Entropy engineering has emerged as a promising paradigm for tailoring the electronic and photoelectric properties of materials. Although high-entropy transition metal sulfides have been achieved, entropy engineering in two-dimensional (2D) tellurides remains challenging. In this work, we report the successful synthesis of a 1T' monolayer heptanary medium-entropy (ME) alloy (MoaWbFecCodSxSeyTez) via a one-step chemical vapor deposition method. Advanced characterizations, including scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, and electron energy loss spectroscopy confirm the uniform atomic-level distribution of the seven constituent elements within the alloy. The 1T' ME alloy device exhibits a high drain current of similar to 6.5 mA, which is 216 times higher than the similar to 30 mu A observed in pristine 1T' MoTe2. Furthermore, the 1T' ME alloy photodetector exhibits responsivities of 27.92 A/W at 1064 nm and 63.74 A/W at 1550 nm, outperforming those of the pristine 1T' MoTe2 by more than two orders of magnitude. This remarkable enhancement is attributed to the reduced Schottky barrier (15.9 meV) at the 1T' ME alloy/electrode interface, along with the enhanced conductance (0.43 S) and reduced thermal activation energy (4.1 meV) in the 1T' ME alloy, collectively facilitating more efficient carrier injection and transport. Our work provides a distinct pathway for tailoring the properties of transition metal dichalcogenides through entropy engineering and offers valuable insights for the design of high-performance infrared photodetectors.

Artificial synapse (AS) offers a promising approach to emulate biomimetic nervous systems and potentially overcomes the von Neumann bottleneck. Despite their potential, current neuromorphic devices still suffer from challenges, including electrolysis risks, material degradation, ferroelectric fatigue, and irreversible conductance changes from ion migration and trapping. Here, we propose a self-trapping mechanism due to the intrinsic structural distortion of FePSe3 induced by strong electron-phonon (e-ph) coupling, which preferentially captures electrons, forming polarons within 1 picosecond (ps) and extending carrier lifetimes to tens of nanoseconds (ns). A memristor based on polarons formed in FePSe3 via the nondestructive capture and release of electrons transferred from graphene (Gr) was realized, exhibiting a large memory window exceeding 124 V and stable electrical performance over more than 103 switching cycles. Furthermore, FePSe3-Gr devices show good synaptic plasticity stimulated by different amplitudes and numbers of electrical pulses, indicating the capacity to be applied in AS devices. Meanwhile, the synaptic reset function is observed due to the saturation formation of polarons under optical injection. Our findings present a microscopic approach for stable, high-performance AS devices, advancing their application potential in neuromorphic systems.

Two-dimensional ferroelectric materials hold promises for non-volatile memory and integrated electronic circuits. However, direct synthesizing and understanding the ferroelectric mechanism of two-dimensional room-temperature ferroelectrics remains challenging. Here, we report the synthesis of intrinsic room-temperature ferroelectric CuVP2S6 via spatially confined chemical vapor deposition method, as demonstrated by second harmonic generation and piezoresponse force microscopy measurements. Importantly, we experimentally uncover the ferroelectric mechanism of CuVP2S6, which originates from the movement of Cu ions, as confirmed by scanning transmission electron microscopy. Additionally, we construct an optoelectronic CuVP2S6 synaptic device, which enables a smooth transition from optical character recognition to neural machine translation using a transformer architecture. Our study not only elucidates the ferroelectric mechanism of two-dimensional metal phosphorus sulfide compounds but also integrates optical character recognition and neural machine translation within a single material, offering significant opportunities for neuromorphic computing systems.

The in situ polymerization method for coating Al–Li alloy exhibits great potential for applications in aerospace and weapon fields as it improves the compatibility, stability and combustibility of Al–Li in solid propellants.

Transition metal dichalcogenides (TMDCs), with excellent merits such as atomic‐layer thickness, tunable bandgaps, high carrier mobility and good compatibility with traditional semiconductor processes, are one of the promising candidates for the next generation of semiconductor channel materials, expected to overcome the physical limitations of conventional silicon‐based materials and extend Moore's Law. Recognizing the vast potential of TMDCs in revolutionizing semiconductor technology, researchers are intensively exploring various preparation techniques for industrialization. Among these, chemical vapor deposition (CVD) has emerged as a frontrunner to synthesize high‐quality and large‐area TMDCs film. In this review, the focus is on the current progress in the growth of large‐area TMDCs films via the CVD method. Insights into the preparation of large‐area TMDCs, including growth strategies and growth mechanisms, are first presented. Second, the transfer approaches are summarized, covering wet and dry transfer methods for the large‐area TMDCs. Third, their applications in logic circuits, optoelectronics and displays are explored. In the end, a summary and outlook are provided in terms of the current challenges and future research directions, inspiring further research and development efforts in this area.

Low-dimensional ternary materials with low-symmetry structure have emerged as promising candidates for constructing polarization-sensitive photodetectors. However, the photodetection applications of ternary materials remain challenging due to the limited varieties and the uncontrollable preparation. Herein, ternary Cu3PS4 nanowires with tunable thickness are successfully synthesized via chemical vapor deposition method. The grown Cu3PS4 nanowires present excellent structural anisotropy and strong in-plane second-order nonlinear optical anisotropy, as evidenced by angle-resolved polarized Raman spectra and second harmonic generation measurements. Impressively, Cu3PS4-based photodetector demonstrates a responsivity of 8.8 mAW(-1), detectivity of 5.01 x 10(9) Jones, and photoresponse speeds with rise (decay) time of 1.5 (3.5) ms. Interestingly, the photodetector achieves polarization-sensitivity photoresponse with an anisotropic ratio of 1.3 at 520 nm based on its inherent structural anisotropy and geometrical shapes. This work broadens the scope of synthesis strategy for various low-dimensional ternary metal chalcohalide semiconductors and provides great opportunities for designing high-performance and multifunctional optoelectronic devices.

Mixing entropy engineering is a promising strategy to tune the physical and chemical properties of materials. Although high-entropy in van der Waals bulk solids have been reported, entropy engineering in 2D monolayers remains unconquered. In this work, the epitaxial growth of a 2-inch 1T '' hexanary medium-entropy alloy monolayer (ReaWbMocIndSxSey) is reported via the chemical vapor deposition method. The atomic structure and chemical composition are confirmed by X-ray photoelectron spectroscopy, scanning transmission electron microscopy, energy dispersive X-ray spectroscopy and electron energy loss spectroscopy, illustrating the uniform distribution of the six elements. The hexanary medium-entropy alloy photodetectors show an ultrawide photo-response from visible to near-infrared wavelengths with a responsivity of 100.2 A W-1 under 520 nm laser illumination. Meanwhile, the hexanary medium-entropy alloy monolayer exhibits excellent electrocatalytic hydrogen production with an overpotential of 176.6 mV in dark. Importantly, an overpotential of 43.7 mV at 10 mA cm-2 with a lowered Tafel slope of 51.9 mV dec-1 under 520 nm laser irradiation is obtained due to the excellent conductivity. The work opens a new way to design mixing = entropy alloys and enables the application of transition metal dichalcogenides in photo-enhanced electrocatalytic hydrogen production.

Solid propellant containing Al-Li particles has attracted much attention because of the high combustion efficiency and effective absorption of HCl in burning tail smoke. However, the highly reactive Li has limited the application due to the lower stability and compatibility with HTPB. In this study, the chemically stable Al-5Li particles were fabricated by a thin organic layer, which was used by the dodecyltrimethoxysilane (DTMS) or 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (FTMS) with the site-selective coating of active Al and Li. Meanwhile, the Li-F coordination bond also provides a deeper protection with the decrease of hygroscopicity with 39.08% mass variation through the XPS test of Al-5Li@FTMS. The Al-5Li@FTMS and Al-5Li@DTMS particles had good stability and compatibility with HTPB to 1 or 2 degree and none pores or cracks on the cross section of propellant. Note here that the Al-5Li@FTMS and Al-5Li@DTMS propellants exhibited a shorter ignition delay time, higher peak flame temperature and smaller particle size of residue corresponded to Al propellant. Meanwhile, the burning rates of propellants had increased by 2.80% and 0.93%. Thus, the coating of FTMS is better than that of DTMS from the stability and combustibility. The micro-explosion characteristic of Al-5Li particles would provide higher combustion efficiency and performance. The feasible fabrication method would provide an relevant guidance for the stability and combustibility of alloy powders in solid propellant.

Localized magnetic moments in non-magnetic materials, by interacting with the itinerary electrons, can profoundly change the metallic properties, developing various correlated phenomena such as the Kondo effect, heavy fermion, and unconventional superconductivity. In most Kondo systems, the localized moments are introduced through magnetic impurities. However, the intrinsic magnetic properties of materials can also be modulated by the dimensionality. Here, we report the observation of Kondo effect in a heterodimensional superlattice VS2-VS, in which arrays of the one-dimensional (1D) VS chains are encapsulated by two-dimensional VS2 layers. In such a heterodimensional Kondo superlattice, we observe the typical Kondo effect but with intriguing anisotropic field dependence. This unique anisotropy is determined to originate from the magnetic anisotropy which has the root in the unique 1D chains in the structure, as corroborated by the first-principles calculation. Our results open up a novel avenue of studying exotic correlated physics in heterodimensional materials.

The remarkable potential of two-dimensional (2D) materials in sustaining Moore's law has sparked a research frenzy. Extensive efforts have been made in the research of utilizing 2D semiconductors as channel materials in field-effect transistors. However, the next generation of integrated devices requires the integration of gate dielectrics with wider bandgaps and higher dielectric constants. Here, insulating α-Sb2O3 single-crystal nanosheets are synthesized by one-step chemical vapor deposition method. Importantly, the α-Sb2O3 single-crystal dielectric exhibits a high dielectric constant of 11.8 and a wide bandgap of 3.78 eV. Besides, the atomically smooth interface between α-Sb2O3 and MoS2 enables the fabrication of dual-gated field-effect transistors with the top gate dielectric of α-Sb2O3 nanosheets. The field-effect transistors exhibit a switching ratio of exceeding 108, which achieves the manipulation of field-effect transistors by using 2D dielectric materials. These results hold significant implications for optimizing the performances of 2D devices and innovating microelectronics.

2D intercalated vanadium chalcogenides have attracted intensive interest based on their physical properties and potential applications. However, controllable synthesis of the intercalated vanadium chalcogenides via chemical vapor deposition is still a big challenge. Here, a binary metal precursor co‐reaction growth mechanism to manipulate the evaporation rate of vanadium precursors is reported, thus the intercalated 2D V 1+ X S 2 – V 3 S 5 single crystal can be controllably synthesized. The quality of 2D V 3 S 5 nanosheets is identified by Raman spectroscopy and high‐resolution scanning transmission electron microscopy. Interestingly, a phase transition in 2D metallic V 3 S 5 nanosheets is observed at 20 K. Meanwhile, the resistance upturn and unsaturated negative magnetoresistance induced by electron–electron interaction is confirmed. This work proposes a new strategy to synthesize the 2D intercalated V x S y single crystals with different compositions for studying their excellent properties and potential applications.

Ultrathin 2D ferroelectrics with high Curie temperature are critical for multifunctional ferroelectric devices. However, the ferroelectric spontaneous polarization is consistently broken by the strong thermal fluctuations at high temperature, resulting in the rare discovery of high-temperature ferroelectricity in 2D materials. Here, a chemical vapor deposition method is reported to synthesize 2D CuCrSe2 nanosheets. The crystal structure is confirmed by scanning transmission electron microscopy characterization. The measured ferroelectric phase transition temperature of ultrathin CuCrSe2 is about ≈800 K. Significantly, the switchable ferroelectric polarization is observed in ≈5.2 nm nanosheet. Moreover, the in-plane and out-of-plane ferroelectric response are modulated by different maximum bias voltage. This work provides a new insight into the construction of 2D ferroelectrics with high Curie temperature.

Fe-based 2D materials exhibit rich chemical compositions and structures, which may imply many unique physical properties and promising applications. However, achieving controllable preparation of ultrathin non-layered FeS crystal on SiO2/Si substrate remains a challenge. Herein, the influence of temperature and molecular sieves is reported on the synthesis of ultrathin FeS nanosheets with a thickness as low as 2.3 nm by molecular sieves-assisted chemical vapor deposition (CVD). The grown FeS nanosheets exhibit a non-layered hexagonal NiAs structure and belong to the P63/mmc space group. The inverted symmetry broken structure is confirmed by the angle-resolved second harmonic generation (SHG) test. In particular, the 2D FeS nanosheets exhibit exceptional metallic behavior, with conductivity up to 1.63 x 106 S m-1 at 300 K for an 8 nm thick sample, which is higher than that of reported 2D metallic materials. This work provides a significant contribution to the synthesis and characterization of 2D non-layered Fe-based materials. In this work, the synthesis of high-quality 2D non-layered FeS nanosheets on SiO2/Si substrates by molecular sieves-assisted chemical vapor deposition (CVD) method is realized. The thickness of ultrathin FeS nanosheets can be as low as 2.3 nm. The inverted symmetry broken structure is confirmed by angle-resolved polarized Raman and SHG characterizations. The synthesized FeS nanosheets exhibit exceptional metallic behavior, with conductivity up to 1.63 x 106 S m-1 at 300 K for an 8 nm thick sample. This work provides a significant contribution to the synthesis and characterization of 2D non-layered Fe-based materials. image

Two-dimensional (2D) semiconductors have attracted considerable attention for their potential in extending Moore's law and advancing next-generation electronic devices. Notably, the discovery and development of 2D ferromagnetic semiconductors (FMSs) open exciting opportunities in manipulating both charge and spin, enabling the exploration of exotic properties and the design of innovative spintronic devices. In this review, we aim to offer a comprehensive summary of emerging 2D FMSs, covering their atomic structures, physical properties, preparation methods, growth mechanisms, magnetism modulation techniques, and potential applications. We begin with a brief introduction of the atomic structures and magnetic properties of novel 2D FMSs. Next, we delve into the latest advancements in the exotic physical properties of 2D FMSs. Following that, we summarize the growth methods, associated growth mechanisms, magnetism modulation techniques and spintronic applications of 2D FMSs. Finally, we offer insights into the challenges and potential applications of 2D FMSs, which may inspire further research in developing high-density, non-volatile storage devices based on 2D FMSs.

Intrinsic ferroelectric materials play a critical role in the development of high-density integrated device. Despite some two-dimensional (2D) ferroelectrics have been reported, the research on one-dimensional (1D) intrinsic ferroelectric materials remains relatively scare since 1D atomic structures limit their van der Waals (vdW) epitaxy growth. Here, we report the synthesis of 1D intrinsic vdW ferroelectric SbSI nanowires via a confined-space chemical vapor deposition. By precisely controlling the partial vapor pressure of I2 and reaction temperature, we can effectively manipulate kinetics and thermodynamics processes, and thus obtain high quality of SbSI nanowires, which is determined by Raman spectroscopy and high-resolution scanning transmission electron microscopy characterizations. The ferroelectricity in SbSI is confirmed by piezo-response force microscopy measurements and the ferroelectric transition temperature of 300 K is demonstrated by second harmonic generation. Moreover, the in-plane polarization switching can be maintained in the thin SbSI nanowires with a thickness of 20 nm. Our prepared 1D vdW ferroelectric SbSI nanowires not only enrich the vdW ferroelectric systems, but also open a new possibility for high-power energy storage nanodevices.

2D materials provide an ideal platform to explore novel superconducting behavior including Ising superconductivity, topological superconductivity and Majorana bound states in different 2D stoichiometric Ta-, Nb-, and Fe-based crystals. However, tuning the element content in 2D compounds for regulating their superconductivity has not been realized. In this work, the synthesis of high quality Fe1+yTe with tunable Fe content by chemical vapor deposition (CVD) is reported. The quality and composition of Fe1+yTe are characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM). The superconducting behavior of Fe1+yTe crystals with varying Fe contents is observed. The superconducting transition of selected Fe1.13 +/- 0.06Te sample is sharp (Delta T-c = 1 K), while Fe1.43 +/- 0.07Te with a high-Fe content shows a relative broad superconducting transition (Delta T-c = 2.6 K) at zero magnetic field. Significantly, the conspicuous vortex flow and a transition from a 3D vortex liquid state to a 2D vortex liquid state is observed in Fe1.43 +/- 0.07Te sample. This work highlights the tunability of the superconducting properties of Fe1+yTe and sheds light on the vortex dynamics in Fe-based superconductors, which facilitates them to understand the intrinsic mechanisms of high-temperature superconductivity.

The 2D ternary transition metal phosphorous chalcogenides (TMPCs) have attracted extensive research interest due to their widely tunable band gap, rich electronic properties, inherent magnetic and ferroelectric properties. However, the synthesis of TMPCs via chemical vapor deposition (CVD) is still challenging since it is difficult to control reactions among multi-precursors. Here, a subtractive element growth mechanism is proposed to controllably synthesize the TMPCs. Based on the growth mechanism, the TMPCs including FePS3 , FePSe3 , MnPS3 , MnPSe3 , CdPS3 , CdPSe3 , In2 P3 S9 , and SnPS3 are achieved successfully and further confirmed by Raman, second-harmonic generation (SHG), and scanning transmission electron microscopy (STEM). The typical TMPCs-SnPS3 shows a strong SHG signal at 1064 nm, with an effective nonlinear susceptibility χ(2) of 8.41 × 10-11  m V-1 , which is about 8 times of that in MoS2 . And the photodetector based on CdPSe3 exhibits superior detection performances with responsivity of 582 mA W-1 , high detectivity of 3.19 × 1011  Jones, and fast rise time of 611 µs, which is better than most previously reported TMPCs-based photodetectors. These results demonstrate the high quality of TMPCs and promote the exploration of the optical properties of 2D TMPCs for their applications in optoelectronics.

A novel class of π-extended 11-ring-fused linear thienoacenes (BBDTB-H, BBDTB-TIPS, and BBDTB-Br) with four thieno[3,2- b ;4,5- b ′]dithiophenes and three benzene rings were synthesized and fully characterized.

Layered metal chalcogenides, as a "rich" family of 2D materials, have attracted increasing research interest due to the abundant choices of materials with diverse structures and rich electronic characteristics. Although the common metal chalcogenide phases such as 2H and 1T have been intensively studied, many other unusual phases are rarely explored, and some of these show fascinating behaviors including superconductivity, ferroelectrics, ferromagnetism, etc. From this perspective, the unusual phases of metal chalcogenides and their characteristics, as well as potential applications are introduced. First, the unusual phases of metal chalcogenides from different classes, including transition metal dichalcogenides, magnetic element-based chalcogenides, and metal phosphorus chalcogenides, are discussed, respectively. Meanwhile, their excellent properties of different unusual phases are introduced. Then, the methods for producing the unusual phases are discussed, specifically, the stabilization strategies during the chemical vapor deposition process for the unusual phase growth are discussed, followed by an outlook and discussions on how to prepare the unusual phase metal dichalcogenides in terms of synthetic methodology and potential applications.