Interfacial Polarization Enhanced Ultrafast Carrier Dynamics in Ferroelectric CuInPS.

Two-dimensional (2D) ferroelectric materials hold great potential for various electronic applications, including nonvolatile memory, ferroelectric field-effect transistors, and functional sensors. Cooperative phenomena associated with ferroelectricity-modulated carrier dynamics in the 2D context have primarily remained unexplored. To address this gap, we investigate the photoinduced dynamics in CuInPS (CIPS) and elucidate the relationship between photoexcited carrier dynamics and interfacial polarizations.

Resonant Quantum Magnetodielectric Effect in Multiferroic Metal-Organic Framework [CHNH]Co(HCOO).

The observation of both resonant quantum tunneling of magnetization (RQTM) and resonant quantum magnetodielectric (RQMD) effect in the perovskite multiferroic metal-organic framework [CHNH]Co(HCOO).is reported. An intrinsic magnetic phase separation emerges at low temperatures due to the hydrogen-bond-modified long-range super-exchange interaction, leading to the coexistence of canted antiferromagnetic order and single-ion (Co) magnets.

A One-Stone-Two-Birds Strategy for Intervertebral Disc Repair: Constructing a Reductive Chelation Hydrogel to Mitigate Oxidative Stress and Promote Disc Matrix Reconstruction.

Intervertebral disc degeneration (IVDD) is characterized by fibrosis of nucleus pulposus (NP) cells and accelerated surrounding extracellular matrix catabolism. Bioactive hydrogels have shown significant potential in regulating cellular functions and tissue homeostasis. In this work, a dynamic hydrogel (HA-NCSN/Cu) is designed via the reductive chelation of hyaluronic acid grafted with thiourea (HA-NCSN) and Cu.

The shift current photovoltaic effect response in wurtzite and zinc blende semiconductors first-principles calculations.

Recently, the search for materials with high photoelectric conversion efficiency has emerged as a significant research hotspot. Unlike p-n junctions, the bulk photovoltaic effect (BPVE) can also materialize within pure crystals. Here, we propose wurtzite and zinc blende semiconductors without inversion symmetry (AgI, GaAs, CdSe, CdTe, SiGe, ZnSe, and ZnTe) as candidates for achieving the BPVE and investigate the factors that affect the shift current.

BiOSe: a two-dimensional high-mobility polar semiconductor with large interlayer and interfacial charge transfer.

Two-dimensional semiconductors with large intrinsic polarity are highly attractive for applications in high-speed electronics, ultrafast and highly sensitive photodetectors and photocatalysis. However, previous studies mainly focus on neutral layered polar 2D materials with limited vertical dipoles and electrostatic potential difference (typically <1.5 eV).

Enhanced Ferromagnetism and Tunable Magnetic Anisotropy in a van der Waals Ferromagnet.

2D van der Waals (vdW) magnets have recently emerged as a promising material system for spintronic device innovations due to their intriguing phenomena in the reduced dimension and simple integration of magnetic heterostructures without the restriction of lattice matching. However, it is still challenging to realize Curie temperature far above room temperature and controllable magnetic anisotropy for spintronics application in 2D vdW magnetic materials. In this work, the pressure-tuned dome-like ferromagnetic-paramagnetic phase diagram in an iron-based 2D layered ferromagnet FeGaTe is reported.

Controllable Synthesis of Transferable Ultrathin BiGe(Si)O Dielectric Alloys with Composition-Tunable High-κ Properties.

Two-dimensional (2D) alloys hold great promise to serve as important components of 2D transistors, since their properties allow continuous regulation by varying their compositions. However, previous studies are mainly limited to the metallic/semiconducting ones as contact/channel materials, but very few are related to the insulating dielectrics. Here, we use a facile one-step chemical vapor deposition (CVD) method to synthesize ultrathin BiSiGeO dielectric alloys, whose composition is tunable over the full range of just by changing the relative ratios of the GeO/SiO precursors.

Observation of giant room-temperature anisotropic magnetoresistance in the topological insulator β-AgTe.

Achieving room-temperature high anisotropic magnetoresistance ratios is highly desirable for magnetic sensors with scaled supply voltages and high sensitivities. However, the ratios in heterojunction-free thin films are currently limited to only a few percent at room temperature. Here, we observe a high anisotropic magnetoresistance ratio of -39% and a giant planar Hall effect (520 μΩ⋅cm) at room temperature under 9 T in β-AgTe crystals grown by chemical vapor deposition.

Anomalous Dependence of Photocarrier Recombination Time on the Polaron Density of TiO(110).

Polarons play a crucial role in energy conversion, but the microscopic mechanism remains unclear since they are susceptible to local atomic structures. Here, by employing nonadiabatic dynamic simulations, we investigate electron-hole (e-h) nonradiative recombination at the rutile TiO(110) surface with varied amounts of oxygen vacancies (V). The isolated V facilitates e-h recombination through forming polarons compared to that in the defect-free surface.

Size-tunable energy gaps of hydrogen-terminated biphenylene segments.

The electronic properties of hydrogen-terminated biphenylene (BP) segments of different sizes on the sub-nanoscale are explored using density functional theory, and the size dependence of the energy gap is evaluated using a structural parameter as a function of the bond lengths and the electronic density contributions. More importantly, the energy gap is observed to decrease linearly with the reduced hydrogen-to-carbon ratio of the corresponding structures, while the decrease-rate undergoes a diminution of four times at a gap of 0.5 eV due to the transformed distribution of the lowest unoccupied molecular orbital.

Vertically grown ultrathin BiSiO as high-κ single-crystalline gate dielectric.

Single-crystalline high-κ dielectric materials are desired for the development of future two-dimensional (2D) electronic devices. However, curent 2D gate insulators still face challenges, such as insufficient dielectric constant and difficult to obtain free-standing and transferrable ultrathin films. Here, we demonstrate that ultrathin BiSiO crystals grown by chemical vapor deposition (CVD) can serve as excellent gate dielectric layers for 2D semiconductors, showing a high dielectric constant (>30) and large band gap (~3.

Transferred Polymer-Encapsulated Metal Electrodes for Electrical Transport Measurements on Ultrathin Air-Sensitive Crystals.

Owing to rapid property degradation after ambient exposure and incompatibility with conventional device fabrication process, electrical transport measurements on air-sensitive 2D materials have always been a big issue. Here, for the first time, a facile one-step polymer-encapsulated electrode transfer (PEET) method applicable for fragile 2D materials is developed, which showed great advantages of damage-free electrodes patterning and in situ polymer encapsulation preventing from H O/O exposure during the whole electrical measurements process. The ultrathin SmTe metals grown by chemical vapor deposition (CVD) are chosen as the prototypical air-sensitive 2D crystals for their poor air-stability, which will become highly insulating when fabricated by conventional lithographic techniques.

The Discovery of a High-Mobility Two-Dimensional Bismuth Oxyselenide Semiconductor and Its Application in Nonvolatile Neuromorphic Devices.

The development of two-dimensional (2D) electronics is always accompanied by the discovery of 2D semiconductors with high mobility and specific crystal structures, which may bring revolutionary breakthrough on proof-of-concept devices and physics. Here, BiOSe, a 2D bismuth oxyselenide semiconductor with non-neutral layered crystal structure is discovered. Ultrathin BiOSe films are readily synthesized by chemical vapor deposition, displaying tunable band gaps and high room-temperature field-effect mobility of >220 cm V s.

Tunable Topological States in Stacked Chern Insulator Bilayers.

The emergence of intrinsic quantum anomalous Hall (QAH) insulators with a long-range ferromagnetic (FM) order triggers unprecedented prosperity for combining topology and magnetism in low dimensions. Built upon atom-thin Chern insulator monolayer MnBr, we propose that the topologically nontrivial electronic states can be systematically tuned by inherent magnetic orders and external electric/optical fields in stacked Chern insulator bilayers. The FM bilayer illustrates a high-Chern-number QAH state characterized by both quantized Hall plateaus and specific magneto-optical Kerr angles.

Single-crystalline van der Waals layered dielectric with high dielectric constant.

The scaling of silicon-based transistors at sub-ten-nanometre technology nodes faces challenges such as interface imperfection and gate current leakage for an ultrathin silicon channel. For next-generation nanoelectronics, high-mobility two-dimensional (2D) layered semiconductors with an atomic thickness and dangling-bond-free surfaces are expected as channel materials to achieve smaller channel sizes, less interfacial scattering and more efficient gate-field penetration. However, further progress towards 2D electronics is hindered by factors such as the lack of a high dielectric constant (κ) dielectric with an atomically flat and dangling-bond-free surface.

High Mobility and Quantum Oscillations in Semiconducting BiOTe Nanosheets Grown by Chemical Vapor Deposition.

BiOTe has the smallest effective mass and preferable carrier mobility in the BiOX (X = S, Se, Te) family. However, compared to the widely explored BiOSe, the studies on BiOTe are very rare, probably attributed to the lack of efficient ways to achieve the growth of ultrathin films. Herein, ultrathin BiOTe crystals were successfully synthesized by a trace amount of O-assisted chemical vapor deposition (CVD) method, enabling the observation of ultrahigh low-temperature Hall mobility of >20 000 cm V s, pronounced Shubnikov-de Haas quantum oscillations, and small effective mass of ∼0.

Step-Climbing Epitaxy of Layered Materials with Giant Out-of-Plane Lattice Mismatch.

Heteroepitaxy with large lattice mismatch remains a great challenge for high-quality epifilm growth. Although great efforts have been devoted to epifilm growth with an in-plane lattice mismatch, the epitaxy of 2D layered crystals on stepped substrates with a giant out-of-plane lattice mismatch is seldom reported. Here, taking the molecular-beam epitaxy of 2D semiconducting Bi O Se on 3D SrTiO substrates as an example, a step-climbing epitaxy growth strategy is proposed, in which the n-th (n = 1, 2, 3…) epilayer climbs the step with height difference from out-of-plane lattice mismatch and continues to grow the n+1-th epilayer.

EFL Learner Engagement in Automatic Written Evaluation.

Recent years have witnessed increasing popularity in the use of automatic written evaluation (AWE) in the writing context for its immediacy and high accessibility for EFL learners. Meanwhile, the effectiveness of the AWE tool in writing accuracy and ability is fully appreciated by the previous researchers. However, students' engagement in the revising process, key factors that mediate the uptake of feedback, and learning effect have not aroused much attention as expected.

Manipulation of the Magnetic Anisotropy of Single Mn Atom via Molecular Ligands.

Magnetic anisotropy is essential for permanent magnets to maintain their magnetization along specific directions. Understanding and controlling the magnetic anisotropy on a single-molecule scale are challenging but of fundamental importance for the future's spintronic technology. Here, by using scanning tunneling microscopy (STM), we demonstrated the ability to control the magnetic anisotropy by tuning the ligand field at the single-molecule level.

Exploiting Two-Dimensional Bi O Se for Trace Oxygen Detection.

We exploit a high-performing resistive-type trace oxygen sensor based on 2D high-mobility semiconducting Bi O Se nanoplates. Scanning tunneling microscopy combined with first-principle calculations confirms an amorphous Se atomic layer formed on the surface of 2D Bi O Se exposed to oxygen, which contributes to larger specific surface area and abundant active adsorption sites. Such 2D Bi O Se oxygen sensors have remarkable oxygen-adsorption induced variations of carrier density/mobility, and exhibit an ultrahigh sensitivity featuring minimum detection limit of 0.

Probing Nonequilibrium Dynamics of Photoexcited Polarons on a Metal-Oxide Surface with Atomic Precision.

Understanding the nonequilibrium dynamics of photoexcited polarons at the atomic scale is of great importance for improving the performance of photocatalytic and solar-energy materials. Using a pulsed-laser-combined scanning tunneling microscopy and spectroscopy, here we succeeded in resolving the relaxation dynamics of single polarons bound to oxygen vacancies on the surface of a prototypical photocatalyst, rutile TiO_{2}(110). The visible-light excitation of the defect-derived polarons depletes the polaron states and leads to delocalized free electrons in the conduction band, which is further corroborated by ab initio calculations.

Finite-temperature violation of the anomalous transverse Wiedemann-Franz law.

The Wiedemann-Franz (WF) law has been tested in numerous solids, but the extent of its relevance to the anomalous transverse transport and the topological nature of the wave function, remains an open question. Here, we present a study of anomalous transverse response in the noncollinear antiferromagnet MnGe extended from room temperature down to sub-kelvin temperature and find that the anomalous Lorenz ratio remains close to the Sommerfeld value up to 100 K but not above. The finite-temperature violation of the WF correlation is caused by a mismatch between the thermal and electrical summations of the Berry curvature and not by inelastic scattering.

Visualizing coexisting surface states in the weak and crystalline topological insulator BiTeI.

Dual topological materials are unique topological phases that host coexisting surface states of different topological nature on the same or on different material facets. Here, we show that BiTeI is a dual topological insulator. It exhibits band inversions at two time reversal symmetry points of the bulk band, which classify it as a weak topological insulator with metallic states on its 'side' surfaces.

Exchange bias and quantum anomalous nomalous Hall effect in the MnBiTe/CrI heterostructure.

The layered antiferromagnetic MnBiTe films have been proposed to be an intrinsic quantum anomalous Hall (QAH) insulator with a large gap. It is crucial to open a magnetic gap of surface states. However, recent experiments have observed gapless surface states, indicating the absence of out-of-plane surface magnetism, and thus, the quantized Hall resistance can only be achieved at the magnetic field above 6 T.

Resolving the topological classification of bismuth with topological defects.

The growing diversity of topological classes leads to ambiguity between classes that share similar boundary phenomenology. This is the status of bulk bismuth. Recent studies have classified it as either a strong or a higher-order topological insulator, both of which host helical modes on their boundaries.