, exhibiting a low threading dislocation density (2.6 × 10⁹ cm^{− 2}) and step-flow morphology. Optimized strain engineering enables the development of a high-performance DUV-LED with a 150 nm AlN buffer, achieving 27.8 mW output power and 3.95% WPE. This approach advances scalable III-nitride deep-UV optoelectronics while reducing material usage and processing complexity.

Abstract

In heteroepitaxial systems with large lattice and thermal mismatches, it is extremely challenging to balance crystalline quality, surface morphology, and strain within a very limited epitaxial thickness range. Consequently, ultrathin, high-quality single-crystalline epilayers with atomically flat surfaces on hetero-substrates with large mismatches are rarely reported, as most practical devices rely on thick epitaxial templates. In this work, using AlN/sapphire as an example, high-quality, wafer-scale, ultrathin single-crystalline AlN layers on sapphire substrates are successfully achieved. These AlN layers, as thin as 50 nm, exhibit an impressively low threading dislocation density of 2.6 × 10⁹ cm⁻² and a step-flow morphology. Furthermore, this novel template shows great promise for the epitaxy of deep-ultraviolet light-emitting diodes (DUV-LEDs). By optimizing strain conditions, a high-performance DUV-LED with a 150-nm-thick AlN buffer layer is demonstrated, significantly reducing the conventional requirement for an AlN thickness exceeding 2 µm. Specifically, the DUV-LED exhibits excellent performance, including a light output power of 27.8 mW and a wall-plug efficiency (WPE) of 3.95%. These achievements establish a high-quality, cost-effective, and scalable platform for III-nitride semiconductor devices, enabling advanced deep-UV optoelectronics. This breakthrough overcomes the challenge of ultrathin epitaxy on mismatched substrates while significantly reducing material usage and processing time.

Nature Communications, Published online: 18 April 2025; doi:10.1038/s41467-025-58968-z

Perovskite oxides, when combined into heterostructures and superlattices can yield emergent properties not present in the constituent components. Here, by combining LaNiO3, a Pauli paramagnetic material, with LaFeO3, an antiferromagnetic insulator, Zhou et al create a strongly ferromagnetic superlattice with a Curie temperature of over 600 K.

Low-dimensional semiconductor materials are promising candidates for photosensitive components in next-generation image sensors. This review offers a thorough and timely examination of novel image sensors, covering their working principles, intriguing materials categorized into four main groups, and advanced imaging applications. Additionally, it delves into the roadmap for next-generation image sensors, exploring future opportunities and challenges in the field.

Abstract

With the rapid advancement of technology of big data and artificial intelligence (AI), the exponential increase in visual information leads to heightened demands for the quality and analysis of imaging results, rendering traditional silicon-based image sensors inadequate. This review serves as a comprehensive overview of next-generation image sensors based on low-dimensional semiconductor materials encompassing 0D, 1D, 2D materials, and their hybrids. It offers an in-depth introduction to the distinctive properties exhibited by these materials and delves into the device structures tailored specifically for image sensor applications. The classification of novel image sensors based on low-dimensional materials, in particular for transition metal dichalcogenides (TMDs), covering the preparation methods and corresponding imaging characteristics, is explored. Furthermore, this review highlights the diverse applications of low-dimensional materials in next-generation image sensors, encompassing advanced imaging sensors, biomimetic vision sensors, and non-von Neumann imaging systems. Lastly, the challenges and opportunities encountered in the development of next-generation image sensors utilizing low-dimensional semiconductor materials, paving the way for further advancements in this rapidly evolving field, are proposed.

Out-of-plane ferroelectricity is observed in 1T′/1H MoS₂ bilayers synthesized via chemical vapor deposition (CVD). The phenomenon is confirmed through structural analysis using scanning transmission electron microscopy (STEM) and second-harmonic generation (SHG), as well as switching behavior characterized by piezoresponse force microscopy (PFM) and ferroelectric tunnel junction (FTJ) measurements. Density functional theory (DFT) calculations reveal that the ferroelectricity originates from interlayer sliding. This discovery extends the scope of 2D ferroelectrics to vertically stacked heterophase systems, offering new opportunities for exploring coupled phenomena in transition metal dichalcogenides (TMDCs).

Abstract

The emergence of heterophase 2D materials, distinguished by their unique structures, has led to the discovery of a multitude of intriguing physical properties and a broad range of potential applications. Here, out-of-plane ferroelectricity is uncovered in a heterophase structure of 1T′/1H MoS₂, which is synthesized via chemical vapor deposition (CVD) by tuning the formation energies for MoS₂ with varied phases. The atomically resolved structures of the obtained 1T′/1H MoS₂ bilayers are captured using scanning transmission electron microscopy (STEM) and are confirmed to be non-centrosymmetric using second-harmonic generation (SHG) characterizations. The intrinsic out-of-plane polarization is visualized by piezoresponse force microscopy (PFM), which reveals that ferroelectric domains can be manipulated under an applied electric field. Ferroelectric tunnel junction (FTJ) devices fabricated on these bilayers exhibit reversible switching between a high resistance state (HRS) and a low resistance state (LRS). Density functional theory (DFT) calculations elucidate that the intrinsic ferroelectricity in 1T′/1H bilayers is attributed to interlayer sliding and lattice mismatch. The findings not only expand the scope of 2D ferroelectrics to include vertically stacked heterophase bilayers but also open avenues for exploring the coupling effect between ferroelectricity and other phenomena such as magnetism, superconductivity, and photocatalysis in 2D heterophase TMDCs.

Nature, Published online: 16 April 2025; doi:10.1038/s41586-025-08839-w

A two-dimensional Dirac graphene-channel flash memory based on a two-dimensional-enhanced hot-carrier-injection mechanism that supports both electron and hole injection is used to make devices with a subnanosecond program speed.

Nature, Published online: 15 April 2025; doi:10.1038/d41586-025-01125-9

A Nature analysis reveals the 25 highest-cited papers published this century and explores why they are breaking records.

Nature, Published online: 15 April 2025; doi:10.1038/d41586-025-01124-w

Some studies have received hundreds of thousands of citations, Nature’s updated analysis shows.

This review provides an overview of the fundamental photodetection mechanisms and key performance metrics of 2D photodetectors targeting the infrared (IR) region. By summarizing enhancing strategies for IR photodetection including defect engineering, heterostructure construction, and optical field enhancement, and showcasing cutting-edge developments in intelligent applications, it offers valuable insights into the development of 2D materials-based IR intelligent photodetectors with integrated real-time sensing and processing capabilities.

Abstract

Infrared (IR) photodetectors based on narrow-bandgap 2D materials and heterojunctions have shown great promise in constructing IR sensing systems, including optical communication, security monitoring, thermal imaging, and astronomy exploration. In recent years, significant progress has been made in developing performance enhancement strategies for 2D material-based IR photodetectors and integrating them with artificial neural networks, paving the way for sophisticated intelligent IR applications. This review offers a detailed overview of recent advancements in enhancing IR photodetection capabilities and fostering related intelligent applications. First, a concise overview of the underlying photodetection mechanisms and key performance metrics of 2D photodetectors designed for operation in the IR region is illustrated. Next, strategies for enhancing sensitivity and light absorption of IR photodetectors, including defect engineering, heterostructure construction, and optical field enhancement, are discussed. Then, recent advances and applications of 2D material-based photodetectors are summarized, with a particular focus on innovations that enable intelligent, real-time sensing and processing capabilities for IR applications. Finally, the review highlights the challenges and provides a forward-looking perspective on the development of advanced intelligent IR photodetectors.

A multimodal secure transistor-integrated in-memory sensing and computing architecture is demonstrated by leveraging its electronic and optoelectronic synaptic behaviors. Key security primitives, such as anticounterfeiting, watermarking, logic locking, and camouflaging, are implemented within a compact single-transistor structure, providing a scalable and resource-efficient solution to address hardware security threats in the era of the Internet of Things.

Abstract

Security is a critical challenge in the integrated circuit (IC) industry, yet device-level hardware security remains largely underexplored. Most existing solutions necessitate modifications to current technology nodes and typically address only a single security threat, leaving them vulnerable to diverse attacks while incurring substantial costs in area, energy, and resources. In this study, an out-of-the-box security solution is proposed that integrates an in-memory sensing and computing (IMSC) architecture based on α-In₂Se₃ transistor, specifically designed for versatile and multimodal secure applications. By leveraging the unique ferroelectric, optoelectronic, and semiconducting properties of α-In₂Se₃, the study demonstrates the secure transistor's electronic and optoelectronic synaptic behaviors, along with its capability for reconfigurable logic operations. Based on these, the secure transistor successfully implements four key security primitives: anticounterfeiting, watermarking, logic locking, and IC camouflaging in a single-transistor structure, offering robust protection against counterfeit ICs, intellectual property theft, and reverse engineering. The multimodal secure transistor demonstrates the functional flexibility in addressing various security threats.

Soft chemical intercalation of the van der Waals magnetic semiconductor CrSBr induces a quasi-1D charge density wave (CDW) phase. The combination of this CDW with ferromagnetism from a spin-polarized band generates an unusual coupling of the charge and spin modulations in the intercalated material.

Abstract

In materials with 1D electronic bands, electron–electron interactions can produce intriguing quantum phenomena, including spin-charge separation and charge density waves (CDW). Most of these systems, however, are non-magnetic, motivating a search for anisotropic materials where the coupling of charge and spin may affect emergent quantum states. Here, chemical intercalation of the van der Waals magnetic semiconductor CrSBr yields Li_0.17(2)(tetrahydrofuran)_0.26(3)CrSBr, which possesses an electronically driven quasi-1D CDW with an onset temperature above room temperature. Concurrently, electron doping increases the magnetic ordering temperature from 132 to 200 K and switches its interlayer magnetic coupling from antiferromagnetic to ferromagnetic. The spin-polarized nature of the anisotropic bands that give rise to this CDW enforces an intrinsic coupling of charge and spin. The coexistence and interplay of ferromagnetism and charge modulation in this exfoliatable material provide a promising platform for studying tunable quantum phenomena across a range of temperatures and thicknesses.

Nature Reviews Chemistry, Published online: 14 April 2025; doi:10.1038/s41570-025-00706-6

Self-healing crystals are an emerging class of materials that are highly responsive to dynamic stimuli. This Perspective gives an overview of the field since its inception, highlights current design principles, and discusses the methodologies used to characterize healed crystals.

A viscosity-tunable, photothermal repairable, and full-component recyclable liquid metal-containing vitrimer exhibited a high resolution of 7.6 µm and an efficient photothermal repairable capability of the reconnection within 15 s through infrared activation. The tunable viscosity and rheology of this system allow for the rapid and mild closed-loop recovery of all printed circuit components.

Abstract

Room-temperature liquid metals (RTLMs) exhibit inherent fluidity, metallic conductivity, remarkable stability, and recyclability, which indicate significant potential for applications in improving the efficiency of electronics recycling and reducing costs. However, the low viscosity of RTLMs and their poor interfacial adhesion to substrates typically necessitate the utilization of intricate fabrication processes. Here, a viscosity-tunable, photothermal repairable, and full-component recyclable eutectic gallium–indium/epoxy-modified lignin/polyethylene glycol diacid/ethylene glycol vitrimer (EGaIn-LPEv) is presented for printed circuits. The vitrimer system displays good interfacial stability and tunable viscosity at room temperature because of the ultra-high reactive site content of the modified lignin and the dual dynamic bonding system by the introduction of ethylene glycol. EGaIn-LPEv-based printed circuit exhibits a high resolution and full component recovery of up to 7.6 µm and 98.3 wt.%, respectively. As the principal component, lignin not only enhances the system's green credentials but also endows it with an efficient photothermal repairable capability. The reconnection of a damaged printed circuit can be achieved in 15 s through the utilization of 808 nm infrared activation. This study opens a new avenue for the development of green manufacturing processes and the sustainable application of advanced, high-resolution, and fully recycled electronic devices.

A novel low-temperature shielded salt (LSS) approach enables the synthesis of MXenes in air at temperatures as low as 150 °C using MgCl₂·6H₂O/LiCl. This method demonstrates successful etching of challenging MXenes like Cr₂CT _x and Nb₂CT _x through the synergistic effects of Li⁺ ions and salt hydrate phase changes, while eliminating the need for inert atmospheres and hazardous intercalants.

Abstract

The conventional Lewis acid molten salt etching approach for synthesizing MXenes typically necessitates elevated temperatures exceeding 550 °C, in addition to the use of inert gas protection to prevent oxidation. Additionally, delamination of molten salt-etched MXenes typically requires hazardous intercalating agents. Herein, a scalable and non-toxic low-temperature shielded salt (LSS) approach for synthesizing MXene in air is reported, with the use of only a small portion of salts and a low reaction temperature down to 150 °C. Especially, the synergistic effect of the increased diffusion rate by Li⁺ ions and the phase change of magnesium chloride hexahydrate (MgCl₂·6H₂O) enables a redox-controlled A-site etching of the parent MAX phase, which even facilitates the synthesis of hard-to-etch MXenes. As a proof-of-concept demonstration, several theoretically hard-to-synthesize MXenes including Cr₂CT _x and Nb₂CT _x are successfully prepared through the LSS technique, where Cr₂CT _x is not achieved by Lewis acidic molten salt yet. Compared to conventional techniques, this low-temperature shielded salt etching method exhibits unconventional molten behavior while offering several advantages, including a non-oxidizing environment, shorter processing time, and elimination of highly corrosive washing agents and organic intercalants. These advances render the LSS approach a promising route for synthesizing MXenes with applications toward diverse practical applications.

Understanding the complex interplay between local structure and physical properties is a key challenge in high entropy oxide (HEO) research, particularly concerning electronic transport. This work demonstrates the profound influence of local chemical inhomogeneity and underlying epitaxial strain on the electronic transport properties of HEO thin film with perovskite structure, paving pathways to tailor electronic properties in high-entropy regime.

Abstract

Understanding the electronic transport properties of thin films of high-entropy oxide (HEO), having multiple elements at the same crystallographic site, is crucial for their potential electronic applications. However, very little is known about the metallic phase of HEOs even in bulk form. This work delves into the interplay between global and local structural distortion and electronic properties of single crystalline thin films of (La_0.2Pr_0.2Nd_0.2Sm_0.2Eu_0.2)NiO₃, which exhibit metal-insulator transition under tensile strain. Employing electron microscopy and elemental resolved electron energy loss spectroscopy, we provide direct evidence of nanoscale chemical inhomogeneities at the rare-earth site, leading to a broad distribution of Ni–O–Ni bond angles. However, the octahedral rotation pattern remains the same throughout. The metallic phase consists of insulating patches with more distorted Ni–O–Ni bond angles, responsible for higher resistance exponents with increased compositional complexity. Moreover, a rare, fully metallic state of HEO thin film is achieved under compressive strain. We further demonstrate a direct correlation between the suppression of the insulating behavior and increased electronic hopping. Our findings provide a foundation for exploring Mott-Anderson electron localization physics in the high-entropy regime.

npj 2D Materials and Applications, Published online: 13 April 2025; doi:10.1038/s41699-025-00549-1

Efficient energy transfer and photoluminescence enhancement in 2D MoS₂/bulk InSe van der Waals heterostructures

npj 2D Materials and Applications, Published online: 09 April 2025; doi:10.1038/s41699-025-00546-4

Novel spintronic effects in two-dimensional van der Waals heterostructures

In this study, plasma-source-assisted metal-layer sulfidation successfully induced large area/uniform/stable 1T phase MoS₂ via an integration-compatible process. The practicality and superiority of the synthesized 1T-MoS₂ are confirmed by applying it as a floating-gate material for flash memory, fabricating a 5 × 5 array architecture, and optical synapse applications.

Abstract

2D transition-metal dichalcogenides (TMDCs) have attracted attention as promising materials for next-generation devices owing to their versatile electronic and optical properties. The phase variety of TMDCs provides strategic opportunities for performance enhancement. Herein, a novel method is proposed to synthesize wafer-scale 1T phase MoS₂ and, simultaneously, induce a phase transition via a plasma-assisted metal-sulfidation process and spontaneous internal strain. With thicker MoS₂ layers, the strong internal strain during synthesis suppresses the undesirable phase transition from the metastable 1T phase to the 2H phase, ensuring stabilization of the 1T phase. Furthermore, as-synthesized 1T-MoS₂ shows remarkable electrical properties owing to the narrow bandgap (0.4 eV) of its semi-metallic state. As a result, the 1T-phase MoS₂ floating gate (1T-FG) flash memory demonstrates a wider memory window, a higher on/off ratio, and improved stability compared to the 2H-phase MoS₂ floating gate (2H-FG) flash memory. A 5 × 5 array structure is constructed to validate large-scale integration. Notably, under light irradiation, a single 1T-FG memory enables carrier trapping in the floating gate, even in the off state. This study introduces a facile phase control strategy and provides insights into advanced nonvolatile memory and optoelectronic synaptic functionalities.