Quantum geometry quadrupole-induced third-order nonlinear transport in antiferromagnetic topological insulator MnBiTe.

The study of quantum geometry effects in materials has been one of the most important research directions in recent decades. The quantum geometry of a material is characterized by the quantum geometric tensor of the Bloch states. The imaginary part of the quantum geometry tensor gives rise to the Berry curvature while the real part gives rise to the quantum metric.

Hexagonal Network of Photocurrent Enhancement in Few-Layer Graphene/InGaN Quantum Dot Junctions.

Strain in two-dimensional (2D) materials has attracted particular attention because of the remarkable modification of electronic and optical properties. However, emergent electromechanical phenomena and hidden mechanisms, such as strain-superlattice-induced topological states or flexoelectricity under strain gradient, remain under debate. Here, using scanning photocurrent microscopy, we observe significant photocurrent enhancement in hybrid vertical junction devices made of strained few-layer graphene and InGaN quantum dots.

Spectroscopy and Theoretical Modeling of Phonon Vibration Modes and Band Gap Energy of CuZnSn(S Se ) Bulk Crystals and Thin Films.

Semiconductor CuZnSn(S Se ) (CZTSSe) solid solution is considered as a perspective absorber material for solar cells. However, during its synthesis or deposition, any modification in the resulting optical properties is hardly predicted. In this study, experimental and theoretical analyses of CZTSSe bulk crystals and thin films are presented based on Raman scattering and absorption spectroscopies together with compositional and morphological characterizations.

Observation of Diffusion and Drift of the Negative Trions in Monolayer WS.

Monolayer transition metal dichalcogenides (ML-TMDCs) are a versatile platform to explore the transport dynamics of the tightly bound excitonic states. The diffusion of neutral excitons in various ML-TMDCs has been observed. However, the transport of charged excitons (trions), which can be driven by an in-plane electric field and facilitate the formation of an excitonic current, has yet been well investigated.

Theoretical study on the photocatalytic properties of 2D InX(X = S, Se)/transition metal disulfide (MoS and WS) van der Waals heterostructures.

Harvesting solar energy for artificial photosynthesis is an emerging field in alternative energy research. In this work, the photocatalytic properties of InX(X = S, Se)/transition metal disulfide (MoS and WS) van der Waals heterostructures have been investigated. The calculation results indicate that these heterostructures exhibit improved photocatalytic performance over that of isolated InX or transition metal disulfide monolayers.

Simulation and Experiment for Growth of High-Quality and Large-Size AlN Seed Crystals by Spontaneous Nucleation.

Seed crystals are the prerequisite for the growth of high quality and large size aluminum nitride (AlN) single crystal boules. The physical vapor transport (PVT) method is adopted to grow AlN seed crystal. However, this method is not available in nature.

New Power MOSFET with Beyond-1D-Limit - Trade-Off and Superior Reverse Recovery Characteristics.

The application of conventional power metal-oxide-semiconductor field-effect transistor (MOSFET) is limited by the famous one-dimensional "silicon limit" (1D-limit) in the trade-off relationship between specific on-resistance () and breakdown voltage (). In this paper, a new power MOSFET architecture is proposed to achieve a beyond-1D-limit - trade-off. Numerical TCAD (technology computer-aided design) simulations were carried out to comparatively study the proposed MOSFET, the conventional power MOSFET, and the superjunction MOSFET.

Interface charge-transfer induced intralayer excited-state biexcitons in graphene/WS van der Waals heterostructures.

Monolayer transition metal dichalcogenides (TMDCs) are an ideal platform for multi-carrier bound states, the excitons and trions of which have been well identified and investigated. However, the formation and identification of biexcitons with certain configurations are more complicated. Here, we report a strategy to generate the hole-trion bound state, i.

The Physical Vapor Transport Method for Bulk AlN Crystal Growth.

In this report, the development of physical vapor transport (PVT) methods for bulk aluminum nitride (AlN) crystal growth is reviewed. Three modified PVT methods with different features including selected growth at a conical zone, freestanding growth on a perforated sheet, and nucleation control with an inverse temperature gradient are discussed and compared in terms of the size and quality of the bulk AlN crystals they can produce as well as the process complexity. The PVT method with an inverse temperature gradient is able to significantly reduce the nucleation rate and realize the dominant growth of only one bulk AlN single crystal, and thus grow centimeter-sized bulk AlN single crystals.

Defect influence on in-plane photocurrent of InAs/InGaAs quantum dot array: long-term electron trapping and Coulomb screening.

Metamorphic InAs/InGaAs and InAs/InGaAs quantum dot (QD) arrays are known to be photosensitive in the telecommunication ranges at 1.3 and 1.55 μm, respectively; however, for photonic applications of these nanostructures, the effect of levels related to defects still needs in-depth investigation.

Interfacially Bound Exciton State in a Hybrid Structure of Monolayer WS and InGaN Quantum Dots.

van der Waals heterostructures that are usually formed using atomically thin transition-metal dichalcogenides (TMDCs) with a direct band gap in the near-infrared to the visible range are promising candidates for low-dimension optoelectronic applications. The interlayer interaction or coupling between two-dimensional (2D) layer and the substrate or between adjacent 2D layers plays an important role in modifying the properties of the individual 2D material or device performances through Coulomb interaction or forming interlayer excitons. Here, we report the realization of quasi-zero-dimensional (0D) photon emission of WS in a coupled hybrid structure of monolayer WS and InGaN quantum dots (QDs).

Interface Engineering of Monolayer MoS/GaN Hybrid Heterostructure: Modified Band Alignment for Photocatalytic Water Splitting Application by Nitridation Treatment.

Interface engineering is a key strategy to deal with the two-dimensional (2D)/three-dimensional (3D) hybrid heterostructure, since the properties of this atomic-layer-thick 2D material can easily be impacted by the substrate environment. In this work, the structural, electronic, and optical properties of the 2D/3D heterostructure of monolayer MoS on wurtzite GaN surface without and with nitridation interfacial layer are systematically investigated by first-principles calculation and experimental analysis. The nitridation interfacial layer can be introduced into the 2D/3D heterostructure by remote N plasma treatment to GaN sample surface prior to stacking monolayer MoS on top.

Improved Gate Dielectric Deposition and Enhanced Electrical Stability for Single-Layer MoS2 MOSFET with an AlN Interfacial Layer.

Transistors based on MoS2 and other TMDs have been widely studied. The dangling-bond free surface of MoS2 has made the deposition of high-quality high-k dielectrics on MoS2 a challenge. The resulted transistors often suffer from the threshold voltage instability induced by the high density traps near MoS2/dielectric interface or inside the gate dielectric, which is detrimental for the practical applications of MoS2 metal-oxide-semiconductor field-effect transistor (MOSFET).

Tunable interaction-induced localization of surface electrons in antidot nanostructured Bi2Te3 thin films.

Recently, a logarithmic decrease of conductivity has been observed in topological insulators at low temperatures, implying a tendency of localization of surface electrons. Here, we report quantum transport experiments on the topological insulator Bi2Te3 thin films with arrayed antidot nanostructures. With increasing density of the antidots, a systematic decrease is observed in the slope of the logarithmic temperature-dependent conductivity curves, indicating the electron-electron interaction can be tuned by the antidots.