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Nanosecond-pulsed laser welding of metallic glass
摘要： This study explores nanosecond-pulsed (ns-pulsed) laser welding on the metallic glass (MG) ribbons of four compositions: Fe78Si9B13, Zr65Cu15Ni10Al10, La55Ni20Al25 and Ce65Al10Cu20Co5. All MGs can be welded in the air by the ns-pulsed laser, and the crystallization of the welding joints can be avoided by proper control of the laser parameters. By varying the travel speed, pulse duration and repetition frequency, the critical crystallization time of MG can be quickly detected in a high-throughput way by ns-pulsed laser welding. At the optimal processing conditions, 70–90% of the tensile strength of the parent melt-spun ribbon can be preserved in the welded MG ribbons. The mechanical strength is well linked to the pro?le of the welding joint, which suggests a simple method to evaluate the welding quality. A welding parameter map has been established based on the experiments, and it is concluded that the laser power-density per sample thickness and the interaction time are the key factors that control the crystallization and strength of the welding joints. The map is valid for a broad range of MG compositions of all sample thickness, and thus the optimal processing conditions may be extended to all MGs with equivalent glass-forming ability.
关键词： Strength,Metallic glass,Thickness,Laser welding,Welding parameter map
更新于2025-09-23 15:19:57
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The effect of absorber thickness on the planar Sb2S3 thin film solar cell: Trade-off between light absorption and charge separation
摘要： Antimony sulfide Sb2S3 is an emerging photovoltaic absorber, which has been widely studied on synthesis route, device structure and interface. However, its device performance is still limited by the unoptimized Sb2S3 absorber and interface recombination, in which the neglected character of thickness is unclear. Here, the effect of absorber thickness on the Sb2S3 thin film solar cell was carefully investigated in the range of 80–620 nm, aiming to reveal the trade-off between charge separation and light absorption in the device. The characterization of JV and Sb2S3 thin film found that too thin Sb2S3 would lower the VOC and JSC, which was attributed to the severe shunt and insufficient absorption. While the too thick Sb2S3 would hinder the charge separation. This tendency was also confirmed by the performance simulation of device. Finally, the best power conversion efficiency of 4.96% is achieved with a 544 nm Sb2S3 absorber. This work provides the guidance to optimize the thickness of Sb2S3 absorber for solar cells.
关键词： Absorption,Recombination,Thickness,Solar cells,Sb2S3
更新于2025-09-23 15:19:57
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Damage characteristics of laser plasma shock wave on rear surface of fused silica glass
摘要： The damage to the rear surface of fused silica under the action of high power laser is more severe than that incurred by the front surface, which hinders the improvement in the energy of the high power laser device. For optical components, the ionization breakdown by laser is a main factor causing damage, particularly with laser plasma shock waves, which can cause large-scale fracture damage in fused silica. In this study, the damage morphology is experimentally investigated, and the characteristics of the damage point are obtained. In the theoretical study, the coupling and transmission of the shock wave in glass are investigated based on the ?nite element method. Thus, both the magnitude and the orientation of stress are obtained. The damage mechanism of the glass can be explained based on the fracture characteristics of glass under different stresses and also on the variation of the damage zone’s Raman spectrum. In addition, the in?uence of the glass thickness on the damage morphology is investigated. The results obtained in this study can be used as a reference in understanding the characteristics and mechanism of damage characteristics induced by laser plasma shock waves.
关键词： different thickness,Raman spectroscopy,rear surface of fused silica,laser-induced plasma,?nite element method
更新于2025-09-23 15:19:57
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Thickness-modulated in-plane Bi<sub>2</sub>O<sub>2</sub>Se homojunctions for ultrafast high-performance photodetectors
摘要： Bi2O2Se thin film could be one of the promising material candidates for next-generation electronic and optoelectronic applications with the outstanding electrical and optoelectrical properties. However, the device performance based on the Bi2O2Se thin films was not fully explored in the photodetecting area. Considering that the electrical properties such as carrier mobility, work function and energy band structure of Bi2O2Se are thickness dependent, in-plane Bi2O2Se homojunctions consisting of layers with different thickness were successfully synthesized by CVD method across the terraces on the mica substrates, where terraces were created during the mica surface layer peeling off process. In this way, effective internal electrical fields were built up along the Bi2O2Se homojunctions, The Bi2O2Se in-plane homojunctions exhibiting diode-like rectification behavior with an on/off ratio of 102, what’s more, the photodetectors based on which were featured as highly sensitive and ultrafast with the maximum photoresponsivity of 2.5A/W and the lifetime of 4.8μs. Compared with the Bi2O2Se uniform thin films, the photo-electric conversion efficiency was greatly improved for the in-plane homojunctions.
关键词： thickness modulation,in-plane homojunction,photodetectors,Bi2O2Se
更新于2025-09-23 15:19:57
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[IEEE 2019 International Conference on Advanced Computer Science and information Systems (ICACSIS) - Bali, Indonesia (2019.10.12-2019.10.13)] 2019 International Conference on Advanced Computer Science and information Systems (ICACSIS) - Wavelength Selection of Persimmon Leafusing Decision Tree Method in Visible Near-Infrared Imaging
摘要： The intima-media thickness (IMT) of the common carotid artery (CCA) is an established indicator of cardiovascular disease (CVD). There have been reports about the difference between the left and the right sides of the CCA IMT and their relation with CVD. In this paper, we propose an automated system based on image normalization, speckle reduction ?ltering, and snakes segmentation, for segmenting the CCA, perform IMT measurements, and provide the differences between the left and the right sides. The study was performed on 1104 longitudinal-section ultrasound images acquired from 568 men and 536 women out of which 125 had cardiovascular symptoms (CVD). A cardiovascular expert manually delineated the IMT for the normal and the CVD groups. The corresponding (normal versus CVD) IMT mean ± standard deviation values for the left and the right sides were 0.74 ± 0.24 versus 0.87 ± 0.24 mm and 0.70 ± 0.17 versus 0.80 ± 0.18 mm, respectively. The main ?ndings of this paper can be summarized as follows: 1) there was no signi?cant difference between the CCA left side IMT and the right side IMT. These ?ndings suggest that the measurement of the CCA IMT on one side only is needed for the normal group (and this is in agreement with other studies); 2) there were statistical signi?cant differences for the IMT measurements between the normal group and the CVD group for both the left and the right sides; 3) there was an increasing linear relationship of the left and the right IMT measurements with age for the normal group; and to a lesser extend for the CVD group; 4) no statistical signi?cant differences were found between the manual and the automated IMT measurements for both sides; and 5) the best result for classi?cation disease modeling, using support vector machines, to discriminate between the normal and the CVD groups was a 64% ± 3.5% correct classi?cations score when using both the left and the right IMT automated measurements. Further research is required for estimating differences and similarities between left and right intima media complex structure and morphology and their variability with texture features for differentiating between the normal and the CVD group.
关键词： B-mode,IMT,common carotid artery,cardiovascular disease,ultrasound imaging,intima media thickness
更新于2025-09-23 15:19:57
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Surface based variable thickness slicing modeling for laser metal deposition
摘要： Laser metal deposition (LMD) has been a promising additive manufacturing technology widely used in mold rapid manufacturing. In order to improve the capacity of LMD for complex curved surface structures, a surface based variable thickness slicing (S-VTS) model is proposed to adaptively generate the LMD process based on the geometric characteristics of structures. Two deposition strategies in scanning and overlapping directions are designed to enable variable thickness of each cladding layer by dynamically adjusting the scanning speed and overlapping rate. To improve the surface quality and forming efficiency, the discrete particle swarm optimization (DPSO) algorithm is adopt to optimize the process parameters of S-VTS model, including the number of cladding layer, scanning pass, and segment per pass. Several experiments are conducted to form the cuboid samples with wavy and freeform surface and verify the feasibility of the S-VTS model. The results demonstrate that under the open-loop control condition, the geometric accuracy, surface quality, and efficiency of the proposed method is improved in comparison with uniform thickness slicing (UTS) deposition. Moreover, heterogeneous microstructure is always generated by the S-VTS method in terms of grain size and growth direction.
关键词： Variable thickness slicing (S-VTS),Laser metal deposition (LMD),Curved surface,Mold
更新于2025-09-23 15:19:57
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Laser-based Thickness Control in a Double-Side Polishing System for Silicon Wafers
摘要： Thickness control is a critical process of automated polishing of large and thin Si wafers in the semiconductor industry. In this paper, an elaborate double-side polishing (DSP) system is demonstrated, which has a polishing unit with feedback control of wafer thickness based on the scan data of a laser probe. Firstly, the mechanical structure, as well as the signal transmission and control of the DSP system, are discussed, in which the thickness feedback control is emphasized. Then, the precise positioning of the laser probe is explored to obtain the continuous and valid scan data of the wafer thickness. After that, a B-spline model is applied for the characterization of the wafer thickness function to provide the thickness control system with credible thickness deviation information. Finally, experiments of wafer-thickness evaluation and control are conducted on the presented DSP system. With the advisable number of control points in B-spline fitting, the thickness variation can be effectively controlled in wafer polishing with the DSP system, according to the experimental results of curve fitting and the statistical analysis of the experimental data.
关键词： silicon wafer,B-spline fitting,double-side polishing system,laser probe,thickness control
更新于2025-09-23 15:19:57
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Enhancing electrostatic coupling in silicon quantum dot array by dual gate oxide thickness for large-scale integration
摘要： We propose a structure with word/bit line control for a two-dimensional quantum dot array, which allows random access for arbitrary quantum dots with a small number of control signals. To control multiple quantum dots with a single signal, every quantum dot should have a wide operating voltage allowance to overcome the property variations. We fabricate two-dimensional quantum dot arrays using silicon-complementary-metal-oxide-semiconductor technology with an alternating dual-standard gate oxide thickness. The quantum dots are designed to have an allowable operating voltage window of 0.2 V to control the number of electrons, which is a window one order of magnitude wider than that of previous works. The proposed structure enables both easy fabrication and operation for multiple quantum dots and will pave the way for practical use of large-scale quantum computers.
关键词： electrostatic coupling,dual gate oxide thickness,quantum dot array,large-scale integration,silicon-complementary-metal-oxide-semiconductor technology
更新于2025-09-23 15:19:57
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Assessment with Controlled In-Situ Data of the Dependence of L-Band Radiometry on Sea-Ice Thickness
摘要： The European Space Agency (ESA) Soil Moisture and Ocean Salinity (SMOS) and the National Aeronautics and Space Administration (NASA) Soil Moisture Active Passive (SMAP) missions are providing brightness temperature measurements at 1.4 GHz (L-band) for about 10 and 4 years respectively. One of the new areas of geophysical exploitation of L-band radiometry is on thin (i.e., less than 1 m) Sea Ice Thickness (SIT), for which theoretical and empirical retrieval methods have been proposed. However, a comprehensive validation of SIT products has been hindered by the lack of suitable ground truth. The in-situ SIT datasets most commonly used for validation are affected by one important limitation: They are available mainly during late winter and spring months, when sea ice is fully developed and the thickness probability density function is wider than for autumn ice and less representative at the satellite spatial resolution. Using Upward Looking Sonar (ULS) data from the Woods Hole Oceanographic Institution (WHOI), acquired all year round, permits overcoming the mentioned limitation, thus improving the characterization of the L-band brightness temperature response to changes in thin SIT. State-of-the-art satellite SIT products and the Cumulative Freezing Degree Days (CFDD) model are veri?ed against the ULS ground truth. The results show that the L-band SIT can be meaningfully retrieved up to 0.6 m, although the signal starts to saturate at 0.3 m. In contrast, despite the simplicity of the CFDD model, its predicted SIT values correlate very well with the ULS in-situ data during the sea ice growth season. The comparison between the CFDD SIT and the current L-band SIT products shows that both the sea ice concentration and the season are fundamental factors in?uencing the quality of the thickness retrieval from L-band satellites.
关键词： sea ice thickness,retrieval model validation,upward looking sonar,Arctic,Soil Moisture Active Passive (SMAP),Soil Moisture and Ocean Salinity (SMOS) mission,L-band radiometry
更新于2025-09-23 15:19:57
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Influence of Film Thickness on the Electronic Band Structure and Optical Properties of Pa??Ia??N CH <sub/>3</sub> NH <sub/>3</sub> PbI <sub/>3a??x</sub> Cl <sub/>x</sub> Perovskite Solar Cells
摘要： The phenomenal optoelectronic properties of lead halide perovskites have spurred a remarkable worldwide effort to develop them as photovoltaic materials. The morphology and crystal structure of the films have a profound effect on the characteristics and performance of devices; however, the influence of underlying hole transport layers (HTLs) or electron transport layers (ETLs) and film thickness on the film morphology and electronic characteristics remains unclear. In this work, we have studied the characteristics of perovskite films with variable thickness, including the morphological, crystal, optical properties and electronic band structure of these films using scanning electron microscopy (SEM), X-ray diffraction (XRD) and ultraviolet-visible (UV-vis) absorption spectra. The corresponding performance of perovskite solar cells (PSCs) devices was correlated with the different thicknesses of perovskite films. Additionally, ultraviolet photoelectron spectroscopy (UPS) results show that for the optimized perovskite thickness (310 nm) the interfacial dipole (?) formed at the interface with the substrate reaches its highest value of 0.23 eV. Hence, this strong dipole compared to other thicknesses allows the carriers to be swept out efficiently.
关键词： Film thickness,Perovskite,Solar cell,Interfacial dipole
更新于2025-09-23 15:19:57