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Spectroscopic diagnostics of continuous and transient microplasma formed in a millimeter wave photonic crystal
摘要： We present spectroscopic measurements of a microplasma formed within a photonic crystal (PhC) at argon gas pressures up to 750 Torr. Continuous and pulsed millimeter waves (MMW) generate plasma at a vacancy defect within the crystal. Rotational gas temperatures of 300-1050 K and electron densities of 0.5-2×1020 m-3 are obtained from the CH rotational emission spectrum and from Stark broadening of the ???? atomic transition. Electron density is found to be weakly dependent on MMW power because the plasma expands within the defect volume at higher power. Pulsed MMWs slightly increase the peak electron density compared to continuous waves with the same peak power. With MMW pulses, a rapid decrease of wave transmission through the PhC is observed at the beginning of plasma formation. During plasma ignition two distinct plasmas are formed, one on the conducting wall of the PhC near the optical access port and a second within the center of the PhC defect. With longer periods between pulses, the weak wall plasma is observed to form before the principal plasma in the defect, which aids in initiating the main plasma.
关键词： photonic crystal,millimeter waves,electron density,spectroscopic diagnostics,microplasma,gas temperature
更新于2025-09-23 15:19:57
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Spectral characteristic of laser-induced plasma in soil
摘要： The spectral characteristic of laser-induced plasma in soil was studied in this work, plasma under the condition of different time delays and irradiances. Moreover, the time evolution characteristics of plasma temperature and electron density were discussed. Within the time delay range of 0–5 μs, the spectral intensity of the characteristic lines of Si Ⅰ: 288.158 nm, Ti Ⅰ: 336.126 nm, Al Ⅰ: 394.400 nm and Fe Ⅰ: 438.354 nm of the four main elements in two kinds of national standard soil decayed exponentially with time. The average lifetime of the spectral lines was nearly 1.56 μs. Under the condition of different time delays, the spectral intensity of Pb Ⅰ: 405.78 nm in soil increased linearly with laser energy. However, the slope between the spectral intensity and laser energy decreased exponentially with the increase of time delay, from 4.91 to 0.99 during 0–5 μs. The plasma temperature was calculated by the Boltzmann plot method and the electron density was obtained by inversion of the full width at half maximum (FWHM) of the spectrum. The plasma temperature decreased from 8900 K to 7800 K and the electron density decreased from 1.5×1017 cm-3 to 7.8×1016 cm-3 in the range of 0–5 μs.
关键词： soil,time delay,electron density,laser energy,LIBS,plasma temperature
更新于2025-09-23 15:19:57
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Modular Synthesis of Waveguide Bandpass Filters Using Dual-Mode Resonators
摘要： We present a new decomposition approach for dual-energy computed tomography (DECT) called SIRZ that provides precise and accurate material description, independent of the scanner, over diagnostic energy ranges (30 to 200 keV). System independence is achieved by explicitly including a scanner-specific spectral description in the decomposition method, and a new X-ray-relevant feature space. The feature space consists of electron density, and a new effective atomic number, which is based on published X-ray cross sections. Reference materials are used in conjunction with the system spectral response so that additional beam-hardening correction is not necessary. The technique is tested against other methods on DECT data of known specimens scanned by diverse spectra and systems. Uncertainties in accuracy and precision are less than 3% and 2% respectively for the results compared to prior methods that are inaccurate and imprecise (over 9%).
关键词： system-independent CT,Beam-hardening correction,electron density,effective atomic number,quantitative x-ray characterization,dual-energy computed tomography,photoelectric-compton decomposition
更新于2025-09-23 15:19:57
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Insight into the electron density distribution in an O,N-heterocyclic stannylene by means of high resolution x-ray diffraction analysis
摘要： In this paper we present the synthesis and results of a high-resolution single crystal X-ray diffraction experiment on the O,N-heterocyclic stannylene (t-BuAPSn) (1) containing the chelate 4,6-di-tert-butyl-N-tert-butyl-o-aminophenolate ligand. The experimental work is accompanied by a charge density study based on a topological analysis according to quantum theory of atoms in molecules (QTAIM) together with a NBO calculation of the crystal packing fragment containing a Sn-Sn bond. According to QTAIM, the Sn-Sn interaction is covalent (?2ρ(r)<0, he(r)<0). In the view of NBO analysis, there are two donor-acceptor bonding interactions between the tin atoms of adjacent molecules. The Sn-Sn bond energy evaluated by the Espinosa-Molins-Lecomte correlation is equal to ?9.1 kcal/mol. We carried out the investigation of source function not only in CP(3,-1) on the Sn-Sn bond but also on NCI-defined isosurface (λ2<0). The source function shows that the electron density from the Sn basins extensively contributes to the formation of this Sn–Sn bond in 1.
关键词： aminophenol,QTAIM theory,electron density distribution,stannylene,nature and energy of Sn-Sn interaction
更新于2025-09-23 15:19:57
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Physical Characteristics of Coupled Plasma and Its Influence on Weld Formation in Hybrid Laser-Double-Arc Welding
摘要： Hybrid laser-double-arc welding (HLDAW) is an e?cient welding method with multi-heat sources comprised of two arcs and a laser beam, which is an intricate process with much randomness and uncertainty due to the mutual e?ect between multi-plasmas. Compared with double-arc welding (DAW), HLDAW can generally obtain a more stable welding process and deeper weld penetration, which is directly a?ected by the synergistic e?ect of multiple heat sources; however, the mechanism has not been systematically studied. In this study, the multi-information analysis method is adopted to study the distribution of electron temperatures, electron densities and electrical conductivity of double-arc welding (DAW) and HLDAW by utilizing synchronous radiation spectrum, high-speed photography and electrical signal sensing technology. The results indicated that the high concentration of charged particles provided a conductive channel for the two arcs to achieve a more stable welding process in HLDAW. The synergy between the laser and the arc changed the ?ow mode of the weld pool, which facilitated the molten metal ?owing toward the bottom of the molten pool. Obtaining the same melting depth, the line energy input of HLDAW was 13% lower than that of DAW; the heat a?ected zone is narrower and the grain size is smaller. The weld penetration depth was improved in HLDAW, which was 1.8 times that of DAW and 1.5 times that of pure laser welding under the laser power of 1.5 kW. The weld penetration of HLDAW increased with laser power.
关键词： hybrid laser-double-arc welding,electron density,coupled plasma,arc shape,electron temperature
更新于2025-09-19 17:13:59
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Three-dimensional measurements of plasma parameters in an inductively coupled plasma processing chamber
摘要： Inductively coupled plasmas (ICPs) are extensively used for materials processing and microelectronics fabrication. However, their electromagnetic properties have not been fully characterized. In this regard, we have performed fully three dimensional (3D), time dependent measurements of the magnetic ?eld, electron density, and electron temperature for an ICP sustained in argon in an industrial reactor designed for plasma etching in microelectronics fabrication. These measurements were compared to modeling results. The plasma was generated using pulsed power delivered at 2 MHz by a planar coil. The magnetic ?eld was measured using a three axis magnetic probe at 15 366 locations throughout the plasma volume during the H-mode portion of the pulse at temporal intervals of 2 ns. A swept Langmuir probe was used to measure plasma parameters at the same locations. The plasma density measurement was calibrated with line-integrated densities obtained using a 96 GHz interferometer. During a single radio frequency (RF) cycle, the 3D current density [derived from Be~r; tT]is initially maximum just below the coil and moves downward toward the center of the chamber. Isosurfaces of current are nearly symmetric toroids. The total electric ?eld, space charge ?eld, and inductive electric ?eld were derived and used to calculate the dissipated power, plasma current, and Poynting ?ux. Computer modeling of the experiment reproduces the phase dependent behavior. Animations showing the time dependent 3D measurements are presented in the supplementary material.
关键词： plasma etching,electron density,magnetic field,electron temperature,microelectronics fabrication,Inductively coupled plasmas
更新于2025-09-16 10:30:52
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Picosecond laser ablation and depth profile of Cu(In, Ga)Se2 thin film layer
摘要： Laser ablation based on picosecond laser was used to achieve the micro-analysis of Cu(In, Ga)Se2 (CIGS) thin film with the ablation crater diameter of 50 μm and the ablation crater central depth of 93 ± 13 nm. We achieved the depth profile of CIGS thin film with different laser shot number. The evolutions of spectral lines intensities of Ca from glass substrate and Ga and In from CIGS thin film layer, and intensity ratios of Ca/Ga and Ca/In could exhibit the change of the ablation volume, which could estimate the thin film thickness of single CIGS thin film layer. The average plasma temperature was calculated to be about 5243 ± 100 K, and the average electron density was calculated to be about 4.5×1016 cm?3. It is shown that our experimental setup is suitable to achieve a precise control and monitor the element compositions in each CIGS thin film layer in the research and in the production of CIGS solar cells.
关键词： Ablation morphology,Electron density,Cu(In, Ga)Se2 thin film,Picosecond laser induced breakdown spectroscopy,Plasma temperature
更新于2025-09-16 10:30:52
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Defect Passivation in Hybrid Perovskite Solar Cells by Tailoring the Electron Density Distribution in Passivation Molecules
摘要： Commercialization of perovskite solar cells (PSCs) requires developing high?efficiency devices with good stability. Ionic defects existing in perovskite layer can serve as non-radiative recombination center to deteriorate the performance of PSCs, and can introduce chemical degradation of the perovskite material introducing instability issues. Here, passivation molecules with various electron density distribution (EDD) are employed as an ideal model to reveal the role of EDD on defect passivation in perovskite thin films. Power conversion efficiency (PCE) exceeding 21% with good stability in humid air was obtained for planar PSCs with 4-aminobenzonitrile (ABN) additive, higher than the reference PSCs with a PCE of 20.22%. The improved stability and performance features are attributed to the efficient passivation for charged defects in perovskites by adding ABN, which guarantees a smaller Urbach energy, longer carrier lifetime and less traps in the perovskite films.
关键词： perovskite solar cell,electron density distribution,stability,defect passivation,recombination
更新于2025-09-12 10:27:22
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Dynamic Characteristics of the Spark Channel Plasma in Nitrogen Trigatron Investigated by the Laser Mach-Zehnder Interferometer
摘要： The spark channel plasma generated in the atmospheric nitrogen trigatron is studied with the laser Mach–Zehnder (M–Z) interferometer. The development of the spark channel plasma is described by analyzing the temporal and spatial evolution of the plasma electron density from the interferograms. The regions of the shock wave and the plasma are distinguished by the phase shift. Different spatial distributions of the anodic and cathodic plasma channels are obtained. The anodic spark channel shows good axial symmetry with constant radial expansion velocity. On the periphery of the main spark channel, a secondary spark channel occurs simultaneously in the cathodic region. After the collision of the two channels, the stagnation forms in the overlapping region and the secondary channel merges with the main one gradually. The leftward expansion velocity of the secondary channel is higher than the rightward velocity of the main channel, but both of them are lower than that near anode. The speculation on the production of the secondary spark channel is given and its influence on the development of the spark discharge in the gap is discussed in this work.
关键词： Mach–Zehnder (M–Z) interferometer,Electron density,spark gas switch,plasma channel
更新于2025-09-12 10:27:22
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Interfacial Passivation for Perovskite Solar Cells: The Effects of Functional Group in Phenethylammonium Iodide
摘要： Defect passivation is an effective method to improve the performance of perovskite solar cells. In this study, four phenethylammonium iodide featured with different functional groups directly linking to benzene ring are introduced on the surface of perovskite films ((FAPbI3)1-x(MAPbBr3-yCly)x) to investigate their passivation effects. It’s found that the electron density of the benzene ring has significant influence on the interfacial passivation: phenethylammonium iodide with electron-donating groups (methoxyl and methyl) present favorable passivation effects, while the salt with electron-drawing group (nitro) delivers undesirable impacts. The passivation is attributed to the electrostatic interaction between the benzene ring and the undercoordinated Pb2+ ions. The salts treated films are employed to fabricate solar cells, and an efficiency of 22.98% is achieved. In addition, the treated device shows good long-term stability within 1000 h storage in the dark ambient environment.
关键词： interfacial passivation,perovskite solar cells,phenethylammonium iodide,electron density,functional groups
更新于2025-09-12 10:27:22