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Interlayer interactions in 2D WS <sub/>2</sub> /MoS <sub/>2</sub> heterostructures monolithically grown by <i>in situ</i> physical vapor deposition
摘要： The understanding of the interlayer interactions in vertical heterostructures of two-dimensional (2D) transition metal dichalcogenides (TMDCs) is essential to exploit their advanced functions for next-generation optoelectronics and electronics. Here we demonstrate a monolithic stacking of TMDC heterostructures with 2D MoS2 and WS2 layers via in situ physical vapor deposition. We find that the kinetically sputtered atoms are able to overcome the interlayer van der Waals forces between the vertical layers, leading to a substantial number of randomly oriented stacks with various twist angles. Our X-ray photoelectron spectroscopy results reveal a type II heterojunction for 2D WS2/MoS2, showing a band alignment with a conduction band offset of 0.41 eV and a valence band offset of 0.25 eV. In particular, we observed a remarkable interlayer coupling and associated exciton relaxation at the hetero-interface due to the misoriented stacks. By analyzing the band structures and charge densities of the vertical stacks using first-principles calculations, we reveal that the interlayer coupling is a function of the interlayer distance and is relatively insensitive to the angle of misorientation.
关键词： band alignment,2D materials,physical vapor deposition,interlayer coupling,heterostructures
更新于2025-09-19 17:15:36
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Energy Band Alignment of a Monolayer MoS <sub/>2</sub> with SiO <sub/>2</sub> and Al <sub/>2</sub> O <sub/>3</sub> Insulators from Internal Photoemission
摘要： Internal photoemission of electrons (IPE) from large area one monolayer 2H-MoS2 films synthesized on top of amorphous (a-) SiO2 or Al2O3 is used to determine the energy of the semiconductor valence band (VB) relative to the reference level of the insulator conduction band (CB). This allows us to compare the VB top energy in MoS2 to that of the (100)Si substrate crystal at the interface with the same insulator. Despite the CB in a–Al2O3 is found to be ~1 eV below that in SiO2 as measured relative to the Si VB edge, the authors observe nearly no shift of the spectral threshold in the case of IPE from the MoS2 VB. This observation indicates violation of electroneutrality at the MoS2/a–Al2O3 interface causing an increase in barrier by ~1 eV. This conclusion is supported by the much weaker field dependence of the IPE threshold at the MoS2/a–Al2O3 interface compared to the MoS2/a–SiO2 one, suggesting the presence of negative charges and/or interface dipoles. Therefore, the commonly accepted electron affinity rule (EAR) appears to be not appropriate to describe the band alignment at 2D/insulator interfaces.
关键词： internal photoemission spectroscopy,MoS2,electron affinity,electron barrier,band alignment
更新于2025-09-19 17:15:36
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P-6.14: The impact of Alignment film and process on the trailing problem of the display
摘要： The PSVA product using the alignment film with initiator can greatly reduce the UV1 time during the alignment process，, but at the same time causes the trajectory of the moving picture trajectory (hereinafter referred to trailing). In this paper, different alignment processes were applied in the same PSVA product, it has been found that the smear can be improved by increasing the UV1 voltage OR UV1 time
关键词： UV1 Voltage,alignment film,UV1 Time
更新于2025-09-19 17:15:36
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Scalable fabrication of geometry-tunable self-aligned superlattice photonic crystals for spectrum-programmable light trapping
摘要： Superlattice photonic crystals (SPhCs) possess considerable potentials as building blocks for constructing high-performance devices because of their great flexibilities in optical manipulation. From the prospective of practical applications, scalable fabrication of SPhCs with large-area uniformity and precise geometrical controllability has been considered as one prerequisite but still remains a challenge. In this work, we developed an anodic aluminum oxide template-guided approach to realize Ni SPhCs with the maximum area (~500 mm2) ever reported. By virtue of the dual-pore self-alignment effect arising from the periodic anodization electric fields, uniform structures over large areas were obtained for Ni SPhCs. Meanwhile, the geometrical parameters for every array of nanopores in terms of pore depth, size, and morphology can be independently controlled due to the sequential pore-opening. Based on the experimental observation about the geometrical dependence of the light absorption for Ni dual-pore SPhCs, we further fabricated Ni SPhCs with simultaneously-shaped nanopores and nanoconcaves, which not only simplified the fabrication process but also achieved omnidirectional stably-strong (~95%) light absorption spectra. Optical simulations elucidated that surface plasmon resonance and cavity resonance are responsible for the strong light trapping. Notably, the fabrication technique is applicable to Ni SPhCs with different periodicities, leading to spectrally programmable light absorption spectra. With Ni SPhCs as solar absorber, the water evaporation efficiency of a solar steam generation system and the open circuit voltage of a solar thermoelectric generator demonstrated 2.3 and 2.5 times improvement, respectively.
关键词： geometrically tunable,surface plasmon resonance,self alignment,superlattice photonic crystal,cavity resonance,anodic aluminum oxide template
更新于2025-09-19 17:15:36
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On-Orbit Camera Misalignment Estimation Framework and Its Application to Earth Observation Satellite
摘要： Despite the efforts for precise alignment of imaging sensors and attitude sensors before launch, the accuracy of pre-launch alignment is limited. The misalignment between attitude frame and camera frame is especially important as it is related to the localization error of the spacecraft, which is one of the essential factors of satellite image quality. In this paper, a framework for camera misalignment estimation is presented with its application to a high-resolution earth-observation satellite—Deimos-2. The framework intends to provide a solution for estimation and correction of the camera misalignment of a spacecraft, covering image acquisition planning to mathematical solution of camera misalignment. Considerations for effective image acquisition planning to obtain reliable results are discussed, followed by a detailed description on a practical method for extracting many GCPs automatically using reference ortho-photos. Patterns of localization errors that commonly occur due to the camera misalignment are also investigated. A mathematical model for camera misalignment estimation is described comprehensively. The results of simulation experiments showing the validity and accuracy of the misalignment estimation model are provided. The proposed framework was applied to Deimos-2. The real-world data and results from Deimos-2 are presented.
关键词： earth-observation satellite,on-orbit calibration,camera misalignment,boresight alignment
更新于2025-09-19 17:15:36
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A Robot-Driven 3D Shape Measurement System for Automatic Quality Inspection of Thermal Objects on a Forging Production Line
摘要： The three-dimensional (3D) geometric evaluation of large thermal forging parts online is critical to quality control and energy conservation. However, this online 3D measurement task is extremely challenging for commercially available 3D sensors because of the enormous amount of heat radiation and complexity of the online environment. To this end, an automatic and accurate 3D shape measurement system integrated with a fringe projection-based 3D scanner and an industrial robot is presented. To resist thermal radiation, a double filter set and an intelligent temperature control loop are employed in the system. In addition, a time-division-multiplexing trigger is implemented in the system to accelerate pattern projection and capture, and an improved multi-frequency phase-shifting method is proposed to reduce the number of patterns required for 3D reconstruction. Thus, the 3D measurement efficiency is drastically improved and the exposure to the thermal environment is reduced. To perform data alignment in a complex online environment, a view integration method is used in the system to align non-overlapping 3D data from different views based on the repeatability of the robot motion. Meanwhile, a robust 3D registration algorithm is used to align 3D data accurately in the presence of irrelevant background data. These components and algorithms were evaluated by experiments. The system was deployed in a forging factory on a production line and performed a stable online 3D quality inspection for thermal axles.
关键词： production line,thermal axles,industrial robot,3D measurement,3D data alignment
更新于2025-09-19 17:15:36
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[IEEE 2019 International Conference on Quality, Reliability, Risk, Maintenance, and Safety Engineering (QR2MSE) - Zhangjiajie, China (2019.8.6-2019.8.9)] 2019 International Conference on Quality, Reliability, Risk, Maintenance, and Safety Engineering (QR2MSE) - Degradation Study of 830nm Laser Diodes Based on PSpice Model and Accelerated Tests
摘要： In this paper, we consider the systematic design and implementation of grasping and transportation by a mobile robot with low implementation complexity. The study is mainly divided into three aspects: 1) design of a mechanical gripper and an arm mounted on the robot for grasping; 2) design of the hardware-communication configuration (HCC) for transportation guidance that includes a destination beacon and a sensor system on the robot that working together with some designed event-triggered communication mechanisms, among which the unique bearing-alignment mechanism is designed to calibrate the heading direction of the robot, the HCC is low cost in the sense of low energy consumption; and 3) an effective and low-cost heuristic transportation algorithm that is tightly incorporated with the designed HCC in an event-triggered manner. The particular contribution is the tight integration of the heuristic transportation algorithm and the HCC, and the very simple nature of the transportation algorithm dues to this integration, which passes some computational functions to the HCC. Numerical simulations and experiments are presented, showing the effectiveness of the proposed system.
关键词： mobile robot manipulation,manipulation,object grasping,localization,path planning,sensor fusion,transportation,navigation guidance,motion planning,Bearing-alignment mechanism,direction alignment,obstacle avoidance
更新于2025-09-19 17:13:59
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Epitaxial growth and determination of the band alignment for NixMg1-xO/MgO interface by laser molecular beam epitaxy
摘要： By laser molecular beam epitaxy, single crystalline NixMg1-xO films have been successfully synthesized on MgO(100) surface. The in situ reflection high-energy electron diffraction patterns show that the induced O2 background gas with at least 1.0 × 10?3 Pa is necessary to the epitaxial growth of NixMg1-xO films. The X-ray diffraction patterns reveal the single-phase growth along (200) direction. The energy band alignment at the interface is investigated by employing in situ X-ray photoelectron spectroscopy. The valence band offsets are determined to be from 1.47 eV to 1.50 eV with the decrease of Ni content (0.39 / 0.35). Furthermore, the work function is evaluated by using in situ ultraviolet photoemission spectroscopy, indicating the values from 4.33 eV to 4.64 eV. This study provides a promising guidance for the solar-blind device design and fabrication.
关键词： Work function,X-ray photoelectron spectroscopy,Band alignment,Ultraviolet photoemission spectroscopy,Laser molecular beam epitaxy
更新于2025-09-19 17:13:59
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Internal Atomic-Scale Structure Determination and Band Alignment of IIa??VI Quantum Dot Heterostructures
摘要： This work shows that ZnTe/CdSe core/shell quantum dots synthesized by a standard literature procedure in actuality have an alloyed CdxZn1?xTe core. We employ X-ray absorption spectroscopy (XAS) at all four K-shell ionization edges (Zn, Te, Cd, and Se) and perform global ?tting analysis to extract the ?rst-shell bond distances. We combine our XAS results with transmission electron microscopy (TEM) sizing and elemental analyses, which allows us to propose models of the internal particle structure. Our multimodal characterization approach con?rms (1) the presence of Cd?Te bonds, (2) cation alloying in the particle core (and the absence of anion alloying), and (3) a patchy pure-phase CdSe shell. We synthesize particles of di?erent shell thicknesses and performed synthetic control studies that allowed us to discard a ZnTe/CdTe/CdSe core/shell/shell structure and con?rm the alloyed core/shell structure. Our structural analysis is extended with electronic band structure calculations and UV/vis absorption spectroscopy, demonstrating that the alloyed CdxZn1?xTe/CdSe core/shell quantum dots exhibit a direct band gap, di?erent from the predicted type II band alignment of the intended ZnTe/CdSe core/shell quantum dots. This study highlights the challenges with synthesizing II?VI quantum dot heterostructures and the power of XAS for understanding the internal structure of heterogeneous nanoparticles.
关键词： X-ray absorption spectroscopy,alloyed core,core/shell,band alignment,quantum dots
更新于2025-09-19 17:13:59
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Preparation and Characterization of Semi-Alicyclic Polyimide Resins and the Derived Alignment Layers for Liquid Crystal Display Technology
摘要： Uniform alignment of rigid-rod liquid crystal (LC) molecules under applied voltage is critical for achievement of high-quality display for thin-film transistor-driven liquid crystal display devices (TFT-LCDs). The polymeric components that can induce the alignment of randomly aligned LC molecules are called alignment layers (ALs). In the current work, a series of organo-soluble polyimide (SPI) ALs were designed and prepared from an alicyclic dianhydride, hydrogenated 3,3',4,4'-biphenyltetracarboxylic dianhydride (HBPDA), and various aromatic diamines, including 4,4'-methylenedianiline (MDA) for SPI-1, 4,4',5,5'-aminodianiline (NDA) for SPI-2, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane (TMMDA) for SPI-3, and 3,3',5,5'-diethyl-4,4'-diaminodiphenylmethane (DMDEDA) for SPI-4. The derived SPI resins were all soluble in N-methyl-2-pyrrolidone (NMP). Four SPI alignment agents with the solid content of 6 wt.% were prepared by dissolving the SPI resins in the mixed solvent of NMP and butyl cellulose (BC) (NMP/BC = 80:20, weight ratio). Liquid crystal minicells were successfully fabricated using the developed SPI varnishes as the LC molecule alignment components. The SPI ALs showed good alignment ability for the LC molecules with the pretilt angles in the range of 1.58°–1.97°. The LC minicells exhibited good optoelectronic characteristics with voltage holding ratio (VHR) values higher than 96%. The good alignment ability of the SPI ALs is mainly attributed to the good comprehensive properties of the SPI layers, including high volume resistivity, high degree of imidization at the processing temperature (230 °C), good rubbing resistance, good thermal stability with glass transition temperatures (Tgs) higher than 260 °C, and excellent optical transparency with the transmittance higher than 97% at the wavelength of 550 nm.
关键词： alignment layer,semi-alicyclic polyimide,thin-film transistor-driven liquid crystal display device (TFT-LCD),residual direct circuit voltage,voltage holding ratio
更新于2025-09-19 17:13:59