Impact of Supply Chain Disruptions on Economic Growth: Insights From a Major Public Health Crisis.

Supply chain disruptions caused by major public health crises will severely impact the economic growth. The main purpose of this paper is to examine the above proposition, taking the strict lockdown policy and supply chain disruption in Hubei Province at the beginning of the COVID-19 epidemic as a case, to provide decision-making reference for the government in supply chain management under major public health crisis. To achieve this goal, this paper firstly measures the supply chain network of Hubei province via the multi-region and multi-sector value-added model; then empirically studies the impact of lockdown policy and supply chain disruption on provincial economic growth, with the monthly data of 31 provinces covering January 2018 to December 2022, by the Difference in Difference method.

Multiresistance states in ferro- and antiferroelectric trilayer boron nitride.

Stacking two atomic layers together can induce interlayer (sliding) ferroelectricity that is absent in their naturally occurring crystal forms. With the flexibility of two-dimensional materials, more layers could be assembled to give rise to even richer polarization states. Here, we show that three-layer boron nitride can host ferro- and antiferroelectric domains in the same sample.

Robust Weak Antilocalization Effect Up to ∼120 K in the van der Waals Crystal FeGeTe with Near-Room-Temperature Ferromagnetism.

The van der Waals FeGeTe is a 3d ferromagnetic metal with a high Curie temperature of 275 K. We report herein the observation of an exceptional weak antilocalization (WAL) effect that can persist up to 120 K in an FeGeTe nanoflake, indicating the dual nature with both itinerant and localized magnetism of 3d electrons. The WAL behavior is characterized by the magnetoconductance peak around zero magnetic field and is supported by the calculated localized nondispersive flat band around the Fermi level.

Measuring Band Modulation of MoS with Ferroelectric Gates.

Electronic properties of two-dimensional (2D) materials can be significantly tuned by an external electric field. Ferroelectric gates can provide a strong polarization electric field. Here, we report the measurements of the band structure of few-layer MoS modulated by a ferroelectric P(VDF-TrFE) gate with contact-mode scanning tunneling spectroscopy.

Signatures of the exciton gas phase and its condensation in monolayer 1T-ZrTe.

The excitonic insulator (EI) is a Bose-Einstein condensation (BEC) of excitons bound by electron-hole interaction in a solid, which could support high-temperature BEC transition. The material realization of EI has been challenged by the difficulty of distinguishing it from a conventional charge density wave (CDW) state. In the BEC limit, the preformed exciton gas phase is a hallmark to distinguish EI from conventional CDW, yet direct experimental evidence has been lacking.

Spatially Resolved Polarization Manipulation of Ferroelectricity in Twisted hBN.

Robust room-temperature interfacial ferroelectricity has been formed in the 2D limit by simply twisting two atomic layers of non-ferroelectric hexagonal boron nitride (hBN). A thorough understanding of this newly discovered ferroelectric system is required. Here, twisted hBN is used as a tunneling junction and it is studied at the nanometer scale using conductive atomic force microscopy.

Gut-Flora-Dependent Metabolite Trimethylamine-N-Oxide Promotes Atherosclerosis-Associated Inflammation Responses by Indirect ROS Stimulation and Signaling Involving AMPK and SIRT1.

Trimethylamine-N-oxide (TMAO), a gut-microbiota-dependent metabolite after ingesting dietary choline, has been identified as a novel risk factor for atherosclerosis through inducing vascular inflammation. However, the underlying molecular mechanism is poorly understood. Using an in vitro vascular cellular model, we found that the TMAO-induced inflammation responses were correlated with an elevation of ROS levels and downregulation of SIRT1 expression in VSMCs and HUVECs.

Natural p-n Junctions at the MoS Flake Edges.

Two-dimensional (2D) semiconductors are holding promises as channel materials for field-effect transistors. Compared to traditional three-dimensional (3D) semiconductors whose electronic and optical properties are hindered by dangling bonds and trap states at the surfaces, 2D materials with saturated chemical bonds on the surface maintain the excellent properties even when device thickness scales down to monolayer. However, dangling bonds are unavoidable at their edges, which are often overlooked and should have important effects on the devices.

Large Photomultiplication by Charge-Self-Trapping for High-Response Quantum Dot Infrared Photodetectors.

PbS colloidal quantum dots (CQDs) are emerging as promising candidates for next-generation, low-cost, and high-performance infrared photodetectors. Recently, photomultiplication has been explored to improve the detectivity of CQD infrared photodetectors by doping charge-trapping material into a matrix. However, this relies on remote doping that could influence carrier transfer giving rise to limited photomultiplication.

Visualizing Band Profiles of Gate-Tunable Junctions in MoS/WSe Heterostructure Transistors.

Heterostructure devices based on two-dimensional materials have been under intensive study due to their intriguing electrical and optical properties. One key factor in understanding these devices is their nanometer-scale band profiles, which is challenging to obtain in devices. Here, we use a technique named contact-mode scanning tunneling spectroscopy to directly visualize the band profiles of MoS/WSe heterostructure devices at different gate voltages with nanometer resolution.

Atomic Level Insights into Metal Halide Perovskite Materials by Scanning Tunneling Microscopy and Spectroscopy.

Metal halide perovskite materials (MHPMs) have attracted significant attention because of their superior optoelectronic properties and versatile applications. The power conversion efficiency of MHPM solar cells (PSCs) has skyrocketed to 25.5 %.

One-Dimensional Metal Embedded in Two-Dimensional Semiconductor in NbSiTe.

The ternary van der Waals material NbSiTe demonstrates many interesting properties as the content of Si is changed, ranging from metallic NbSiTe ( = 5/3) to narrow-gap semiconductor NbSiTe ( = 2) and with the emergence of one-dimensional Dirac fermion excitations in between. An in-depth understanding of their properties with different stoichiometry is important. Here we use scanning tunneling microscopy and spectroscopy to reveal that NbSiTe is a system with spontaneously developed and self-aligned one-dimensional metallic chains embedded in a two-dimensional semiconductor.

Detecting band profiles of devices with conductive atomic force microscopy.

Band profiles of electronic devices are of fundamental importance in determining their properties. A technique that can map the band profile of both the interior and edges of a device at the nanometer scale is highly demanded. Conventional scanning tunneling spectroscopy (STS) can map band structure at the atomic scale but is limited to the interior of large and conductive samples.

Promotion of CO Electrochemical Reduction via Cu Nanodendrites.

The electrochemical conversion of carbon dioxide (CO) to fuels and chemicals is an opportunity for sustainable energy research that can realize both renewable energy storage and negative carbon cycle feedback. However, the selective generation of multicarbon products is challenging because of the competitive hydrogen evolution reaction (HER) and protonation of the reacting adsorbate. Copper-based materials have been the most commonly studied catalysts for CO electroreduction due to their ability to produce a substantial amount of C products.

Interlayer Decoupling in 30° Twisted Bilayer Graphene Quasicrystal.

Stacking order has a strong influence on the coupling between the two layers of twisted bilayer graphene (BLG), which in turn determines its physical properties. Here, we report the investigation of the interlayer coupling of the epitaxially grown single-crystal 30°-twisted BLG on Cu(111) at the atomic scale. The stacking order and morphology of BLG is controlled by a rationally designed two-step growth process, that is, the thermodynamically controlled nucleation and kinetically controlled growth.

NbSiTe: A Stable Narrow-Gap Two-Dimensional Material with Ambipolar Transport and Mid-Infrared Response.

Two-dimensional (2D) materials with narrow band gaps (∼0.3 eV) are of great importance for realizing ambipolar transistors and mid-infrared (MIR) detections. However, most of the 2D materials studied to date have band gaps that are too large.

Discovery of Superconductivity in 2M WS with Possible Topological Surface States.

Recently the metastable 1T'-type VIB-group transition metal dichalcogenides (TMDs) have attracted extensive attention due to their rich and intriguing physical properties, including superconductivity, valleytronics physics, and topological physics. Here, a new layered WS dubbed "2M" WS , is constructed from 1T' WS monolayers, is synthesized. Its phase is defined as 2M based on the number of layers in each unit cell and the subordinate crystallographic system.

Electronic structures and unusually robust bandgap in an ultrahigh-mobility layered oxide semiconductor, BiOSe.

Semiconductors are essential materials that affect our everyday life in the modern world. Two-dimensional semiconductors with high mobility and moderate bandgap are particularly attractive today because of their potential application in fast, low-power, and ultrasmall/thin electronic devices. We investigate the electronic structures of a new layered air-stable oxide semiconductor, BiOSe, with ultrahigh mobility (~2.

Lateral Heterostructures Formed by Thermally Converting n-Type SnSe to p-Type SnSe.

Different two-dimensional (2D) materials, when combined together to form heterostructures, can exhibit exciting properties that do not exist in individual components. Therefore, intensive research efforts have been devoted to their fabrication and characterization. Previously, vertical and in-plane 2D heterostructures have been formed by mechanical stacking and chemical vapor deposition.

Two-Dimensional SnS: A Phosphorene Analogue with Strong In-Plane Electronic Anisotropy.

We study the anisotropic electronic properties of two-dimensional (2D) SnS, an analogue of phosphorene, grown by physical vapor transport. With transmission electron microscopy and polarized Raman spectroscopy, we identify the zigzag and armchair directions of the as-grown 2D crystals. The 2D SnS field-effect transistors with a cross-Hall-bar structure are fabricated.

Giant Frictional Drag in Double Bilayer Graphene Heterostructures.

We study the frictional drag between carriers in two bilayer graphene flakes separated by a 2-5 nm thick hexagonal boron nitride dielectric. At temperatures (T) lower than ∼10  K, we observe a large anomalous negative drag emerging predominantly near the drag layer charge neutrality. The anomalous drag resistivity increases dramatically with reducing T, and becomes comparable to the layer resistivity at the lowest T=1.

Band Alignment in WSe2-Graphene Heterostructures.

Using different types of WSe2 and graphene-based heterostructures, we experimentally determine the offset between the graphene neutrality point and the WSe2 conduction and valence band edges, as well as the WSe2 dielectric constant along the c-axis. In a first heterostructure, consisting of WSe2-on-graphene, we use the WSe2 layer as the top dielectric in dual-gated graphene field-effect transistors to determine the WSe2 capacitance as a function of thickness, and the WSe2 dielectric constant along the c-axis. In a second heterostructure consisting of graphene-on-WSe2, the lateral electron transport shows ambipolar behavior characteristic of graphene combined with a conductivity saturation at sufficiently high positive (negative) gate bias, associated with carrier population of the conduction (valence) band in WSe2.

Intrinsic disorder in graphene on transition metal dichalcogenide heterostructures.

Semiconducting transition metal dichalchogenides (TMDs) are a family of van der Waals bonded materials that have recently received interest as alternative substrates to hexagonal boron nitride (hBN) for graphene, as well as for components in novel graphene-based device heterostructures. We elucidate the local structural and electronic properties of graphene on TMD heterostructures through scanning tunneling microscopy and spectroscopy measurements. We find that crystalline defects intrinsic to TMDs induce substantial electronic scattering and charge carrier density fluctuations in the graphene.

Gate-tunable resonant tunneling in double bilayer graphene heterostructures.

We demonstrate gate-tunable resonant tunneling and negative differential resistance in the interlayer current-voltage characteristics of rotationally aligned double bilayer graphene heterostructures separated by hexagonal boron nitride (hBN) dielectric. An analysis of the heterostructure band alignment using individual layer densities, along with experimentally determined layer chemical potentials indicates that the resonance occurs when the energy bands of the two bilayer graphene are aligned. We discuss the tunneling resistance dependence on the interlayer hBN thickness, as well as the resonance width dependence on mobility and rotational alignment.