A library of atomically thin metal chalcogenides

Controlled growth of Large-Area 2D palladium diselenide with tunable electronic properties for optoelectronics and artificial synapses devices

Two-dimensional palladium selenide (PdSe2) is a promising material for next-generation optoelectronic and neuromorphic applications due to its high carrier mobility, tunable bandgap, and excellent air stability. In this work, we report a scalable liquid-phase-precursor-assisted chemical vapor deposition (CVD) strategy for the large-scale growth of high-uniformity, thickness-tunable 2D PdSe2 films. By precisely controlling precursor concentration and spin-coating speed, we achieve fine modulation of electronic properties including bandgap, work function, and band alignment. The as-grown films exhibit excellent device performance across multiple platforms: arrayed field-effect transistors (FETs) demonstrate intrinsic bipolar transport with electron mobilities up to 30 cm2·V-1·s-1 and stable on/off ratios; broadband photodetectors show high responsivity (up to 102.2 A·W-1) and detectivity (∼109 Jones); and flexible artificial synapses deliver exceptional linearity (R2 = 0.995), mechanical robustness, and up to 83.26 % recognition accuracy on the MNIST dataset. This work offers a unified approach that links growth-process engineering with functional device performance, paving the way for large-scale applications of 2D PdSe2 in neuromorphic and flexible optoelectronics.

Coherently confined single-metal-atom chains in 2D semiconductors

Single-metal-atom chains (SMACs) possess a variety of unique properties and functionalities but suffer from ambient vulnerability due to their delicate one-atom-width structures. While some SMACs can be effectively stabilized by nanochannel confining, it remains a pressing challenge to experimentally realize more versatile atomic chains with sufficient stability and extended length. Here, we propose a computational protocol to identify transition metals capable of forming SMACs along mirror twin boundaries in two-dimensional metal dichalcogenides. Taking MoS2 as a prototypical example, our thermodynamics and kinetics calculations indicate that Co, Ni, Rh, Pd, and Pt atoms can be enticed by the progressive formation of mirror twin boundaries to yield robust SMACs; whereas other transition metal elements tend to result in either substitutional doping or nanoclusters. These findings are supported by successful experimental synthesis of Co-, Ni-, Pd- and Pt-based SMACs using a chemical vapor co-deposition method, which exhibit high stability due to their covalent bonding with MoS2 grains. These results lay a solid foundation for investigating exotic transport behaviors within extremely confined channels.

Synergistic Self-Assembly Enabled Highly Ordered Mesoporous WSe2/WO3 Crystalline Heterostructures for Rapid NO2 Sensing at Room Temperature

A rapid and highly sensitive detection of harmful gas molecules is crucial in artificial olfaction (electronic nose), which plays a significant role in areas such as environmental monitoring and healthcare. However, it remains a significant challenge to construct highly sensitive molecular sensors with fast response at room temperature due to the limitations in structures and properties (e.g., porosity, crystallinity, and carrier mobility) of the sensing materials. Herein, this study proposes a facile method to enable highly crystalline mesoporous WSe2/WO3 (m-WSe2/WO3) semiconductor heterostructures through controllable interfacial self-assembly of polyoxometalate (POM) clusters and amphiphilic block copolymers combined with a thermal-assisted conversion process. It allows uniform pore size, open channels, large specific surface area, highly crystalline framework, and abundant transition metal chalcogenide/metal oxide heterojunction interfaces. The m-WSe2/WO3-based chemiresistive semiconductor sensor achieves efficient detection of NO2 at room temperature, including ultrafast response (5 s), high selectivity (SNO2/Sgas > 5), high sensitivity (62.5%@50 ppm), low detection limit (50 ppb), and long-term stability (>30 days). Thanks to the synergistic improvement of sensing dynamics between mesostructure and heterojunction, such a few-second response time has been reduced by half of the reported values in most existing counterparts based on two-dimensional materials. Our work paves the way for the application of high-performance and cost-effective molecular sensors in artificial olfaction, electronic skins, and wearable integrated circuits at room temperature.

Atomic-Scale Origins and Shielding-Corrected Dipole Predictions of Surface Electrostatic Potential Difference in Metal-TMDC Contacts

The atomic-scale origins and quantitative description of the surface electrostatic potential difference (ΔV) in metal-semiconductor contacts remain elusive, limiting rational interface barrier design. Through first-principles calculations on Au/Ag/Pt/Pd-transition-metal dichalcogenide (TMDC) contacts, we establish a robust linear correlation between ΔV and shielding-corrected dipole terms parametrized by atomic number (Z), valence electron count, and atomic radii. Three critical insights are identified. First, the dipole terms from metal-TMDC and TMDC-TMDC interfaces as well as TMDC layers dominate linearity with a contribution of about 90%-92%. Second, the interfaces and TMDC layers in closer proximity to the metal layer show reduced contributions due to suppression by the metallic free-electron region. Third, incorporating high-Z atomic shielding corrections collectively enhances linearity by 8%-10%, with a maximal correction from metal-TMDC interfaces. Using this correlation, interface barriers are predicted, matching those from band structures. This work clarifies the atomic origins of ΔV and establishes a predictive framework for designing metal-TMDC contact barriers.

NaCl-Assisted One-Step CVD for In-Plane 1T/1H Heterophase Homojunctions in Monolayer WS2

Two-dimensional WS2 offers promising advantages for various applications due to its semiconducting 1H phase and metallic 1T phase. However, the instability of the 1T phase and the difficulty of achieving a stable phase coexistence present significant challenges. Here, we adopt the NaCl-assisted one-step chemical vapor deposition method that enables the spatial coexistence and precise control of 1H and 1T phases within monolayer WS2. The phase diagram establishes a clear correlation between precursor ratios and the structural phases of WS2. Density functional theory calculations reveal the stability difference between the 1H and the 1T phases at the electronic level. Calculated work functions are consistent with experimental Kelvin probe force microscopy, confirming the electronic properties of the heterophase interface. This work provides a scalable and efficient approach for phase engineering in WS2, with great potential for advancing optoelectronic devices and catalytic systems.

Chemical Vapor Deposition of "Stand-On" 2D Single-Crystal Flakes

Two-dimensional (2D) superconductors are highly valued for their reduced dimensionality and unique quantum properties. However, their susceptibility to oxidation and degradation, particularly during wet transfer processes, often leads to undesirable deterioration of their electrical properties. In this work, we present an innovative and facile synthesis strategy for producing ultrathin "stand-on" superconducting FeTe1-xSex nanosheets, enabling a highly efficient and damage-free transfer process. Low-temperature transport measurements confirm the superior superconducting performance of the transferred materials. Furthermore, by employing a convenient dry poly(dimethylsiloxane) (PDMS) stamping technique, we successfully fabricated high-quality 2D superlattices with precise angle control. Moreover, this synthesis strategy has been extended to various substrate and material systems, providing a versatile platform for studying high-performance integrated systems.

Intelligent self-correcting growth of uniform Bernal-stacked bi-/trilayer graphene

State-of-the-art synthesis strategies of two-dimensional (2D) materials have been designed following the nucleation-dominant pattern for structure control. However, this classical methodology fails to achieve the precise layer- and stacking-resolved growth of wafer-scale few-layer 2D materials due to its intrinsically low energy resolution. Here, we present an intelligent self-correcting method for the high-resolution growth of uniform few-layer graphene. We demonstrate the layer-resolved growth of wafer-scale bilayer and trilayer graphene (BLG and TLG) with selective Bernal stacking through spontaneous correction of the single-layer graphene film with disordered multilayer graphene islands. Theoretical calculations reveal that the self-correcting growth is driven by the stepwise energy minimization of the closed system and kinetically activated by forming a low-barrier pathway for the carbon detachment-diffusion-attachment. Such uniform Bernal-stacked BLG and TLG films show high quality with distinct quantum Hall effect being observed. Our work opens an avenue for developing an intelligent methodology to realize the precise synthesis of diverse 2D materials.

Stoichiometry-engineered phase transition in a two-dimensional binary compound

Due to complex thermodynamic and kinetic mechanism, phase engineering in nanomaterials is often limited by restricted phases and small-scale synthesis, hindering material diversity and scalability. Here, we demonstrate the exploration to unlock the stoichiometry as a degree of freedom for phase engineering in the Pd-Te binary compound. By reducing diffusion rates, we effectively engineer the stoichiometry of the reactants. We visualize the kinetic process, showing the stoichiometry transition from Pd10Te3 to PdTe2 through a sequential multi-step nucleation process. In total, five distinct phases are identified, demonstrating the potential to enhance phase diversity by fine-tuning stoichiometry. By controlling spatially uniform nucleation and halting the phase transition at precise points, we achieve stoichiometry-controllable wafer-scale growth. Notably, four of these phases exhibit superconducting properties. Our findings offer insights into the mechanism of phase transition through stoichiometry engineering, enabling the expansion of the phase library in nanomaterials and advancing scalable applications.

Activating Basal Plane Inert Sites of Iron Telluride for Motivational Electromagnetic Microwave Absorption

The basal plane inert sites and inadequate intrinsic dielectric relaxation are the major bottlenecks limiting the electromagnetic microwave (EMW) absorption performance of transition metal tellurides (TMTs). Here, an effective dual defect model based on electron polarization relaxation is established on iron telluride (FeTe) flakes via one-step O2 plasma treatment. Therefore, the basal plane inert sites of FeTe are activated by Te vacancies and O incorporation, which form abundant polarization centers, resulting in charge redistribution and increased dipole site density, thereby effectively optimizing dielectric relaxation loss. Consequently, the optimal EMW attenuation performance achieves a minimum reflection loss exceeding -69.6 dB at a thickness of 2.2 mm, with an absorption bandwidth of up to 4.9 GHz at a thickness of 1.3 mm. Besides, FeTe with dual defect exhibits a prominent radar cross-section reduction of 42 dBsm, indicating excellent radar wave attenuation capability. This study illustrates an innovative model system for elucidating dielectric relaxation loss mechanisms and provides a feasible approach to developing high-loss TMTs-based absorbers.

Template-Catalyzed Mass Production of Size-Tunable h-BN Nanosheet Powders

Bulk availability of 2D material powders presents broad opportunities for various industrial applications. Particle size and morphology control are critical factors that govern their properties, and in particular, large-scale size-controlled production of 2D materials nanosheets remains extremely challenging. Herein, a novel 3D template-catalyzed growth (3D-TCG) method is demonstrated that allows the mass production of size-tunable 2D hexagonal boron nitride (h-BN) nanosheet powders, a key material in the 2D materials family. Rather than limiting the nanosheet growth on 2D substrate surfaces, this method provides large numbers of active sites distributed in 3D space, leading to the feasibility of scale-up production with excellent product homogeneity and high efficiency. Ultrathin h-BN nanosheets are synthesized with high throughput (kilogram quantities) and lateral sizes that can be tuned from 100 nm to 10 µm with thicknesses of few layers. Their practical application is demonstrated in lithium metal batteries, where the obtained nanosheet powders are processed and roll-to-roll coated on commercial separators (>10 m2). The prototype pouch cell delivers high energy density (501.8 Wh kg-1) and improved cycling stability. The template-based large-scale production strategy can be used to generically produce various types of bulk pristine 2D nanopowders with potential for many large-scale applications.

Exploring the frontier: nonlinear optics in low dimensional materials

Nonlinear optics, the study of intense light-matter interactions, traditionally uses bulk materials like LiNbO3 for device fabrication. However, these materials face challenges such as limited nonlinear susceptibility, large dimensions, and phase matching issues, limiting compact and integrated devices. Recent research has illuminated that a variety of low-dimensional materials exhibit markedly stronger nonlinear optical responses than their bulk counterparts. This has made nonlinear optics in low-dimensional materials a dynamic area of study, allowing for rapid light-matter interactions and advancing nonlinear nanophotonic and optoelectronic applications. These applications span diverse areas, from wavelength conversion and the generation of ultrashort laser pulses to advancements in quantum photonics and integrated photonic technologies. This review covers two-dimensional materials such as graphene and transition metal dichalcogenides to one-dimensional forms like carbon nanotubes and nanowires, and further to zero-dimensional structures including nanoparticles and quantum dots. By providing a comprehensive overview of the current state of non-linear optics in the context of low-dimensional materials, this review not only encapsulates the existing knowledge base but also charts a course for future explorations in this rapidly progressing domain.

Vapour-liquid-solid-solid growth of two-dimensional non-layered β-Bi2O3 crystals with high hole mobility

Currently, p-type two-dimensional (2D) materials lag behind n-type ones in both quantity and performance, hindering their use in advanced p-channel transistors and complementary logic circuits. Non-layered materials, which make up 95% of crystal structures, hold the potential for superior p-type 2D materials but remain challenging to synthesize. Here we show a vapour-liquid-solid-solid growth of atomically thin (<1 nm), high-quality, non-layered 2D β-Bi2O3 crystals on a SiO2/Si substrate. These crystals form via a transformation from layered BiOCl intermediates. We further realize 2D β-Bi2O3 transistors with room-temperature hole mobility and an on/off current ratio of 136.6 cm2 V-1 s-1 and 1.2 × 108, respectively. The p-type nature is due to the strong suborbital hybridization of Bi 6s26p3 with O 2p4 at the crystal's M-point valence band maximum. Our work can be used as a reference that adds more 2D non-layered materials to the 2D toolkit and shows 2D β-Bi2O3 to be promising candidate for future electronics.

Low-Temperature Chemical Vapor Deposition Growth of Monolayer MoS2 Using a Dual-Assisted Approach

The growth of monolayer MoS2 via chemical vapor deposition typically necessitates high temperatures over 700 °C, which presents challenges for application in the integrated circuit industry where back-end-of-line processes require temperatures possibly below 500 °C. In this study, we demonstrate a method that combines potassium chloride mixed with a MoO3 precursor and perylene-3,4,9,10-tetracarboxylic acid tetra potassium salt as a seeding promoter for substrate pretreatment, which can effectively lower the growth temperature of MoS2 on sapphire and SiO2/Si substrates to 460 °C. The reduced growth temperature is achieved without compromising the material's quality, making this method potentially transformative for the semiconductor industry. Our first-principles calculations and theoretical modeling accurately describe the observed morphological evolution of monolayer MoS2 crystals during growth. The crystal growth is governed by the probability of atom attachment to different edge types, which is determined by the varying formation energies of the nuclei at these edges. The grown monolayer MoS2 was characterized through atomic force microscopy, Raman and photoluminescence spectroscopy, and electrical transport measurements, confirming its high quality and suitability for electronic applications.

Lightly Se-Doped Monolayer MoS2 Grown by Chemical Vapor Deposition Using SeS2 Precursor

Transition metal dichalcogenide (TMDC)-based two-dimensional semiconductors are promising materials for next-generation electronic devices. However, challenges such as optimizing the carrier mobility, on/off current ratio, threshold voltage, and minimization of hysteresis remain. Herein, we report lightly Se-doped monolayer MoS2 via chemical vapor deposition (CVD) using selenium disulfide (SeS2) as a chalcogen source. Interestingly, doping with 5.5% Se (MoS1.89Se0.11) enhanced the electron mobility compared to conventional MoS2, contrary to the typical trend of increased effective mass with substitutional doping. Additionally, bandgap tunability was achieved by controlling the Se content via temperature control of SeS2. This approach offers a pathway for tailoring the properties of TMDCs for advanced applications.

Spin-valley coupling enhanced high-TC ferromagnetism in a non-van der Waals monolayer Cr2Se3 on graphene

Spin-valley magnetic ordering is restricted to layered van der Waals type transition-metal dichalcogenides with ordering temperatures below 55 K. Recent theoretical studies on non-van der Waals structures have predicted spin-valley polarization induced semiconducting ferromagnetic ground states, but experimental validation is missing. We report high-Curie temperature (TC ~ 225 K) metallic ferromagnetism with spontaneous spin-valley polarization in monolayer Cr2Se3 on graphene. Angle-resolved photoemission spectroscopy (ARPES) reveals systematic temperature-dependent energy shifts and splitting of localized Cr 3 d↑-t2g bands, accompanied by occupancy of the itinerant Cr 3d-eg valleys. The t2g-eg spin-valley coupling at the K/K' points of hexagonal Brillouin zone leads to ferromagnetic ordering. Circular dichroism in ARPES shows clear evidence of spin-valley polarized states. Comparison with bilayer and trilayer Cr2Se3 reveals the crucial role of valley carrier density in enhancing TC and provides a guiding principle to realize 2D ferromagnetism at higher temperatures in non-van der Waals materials.

Realization of fractional-layer transition metal dichalcogenides

Layered van der Waals transition metal dichalcogenides (TMDCs), generally composed of three atomic X-M-X planes in each layer (M = transition metal, X = chalcogen), provide versatile platforms for exploring diverse quantum phenomena. In each MX2 layer, the M-X bonds are predominantly covalent in nature and, as a result, the cleavage of TMDC crystals normally occurs between the layers. Here we report the controllable realization of fractional-layer WTe2 via an in-situ scanning tunneling microscopy (STM) tip manipulation technique. By applying STM tip pulses, hundreds of the topmost Te atoms are removed to form a nanoscale monolayer Te pit in the 1 T'-WTe2, thus realizing a 2/3-layer WTe2 film. Such a configuration undergoes a spontaneous atomic reconstruction, yielding a unidirectional charge density redistribution with the wavevector and geometry quite distinct from that of pristine 1 T'-WTe2. Our results expand the conventional understanding of the TMDCs and are expected to stimulate further research on the structure and properties of fractional-layer TMDCs.

Design and application of Solid Solution Materials in Heterogeneous Photocatalysis

The research progress of solid solution materials in the field of photocatalysis was introduced. The synthesis methods of solid solution photocatalytic materials are comprehensively expounded, and the modification strategies of solid solution photocatalysts are analyzed and discussed. This paper systematically summarizes the characteristics and development of the main catalytic systems of solid solution materials, and explored the application of first-principles calculations in the photocatalysis of solid solution materials in combination with practical research. Subsequently, the main application progress of photocatalysis of solid solution materials in the fields of environmental remediation and energy conversion was introduced. Finally, the current challenges, development directions and prospects are prospected.

Geminal Mirror Twin Boundaries in H-Phase NbTe2

Grain boundaries (GBs) in transition metal dichalcogenides (TMDs) significantly influence their physicochemical properties. Mirror twin boundaries (MTBs), a special GB type, reveal one-dimensional quantum features such as topological states and charge density waves. However, the large-scale fabrication of well-aligned MTBs remains challenging. Here, we present a simple solution method to introduce high-density paired MTBs in monolayer 1H-NbTe2. Using atomic-resolution scanning transmission electron microscopy (STEM), we identify two "MTB" types─metastable Nb-oriented 4|4E and Te-oriented 4|4P, forming aligned MTBs with quantized spacings. The formation mechanism of paired MTBs is hypothesized to involve specific intralayer atomic rearrangements within a distorted 1T-phase, followed by H-phase core coalescence, facilitated by strain-induced energy barrier reduction and electron doping stabilization. Density functional theory (DFT) calculations indicate that paired MTBs stabilize metastable H-phase, enabling the coexistence of superconductivity and nontrivial band topology. The approach of our group to fabricating high-density paired MTBs advances boundary engineering in TMDs for designing functional quantum devices.

Observation of Complex Conjugate Roots and Resonant Behavior in Quasi-Solid Supercapacitors as an Indication of Its Electrochemical instability

Quasi-solid supercapacitors are promising electrochemical devices for energy storage applications due to their high-power density, long life cycle, and environmental benefits. However, their electrochemical performance can change over time as a result of interactions between the electrodes and electrolyte, as well as the fabrication process. In this study, the electrochemical behavior of quasi-solid supercapacitors with activated carbon electrodes immersed in 4 M H2SO4 poly(vinyl alcohol) electrolyte for periods of 10 min and 24 h were investigated. Initial measurements show a lack of energy storing properties in newly fabricated devices, which improve with the aging time, as observed in cyclic voltammetry and charge-discharge cycles. Anticlockwise arcs and resonant peaks were observed in Nyquist and Bode plots, respectively, and were modeled by introducing complex conjugate roots and a damping factor ξ in the transfer function of the electronic equivalent circuit. This unfavorable behavior disappeared after 14 days in devices with shorter immersion times. On the other hand, the effects persisted in devices with longer immersion times even after 28 days. The stability of quasi-solid supercapacitors is thus demonstrated to be linked to complex conjugate roots and resonant behavior in impedance spectroscopy.

2D Materials-Based Field-Effect Transistor Biosensors for Healthcare

The need for accurate point-of-care (POC) tools, driven by increasing demands for precise medical diagnostics and monitoring, has accelerated the evolution of biosensor technology. Integrable 2D materials-based field-effect transistor (2D FET) biosensors offer label-free, rapid, and ultrasensitive detection, aligning perfectly with current biosensor trends. Given these advancements, this review focuses on the progress, challenges, and future prospects in the field of 2D FET biosensors. The distinctive physical properties of 2D materials and recent achievements in scalable synthesis are highlighted that significantly improve the manufacturing process and performance of FET biosensors. Additionally, the advancements of 2D FET biosensors are investigated in fatal disease diagnosis and screening, chronic disease management, and environmental hazards monitoring, as well as their integration in flexible electronics. Their promising capabilities shown in laboratory trials accelerate the development of prototype products, while the challenges are acknowledged, related to sensitivity, stability, and scalability that continue to impede the widespread adoption and commercialization of 2D FET biosensors. Finally, current strategies are discussed to overcome these challenges and envision future implications of 2D FET biosensors, such as their potential as smart and sustainable POC biosensors, thereby advancing human healthcare.

Two-Dimensional Cr3Te4/WS2/Fe3GeTe2/WTe2 Magnetic Memory with Field-Free Switching and Low Power Consumption

Spin-orbit torque (SOT) magnetic memory technology has garnered significant attention due to its ability to enable field-free switching of magnets with strong perpendicular magnetic anisotropy (PMA). However, concerns regarding power consumption of SOT-memory are persisting. Here, this work proposes a method to construct magnetic tunnel junction (MTJ) by transferring chemically vapor-deposited two-dimensional (2D) Cr3Te4/WS2 van der Waals (vdW) heterostructures onto 2D Fe3GeTe2 (FGT) magnet. The robustness and tunability of 2D magnets allow MTJs to exhibit non-volatility, multiple output states, and impressive cycling durability. MTJs with thin WS2 barriers (fewer than six layers) exhibit a linear tunneling effect, achieving a low resistance-area product (RA) of 15.5 kΩ·µm2 using bilayer WS2, which facilitats low-power operation. Furthermore, the different 2D magnets display a significant anti-parallel window of up to 8 kOe. SOT-memory based on the typical MTJ demonstrates a low write consumption of 0.3 mJ and read consumption of 9.7 nJ, marking a significant advancement in 2D vdW SOT-memory. This research has pointed out a new direction for constructing low power consumption SOT-memory with PMA field-free switching.

Van der Waals Epitaxy of High-Quality Transition Metal Dichalcogenides on Single-Crystal Hexagonal Boron Nitride

Van der Waals (vdW) heterostructures comprising of transition metal dichalcogenides (TMDs) and hexagonal boron nitride (h-BN) are promising building blocks for novel 2D devices. The vdW epitaxy provides a straightforward integration method for fabricating high-quality TMDs/h-BN vertical heterostructures. In this work, the vdW epitaxy of high-quality single-crystal HfSe2 on epitaxial h-BN/sapphire substrates by chemical vapor deposition is demonstrated. The epitaxial HfSe2 layers exhibit a uniform and atomically sharp interface with the underlying h-BN template, and the epitaxial relationship between HfSe2 and h-BN/sapphire is determined to HfSe2 (0001)[12 ¯ ${\mathrm{\bar{2}}}$ 10]//h-BN (0001)[11 ¯ ${\mathrm{\bar{1}}}$ 00]//sapphire (0001)[11 ¯ ${\mathrm{\bar{1}}}$ 00]. Impressively, the full width at half maximum of the rocking curve for the epitaxial HfSe2 layer on single-crystal h-BN is as narrow as 9.6 arcmin, indicating an extremely high degree of out-plane orientation and high crystallinity. Benefitting from the high crystalline quality of HfSe2 epilayers and the weak interfacial scattering of HfSe2/h-BN, the photodetector fabricated from the vdW epitaxial HfSe2 on single-crystal h-BN shows the best performance with an on/off ratio of 1 × 104 and a responsivity up to 43 mA W-1. Furthermore, the vdW epitaxy of other TMDs such as HfS2, ZrS2, and ZrSe2 is also experimentally demonstrated on single-crystal h-BN, suggesting the broad applicability of the h-BN template for the vdW epitaxy.

Ultrafast and Universal Synthetic Route for Nanostructured Transition Metal Oxides Directly Grown on Substrates

Nanostructured transition metal oxides (NTMOs) have consistently piqued scientific interest for several decades due to their remarkable versatility across various fields. More recently, they have gained significant attention as materials employed for energy storage/harvesting devices as well as electronic devices. However, mass production of high-quality NTMOs in a well-controlled manner still remains challenging. Here, a universal, ultrafast, and solvent-free method is presented for producing highly crystalline NTMOs directly onto target substrates. The findings reveal that the growth mechanism involves the solidification of condensed liquid-phase TMO microdroplets onto the substrate under an oxygen-rich ambient condition. This enables a continuous process under ambient air conditions, allowing for processing within just a few tens of seconds per sample. Finally, it is confirmed that the method can be extended to the synthesis of various NTMOs and their related compounds.

Pd-based chalcogenides for energy conversion electrocatalysis

The research and development of high-performance electrocatalysts are crucial for advancing highly efficient energy conversion technologies. Pd-based chalcogenides, an innovative class of materials, have been extensively studied as electrocatalysts due to their diverse advantages for energy conversion reactions. This review summarizes recent progress in the synthesis, modification, and application of various Pd-based chalcogenides. It begins by presenting four effective synthesis methods with typical examples, followed by strategies for increasing the active sites, adjusting the electronic structure, and optimizing the binding energy with intermediates. The review also explores the applications of representative Pd-S, Pd-Se, and Pd-Te catalysts for electrocatalytic reactions. It is anticipated that this review will inspire further research into the development of advanced Pd-based chalcogenide electrocatalysts.

Metallic 2D Janus SNbSe layers driven by a structural phase change

The discovery of two-dimensional (2D) Janus materials has ignited significant research interest, particularly for their distinct properties diverging from their classical 2D transition metal dichalcogenide (TMD) counterparts. While semiconducting 2D Janus TMDs have been demonstrated, examples of metallic Janus layers are still rather limited. Here, we address this gap by experimentally synthesizing and characterizing metallic Janus layers, focusing on SNbSe and SeNbS, derived from monolayer NbS2 and NbSe2 using a plasma-assisted technique. Our results show that Nb-based 2D Janus layers form after 1H-to-1T phase transition, marking a phase transition-induced formation of Janus layers. Our comprehensive spectroscopy and microscopy studies, including Z-contrast high angle annular dark field scanning transmission electron microscopy, reveal the phononic and structural properties during Janus SeNbS formation and establish their energetic stability. Density functional theory (DFT) simulations provide insights into the phononic and electronic properties of these materials, shedding light on their potential for diverse applications. Overall, our results demonstrate the realization of niobium-based Janus metals and expand the library of metallic Janus layers.

Controllable p-Type Doping Strategy for High-Performance 2D Material Complementary Inverters

Controllable doping is required to modulate the electrical properties of the semiconductor devices. Such controllability is a particular issue in p-type doping for two-dimensional (2D) semiconductors. Here, we present a controllable doping strategy for modulating carrier density and threshold voltage of WSe2 transistors via surface oxidation at 200 °C in air. The hole density in the WSe2 channel can be precisely modulated from 1 × 1011 cm-2 to 3.5 × 1012 cm-2 by increasing oxidation duration, while its carrier mobility is virtually unaffected, maintaining a high value of 94.3 cm2·V-1·s-1. This controllable doping method can help to achieve balanced carrier transport in the n-type and p-type transistors in CMOS devices. The doped p-type WSe2 transistor in a CMOS inverter resulted in a high gain of 52 and a lower static power of 0.256 nW at a bias voltage of 1 V. Therefore, our findings might pave the way for reliable fabrication of high-performance 2D electronic circuits.

Low-Temperature Growth of Centimeter-Sized 2D PdSe2 by Self-Limiting Liquid-Phase Edge Epitaxy

Two-dimensional (2D) PdSe2 atomic crystals hold great potential for optoelectronic applications due to their bipolar electrical characteristics, tunable bandgap, high electron mobility, and exceptional air stability. Nevertheless, the scalable synthesis of large-area, high-quality 2D PdSe2 crystals using chemical vapor deposition (CVD) remains a significant challenge. Here, we present a self-limiting liquid-phase edge-epitaxy (SLE) low-temperature growth method to achieve high-quality, centimeter-sized PdSe2 films with single-crystal domain areas exceeding 30 μm. The SLE growth mechanism, clarified by theoretical calculations and time-of-flight secondary ion mass spectrometry (ToF-SIMS), reveals that hydrogen ions on the precursor surface inhibit vertical growth while promoting lateral growth. The as-grown PdSe2 few-layer exhibits a surface roughness of 1.20 nm and an average conductivity of 1.67 × 10-6 S/m, demonstrating their smoothness and uniformity. Temperature-dependent electrical measurements and transfer characteristic curves confirm the orthorhombic PdSe2's bipolar semiconductor behavior. The photodetector based on few-layer PdSe2 films exhibit excellent optoelectronic performance in the 405-1650 nm wavelength range, achieving a responsivity of 6262.37 A W-1, a detectivity of ∼1012 Jones under 1064 nm illumination, and a fast response time of 37.1 μs, making them highly suitable for broadband photodetection applications. This work provides valuable insights into the scalable synthesis of PdSe2 few-layers and establishes a foundation for the development of PdSe2-based integrated functional devices.

Unveiling magnetic transition-driven lattice thermal conductivity switching in monolayer VS2

Effective thermal management is essential for maintaining the operational stability and data security of magnetic devices across diverse fields, including thermoelectric, sensing, data storage, and spintronics. In this study, density functional theory calculations were conducted to explore the spin-induced modifications in the phonon-mediated thermal properties of H-phase monolayer VS2, a two-dimensional (2D) ferromagnet. Our investigation revealed that the 2D H-phase of VS2 exhibits a substantial thermal switching ratio, exceeding four at the Curie temperature, due to the coupling between magnetic order and lattice vibrations. This sensitivity arises from spin-dependent lattice anharmonicity, which results in the stiffening of the V-S bonds, thereby modifying the frequencies of different vibrational modes. Phonon-phonon interaction calculations indicated that phonon-magnon scattering was more predominant in the paramagnetic (PM) phase than in the ferromagnetic (FM) phase, which resulted in a reduced phonon lifetime, mean free path and group velocity. As a result, the lattice thermal conductivity was calculated to drop from 53.98 W m-1 K-1 in the ferromagnetic phase to 12.10 W m-1 K-1 in the paramagnetic phase. By elucidating heat transport in two-dimensional ferromagnets, our study offers valuable insights for manipulating and converting thermal energy.

High-Throughput Computation of ab initio Raman Spectra for Two-Dimensional Materials

Raman spectra play an important role in characterizing two-dimensional materials, as they provide a direct link between the atomic structure and the spectral features. In this work, we present an automatic computational workflow for Raman spectra using all-electron density functional perturbation theory. Utilizing this workflow, we have successfully completed the Raman spectra calculation for 3504 different two-dimensional materials, with the resultant data saved in a data repository.

Advances in wearable electronics for monitoring human organs: Bridging external and internal health assessments

Devices used for diagnosing disease are often large, expensive, and require operation by trained professionals, which can result in delayed diagnosis and missed opportunities for timely treatment. However, wearable devices are being recognized as a new approach to overcoming these difficulties, as they are small, affordable, and easy to use. Recent advancements in wearable technology have made monitoring information possible from the surface of organs like the skin and eyes, enabling accurate diagnosis of the user's internal status. In this review, we categorize the body's organs into external (e.g., eyes, oral cavity, neck, and skin) and internal (e.g., heart, brain, lung, stomach, and bladder) organ systems and introduce recent developments in the materials and designs of wearable electronics, including electrochemical and electrophysiological sensors applied to each organ system. Further, we explore recent innovations in wearable electronics for monitoring of deep internal organs, such as the heart, brain, and nervous system, using ultrasound, electrical impedance tomography, and temporal interference stimulation. The review also addresses the current challenges in wearable technology and explores future directions to enhance the effectiveness and applicability of these devices in medical diagnostics. This paper establishes a framework for correlating the design and functionality of wearable electronics with the physiological characteristics and requirements of various organ systems.

WS2/MHS PdTe2/Si Mixed-Dimensional Heterojunction as Ultra-Broadband Photodetector for Health and Safety Monitoring

Ultra-broadband photodetectors (UB-PDs) are essential in medical applications, public safety monitoring, and various other fields. However, developing UB-PDs covering multiple bands from ultraviolet to medium infrared remains a challenge due to material limitations. Here, a mixed-dimensional heterojunction composed of 2D WS2/monodisperse hexagonal stacking (MHS) 3D PdTe2 particles on 3D Si is proposed, capable of detecting light from 365 to 9600 nm. The exceptional performance of this photodetector is attributed to MHS PdTe₂ particles, which increase the specific surface area and enhance UV-to-NIR absorption of the 2D WS₂ nanofilm. At 980 nm (0 V), the device achieves a responsivity of 7.8 × 102 mA W-1, a detectivity of 2.5 × 1013 Jones, and a sensitivity of 2.6 × 108 cm2 W-1. The MHS PdTe₂ layer amplifies the built-in electric field and enhances heterojunction self-powered capability. This photodetector exhibits a high switching ratio (104), a rapid response time (24.14 µs), and a significant photocurrent gain at zero bias. Its application in blood oxygen saturation analysis is demonstrated based on dual-wavelength photoplethysmography (PPG) at 650 and 905 nm, and infrared perspective imaging at 808 nm. Additionally, the device can differentiate materials based on their transmittance at 9600 nm. This research opens new avenues for the multifunctional use of UB-PDs.

Interfacial Atomic Mechanisms of Single-Crystalline MoS2 Epitaxy on Sapphire

The epitaxial growth of molybdenum disulfide (MoS₂) on sapphire substrates enables the formation of single-crystalline monolayer MoS₂ with exceptional material properties on a wafer scale. Despite this achievement, the underlying growth mechanisms remain a subject of debate. The epitaxial interface is critical for understanding these mechanisms, yet its exact atomic configuration has previously been unclear. In this study, a monolayer single-crystalline MoS₂ grown on a sapphire substrate is analyzed, decisively visualizing the atomic structure of the epitaxial interface and elucidating its role in epitaxial growth from an atomic perspective. The findings reveal that the interface consists of a periodic molecular MoO3 interlayer, van der Waals epitaxially grown on a single Al-terminated sapphire surface. Additionally, it is discovered that MoO3 coverage enhances surface interactions and introduces a unique atomic arrangement with 1-fold symmetry at the sapphire surface, thereby facilitating the unidirectional alignment of MoS₂. This discovery provides valuable insights into the growth mechanisms leading to single-crystalline MoS₂ formation, and suggests pathways for quantitatively monitoring and controlling growth dynamics, for the improvement of material quality and process repeatability, applicable for single-crystalline MoS₂ or potentially other transition metal dichalcogenides epitaxially grown on sapphire.

Phosphorus doped few layer WS2 flakes grown by chemical vapor deposition for hydrogen evolution reactions

Water splitting is a promising pathway for hydrogen production, providing an environmentally friendly fuel source. More recently, great attention has been given to transition metal dichalcogenides (TMDCs) because of their interesting chemical and physical properties. In particular, tungsten disulfide (WS2) has garnered significant attention as a catalyst for this application due to its unique layered 2D structure. In this study, few-layered WS2 and phosphorus-doped WS2 (WS2/P) nanoflakes are synthesized on SiO2/Si substrates as electrocatalysts for hydrogen evolution reactions (HER) in acidic conditions. Analyses of the synthesized WS2 and WS2/P films reveal that the few-layered WS2 is of high quality, exhibiting continuity and uniformity. The presence of a strong peak in the photoluminescence spectrum confirms the mono/few layer nature of the synthesized samples. In additionally, scanning force microscopy in quantitative imaging mode reveals that the thinnest layers observed on the substrate have a height of 1.35 nm, indicating the presence of double-layer WS2. The WS2/P electrocatalyst demonstrates superior HER performance compared to pristine WS2, showing a low overpotential of 245 mV at 10 mA.cm-2 and a small Tafel slope of 123 mV.dec-1. Furthermore, WS2/P exhibits a greater electrochemical surface area and excellent catalytic stability under acidic conditions. Consequently, few layer phosphorus-doped WS2 proves to be a highly suitable electrocatalyst for hydrogen production compared to the WS2.

Recent advances in CMOS-compatible synthesis and integration of 2D materials

The upcoming generation of functional electronics in the era of artificial intelligence, and IoT requires extensive data storage and processing, necessitating further device miniaturization. Conventional Si CMOS technology is struggling to enhance integration density beyond a certain limit to uphold Moore's law, primarily due to performance degradation at smaller dimensions caused by various physical effects, including surface scattering, quantum tunneling, and other short-channel effects. The two-dimensional materials have emerged as highly promising alternatives, which exhibit excellent electrical and mechanical properties at atomically thin thicknesses and show exceptional potential for future CMOS technology. This review article presents the chronological progress made in the development of two-dimensional materials-based CMOS devices with comprehensively discussing the advancements made in material production, device development, associated challenges, and the strategies to address these issues. The future prospects for the use of two-dimensional materials in functional CMOS circuitry are outlooked, highlighting key opportunities and challenges toward industrial adaptation.

Solvent-free fabrication of ultrathin two-dimensional metal oxides/sulfides in a fixed interlayer by geometric confinement

Two-dimensional (2D) nanomaterials display unique characteristics owing to their ultrahigh surface-to-volume ratio and quantum confinement effects. Nonetheless, seeking a versatile and facile method to rationally shape ultrathin 2D frameworks is still an appealing challenge. Herein, a series of ultrathin 2D metal oxide crystals (2D MOs), including 3d transition metals (Ti, Cr, Mn, Fe, Co, Ni, Cu, Zr, W), lanthanide (Ce) and nontransition metal (In, Sn, Bi) oxides, were created through a confined interlayer growth strategy in combination with melt infiltration, in which no complicated chemistry or sophisticated equipment was needed. The 2D oxides presented lamellar constructions with high crystallinity, and the thickness was strictly limited to ~ 1 nm. The crystallization process, including the Frank-van der Merwe mode and the Volmer-Weber mode, was described. The defects and distortions of 2D TiO2 reduced the optical band gap and improved the sunlight utilization efficiency, thus accelerating the photocatalytic activity. This method could be extended to the preparation of 2D polymetallic oxides, metal sulfides etc., which enables the development of versatile systems for ultrathin 2D frameworks, especially for nonlayered structures originally.

Operando Scanning Electron Microscopy Study of Support Interactions and Mechanisms of Salt-Assisted WS2 Growth

Salt enhanced chemical vapor deposition of WS2 and related 2D materials is widespread, and while many mechanisms including vapor-liquid-solid (VLS) mediated growth have been suggested, gaining a more detailed understanding remains challenging. We employ operando scanning electron microscopy to resolve the entire process of salt-assisted CVD of WS2, focusing on a model system of individual, small (<100 μm), sapphire supported sodium tungstate (Na2WO4) salt particles. We reveal support interactions that lead a salt particle to develop a lateral halo interface, driven by surface eutectic melting above 630 °C. This halo dictates the salt wetting as well as Na and W transport, and thus upon gaseous sulfur precursor exposure dominates the spatiotemporal WS2 nucleation and mono- and multilayer domain expansion kinetics, all of which we can directly track by secondary electron (SE) contrast with a conventional In-Lens SE detector. Unlike for a conventional VLS mechanism, large (>20 μm) monolayer WS2 formation does not involve the salt droplet directly attached to the growth facets, rather the salt droplet drives WS2 layer growth in the contiguous halo interface region with a continuous supply of W. We compare this to SiO2 and NaOH treated sapphire where corrosive surface roughening dictates the salt wetting, and critically discuss our findings in the context of the connected wider literature.

Two-dimensional Czochralski growth of single-crystal MoS2

Batch production of single-crystal two-dimensional (2D) transition metal dichalcogenides is one prerequisite for the fabrication of next-generation integrated circuits. Contemporary strategies for the wafer-scale high-quality crystallinity of 2D materials centre on merging unidirectionally aligned, differently sized domains. However, an imperfectly merged area with a translational lattice brings about a high defect density and low device uniformity, which restricts the application of the 2D materials. Here we establish a liquid-to-solid crystallization in 2D space that can rapidly grow a centimetre-scale single-crystal MoS2 domain with no grain boundaries. The large MoS2 single crystal obtained shows superb uniformity and high quality with an ultra-low defect density. A statistical analysis of field effect transistors fabricated from the MoS2 reveals a high device yield and minimal variation in mobility, positioning this FET as an advanced standard monolayer MoS2 device. This 2D Czochralski method has implications for fabricating high-quality and scalable 2D semiconductor materials and devices.

Scalable Synthesis of 2D ErOCl with Sub-meV Narrow Emissions at Telecom Band

Van der Waals (vdWs) materials are promising candidates for hetero-integration with silicon photonics toward miniaturization and integration. VdWs materials like molybdenum telluride and black phosphorus, despite being prominent, exhibit air sensitivity, and their room temperature emissions can be significantly broadened by tens of meV. Here, a self-encapsulation strategy is developed to scalably synthesize robust 2D vdWs ErOCl with sub-meV narrow emissions at the telecom C-band. Diverse 2D rare earth materials are also grown via chemical vapor deposition (TmOCl, YbOCl, HoOCl, DyOCl, SmOCl, NdOCl, TbOCl, GdOCl, EuOCl, and PrOCl), demonstrating the strategy's generalizability. The as-grown ErOCl exhibits high crystalline quality and excellent ambient and thermal stability (300 °C). Photoluminescence analysis reveals a series of narrow emissions across the visible to near-infrared spectrum. The ErOCl's emission at the telecom band is narrowest among 2D luminescent materials, and suitable for integrating with photonic chips. Temperature-dependent photoluminescence spectra facilitate the understanding of emission mechanisms, analyzed using a crystal field perturbation model. Moreover, these emissions can be tuned by external magnetic fields. This research not only pioneers a novel strategy for synthesizing 2D rare earth materials but also paves the way for innovative building blocks in the realm of on-chip optical communications.

Highly Oriented WS2 Monolayers for High-Performance Electronics

2D transition-metal dichalcogenide (TMDC) semiconductors represent the most promising channel materials for post-silicon microelectronics due to their unique structure and electronic properties. However, it remains challenging to synthesize wide-bandgap TMDCs monolayers featuring large areas and high performance simultaneously. Herein, highly oriented WS2 monolayers are reproducibly synthesized through a templated growth strategy on vicinal C/A-plane sapphire wafers. Various spectroscopic characterizations confirm the high crystallographic orientation and uniformity across the entire wafers. Electronic measurements for samples transferred onto SiO2/Si substrates reveal high average field-effect mobilities of 62 and 180 cm2V-1s-1 at room temperature and 8 K, respectively. On hexagonal boron nitride substrates, these mobilities increase to 94 and 473 cm2V-1s-1, respectively. A record high saturation current density of 675 µA µm-1 is observed, outperforming the index required for high-density integration circuits in IRDS 2025. This work paves the way for the application of wide-bandgap TMDC monolayers in post-silicon electronics.

Kinetically Tailored Chemical Vapor Deposition Approach for Synthesizing High-Quality Large-Area Non-Layered 2D Materials

Non-layered 2D materials offer unique and more advantageous physicochemical properties than those of conventional 2D layered materials. However, the isotropic chemical bonding nature of non-layered materials hinders their lateral growth, making the synthesis of large-area continuous thin films challenging. Herein, a facile kinetically tailored chemical vapor deposition (KT-CVD) approach is introduced for the synthesis of 2D molybdenum nitride (MoN), a representative non-layered material. Large-scale thin films of MoN with lateral dimensions of up to 1.5 cm × 1.5 cm are obtained by modulating the vapor pressure of nitrogen feedstock and disrupting the thermodynamically favored growth kinetics of non-layered materials. The growth of stable crystalline phases of MoN (δ-MoN and γ-Mo2N) is also realized using the proposed KT-CVD approach. The δ-MoN synthesized via KT-CVD demonstrates excellent surface-enhanced Raman scattering and robust thermal stability. This study provides an effective strategy for developing scalable and high-quality non-layered 2D materials, expanding the fabrication and application of devices based on non-layered materials.

Robust Ferroelectricity in Nonstoichiometric 2D AgCr1-xS2 via Chemical Vapor Deposition

Ferroelectricity in two-dimensional (2D) materials at room temperature has attracted significant interest due to their substantial potential for applications in non-volatile memory, nanoelectronics, and optoelectronics. The intrinsic tendency of 2D materials toward nonstoichiometry results in atomic configurations that differ from those of their stoichiometric counterparts, thereby giving rise to potential ferroelectric polarization properties. However, reports on the emergence of room temperature ferroelectric effects in nonstoichiometric 2D materials remain limited. This study reports the observation of room temperature ferroelectricity in nonstoichiometric AgCr1-xS2 ternary 2D transition metal dichalcogenides synthesized via chemical vapor deposition. The noncentrosymmetric crystal structure and switchable ferroelectric polarization are confirmed through second harmonic generation (SHG) and piezoresponse force microscopy (PFM) measurements. It is determined that the primary cause of ferroelectric polarization is the interlayer movement of ordered asymmetric Ag atoms under the influence of numerous chromium (Cr) vacancies along with interlayer atom displacement. Furthermore, two types of electrical devices based on in-plane (IP) and out-of-plane (OOP) polarization are demonstrated. This work offers a new perspective for fabricating ternary ultrathin 2D transition metal dichalcogenides ferroelectric materials and presents a potential pathway for creating exceptional multifunctional materials.

Boron Trioxide-Assisted Post-Annealing Enables Vertical Oriented Recrystallization of Sb2Se3 Thin Film for High-Efficiency Solar Cells

Crystallization process is critical for enhancing the crystallinity, regulating the crystal orientation of polycrystalline thin films, as well as repairing defects within the films. For quasi-1D Sb2Se3 photovoltaic materials, the preparation of Sb2Se3 thin films still faces great challenges in adjusting orientation and defect properties, which limits the device performance. In this study, a novel post-treatment strategy is developed that uses a low melting point B2O3 coating layer as a flux to drive the recrystallization of Sb2Se3, thereby regulating the micro-orientation of thermal evaporation-derived Sb2Se3 films and optimizing their electrical properties. Mechanistic investigations show that B2O3 exhibits stronger adsorption with (hk1) planes of Sb2Se3 to induce a vertical orientation growth of the film, while blocking the volatilization channels of Se and inhibiting Se vacancy defects by interacting with Sb2Se3. The Sb2Se3 film with [hk1] preferential orientation and suppressed deep-level defects promotes the effective transport of charge carriers in solar cells. As a result, the B2O3-treated device delivers a champion efficiency of 9.37% without MgF2 anti-reflection coating, which is currently the highest efficiency in Sb2Se3 solar cells achieved by thermal evaporation method. This study provides a new method and mechanism for regulating optical and electrical properties of low-dimensional inorganic thin films.

Hypotaxy of wafer-scale single-crystal transition metal dichalcogenides

Two-dimensional (2D) semiconductors, particularly transition metal dichalcogenides (TMDs), are promising for advanced electronics beyond silicon1-3. Traditionally, TMDs are epitaxially grown on crystalline substrates by chemical vapour deposition. However, this approach requires post-growth transfer to target substrates, which makes controlling thickness and scalability difficult. Here we introduce a method called hypotaxy ('hypo' meaning downward and 'taxy' meaning arrangement), which enables wafer-scale single-crystal TMD growth directly on various substrates, including amorphous and lattice-mismatched substrates, while preserving crystalline alignment with an overlying 2D template. By sulfurizing or selenizing a pre-deposited metal film under graphene, aligned TMD nuclei form, coalescing into a single-crystal film as graphene is removed. This method achieves precise MoS2 thickness control from monolayer to hundreds of layers on diverse substrates, producing 4-inch single-crystal MoS2 with high thermal conductivity (about 120 W m-1 K-1) and mobility (around 87 cm2 V-1 s-1). Furthermore, nanopores created in graphene using oxygen plasma treatment allow MoS2 growth at a lower temperature of 400 °C, compatible with back-end-of-line processes. This hypotaxy approach extends to other TMDs, such as MoSe2, WS2 and WSe2, offering a solution to substrate limitations in conventional epitaxy and enabling wafer-scale TMDs for monolithic three-dimensional integration.

Optimizing Interfacial Charge Dynamics and Quantum Effects in Heterodimensional Superlattices for Efficient Hydrogen Production

Superlattice materials have emerged as promising candidates for water electrocatalysis due to their tunable crystal structures, electronic properties, and potential for interface engineering. However, the catalytic activity of transition metal-based superlattice materials for the hydrogen evolution reaction (HER) is often constrained by their intrinsic electronic band structures, which can limit charge carrier mobility and active site availability. Herein, a highly efficient electrocatalyst based on a VS2-VS heterodimensional (2D-1D) superlattice with sulfur vacancies is designed addressing the limitations posed by the intrinsic electronic structure. The enhanced catalytic performance of the VS2-VS superlattice is primarily attributed to the engineered heterojunction, where the work function difference between the VS2 layer and VS chain induces a charge separation field that promotes efficient electron-hole separation. Introducing sulfur vacancies further amplifies this effect by inducing quantum localization of the separated electrons, thereby significantly boosting HER activity. Both theoretical and experimental results demonstrate that the superlattice achieves a ΔGH* of -0.06 eV and an impressively low overpotential of 46 mV at 10 mA·cm-2 in acidic media, surpassing the performance of commercial Pt/C while maintaining exceptional stability over 15 000 cycles. This work underscores the pivotal role of advanced material engineering in designing catalysts for sustainable energy applications.

Recent Advances in Salt-Assisted Synthesis of 2D Materials

Two-dimensional (2D) materials have been attracting extensive interest due to their remarkable chemical, optical, electrical, and magnetic properties, making them ideal candidates for a broad range of applications. Developing facile synthesis methods that can fabricate high-quality 2D materials in an efficient, scalable, and cost-effective way is essential. Among the emerging techniques, salt-assisted methods to synthesize 2D materials, including molten salt method, salt-assisted chemical vapor deposition, and salt-template method, has demonstrated significant potential in fulfilling these requirements. This review highlights recent advancements in the synthesis of 2D materials through salt-assisted methods, focusing on their preparation processes and wide-ranging applications. It also explores the role of salts, in various forms, in directing the formation of 2D structures, providing insights for strategic synthesis design. Finally, challenges and future directions in salt-assisted synthesis are discussed, emphasizing strategies to enable controllable, high-yield production of 2D materials.

Synthesis of Highly Anisotropic 2D Insulator CrOCl Nanosheets for Interfacial Symmetry Breaking in Isotropic 2D Semiconductors

Chromium oxychloride (CrOCl), a van der Waals antiferromagnetic insulator, has attracted significant interest in 2D optoelectronic, ferromagnetic, and quantum devices. However, the bottom-up preparation of 2D CrOCl remains challenging, limiting its property exploration and device application. Herein, the controllable synthesis of 2D CrOCl crystals by chemical vapor deposition is demonstrated. The combination reaction of precursors together with the space-confined growth strategy, providing stable and stoichiometric growth conditions, enable a robust synthesis of high-crystallinity CrOCl nanosheets with regular rhombus-like morphology and uniform thickness. By tuning the growth temperature from 675 to 800 °C, the thickness of CrOCl nanosheets can be continuously modulated from 10.2 to 30.8 nm, with the domain size increasing from 16.9 to 25.5 µm. The as-grown CrOCl nanosheets exhibit significant structural/optical anisotropy, ultrahigh insulativity, and superior air stability. Furthermore, a MoS2/CrOCl heterostructure with single-mirror symmetry stacking and ultrastrong interfacial coupling is built to realize interfacial symmetry breaking, a novel interface phenomenon that converts MoS2 from isotropy to anisotropy. Consequently, the MoS2/CrOCl heterostructure device achieves polarization-sensitive photodetection and bulk photovoltaic effect, which are nonexistent in high-symmetry 2D materials. This work paves the way for the future exploration of CrOCl-based 2D physics and devices via symmetry engineering.

Data-Driven Discovery of High-Performance Heterobilayer Transition Metal Dichalcogenide-Based Sliding Ferroelectrics

The development of efficient sliding ferroelectric (FE) materials is crucial for advancing next-generation low-power nanodevices. Currently, most efforts focus on homobilayer two-dimensional materials, except for the experimentally reported heterobilayer sliding FE, MoS2/WS2. Here, we first screened 870 transition metal dichalcogenide (TMD) bilayer heterostructures derived from experimentally characterized monolayer TMDs and systematically investigated their sliding ferroelectric behavior across various stacking configurations using high-throughput calculations. On the basis of the generated data, we developed an efficient descriptor, named the amplitude of Allen electronegativity difference (Δχm), for identifying van der Waals heterobilayers with sliding FE properties. Finally, 16 semiconducting TMD heterobilayers are identified as exhibiting interlayer sliding FE alongside low switching barriers (<21 meV/f.u.), with 10 outperforming the experimental MoS2/WS2 system, showing the largest out-of-plane polarization (OPP) values up to 10 times higher than MoS2/WS2. These materials exhibit favorable band gaps (0.60-1.80 eV) using the HSE06 method, making them suitable for sliding FE applications. Our findings reveal that polarization switching in these heterobilayers is strongly influenced by the interplay of stacking patterns, material electronegativity, charge transfer, and electronic structures. This study provides a robust framework for designing novel sliding ferroelectric materials and offers a theoretical basis for future experimental research.

High-pressure chemistry of functional materials

Functional materials, possessing specific properties and performing particular functions beyond their mechanical or structural roles, are the foundation of modern matter science including energy, environment, and quantum sciences. The atomic and electronic structures of these materials can be significantly altered by external stimuli such as pressure. High-pressure techniques have been extensively utilized to deepen our understanding of structure-property relationships of materials, while also enabling emergent or enhanced properties. In this feature article, we review the transformative impact of high pressure on the chemical and physical properties of functional materials, including perovskite materials, low-dimensional metal halides, metal chalcogenides, metal oxides, and inorganic molecular crystals. By analyzing recent advancements and methodological approaches in high-pressure research, we provide insights into the mechanisms driving structural and property changes in these materials. We also emphasize the significance of translating the knowledge gained from high pressure research to the design of new functional materials. Finally, we highlight the potential of high-pressure chemistry and nano-architectonics in advancing functional materials and discuss the future directions and challenges in this field.

Two-Dimensional Materials for Brain-Inspired Computing Hardware

Recent breakthroughs in brain-inspired computing promise to address a wide range of problems from security to healthcare. However, the current strategy of implementing artificial intelligence algorithms using conventional silicon hardware is leading to unsustainable energy consumption. Neuromorphic hardware based on electronic devices mimicking biological systems is emerging as a low-energy alternative, although further progress requires materials that can mimic biological function while maintaining scalability and speed. As a result of their diverse unique properties, atomically thin two-dimensional (2D) materials are promising building blocks for next-generation electronics including nonvolatile memory, in-memory and neuromorphic computing, and flexible edge-computing systems. Furthermore, 2D materials achieve biorealistic synaptic and neuronal responses that extend beyond conventional logic and memory systems. Here, we provide a comprehensive review of the growth, fabrication, and integration of 2D materials and van der Waals heterojunctions for neuromorphic electronic and optoelectronic devices, circuits, and systems. For each case, the relationship between physical properties and device responses is emphasized followed by a critical comparison of technologies for different applications. We conclude with a forward-looking perspective on the key remaining challenges and opportunities for neuromorphic applications that leverage the fundamental properties of 2D materials and heterojunctions.

Two-Dimensional Transition Metal Dichalcogenides: A Theory and Simulation Perspective

Two-dimensional transition metal dichalcogenides (2D TMDs) are a promising class of functional materials for fundamental physics explorations and applications in next-generation electronics, catalysis, quantum technologies, and energy-related fields. Theory and simulations have played a pivotal role in recent advancements, from understanding physical properties and discovering new materials to elucidating synthesis processes and designing novel devices. The key has been developments in ab initio theory, deep learning, molecular dynamics, high-throughput computations, and multiscale methods. This review focuses on how theory and simulations have contributed to recent progress in 2D TMDs research, particularly in understanding properties of twisted moiré-based TMDs, predicting exotic quantum phases in TMD monolayers and heterostructures, understanding nucleation and growth processes in TMD synthesis, and comprehending electron transport and characteristics of different contacts in potential devices based on TMD heterostructures. The notable achievements provided by theory and simulations are highlighted, along with the challenges that need to be addressed. Although 2D TMDs have demonstrated potential and prototype devices have been created, we conclude by highlighting research areas that demand the most attention and how theory and simulation might address them and aid in attaining the true potential of 2D TMDs toward commercial device realizations.