A Waveguide-Integrated Two-Dimensional Light-Emitting Diode Based on p-Type WSe2/n-Type CdS Nanoribbon Heterojunction.

Transition metal dichalcogenides (TMDs) have emerged as two-dimensional (2D) building blocks to construct nanoscale light sources. To date, a wide array of TMD-based light-emitting devices (LEDs) have been successfully demonstrated. Yet, their atomically thin and planar nature entails an additional waveguide/microcavity for effective optical routing/confinement. In this sense, integration of TMDs with electronically active photonic nanostructures to form a functional heterojunction is of crucial importance for 2D optoelectronic chips with reduced footprint and higher integration capacity. Here, we report a room-temperature waveguide-integrated light-emitting device based on a p-type monolayer (ML) tungsten diselenide (WSe2) and n-type cadmium sulfide (CdS) nanoribbon (NR) heterojunction diode. The hybrid LED exhibited clear rectification under forward biasing, giving pronounced electroluminescence (EL) at 1.65 eV from exciton resonances in ML WSe2. The integrated EL intensity against the driving current shows a superlinear profile at a high current level, implying a facilitated carrier injection via intervalley scattering. By leveraging CdS NR waveguides, the WSe2 EL can be efficiently coupled and further routed for potential optical interconnect functionalities. Our results manifest the waveguided LEDs as a dual-role module for TMD-based optoelectronic circuitries.

Van der Waals epitaxial growth and optoelectronics of a vertical MoS2/WSe2 p-n junction.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted extensive attention due to their unique electronic and optical properties. In particular, TMDs can be flexibly combined to form diverse vertical van der Waals (vdWs) heterostructures without the limitation of lattice matching, which creates vast opportunities for fundamental investigation of novel optoelectronic applications. Here, we report an atomically thin vertical p-n junction WSe2/MoS2 produced by a chemical vapor deposition method. Transmission electron microscopy and steady-state photoluminescence experiments reveal its high quality and excellent optical properties. Back gate field effect transistor (FET) constructed using this p-n junction exhibits bipolar behaviors and a mobility of 9 cm2/(V·s). In addition, the photodetector based on MoS2/WSe2 heterostructures displays outstanding optoelectronic properties (R = 8 A/W, D* = 2.93 × 1011 Jones, on/off ratio of 104), which benefited from the built-in electric field across the interface. The direct growth of TMDs p-n vertical heterostructures may offer a novel platform for future optoelectronic applications.

Double-Gate MoS2 Field-Effect Transistors with Full-Range Tunable Threshold Voltage for Multifunctional Logic Circuits.

Multifunctional reconfigurable devices, with higher information capacity, smaller size, and more functions, are urgently needed and draw most attention in frontiers in information technology. 2D semiconductors, ascribing to ultrathin body and easy electrostatic control, show great potential in developing reconfigurable functional units. This work proposes a novel double-gate field-effect transistor architecture with equal top and bottom gate (TG and BG) and realizes flexible optimization of the subthreshold swing (SS) and threshold voltage (VTH ). While the TG and BG are used simultaneously, as a single gate to drive the transistor, ultralow average SS value of 65.5 mV dec-1 can be obtained in a large current range over 104 , enabling the application in high gain inverter. While one gate is used to initialize the channel doping, full logic swing inverter circuit with high noise margin (over 90%) is demonstrated. Such device prototype is further extended for designing reconfigurable logic applications and can be dynamically switched and well maintained between binary and ternary logics. This study provides important concept and device prototype for future multifunctional logic applications.

Predictors of Poor Outcome in Patients with Minor Ischemic Stroke by Using Magnetic Resonance Imaging.

Although the symptoms of minor ischemic stroke are mild, poor prognosis may occur if left untreated. Therefore, it is particularly important to identify the predictors that associated with poor outcome in patients presenting minor ischemic stroke. The aim of this study was to elucidate the predictors of progression by using magnetic resonance imaging (MRI). A total of 516 patients diagnosed with minor ischemic stroke were enrolled in this study. They were divided into two groups, the progressive group and non-progressive group, according to the modified Rankin Scale (mRS) with the cutoff value of 2 points on day 90 after the stroke onset. We compared the results of MRI scan between the two groups to investigate the potential independent determinants of progression using multivariate logistic regression analysis. Ninety of 516 patients (17.44%) underwent progression. There were 9 factors that were independently associated with poor outcome, including age (OR = 1.045, 95% CI 1.017-1.074), heart disease (OR = 2.021, 95% CI 1.063-3.841), baseline NIHSS score (OR = 1.662, 95% CI 1.177-2.347), limb motor disturbance (OR = 2.430, 95% CI 1.010-5.850), ataxia (OR = 2.929, 95% CI 1.188-7.221), early neurological deterioration (OR = 50.994, 95% CI 17.659-147.258), diameter of infarction (OR = 1.279, 95% CI 1.075-1.521), non-responsible vessel size (OR = 2.518, 95% CI 1.145-5.536), and large-artery atherosclerosis (OR = 2.010, 95% CI 1.009-4.003). This study indicated that age, heart disease, motor disturbance of limb, ataxia, early neurological deterioration, diameter of infarction, size of non-responsible vessels, and large-artery atherosclerosis can be used to assess the prognosis of patients with minor ischemic stroke.

Characteristic linear lesions and longitudinally extensive spinal cord lesions in Chinese patients with neuromyelitis optica.

OBJECTIVE: To investigate the characteristics of the linear lesions and longitudinally extensive spinal cord (LESC) lesions in Chinese patients with neuromyelitis optica (NMO). METHODS: The medical records and magnetic resonance imaging (MRI) scans of 29 patients with NMO were reviewed. The frequencies and distributions of linear and LESC lesions were compared against those displayed by 22 multiple sclerosis (MS) patients. Furthermore, the association of lesions with aquaporin-4 IgG (AQP4-IgG) antibody was investigated. RESULTS: The NMO patients had significantly more linear lesions than MS patients (48.3 vs 0%, p<0.001). In the NMO group, linear lesions were found in the medulla in 34.5% (10/29) of patients, across the medullospinal region in 10.3% (3/29) and in the spinal cord in 13.8% (4/29). LESC lesions can be seen more frequently in NMO than MS (72.4 vs 22.7%, p<0.001). In 93.1% (27/29) of the NMO cases, the axial section of the spinal MRI showed lesions on the central gray matter only, whilst the spinal lesions in MS were usually located in the peripheral white matter (72.7%, 16/22). The AQP4-IgG antibody was found to be associated with both linear and LESC lesions in NMO cases. CONCLUSIONS: High frequency of linear lesions and LESC lesions were found in Chinese patients with NMO and linear lesions were correlated with AQP4-IgG antibody.