Bias-dependent photoresponse of T-WTegrown by chemical vapor deposition.

The type-II Weyl semimetal T-WTeis one of the wonder materials for high-performance optoelectronic devices. We report the self-powered T-WTephotodetectors and their bias-dependent photoresponse in the visible region (405, 520, 638 nm) driven by the bulk photovoltaic effect. The device shows the responsivity of 15.

Phase transition in WSeTe monolayers driven by charge injection and pressure: a first-principles study.

Alloying strategies permit new probes for governing structural stability and semiconductor-semimetal phase transition of transition metal dichalcogenides (TMDs). However, the possible structure and phase transition mechanism of the alloy TMDs, and the effect of an external field, have been still unclear. Here, the enrichment of the Te content in WSeTe monolayers allows for coherent structural transition from the H phase to the T' phase.

Optically Induced Multistage Phase Transition in Coherent Phonon-Dominated -GeTe.

Ultrafast photoexcitation can decouple the multilevel nonequilibrium dynamics of electron-lattice interactions, providing an ideal probe for dissecting photoinduced phase transition in solids. Here, real-time time-dependent density functional theory simulations combined with occupation-constrained DFT methods are employed to explore the nonadiabatic paths of optically excited -GeTe. Results show that the short-wavelength ultrafast laser is capable of generating full-domain carrier excitation and repopulation, whereas the long-wavelength ultrafast laser favors the excitation of lone pair electrons in the antibonded state.

Mid-infrared photoluminescence revealing internal quantum efficiency enhancement of type-I and type-II InAs core/shell nanowires: publisher's note.

This publisher's note contains corrections to Opt. Lett.47, 5208 (2022)10.

Directly measuring flexoelectric coefficients of the van der Waals materials.

Flexoelectricity originates from the electromechanical coupling interaction between strain gradient and polarization, broadly applied in developing electromechanical and energy devices. However, the study of quantifying the longitudinal flexoelectric coefficient () which is important for the application of atomic-scale two-dimensional (2D) materials is still in a slow-moving stage, owing to the technical challenges. Based on the free-standing suspension structure, this paper proposes a widely applicable method and a mensurable formula for determining the constant of layer-dependent 2D materials with high precision.

Tunable lattice dynamics and dielectric functions of two-dimensional BiOSe: striking layer and temperature dependent effects.

Two-dimensional (2D) BiOSe semiconductors with a narrow band gap and ultrahigh mobility have been regarded as an emerging candidate for optoelectronic devices, whereas the ambiguous phonon characteristics and optical properties still limit their future applications. Herein, high-quality centimeter-scale 2D BiOSe films are successfully synthesized to disclose the lattice dynamics and dielectric functions under the control of thickness and temperature. It has been demonstrated that the stronger electrostatic Bi-Se interactions result in a stiffened phonon vibration of thicker BiOSe layers.

Mid-infrared photoluminescence revealing internal quantum efficiency enhancement of type-I and type-II InAs core/shell nanowires.

Internal quantum efficiency (IQE) is an important figure of merit for photoelectric applications. While the InAs core/shell (c/s) nanowire (NW) is a promising solution for efficient quantum emission, the relationship between the IQE and shell coating remains unclear. This Letter reports mid-infrared PL measurements on InAs/InGaAs, InAs/AlSb, and InAs/GaSb c/s NWs, together with bare InAs NWs as a reference.

Ultra-Stable, Endurable, and Flexible SbTeSe Phase Change Devices for Memory Application and Wearable Electronics.

Flexible memory and wearable electronics represent an emerging technology, thanks to their reliability, compatibility, and superior performance. Here, an SbTeSe (STSe) phase change material was grown on flexible mica, which not only exhibited superior nature in thermal stability for phase change memory application but also revealed novel function performance in wearable electronics, thanks to its excellent mechanical reliability and endurance. The thermal stability of SbTe was improved obviously with the crystallization temperature elevated 60 K after Se doping, for the enhanced charge localization and stronger bonding energy, which was validated by the Vienna simulation package calculations.

Designing Monoclinic Heterophase Coexistence for the Enhanced Piezoelectric Performance in Ternary Lead-Based Relaxor Ferroelectrics.

Enhanced piezoelectric, dielectric properties and thermal stability in ternary relaxor-PbTiO based ferroelectric crystals are expected to develop the next-generation of electromechanical devices. However, due to their increased disorder compared to other ferroelectrics, designing a controllable phase boundary structure and engineered domain remains a challenging task. Here, we construct a monoclinic heterophase coexisting in a ternary Pb(InNb)O-Pb(MgNb)O-PbTiO single crystal with optimized composition and an ultrahigh piezoelectric coefficient of 1400 pC N, to quantify the correlation between spontaneous nanopolarity and phase heterogeneity, in an attempt to understand the origin of the exceptional functionalities.

Flexo-photoelectronic effect in n-type/p-type two-dimensional semiconductors and a deriving light-stimulated artificial synapse.

Flexoelectricity and photoelectricity with their coupled effect (the so-called flexo-photoelectronic effect), are of increasing interest in the study of electronics and optoelectronics in van der Waals layered semiconductors. However, the related device design is severely restricted owing to the ambiguous underlying physical nature of flexo-photoelectronic effects originating from the co-manipulation of light and strain-gradients. Here, flexoelectric polarization and the flexo-photoelectronic effect of few-layered semiconductors have been multi-dimensionally investigated from high-resolution microscopic characterization on the nanoscale, physics analysis, and deriving a device design.

Thermal Conductivity of Large-Area Polycrystalline MoSe Films Grown by Chemical Vapor Deposition.

It is of great importance to understand the thermal properties of MoSe films for electronic and optoelectronic applications. In this work, large-area polycrystalline MoSe films are prepared using a low-cost, controllable, large-scale, and repeatable chemical vapor deposition method, which facilitates direct device fabrication. Raman spectra and X-ray diffraction patterns indicate a hexagonal (2H) crystal structure of the MoSe film.

Ferroelectric-Modulated MoS Field-Effect Transistors as Multilevel Nonvolatile Memory.

Ferroelectric field-effect transistors (FeFETs) with semiconductors as the channel material and ferroelectrics as the gate insulator are attractive and/or promising devices for application in nonvolatile memory. In FeFETs, the conductivity states of the semiconductor are utilized to explore the polarization directions of the ferroelectric material. Herein, we report FeFETs based on a few layers of MoS on a 0.

Effects of SF decomposition components and concentrations on the discharge faults and insulation defects in GIS equipment.

Gas-insulated switchgear (GIS) is widely used across multiple electric stages and different power grid levels. However, the threat from several inevitable faults in the GIS system surrounds us for the safety of electricity use. In order to improve the evaluation ability of GIS system safety, we propose an efficient strategy by using machine learning to conduct SF decomposed components analysis (DCA) for further diagnosing discharge fault types in GIS.

Effects of composition and temperature on the exciton emission behaviors of Mo(S Se ) monolayer: experiment and theory.

Exploring the excitonic behavior of two-dimensional (2D) alloys is of great significance, which not only could promote the understanding of fundamental photophysics in optoelectric devices, but could also guide the functional improvement of future applications. Here, we demonstrate the controllable synthesis of monolayer Mo(S Se ) nanosheets using a one-step chemical vapor deposition method and systematical investigation on the exciton emission characteristics based on the temperature-dependent photoluminescence spectroscopy (PL) experiments. As a result, the tunable bandgap of Mo(S Se ) alloys between 1.

Ferroelectric and dipole control of band alignment in the two dimensional InTe/InSe heterostructure.

Two dimensional (2D) ferroelectric materials are gaining growing attention due to their nontrival ferroelectricity, and the 2D ferroelectric heterostructures with tunable electronic, optoelectronic, or even magnetic properties, show many novel properties that do not exist in their constituents. In this work, by using the first-principles calculations, we investigate the ferroelectric and dipole control of electronic structures of the 2D ferroelectric heterostructure InTe/InSe. It is found that band alignment is closely dependent on the ferroelectric polarization of InSe.

Spatially resolved and two-dimensional mapping modulated infrared photoluminescence spectroscopy with functional wavelength up to 20 μm.

The pixel-scale nonuniformity of the photoelectric response may be due either to the in-plane electronic inhomogeneity of the narrow-gap semiconductor or to the craft fluctuation during the fabrication process, which limits the imaging performance of the infrared focal plane array (FPA) photodetector. Accordingly, a nondestructive technique is most desirable for examining the spatial uniformity of the optoelectronic properties of the narrow-gap semiconductor to identify the origin of the FPA response nonuniformity. This article introduces a spatially resolved and two-dimensional mapping infrared photoluminescence (PL) technique, especially suitable for characterizing FPA narrow-gap semiconductors, based on the modulated PL method with a step-scan Fourier transform infrared spectrometer.

Electric manipulation of magnetism in bilayer van der Waals magnets.

The ferromagnetism of the two dimensional (2D) CrGeTe atomic layers with the perpendicular magnetic anisotropy and the Curie temperature 30-50 K has recently been experimentally confirmed. By performing the density-functional theory calculations, we demonstrate that the magnetic properties of bilayer CrGeTe can be flexibly tailored, due to the effective band structure tuning by the external electric field. The electric field induces the semiconductor-metal transition and redistributes charge and spin between the two layers.

Photoluminescence spectra of the Mnd-d multiplets transitions of zinc-blende MnTe epitaxial films: laser and deuterium lamp excitation study.

The luminescences of zinc-blende MnTe epitaxial films are respectively excited by a laser and deuterium lamp to study Mnd-d multiplets transitions. Besides the inclusion of the band gap, all other excited states related to Mnd-d transitions including T4(G4), T4(G4), A4[E4(G4)], T4(D4), E4(D4), and T2(I2) are observed. The shift and broadening of the T4(G4) and T4(G4) lines with increasing temperature are described by the electron-phonon coupling.

Midinfrared Photoluminescence up to 290 K Reveals Radiative Mechanisms and Substrate Doping-Type Effects of InAs Nanowires.

Photoluminescence (PL) as a conventional yet powerful optical spectroscopy may provide crucial insight into the mechanism of carrier recombination and bandedge structure in semiconductors. In this study, mid-infrared PL measurements on vertically aligned InAs nanowires (NWs) are realized for the first time in a wide temperature range of up to 290 K, by which the radiative recombinations are clarified in the NWs grown on n- and p-type Si substrates, respectively. A dominant PL feature is identified to be from the type-II optical transition across the interfaces between the zinc-blend (ZB) and the wurtzite (WZ) InAs, a lower-energy feature at low temperatures is ascribed to impurity-related transition, and a higher-energy feature at high temperatures originates in the interband transition of the WZ InAs being activated by thermal-induced electron transfer.

Infrared photoreflectance investigation of resonant levels and band edge structure in InSb.

Temperature-dependent infrared photoreflectance (PR) is employed on InSb for clarifying resonant levels (RLs) and band edge structure. Abundant PR features are well resolved around the bandgap and are verified to be of electronic inter-level transitions rather than the Franz-Keldysh oscillations. The evolution of the critical energies with temperature reveals the nature of the PR processes, from which one acceptor RL, two donor RLs, and a shallow acceptor level are quantitatively identified, and a detailed band edge structure is derived.