Pub Date : 2024-09-11DOI: 10.1088/1361-6463/ad76bd
Chun Liu, Ming Xu, Shengtao Chen, Li Sun, Liqing Zhang, Qianqian Li and Jiahao Wang
The lock-on effect of the gallium arsenide photoconductive semiconductor switch (GaAs PCSS) at repetition rate aggravates the current crowding and electric field distortion, which significantly increases the risk of switch damage or even failure. Therefore, it is of great significance to investigate the carrier transport and the heat generation mechanism for improving the performance and longevity of GaAs PCSS in lock-on mode. The internal physical process of an opposed-electrode GaAs PCSS at low optical energy and strong electric field is analyzed and discussed by experiment and simulation. A device-circuit hybrid simulation is employed to investigate the transient electric field, carrier concentration, and lattice temperature distribution within the GaAs PCSS in lock-on mode. The device temperature exhibits a positive correlation with the applied bias electric field, resulting in a peak temperature of 1037.25 K at an electric field of 38 kV cm−1. The temperature distribution within the GaAs PCSS indicates a greater possibility for thermal breakdown and damage near the electrodes.
{"title":"Analysis of carrier dynamics and thermal effect of the GaAs photoconductive semiconductor switch in lock-on mode","authors":"Chun Liu, Ming Xu, Shengtao Chen, Li Sun, Liqing Zhang, Qianqian Li and Jiahao Wang","doi":"10.1088/1361-6463/ad76bd","DOIUrl":"https://doi.org/10.1088/1361-6463/ad76bd","url":null,"abstract":"The lock-on effect of the gallium arsenide photoconductive semiconductor switch (GaAs PCSS) at repetition rate aggravates the current crowding and electric field distortion, which significantly increases the risk of switch damage or even failure. Therefore, it is of great significance to investigate the carrier transport and the heat generation mechanism for improving the performance and longevity of GaAs PCSS in lock-on mode. The internal physical process of an opposed-electrode GaAs PCSS at low optical energy and strong electric field is analyzed and discussed by experiment and simulation. A device-circuit hybrid simulation is employed to investigate the transient electric field, carrier concentration, and lattice temperature distribution within the GaAs PCSS in lock-on mode. The device temperature exhibits a positive correlation with the applied bias electric field, resulting in a peak temperature of 1037.25 K at an electric field of 38 kV cm−1. The temperature distribution within the GaAs PCSS indicates a greater possibility for thermal breakdown and damage near the electrodes.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"60 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1088/1361-6463/ad726d
J Y Yang, X J Xiang, Z J Tan, X K Zhang, S Pan, J Chen and G Z Xu
In this study, we report on the detailed atomic ordering, magnetic and electrical properties of the Heusler alloy Mn2CoAl, studied via combined experimental methods and a theoretical calculation approach. Our studies confirm the Hg2CuTi-type crystal structure of Mn2CoAl with 25% anti-site disorder between Mn (B:1/4,1/4,1/4) and Co(C:1/2,1/2,1/2) sites. Neutron powder diffraction measurements identify the antiparallel spin couplings between Mn:A↓ and Mn:B↑, Co:C↑, resulting in a ferrimagnetic structure with a net magnetic moment of ∼1.6 μB at room temperature. In terms of the electronic calculations, we find that the anti-site atoms will contribute large densities of states at the Fermi level, thus destroying the spin gapless band structure and making Mn2CoAl a normal ferrimagnetic metal. This report is intended to establish a basic understanding of the structure and physical properties of Mn2CoAl.
{"title":"Heusler alloy Mn2CoAl: structural, magnetic and electronic properties","authors":"J Y Yang, X J Xiang, Z J Tan, X K Zhang, S Pan, J Chen and G Z Xu","doi":"10.1088/1361-6463/ad726d","DOIUrl":"https://doi.org/10.1088/1361-6463/ad726d","url":null,"abstract":"In this study, we report on the detailed atomic ordering, magnetic and electrical properties of the Heusler alloy Mn2CoAl, studied via combined experimental methods and a theoretical calculation approach. Our studies confirm the Hg2CuTi-type crystal structure of Mn2CoAl with 25% anti-site disorder between Mn (B:1/4,1/4,1/4) and Co(C:1/2,1/2,1/2) sites. Neutron powder diffraction measurements identify the antiparallel spin couplings between Mn:A↓ and Mn:B↑, Co:C↑, resulting in a ferrimagnetic structure with a net magnetic moment of ∼1.6 μB at room temperature. In terms of the electronic calculations, we find that the anti-site atoms will contribute large densities of states at the Fermi level, thus destroying the spin gapless band structure and making Mn2CoAl a normal ferrimagnetic metal. This report is intended to establish a basic understanding of the structure and physical properties of Mn2CoAl.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"7 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1088/1361-6463/ad76b9
Shengpeng Yang, Hongyang Guo, Ping Zhang, Shaomeng Wang and Yubin Gong
The plasmon excitation in two-dimensional electron gases is a significant way of achieving micro-nanoscale terahertz (THz) devices. Here, we establish a kinetic simulation model to study the THz plasmons amplification in a semiconductor double-quantum-well system with counter-streaming electron drift velocities. By comparing the simulation results with theoretical dispersion relations, we confirm two competing mechanisms of negative damping suitable for THz amplification: Cherenkov-type two-stream instability and a new non-Cherenkov mechanism called kinetic relaxation instability. The former is caused by the interlayer coupling of two slow plasmon modes and only exists when the drift velocities are much greater than the fermi velocities. The latter is a statistical effect caused by the momentum relaxation of electron-impurity scattering and predominates at lower drift velocities. We show that an approximate kinetic dispersion relation can accurately predict the wave growth rates of the two mechanisms. The results also indicate that the saturated plasmonic waves undergo strong nonlinearities such as wave distortion, frequency downshift, wave-packet formation, and spectrum broadening. The nonlinear evolution can be interpreted as the merging of bubble structures in the electron phase-space distribution. The present results not only reveal the potential mechanisms of the plasmonic instabilities in double-layer 2DEGs, but also provide a new guideline for the design of on-chip THz amplifiers.
{"title":"Negative damping of terahertz plasmons in counter-streaming double-layer two-dimensional electron gases","authors":"Shengpeng Yang, Hongyang Guo, Ping Zhang, Shaomeng Wang and Yubin Gong","doi":"10.1088/1361-6463/ad76b9","DOIUrl":"https://doi.org/10.1088/1361-6463/ad76b9","url":null,"abstract":"The plasmon excitation in two-dimensional electron gases is a significant way of achieving micro-nanoscale terahertz (THz) devices. Here, we establish a kinetic simulation model to study the THz plasmons amplification in a semiconductor double-quantum-well system with counter-streaming electron drift velocities. By comparing the simulation results with theoretical dispersion relations, we confirm two competing mechanisms of negative damping suitable for THz amplification: Cherenkov-type two-stream instability and a new non-Cherenkov mechanism called kinetic relaxation instability. The former is caused by the interlayer coupling of two slow plasmon modes and only exists when the drift velocities are much greater than the fermi velocities. The latter is a statistical effect caused by the momentum relaxation of electron-impurity scattering and predominates at lower drift velocities. We show that an approximate kinetic dispersion relation can accurately predict the wave growth rates of the two mechanisms. The results also indicate that the saturated plasmonic waves undergo strong nonlinearities such as wave distortion, frequency downshift, wave-packet formation, and spectrum broadening. The nonlinear evolution can be interpreted as the merging of bubble structures in the electron phase-space distribution. The present results not only reveal the potential mechanisms of the plasmonic instabilities in double-layer 2DEGs, but also provide a new guideline for the design of on-chip THz amplifiers.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"10 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-10DOI: 10.1088/1361-6463/ad703a
Gazal Gupta, Raghvendra Gupta, Amit Gupta and Deepak Kumar
Based on its availability, cost and stability, rechargeable Mg batteries (RMBs) are potential candidates to fulfill the futuristic demand for high energy density storage devices. However, they are minimally explored due to sluggish Mg ion diffusion in cathode materials. Literature suggests that the Chevrel phase (CP) (Mo6S8) holds promise as a cathode (positive electrode) for RMBs due to its open structure and self-healing properties during cycling. This study reports the electrochemical performance of Mo6S8 (synthesized using cost effective precursors (Cu–Mo–MoS2)) as a cathode for RMBs for the first time. The development of Mo6S8 is a two-step process: (i) synthesis of Cu2Mo6S8 via high energy milling method using Cu, Mo and MoS2 as precursors and (ii) leaching of Cu from Cu2Mo6S8. The morphological and structural characteristics of the developed materials are recorded using x-ray diffraction and field emission scanning electron microscopy. The developed Mo6S8 is cuboid-shaped with a rhombohedral unit cell. To record the electrochemical performance of Mo6S8 as a positive electrode for rechargeable Mg batteries (RMBs), CR2016 type half-cells are fabricated. It is observed that the initial discharge capacity was 89 mA h g−1 at a current density of 25 mA g−1 (1C = 128 mA g−1). Interestingly, the capacity increases from 89 to ≈100 mA h g−1 during 50 cycles which is higher than reported in the literature. The coulombic efficiency (CE) of ≈90% is observed for 100 cycles. Additionally, the over-potential decreases with an increase in cycle number. Importantly, the authors explained the diffusion behavior of Mg ions in Mo6S8 with 0.4 M 2(PhMgCl)-AlCl3/THF (APC) electrolyte via cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic intermittent titration (GITT) technique. The diffusion coefficients have been calculated and fall in the range of 10−8−10−14 cm2 s−1. Also, the authors explain the effect of outer site activation during cycling on the diffusion kinetics of the materials using the GITT technique. This investigation of diffusion kinetics of Mg ions in Mo6S8 may pave the way for evaluating various CPs as electrode materials for future rechargeable magnesium battery systems.
可充电镁电池（RMB）具有易得性、成本低和稳定性等优点，是满足未来对高能量密度存储设备需求的潜在候选材料。然而，由于镁离子在阴极材料中扩散缓慢，对它们的研究还很少。文献表明，Chevrel 相（CP）（Mo6S8）因其开放式结构和循环过程中的自修复特性，有望成为人民币的阴极（正极）。本研究首次报道了作为人民币阴极的 Mo6S8（使用成本低廉的前驱体（Cu-Mo-MoS2）合成）的电化学性能。Mo6S8 的开发分为两步：(i) 以 Cu、Mo 和 MoS2 为前驱体，通过高能研磨法合成 Cu2Mo6S8；(ii) 从 Cu2Mo6S8 中浸出 Cu。利用 X 射线衍射和场发射扫描电子显微镜记录了所开发材料的形态和结构特征。所开发的 Mo6S8 呈立方体状，具有斜方体单胞。为了记录作为可充电镁电池（RMB）正极的 Mo6S8 的电化学性能，制作了 CR2016 型半电池。据观察，在电流密度为 25 mA g-1 （1C = 128 mA g-1）时，初始放电容量为 89 mA h g-1。有趣的是，在 50 个循环期间，容量从 89 mA h g-1 增加到 ≈100 mA h g-1，高于文献报道的水平。循环 100 次后，库仑效率（CE）≈90%。此外，过电位随着循环次数的增加而降低。重要的是，作者通过循环伏安法、电化学阻抗光谱法和电静电间歇滴定（GITT）技术解释了镁离子在 0.4 M 2(PhMgCl)-AlCl3/THF (APC) 电解质的 Mo6S8 中的扩散行为。计算得出的扩散系数在 10-8-10-14 cm2 s-1 之间。此外，作者还利用 GITT 技术解释了循环过程中外位点活化对材料扩散动力学的影响。这项关于镁离子在 Mo6S8 中扩散动力学的研究可能会为评估各种氯化石蜡作为未来可充电镁电池系统的电极材料铺平道路。
{"title":"Electrochemical studies and diffusion kinetics in the Chevrel phase (Mo6S8) for rechargeable Mg batteries","authors":"Gazal Gupta, Raghvendra Gupta, Amit Gupta and Deepak Kumar","doi":"10.1088/1361-6463/ad703a","DOIUrl":"https://doi.org/10.1088/1361-6463/ad703a","url":null,"abstract":"Based on its availability, cost and stability, rechargeable Mg batteries (RMBs) are potential candidates to fulfill the futuristic demand for high energy density storage devices. However, they are minimally explored due to sluggish Mg ion diffusion in cathode materials. Literature suggests that the Chevrel phase (CP) (Mo6S8) holds promise as a cathode (positive electrode) for RMBs due to its open structure and self-healing properties during cycling. This study reports the electrochemical performance of Mo6S8 (synthesized using cost effective precursors (Cu–Mo–MoS2)) as a cathode for RMBs for the first time. The development of Mo6S8 is a two-step process: (i) synthesis of Cu2Mo6S8 via high energy milling method using Cu, Mo and MoS2 as precursors and (ii) leaching of Cu from Cu2Mo6S8. The morphological and structural characteristics of the developed materials are recorded using x-ray diffraction and field emission scanning electron microscopy. The developed Mo6S8 is cuboid-shaped with a rhombohedral unit cell. To record the electrochemical performance of Mo6S8 as a positive electrode for rechargeable Mg batteries (RMBs), CR2016 type half-cells are fabricated. It is observed that the initial discharge capacity was 89 mA h g−1 at a current density of 25 mA g−1 (1C = 128 mA g−1). Interestingly, the capacity increases from 89 to ≈100 mA h g−1 during 50 cycles which is higher than reported in the literature. The coulombic efficiency (CE) of ≈90% is observed for 100 cycles. Additionally, the over-potential decreases with an increase in cycle number. Importantly, the authors explained the diffusion behavior of Mg ions in Mo6S8 with 0.4 M 2(PhMgCl)-AlCl3/THF (APC) electrolyte via cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic intermittent titration (GITT) technique. The diffusion coefficients have been calculated and fall in the range of 10−8−10−14 cm2 s−1. Also, the authors explain the effect of outer site activation during cycling on the diffusion kinetics of the materials using the GITT technique. This investigation of diffusion kinetics of Mg ions in Mo6S8 may pave the way for evaluating various CPs as electrode materials for future rechargeable magnesium battery systems.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"178 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-10DOI: 10.1088/1361-6463/ad726f
Tao Shi, Ge Jin, Hong Zhang and Sheng Zou
We have constructed a transverse modulated magnetometer based on spin alignment in a paraffin-coated 85 Rb cell operated in a geophysical magnetic field of 47.1 µT. When an orthogonal driving magnetic field ( axis) is resonant on the Larmor frequency ( axis), we have proposed a new method to zero the static residual magnetic fields in the transverse plane and achieved a sensitivity of with bandwidth of 200 Hz. The repump light ( ) redistributes the populations in the ground state, rendering the state dark. This effect significantly amplifies the optical rotation signals nearly fourfold. The numerical solution of the Liouville equation is in good agreement with the experimental results. By using perturbation treatment and employing appropriate approximations, the derived analytical expressions for optical rotation are deduced to succinctly elucidate the dynamics of atomic alignment under parametric modulation. These outcomes could be extended for the advancement of an alignment magnetometer that has been designed to detect a weak magnetic signal in the geophysical range.
{"title":"A 85Rb transverse modulation magnetometer in the geophysical range based on atomic alignment states","authors":"Tao Shi, Ge Jin, Hong Zhang and Sheng Zou","doi":"10.1088/1361-6463/ad726f","DOIUrl":"https://doi.org/10.1088/1361-6463/ad726f","url":null,"abstract":"We have constructed a transverse modulated magnetometer based on spin alignment in a paraffin-coated 85 Rb cell operated in a geophysical magnetic field of 47.1 µT. When an orthogonal driving magnetic field ( axis) is resonant on the Larmor frequency ( axis), we have proposed a new method to zero the static residual magnetic fields in the transverse plane and achieved a sensitivity of with bandwidth of 200 Hz. The repump light ( ) redistributes the populations in the ground state, rendering the state dark. This effect significantly amplifies the optical rotation signals nearly fourfold. The numerical solution of the Liouville equation is in good agreement with the experimental results. By using perturbation treatment and employing appropriate approximations, the derived analytical expressions for optical rotation are deduced to succinctly elucidate the dynamics of atomic alignment under parametric modulation. These outcomes could be extended for the advancement of an alignment magnetometer that has been designed to detect a weak magnetic signal in the geophysical range.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"61 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223159","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-10DOI: 10.1088/1361-6463/ad760e
Sicheng Cao, Zhenxuan Chen, Runxuan Zhang, Chaoxian Tang, Zijun Chen, Ruixing Nie, Feng Zhao, Shenyi Huang and Zhengyong Song
Holography plays a significant role in optical research and has been utilized in numerous applications. Metasurface holograms are attracting more and more attention with the advancement of their efficient wavefront reshaping. However, the realization of multi-channel holograms and dynamic switching of them still remain challenging in the terahertz band. In this paper, anisotropic vanadium dioxide (VO2) metasurfaces are used to realize four-channel holograms at 1.5 THz. It is assembled by a set of VO2 meta-atoms with independent phase control for different channels. Depending on the polarization of incident wave and the state of VO2, four channels are independently selected. After optimization to eliminate crosstalk between top and bottom layers, two holograms are projected under x- and y-polarized incidences when VO2 is metallic. Similarly, two additional holograms are achieved as VO2 is insulating. As a novel solution to terahertz multi-channel holography, this work may be applied to compact optical system and high-volume optical encryption.
全息技术在光学研究中发挥着重要作用，并被广泛应用于各种领域。随着高效波前重塑技术的发展，元面全息图正吸引着越来越多的关注。然而，在太赫兹波段实现多通道全息图及其动态切换仍是一项挑战。本文利用各向异性的二氧化钒（VO2）元表面实现了 1.5 太赫兹的四通道全息图。它由一组可对不同通道进行独立相位控制的二氧化钒元原子组装而成。根据入射波的偏振和 VO2 的状态，可独立选择四个通道。经过优化以消除顶层和底层之间的串扰后，当 VO2 为金属时，在 x 偏振和 y 偏振入射波下投射出两幅全息图。同样，当 VO2 为绝缘层时，还能获得另外两幅全息图。作为太赫兹多通道全息技术的新型解决方案，这项研究成果可应用于紧凑型光学系统和大批量光学加密。
{"title":"Anisotropic vanadium dioxide-based metasurfaces for polarization-multiplexed holograms in the terahertz region","authors":"Sicheng Cao, Zhenxuan Chen, Runxuan Zhang, Chaoxian Tang, Zijun Chen, Ruixing Nie, Feng Zhao, Shenyi Huang and Zhengyong Song","doi":"10.1088/1361-6463/ad760e","DOIUrl":"https://doi.org/10.1088/1361-6463/ad760e","url":null,"abstract":"Holography plays a significant role in optical research and has been utilized in numerous applications. Metasurface holograms are attracting more and more attention with the advancement of their efficient wavefront reshaping. However, the realization of multi-channel holograms and dynamic switching of them still remain challenging in the terahertz band. In this paper, anisotropic vanadium dioxide (VO2) metasurfaces are used to realize four-channel holograms at 1.5 THz. It is assembled by a set of VO2 meta-atoms with independent phase control for different channels. Depending on the polarization of incident wave and the state of VO2, four channels are independently selected. After optimization to eliminate crosstalk between top and bottom layers, two holograms are projected under x- and y-polarized incidences when VO2 is metallic. Similarly, two additional holograms are achieved as VO2 is insulating. As a novel solution to terahertz multi-channel holography, this work may be applied to compact optical system and high-volume optical encryption.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"73 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223162","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-10DOI: 10.1088/1361-6463/ad759f
Yuexuan Sun, Chang-Heng Li, Yunfeng Long, Zhengyong Huang and Jian Li
Power transformer is an important part of the power system, and continuous monitoring of partial discharges can provide a more reasonable program for fault diagnosis and operational maintenance of the transformer. However, the rigid partial discharge UHF antenna can not be installed in a conformal fit with the monitored equipment, and the partial discharge UHF signal attenuation is serious, resulting in low detection energy efficiency and gain performance can not meet the demand. The centralized deep learning local discharge pattern recognition method has low training efficiency, and distributed deep learning can improve the training efficiency, but the heterogeneous data from multiple sources will reduce the model accuracy. Due to this, this paper designs a UHF flexible composite helical antenna with miniaturization, wide bandwidth, high gain and high bending deformation stability, and investigates a federated learning pattern recognition method based on residual contraction network, which substantially improves the training efficiency while ensuring the accuracy.
{"title":"Research on flexible antenna and distributed deep learning pattern recognition for partial discharge monitoring of transformer","authors":"Yuexuan Sun, Chang-Heng Li, Yunfeng Long, Zhengyong Huang and Jian Li","doi":"10.1088/1361-6463/ad759f","DOIUrl":"https://doi.org/10.1088/1361-6463/ad759f","url":null,"abstract":"Power transformer is an important part of the power system, and continuous monitoring of partial discharges can provide a more reasonable program for fault diagnosis and operational maintenance of the transformer. However, the rigid partial discharge UHF antenna can not be installed in a conformal fit with the monitored equipment, and the partial discharge UHF signal attenuation is serious, resulting in low detection energy efficiency and gain performance can not meet the demand. The centralized deep learning local discharge pattern recognition method has low training efficiency, and distributed deep learning can improve the training efficiency, but the heterogeneous data from multiple sources will reduce the model accuracy. Due to this, this paper designs a UHF flexible composite helical antenna with miniaturization, wide bandwidth, high gain and high bending deformation stability, and investigates a federated learning pattern recognition method based on residual contraction network, which substantially improves the training efficiency while ensuring the accuracy.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"11 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-10DOI: 10.1088/1361-6463/ad7153
Saurav Lahiri, Manish Kumar, Ujjal Bikash Parashar and R Thangavel
VS2 nanosheets were synthesized using a facile hydrothermal method with varying hydrothermal durations for detailed study of their magnetic properties for spintronics applications. The (001) peak near 15.45° in the x-ray diffraction pattern confirmed the formation of the hexagonal phase of VS2 consistent with the Raman spectrum and high-resolution transmission electron microscopy study. X-ray photoelectron spectroscopy confirmed the formation of VS2 with the +4 oxidation state of V. Morphology was determined by field emission scanning electron microscopy that showed the morphological transition from nanoflowers to nanosheets with increase in the hydrothermal duration from 16 h to 24 h. The VS2 nanosheets were subject to magnetic measurements using a superconducting quantum interference device. The isothermal magnetization versus magnetic field plot showed typical hysteresis behaviour at low fields with maximum saturation magnetization of 3.25 memu g−1 at 50 K which gradually decreased with increase in temperature. The coercivity , however, increased with increase in temperature, hinting at the possible short range of the existing ferromagnetic (FM) order. The field-cooled and zero-field-cooled curves showed a lack of FM clustering. Fitting of the magnetization versus temperature plot showed the formation of a mixed magnetic phase, that is both a paramagnetic (PM) phase (at high fields) and a FM phase (at low fields). The PM Curie temperature obtained from the fitting hinted at canted antiferromagnetic order. Magnetoresistance (MR) measurement in a current parallel to the field configuration revealed a negative MR of 10.4%. Further, density functional theory and Monte Carlo simulations based on the Metropolis algorithm were used to study the layer-dependent electronic band structure of VS2 as well as its Curie temperature for its applicability in spintronics devices.
{"title":"Insights into the magnetic signature in VS2 nanosheets for spintronics applications: an experimental and ab initio approach","authors":"Saurav Lahiri, Manish Kumar, Ujjal Bikash Parashar and R Thangavel","doi":"10.1088/1361-6463/ad7153","DOIUrl":"https://doi.org/10.1088/1361-6463/ad7153","url":null,"abstract":"VS2 nanosheets were synthesized using a facile hydrothermal method with varying hydrothermal durations for detailed study of their magnetic properties for spintronics applications. The (001) peak near 15.45° in the x-ray diffraction pattern confirmed the formation of the hexagonal phase of VS2 consistent with the Raman spectrum and high-resolution transmission electron microscopy study. X-ray photoelectron spectroscopy confirmed the formation of VS2 with the +4 oxidation state of V. Morphology was determined by field emission scanning electron microscopy that showed the morphological transition from nanoflowers to nanosheets with increase in the hydrothermal duration from 16 h to 24 h. The VS2 nanosheets were subject to magnetic measurements using a superconducting quantum interference device. The isothermal magnetization versus magnetic field plot showed typical hysteresis behaviour at low fields with maximum saturation magnetization of 3.25 memu g−1 at 50 K which gradually decreased with increase in temperature. The coercivity , however, increased with increase in temperature, hinting at the possible short range of the existing ferromagnetic (FM) order. The field-cooled and zero-field-cooled curves showed a lack of FM clustering. Fitting of the magnetization versus temperature plot showed the formation of a mixed magnetic phase, that is both a paramagnetic (PM) phase (at high fields) and a FM phase (at low fields). The PM Curie temperature obtained from the fitting hinted at canted antiferromagnetic order. Magnetoresistance (MR) measurement in a current parallel to the field configuration revealed a negative MR of 10.4%. Further, density functional theory and Monte Carlo simulations based on the Metropolis algorithm were used to study the layer-dependent electronic band structure of VS2 as well as its Curie temperature for its applicability in spintronics devices.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"35 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-09DOI: 10.1088/1361-6463/ad75a2
Soyeon Kim, Jaewook Yoo, Seohyeon Park, Hongseung Lee, Hyeonjun Song, Seongbin Lim, Minah Park, Choong-Ki Kim, TaeWan Kim, Bongjoong Kim and Hagyoul Bae
Molybdenum disulfide (MoS2) has excellent optoelectronic properties, chemical stability, and a two-dimensional (2D) structure, making MoS2 a very versatile field-effect device material. Herein, we characterize MoS2 and utilize a photo-responsive I–V technique for extracting the energy distribution of the bulk traps in multi-layer MoS2 field effect transistors (FET). This method uses the differential ideality factor in both dark and light conditions. The differential ideality factor enables the efficient quantitative extraction of the device trap density by considering the nonlinear characteristics of the subthreshold region (VON < VGS < VT). To accurately differentiate between the sub-bandgap traps and the interface traps near the conduction band, near-infrared light (λ= 1530 nm) optical illumination was used for the light state characterization. The bulk trap densities under dark state and light state conditions were derived for multi-layer (7-layer and 9-layer) MoS2 FET channels, and the influence of light illumination and overall multi-layer thickness on the bulk trap density was confirmed. The accurate extraction of the trap density enables the design of MoS2 FETs with long-term stability and high optoelectronic performance.
{"title":"Characterization of bulk trap density using fully I–V-based optoelectronic differential ideality factor in multi-layer MoS2 FETs","authors":"Soyeon Kim, Jaewook Yoo, Seohyeon Park, Hongseung Lee, Hyeonjun Song, Seongbin Lim, Minah Park, Choong-Ki Kim, TaeWan Kim, Bongjoong Kim and Hagyoul Bae","doi":"10.1088/1361-6463/ad75a2","DOIUrl":"https://doi.org/10.1088/1361-6463/ad75a2","url":null,"abstract":"Molybdenum disulfide (MoS2) has excellent optoelectronic properties, chemical stability, and a two-dimensional (2D) structure, making MoS2 a very versatile field-effect device material. Herein, we characterize MoS2 and utilize a photo-responsive I–V technique for extracting the energy distribution of the bulk traps in multi-layer MoS2 field effect transistors (FET). This method uses the differential ideality factor in both dark and light conditions. The differential ideality factor enables the efficient quantitative extraction of the device trap density by considering the nonlinear characteristics of the subthreshold region (VON < VGS < VT). To accurately differentiate between the sub-bandgap traps and the interface traps near the conduction band, near-infrared light (λ= 1530 nm) optical illumination was used for the light state characterization. The bulk trap densities under dark state and light state conditions were derived for multi-layer (7-layer and 9-layer) MoS2 FET channels, and the influence of light illumination and overall multi-layer thickness on the bulk trap density was confirmed. The accurate extraction of the trap density enables the design of MoS2 FETs with long-term stability and high optoelectronic performance.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"40 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The scattering of plasmons at a junction within a double-layer two-dimensional electron gas plasmonic waveguide is studied via a full electromagnetic method. The dispersion relation is derived by utilizing the transfer matrix method and can be extended to the situation of an arbitrary number of layers. By numerically solving the dispersion equations, both the acoustic and optical plasmon modes are identified in this double layer system, and the unstable plasmon modes arising from plasmon coupling in different layers are discussed elaborately. Subsequently, the total fields are expanded with eigenmodes and matched at the interface to analyze the scattering characteristics at the junction. The results indicate that the total power of the plasmon mode is amplified when the electron fluid flows from a high concentration region to a low concentration region, and the amplification is more evident at a higher drift velocity. Additionally, we address the scattering of unstable plasmons caused by the two-stream instability and find that the transmitted plasmons are excited intensively at the incidence of the growing plasmon, leading to the plasmon amplification. The detailed examination of plasmon scattering at junction is the prerequisite for studying more complex structures of terahertz plasmonic devices and comprehending the corresponding amplification mechanism.
{"title":"Plasmon scattering at a junction in double-layer two-dimensional electron gas plasmonic waveguide","authors":"Hanghui Deng, Shengpeng Yang, Hongyang Guo, Zijian Qiu, Ping Zhang, Shaomeng Wang, Zhanliang Wang, Zhigang Lu, Yuan Zheng, Yubin Gong","doi":"10.1088/1361-6463/ad7472","DOIUrl":"https://doi.org/10.1088/1361-6463/ad7472","url":null,"abstract":"The scattering of plasmons at a junction within a double-layer two-dimensional electron gas plasmonic waveguide is studied via a full electromagnetic method. The dispersion relation is derived by utilizing the transfer matrix method and can be extended to the situation of an arbitrary number of layers. By numerically solving the dispersion equations, both the acoustic and optical plasmon modes are identified in this double layer system, and the unstable plasmon modes arising from plasmon coupling in different layers are discussed elaborately. Subsequently, the total fields are expanded with eigenmodes and matched at the interface to analyze the scattering characteristics at the junction. The results indicate that the total power of the plasmon mode is amplified when the electron fluid flows from a high concentration region to a low concentration region, and the amplification is more evident at a higher drift velocity. Additionally, we address the scattering of unstable plasmons caused by the two-stream instability and find that the transmitted plasmons are excited intensively at the incidence of the growing plasmon, leading to the plasmon amplification. The detailed examination of plasmon scattering at junction is the prerequisite for studying more complex structures of terahertz plasmonic devices and comprehending the corresponding amplification mechanism.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"16 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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