High‐Performance Transition Metal Dichalcogenide Photodetectors Enhanced by Self‐Assembled Monolayer Doping

Most doping research into transition metal dichalcogenides (TMDs) has been mainly focused on the improvement of electronic device performance. Here, the effect of self‐assembled monolayer (SAM)‐based doping on the performance of WSe₂‐ and MoS₂‐based transistors and photodetectors is investigated. The achieved doping concentrations are ≈1.4 × 10¹¹ for octadecyltrichlorosilane (OTS) p‐doping and ≈10¹¹ for aminopropyltriethoxysilane (APTES) n‐doping (nondegenerate). Using this SAM doping technique, the field‐effect mobility is increased from 32.58 to 168.9 cm² V^?1 s in OTS/WSe₂ transistors and from 28.75 to 142.2 cm² V^?1 s in APTES/MoS₂ transistors. For the photodetectors, the responsivity is improved by a factor of ≈28.2 (from 517.2 to 1.45 × 10⁴ A W^?1) in the OTS/WSe₂ devices and by a factor of ≈26.4 (from 219 to 5.75 × 10³ A W^?1) in the APTES/MoS₂ devices. The enhanced photoresponsivity values are much higher than that of the previously reported TMD photodetectors. The detectivity enhancement is ≈26.6‐fold in the OTS/WSe₂ devices and ≈24.5‐fold in the APTES/MoS₂ devices and is caused by the increased photocurrent and maintained dark current after doping. The optoelectronic performance is also investigated with different optical powers and the air‐exposure times. This doping study performed on TMD devices will play a significant role for optimizing the performance of future TMD‐based electronic/optoelectronic applications.     

一种基于多传感器的红外图像正则化超分辨率算法

提出一种红外图像多传感器超分辨率重建算法。 算法存在两个关键点:一是有效利用两类图像的相关性;二是针对红外图像的特点利用其自 身信息 构造正则化模型。采用相位一致性算法提取可见光图像边缘,利用此边缘信息对正则化模型 加权,以 充分利用可见光和红外图像的相关性;将一阶梯度锐化算子引入总广义变分模型,构成针对 红外 图像特点的正则化模型;最后采用一阶主-对偶优化算法求得加权后模型的最优解。实验表 明,本文算法可获得边缘清晰的重建结果,并且有效抑制噪声,在主观视觉效果和客观评价 指标方面均优于其他算法。     

Semi-transparent thin film solar cells by a solution process

Easily processed, low cost, and highly efficient solar cells are desirable for photovoltaic conversion of solar energy to electricity. We present the fabrication of precursor solution processed CuInGaS2 (CIGS) thin film solar cells on transparent indium tin oxide (ITO) substrates. The CIGS absorber film was prepared by a spin-coating method, followed by two successive heat treatment processes. The first annealing process was on a hot plate at 300 °C for 30 min in air to remove carbon impurities in the film; this was followed by a sulfurization process at 500 °C in an H₂S(1%)/Ar environment to form a polycrystalline CIGS film. The absorber film with an optical band-gap of 1.52 eV and a thickness of about 1.1 µm was successfully synthesized. Because of the usage of a transparent glass substrate, a bifacial CIGS thin film device could be achieved; its power conversion efficiency was measured to be 6.64% and 0.96% for front and rear illumination, respectively, under standard irradiation conditions.     

Effects of walking speed and age on the directional stride regularity and gait variability in treadmill walking

Journal of Mechanical Science and Technology - In Inertial measurement unit (IMU) based gait analysis systems, the shoe-type sensor is not commonly used, unlike trunk attached sensors. The purpose...     

Effects of the Surface Contact on the Uncertainty in Indentation Yield Strength: Surface Roughness and Angular Misalignment

Metals and Materials International - We suggest a method for accurately estimating the uncertainty of indentation yield strength determined from the modified Meyer relation as a mathematical...     

Finite element analysis of the impact of liner thickness and hydrodynamic limit on the penetration depth of a shaped charge warhead

In this work, an identification method for the hydrodynamic limit of shaped charge jets (SCJs) is proposed using numerical analysis. To identify the hydrodynamic limit, we consider situations where two targets of the same density but different strengths are penetrated by the same SCJ. As a result, the SCJ corresponding with the hydrodynamic theory is a jet region with a velocity larger than 4 km/s. In addition, an investigation based on the hydrodynamic limit and liner thickness indicates that the penetration capability before and after the hydrodynamic limit improves as apex thickness decreases and base thickness increases, respectively. The simple and clear identification of the hydrodynamic limit is expected to be possible using the proposed method. Accordingly, a selective and organized liner thickness design can be developed.

     

Removal of cesium ion in aqueous solution using immobilized sericite beads

To apply sericite effectively in the adsorption process, it was immobilized by entrapment method using sodium alginate. Since the immobilized sericite beads have excellent mechanical strength and swelling characteristics, channeling of flow and the increase of pressure drop were not observed through column operations. In addition, it was also stable under pH 10 and 45 °C of cesium solution. The maximum adsorption capacity and Langmuir adsorption constant was 1.430mg/g and 2.329 L/mg, respectively, at initial pH 5 of cesium solution in batch type and the Langmuir model with higher correlation coefficient of 0.997 fits experimental data better than Freundlich model. The breakthrough point emerged around 15 (1.0 mL/min) and 20 bed volumes (0.5 mL/min), and the cesium ions bound to the immobilized sericite beads were readily released and quantitatively recovered by a few bed volumes of 1.0M of HNO₃ solution. Furthermore, bed volumes of cesium ions for firstly reused sericite beads can be still maintained as 18, which shows good regeneration ability.     

Phosphaannulation of Aryl‐ and Benzylphosphonic Acids with Unactivated Alkenes via Palladium‐Catalyzed C?H Activation/Oxidative Cyclization Reaction

An efficient phosphaannulation via palladium(II)‐catalyzed C H activation/oxidative cyclization by the 6‐endo mode is reported for the synthesis of 3‐substituted phosphaisocoumarins from the reaction of arylphosphonic acids with unactivated alkenes under aerobic conditions. Also, α,α‐disubstituted benzylphosphonic acids were phosphaannulated with unactivated alkenes, producing phosphaisochromanones having (Z)‐alkylidenyl groups via anti‐phosphoryloxypalladation by the 6‐exo mode.

     

Three-dimensional locomotion control of single-legged robot: Resonance hopping and running direction

This study proposes a locomotion controller for a single-legged robot. The locomotion controller comprises five parts: virtual spring, height control, forward velocity control, body attitude control, and angular momentum control. First, we propose an effective method called a virtual spring to generate a springy force using a linear actuator. Two virtual springs are adopted to compute the energy exchange and to compensate the energy loss during hopping. A simple and intuitive method is proposed to implement resonance oscillation in terms of energy loss. A height controller is proposed based on the resonance oscillation using a virtual spring. In addition, a running direction controller, which has never been resolved in previous studies, is proposed. This novel controller can remove the unexpected angular momentum about the yaw direction during running. All of the proposed algorithms and methods are validated through dynamic simulations.