Twist-angle-dependent momentum-space direct and indirect interlayer excitons in WSe/WS heterostructure.

Interlayer excitons (ILEs) in the van der Waals (vdW) heterostructures of type-II band alignment transition metal dichalcogenides (TMDCs) have attracted significant interest owing to their unique exciton properties and potential in quantum information applications. However, the new dimension that emerges with the stacking of structures with a twist angle leads to a more complex fine structure of ILEs, presenting both an opportunity and a challenge for the regulation of the interlayer excitons. In this study, we report the evolution of interlayer excitons with the twist angle in the WSe/WS heterostructure and identify the direct (indirect) interlayer excitons by combining photoluminescence (PL) and density functional theory (DFT) calculations.

CVD growth of large-area monolayer WS film on sapphire through tuning substrate environment and its application for high-sensitive strain sensor.

Large-area, continuous monolayer WS exhibits great potential for future micro-nanodevice applications due to its special electrical properties and mechanical flexibility. In this work, the front opening quartz boat is used to increase the amount of sulfur (S) vapor under the sapphire substrate, which is critical for achieving large-area films during the chemical vapor deposition processes. COMSOL simulations reveal that the front opening quartz boat will significantly introduce gas distribute under the sapphire substrate.

Self-powered acceleration sensors arrayed by swarm intelligence for table tennis umpiring system.

Table tennis competition is voted as one of the most popular competitive sports. The referee umpires the competition mainly based on visual observation and experience, which may make misjudgments on competition results due to the referee's subjective uncertainty or imprecision. In this work, a novel intelligent umpiring system based on arrayed self-powered acceleration sensor nodes was presented to enhance the competition accuracy.

A Review of Transition Metal Dichalcogenides-Based Biosensors.

Transition metal dichalcogenides (TMDCs) are widely used in biosensing applications due to their excellent physical and chemical properties. Due to the properties of biomaterial targets, the biggest challenge that biosensors face now is how to improve the sensitivity and stability. A lot of materials had been used to enhance the target signal.

Correction: A highly sensitive silicon nanowire array sensor for joint detection of tumor markers CEA and AFP.

Correction for 'A highly sensitive silicon nanowire array sensor for joint detection of tumor markers CEA and AFP' by Ke Lu , , 2022, https://doi.org/10.1039/D2BM00555G.

A highly sensitive silicon nanowire array sensor for joint detection of tumor markers CEA and AFP.

Liver cancer is one of the malignant tumors with the highest fatality rate and increasing incidence, which has no effective treatment plan. Early diagnosis and early treatment of liver cancer play a vital role in prolonging the survival period of patients and improving the cure rate. Carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) are two crucial tumor markers for liver cancer diagnosis.

An electrochemical biosensor based on few-layer MoS nanosheets for highly sensitive detection of tumor marker ctDNA.

An electrochemical biosensor based on few-layer molybdenum disulfide (MoS) nanosheets was fabricated for the highly sensitive detection of tumor marker circulating tumor DNA (ctDNA) in this paper. The MoS nanosheets with few layers were prepared by the shear stripping. Compared with the mechanical stripping method and the lithium ion intercalation method, this method is simpler to operate, and the prepared MoS nanosheets had good electrochemical activity.

Harvesting Water-Evaporation-Induced Electricity Based on Liquid-Solid Triboelectric Nanogenerator.

Harvesting energy from natural water evaporation has been proposed as a promising alternative to supply power for self-powered and low-power devices and systems, owing to its spontaneous, ubiquitous, and sustainability. Herein, an approach is presented for harvesting water-evaporation-induced electricity based on liquid-solid triboelectric nanogenerators (LS-TENGs), which has various advantages of easy preparation, substrate needless, and robustness. This developed harvester with porous Al O ceramic sheet can generate a continuous and stable direct current of ≈0.

A Review of Biosensors for Detecting Tumor Markers in Breast Cancer.

Breast cancer has the highest cancer incidence rate in women. Early screening of breast cancer can effectively improve the treatment effect of patients. However, the main diagnostic techniques available for the detection of breast cancer require the corresponding equipment, professional practitioners, and expert analysis, and the detection cost is high.

Localization of Laterally Confined Modes in a 2D Semiconductor Microcavity.

Monolayer semiconductor embedded planar microcavities are becoming a promising light-matter interacting system to uncover a wealth of photonic, excitonic, and polaritonic physics at the two-dimensional (2D) limit. In these 2D semiconductor microcavities employing the longitudinal Fabry-Perot resonance, major attention has been paid to the coupling of excitons with vertically confined cavity photons; by contrast, the lateral confinement effect on exciton-photon interactions is still elusive. Here we observe the localized distribution of laterally confined modes with discrete energies in a 2D semiconductor embedded microcavity.

Enhancement of Room-Temperature Photoluminescence and Valley Polarization of Monolayer and Bilayer WS via Chiral Plasmonic Coupling.

Transition-metal dichalcogenides with intrinsic spin-valley degree of freedom have enabled great potentials for valleytronic and optoelectronic applications. However, the degree of valley polarization is usually low under nonresonant excitation at room temperature due to the phonon-assisted intervalley scattering. Here, achiral and chiral Au arrays are designed to enhance the optical response and valley polarization in monolayer and bilayer WS.

Observation of Strong Valley Magnetic Response in Monolayer Transition Metal Dichalcogenide Alloys of MoWSe and MoWSe/WS Heterostructures.

Monolayer transition metal dichalcogenide (TMD) alloys have emerged as a unique material system for promising applications in electronics, optoelectronics, and spintronics due to their tunable electronic structures, effective masses of carriers, and valley polarization with various alloy compositions. Although spin-orbit engineering has been extensively studied in monolayer TMD alloys, the valley Zeeman effect in these alloys still remains largely unexplored. Here we demonstrate the enhanced valley magnetic response in MoWSe alloy monolayers and MoWSe/WS heterostructures probed by magneto-photoluminescence spectroscopy.

Strain manipulation of the polarized optical response in two-dimensional GaSe layers.

We report tunable optical performances of gallium selenide (GaSe) layers in phonon vibrations, band edge emission, circular polarization, and anisotropic response via strain manipulation. By applying a uniaxial tensile strain, frequency shift and peak broadening are observed in Raman spectra. A shrink in bandgap is demonstrated in photoluminescence (PL) spectra and confirmed by first-principles calculations.

Synthesis of Wafer-Scale Monolayer WS Crystals toward the Application in Integrated Electronic Devices.

Two-dimensional transition-metal dichalcogenides (TMDCs) possess unique electronic and optical properties, which open up a new opportunity for atomically thin optoelectronic devices. Synthesizing large-scale monolayer TMDCs on the SiO/Si substrate is crucial for practical applications, however, it remains a big challenge. In this work, a method which combines chemical vapor deposition (CVD) and thermal evaporation was employed to grow monolayer tungsten disulfide (WS) crystals.

Polarization-Controllable Plasmonic Enhancement on the Optical Response of Two-Dimensional GaSe Layers.

Resonant plasmonic coupling has been considered as a promising strategy to enhance the optical response and manipulate the polarization of two-dimensional (2D) layer materials toward the practical applications. Here, a hybrid structure with periodic Ag nanoprism arrays was designed and fabricated on 2D GaSe layers to enhance these optical properties. By using the optimized hybrid structure with well-matched resonance, significant enhanced Raman scattering and band edge emission were successfully realized, and it is also interestingly found that the higher enhancement would be achieved while decreasing the thickness of GaSe layers.

In-Plane Anisotropic Thermal Conductivity of Few-Layered Transition Metal Dichalcogenide Td-WTe.

2D Td-WTe has attracted increasing attention due to its promising applications in spintronic, field-effect chiral, and high-efficiency thermoelectric devices. It is known that thermal conductivity plays a crucial role in condensed matter devices, especially in 2D systems where phonons, electrons, and magnons are highly confined and coupled. This work reports the first experimental evidence of in-plane anisotropic thermal conductivities in suspended Td-WTe samples of different thicknesses, and is also the first demonstration of such anisotropy in 2D transition metal dichalcogenides.

Electrically Tunable Valley-Light Emitting Diode (vLED) Based on CVD-Grown Monolayer WS2.

Owing to direct band gap and strong spin-orbit coupling, monolayer transition-metal dichalcogenides (TMDs) exhibit rich new physics and great applicable potentials. The remarkable valley contrast and light emission promise such two-dimensional (2D) semiconductors a bright future of valleytronics and light-emitting diodes (LEDs). Though the electroluminescence (EL) has been observed in mechanically exfoliated small flakes of TMDs, considering real applications, a strategy that could offer mass-product and high compatibility is greatly demanded.

Mechanism of charge transfer and its impacts on Fermi-level pinning for gas molecules adsorbed on monolayer WS2.

Density functional theory calculations were performed to assess changes in the geometric and electronic structures of monolayer WS2 upon adsorption of various gas molecules (H2, O2, H2O, NH3, NO, NO2, and CO). The most stable configuration of the adsorbed molecules, the adsorption energy, and the degree of charge transfer between adsorbate and substrate were determined. All evaluated molecules were physisorbed on monolayer WS2 with a low degree of charge transfer and accept charge from the monolayer, except for NH3, which is a charge donor.

Chemically driven tunable light emission of charged and neutral excitons in monolayer WS₂.

Monolayer (1L) semiconducting transition metal dichacogenides (TMDs) possess remarkable physical and optical properties, promising for a wide range of applications from nanoelectronics to optoelectronics such as light-emitting and sensing devices. Here we report how the molecular adsorption can modulate the light emission and electrical properties of 1L WS2. The dependences of trion and exciton emission on chemical doping are investigated in 1L WS2 by microphotoluminescence (μPL) measurements, where different responses are observed and simulated theoretically.

High density GaN/AlN quantum dots for deep UV LED with high quantum efficiency and temperature stability.

High internal efficiency and high temperature stability ultraviolet (UV) light-emitting diodes (LEDs) at 308 nm were achieved using high density (2.5 × 10(9) cm(-2)) GaN/AlN quantum dots (QDs) grown by MOVPE. Photoluminescence shows the characteristic behaviors of QDs: nearly constant linewidth and emission energy, and linear dependence of the intensity with varying excitation power.

High Mg effective incorporation in Al-rich AlxGa1 - xN by periodic repetition of ultimate V/III ratio conditions.

According to first-principles calculations, the solubility of Mg as a substitute for Ga or Al in AlxGa1 - xN bulk is limited by large, positive formation enthalpies. In contrast to the bulk case, the formation enthalpies become negative on AlxGa1 - xN surface. In addition, the N-rich growth atmosphere can also be favorable to Mg incorporation on the surface by changing the chemical potentials.

Vacuum Rabi splitting of exciton-polariton emission in an AlN film.

The vacuum Rabi splitting of exciton-polariton emission is observed in cathodoluminescence (CL) and photoluminescence spectra of an AlN epitaxial film. Atomic force microscopy and CL measurements show that the film has an atomically flat surface, high purity, and high crystal quality. By changing the temperature, anticrossing behavior between the upper and lower polariton branch can be obtained in low temperature with a Rabi splitting of 44 meV, in agreement with the calculation.