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Influence of Annealing Atmosphere on Microstructure and Optical Properties of ZnO Thin Films
摘要： In this work, the ZnO films are deposited on conducting silicon chips by radio frequency magnetron sputtering. The as-deposited thin films are annealed at 800°C in a N2, O2 and CO+N2 atmosphere for 1h, respectively. The microstructure and electrical properties of the films are comprehensively investigated. XRD studies reveal that the ZnO films have a hexagonal wurtzite structure and they are highly oriented along (002) direction. The surface roughness of ZnO films decreased after annealing, which indicates better film quality. Room temperature PL spectrum is used to investigate the band gap and native defects existing in the films. Defects of thin films for different annealing conditions are analyzed in detail and the possible mechanism of the defects emission is discussed. We suggest that annealing atmosphere of CO+N2 is the most suitable annealing conditions for obtaining ZnO thin films with better crystal quality and good luminescence performance.
关键词： optical properties,ZnO thin films,annealing atmosphere
更新于2025-09-23 15:21:01
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Triggering Mechanism and Material Transfer of a Failed Solar Filament Eruption
摘要： Solar ?lament eruptions are often associated with solar ?ares and coronal mass ejections, which have the greatest impact on space weather. However, the ?ne structures and the trigger mechanisms of solar ?laments are still unclear. To address these issues, we studied a failed solar active-region ?lament eruption associated with a C-class ?are by using high-resolution Hα images from the New Vacuum Solar Telescope, supplemented by EUV observations from the Solar Dynamics Observatory. Before the ?lament eruption, a small bipolar magnetic ?eld emerged below the ?lament. Then magnetic reconnection between the ?lament and the emerging bipolar magnetic ?eld triggered the ?lament eruption. During the ?lament eruption, the untwisting motion of the ?lament can be clearly traced by the eruptive threads. Moreover, the footpoints of the eruptive threads are determined by tracing the descending ?lament material. Note that the twisted structure of the ?lament and the right part of the eruptive ?lament threads cannot be seen before the ?lament eruption. These eruptive threads in the right part of the ?lament are found to be rooting in the weak negative polarities near the main negative sunspot. Moreover, a new ?lament formed in the ?lament channel due to material injection from the eruptive ?lament. The above observations and the potential ?eld extrapolations are inclined to support the idea that the ?lament materials were transferred into the overlying magnetic loops and the nearby ?lament channel by magnetic reconnection. These observations improve our understanding of the complexity of ?lament eruptions.
关键词： Solar activity,Solar magnetic ?elds,Solar magnetic reconnection,Sunspots,Solar active region magnetic ?elds,Solar ?lament eruptions,Solar active region ?laments,Solar ?ares,Solar physics,Solar atmosphere
更新于2025-09-23 15:19:57
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Influence of processing parameters on the density of 316L stainless steel parts manufactured through laser powder bed fusion
摘要： Additive manufacturing technologies are becoming more popular, as they allow the fabrication of specific parts with complex geometries not achievable by conventional manufacturing. In metal additive manufacturing, one of the most widely used technologies is laser powder bed fusion. This work focuses on the influence of different processing parameters on the density of AISI 316L stainless parts obtained through this technology. The article presents a review of published works on the deposition of AISI 316L stainless steel using laser powder bed fusion to define an optimal range of parameters to produce parts with densities above 99%, complemented by density measurements for new sets of laser powder bed fusion processing parameters within the defined optimal range. The investigation provides a further insight on the effect of operating parameters such as vector size and gas atmosphere (Nitrogen and Argon) on the part density. The density measurements were performed using two techniques: micrograph analysis and Archimedes method. Results reveal that an increase in vector size has a negative influence on part density. With the Archimedes method, a maximum relative density of 99.87% was achieved using Nitrogen atmosphere, showing that it is possible to produce near fully dense parts by laser powder bed fusion without post-processing by laser re-melting.
关键词： hatch spacing,gas atmosphere,vector size,energy density,Additive manufacturing,AISI 316L,laser powder bed fusion
更新于2025-09-23 15:19:57
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Laser Powder Bed Fusion of Precipitation-Hardened Martensitic Stainless Steels: A Review
摘要： Martensitic stainless steels are widely used in industries due to their high strength and good corrosion resistance performance. Precipitation-hardened (PH) martensitic stainless steels feature very high strength compared with other stainless steels, around 3-4 times the strength of austenitic stainless steels such as 304 and 316. However, the poor workability due to the high strength and hardness induced by precipitation hardening limits the extensive utilization of PH stainless steels as structural components of complex shapes. Laser powder bed fusion (L-PBF) is an attractive additive manufacturing technology, which not only exhibits the advantages of producing complex and precise parts with a short lead time, but also avoids or reduces the subsequent machining process. In this review, the microstructures of martensitic stainless steels in the as-built state, as well as the effects of process parameters, building atmosphere, and heat treatments on the microstructures, are reviewed. Then, the characteristics of defects in the as-built state and the causes are specifically analyzed. Afterward, the effect of process parameters and heat treatment conditions on mechanical properties are summarized and reviewed. Finally, the remaining issues and suggestions on future research on L-PBF of martensitic precipitation-hardened stainless steels are put forward.
关键词： 17–4 stainless steel,heat treatment,microstructure,precipitation-hardened stainless steels,ferrite,selective laser melting,building atmosphere,defects,laser powder bed fusion
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Analysis of GaAs Solar Cells Grown on 50 mm Wafers at 700 ?°C by Dynamic Hydride Vapor Phase Epitaxy
摘要： The Soil Moisture and Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP) missions provide Level-1 brightness temperature (Tb) observations that are used for global soil moisture estimation. However, the nature of these Tb data differs: the SMOS Tb observations contain atmospheric and select reflected extraterrestrial (“Sky”) radiation, whereas the SMAP Tb data are corrected for these contributions, using auxiliary near-surface information. Furthermore, the SMOS Tb observations are multiangular, whereas the SMAP Tb is measured at 40? incidence angle only. This letter discusses how SMOS Tb, SMAP Tb, and radiative transfer modeling components can be aligned in order to enable a seamless exchange of SMOS and SMAP Tb data in soil moisture retrieval and assimilation systems. The aggregated contribution of the atmospheric and reflected Sky radiation is, on average, about 1 K for horizontally polarized Tb and 0.5 K for vertically polarized Tb at 40? incidence angle, but local and short-term values regularly exceed 5 K.
关键词： galaxy,Soil Moisture Ocean Salinity (SMOS),soil moisture,Atmosphere,Soil Moisture Active Passive (SMAP),brightness temperature (Tb)
更新于2025-09-23 15:19:57
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Electrodynamic influence on the diurnal behaviour of neutral daytime airglow emissions
摘要： The diurnal variations in daytime airglow emission intensity measurements at three wavelengths OI 777.4 nm, OI 630.0 nm, and OI 557.7 nm made from a low-latitude location, Hyderabad (17.5? N, 78.4? E; 8.9? N MLAT) in India have been investigated. The intensity patterns showed both symmetric and asymmetric behaviour in their respective diurnal emission variability with respect to local noon. The asymmetric diurnal behaviour is not expected considering the photochemical nature of the production mechanisms. The reason for this observed asymmetric diurnal behaviour has been found to be predominantly the temporal variation in the equatorial electrodynamics. The plasma that is transported across latitudes due to the action of varying electric field strengths over the magnetic equator in the daytime contributes to the asymmetric diurnal behaviour in the neutral daytime airglow emissions. Independent magnetic and radio measurements support this finding. It is also noted that this asymmetric diurnal behaviour in the neutral emission intensities has a solar cycle dependence with a greater number of days during high solar activity period showing asymmetric diurnal behaviour compared to those during a low solar activity epoch. These intensity variations over a long timescale demonstrate that the daytime neutral optical emissions are extremely sensitive to the changes in the eastward electric field over low and equatorial latitudes.
关键词： Ionosphere (equatorial ionosphere–atmosphere interactions),Atmospheric composition and structure (airglow and aurora)
更新于2025-09-23 15:19:57
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Solar jet-like features rooted in flare ribbons
摘要： Employing the high spatio-temporal Interface Region Imaging Spectrograph 1330 ?A observations, we investigated the jet-like features that occurred during the X8.2 class ?are in NOAA active region (AR) 12673 on 2017 September 10. These jet-like features were rooted in the ?are ribbons. We examined 15 features, and the mean values of the lifetimes, projected widths, lengths, and velocities of these features were 87 s, 890 km, 2.7 Mm, and 70 km s?1, respectively. We also observed many jet-like features which happened during the X1.0 class ?are on 2014 October 25. We studied the spectra at the base of a jet-like feature during its development. The Fe XXI 1354.08 ?A line in the corona displays blueshift, while the Si IV 1402.77 ?A line in the transition region exhibits redshift, which indicates the chromospheric evaporation. This is the ?rst time that the jet-like features are reported to be rooted in the ?are ribbons, and we suggest that these jet-like features were driven by the mechanism of chromospheric evaporation.
关键词： Sun: atmosphere,Sun: ?ares,Sun: evolution,Sun: activity
更新于2025-09-19 17:15:36
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Upgraded CdZnTe Based on the Infrared Attenuation Spectrum
摘要： According to the infrared attenuation spectrum, we can know the conduction type and major point defect of CdZnTe crystals. Based on point defect modelling, an appropriate modus of atmosphere annealing was described in this paper. In this paper, annealing with Cd pressure control technology was used to upgrade p-CdZnTe and n-CdZnTe, respectively. Characterizations reveal that the optical and electrical performance of the CZT crystals is patently improved after annealing. Employment of the infrared attenuation spectrum as the annealing guideline has been veri?ed to be feasible and effectual in this paper.
关键词： CdZnTe,atmosphere annealing,infrared attenuation spectrum,free carrier absorption
更新于2025-09-19 17:15:36
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Remote sensing estimation of the biomass of floating Ulva prolifera and analysis of the main factors driving the interannual variability of the biomass in the Yellow Sea
摘要： Since 2007, green tide blooms with Ulva prolifera as the dominant species have occurred every summer in the Yellow Sea. Biomass is a critical parameter used to describe the severity of green tide blooms. In this study, we analyzed the relationships between several indices (normalized difference vegetation index (NDVI), floating algae index (FAI), ratio vegetation index (RVI), enhanced vegetation index (EVI), ocean surface algal bloom index (OSABI), Korea Ocean Satellite Center (KOSC) approach) and the biomass per unit area of Ulva prolifera by using the in situ measurements from a water tank experiment. EVI, NDVI, and FAI showed strong exponential relationships with Ulva prolifera biomass per unit area. In order to apply the relationships to satellite remote sensing data, the impacts of the atmosphere (different aerosol optical depth at 550 nm) and mixed pixels to the relationships were analyzed. The results show that atmosphere has little effect on the relationship between EVI and Ulva prolifera biomass per unit area with R2 = 0.94 and APD (the average percentage deviation) = 19.55% when EVI is calculated from Rrc (Rayleigh-corrected reflectance), and R2 = 0.95 and APD = 17.53% when EVI is calculated from Rtoa (top-of-atmosphere reflectance). Due to the low sensitivity to the atmosphere, the EVI relationship can be directly utilized in the top-of-atmosphere (TOA) reflectance without atmospheric correction. In addition, the EVI was slightly affected by mixed pixels with the APD only increased by ~10%. The EVI relationship was then applied to a long MODIS image time series to obtain the maximal total biomass of floating Ulva prolifera in the Yellow Sea from 2007 to 2016. The results showed that the maximum and minimum total biomass occurred in 2016 (~1.17 million tons) and 2012 (~0.074 million tons), respectively. The main factors that caused the inter-annual biomass variability were analyzed. The total amount of nutrients from Sheyang River which was the largest river on the northern coast of Jiangsu Province, and Porphyra cultivation in the Radial Sand Ridges of Jiangsu Province had both strong correlation with Ulva prolifera total biomass.
关键词： Atmosphere effect,Remote sensing,Ulva prolifera,Ocean color,Biomass,EVI
更新于2025-09-19 17:15:36
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<i>Ab initio</i> quantum-chemical computations of the absorption cross sections of HgX <sub/>2</sub> and HgXY (X, Y = Cl, Br, and I): molecules of interest in the Earth's atmosphere
摘要： The electronic-structure properties of the low-lying electronic states and the absorption cross sections (σ(E)) of mercury halides HgCl2, HgBr2, HgI2, HgBrCl, HgClI, and HgBrI have been determined within the UV-vis spectrum range (170 nm ≤ λphoton ≤ 600 nm) by means of the DKH3-MS-CASPT2/SO-RASSI quantum-chemical methodology (with the ANO-RCC basis set) and a semi-classical computational strategy based on nuclear sampling for simulating the band shapes. Computed band energies show a good agreement with the available experimental data for HgX2 with errors around 0.1–0.2 eV; theoretical and σ(E) are within the same order of magnitude. For the mixed HgXY compounds, the present computed data allow us to interpret previously proposed absorption bands estimated from the spectra of the parent molecules HgX2 and HgY2, measured in methanol solution. The analyses performed on the excited-state electronic structure and its changes around the Franck–Condon region provide a rationale on the singlet–triplet mixing of the absorption bands and the heavy-atom effect of the Hg compounds. Furthermore, the present benchmark of HgX2 and HgXY absorption σ values together with the previous benchmark of the electronic-structure properties of HgBr2 [see S. P. Sitkiewicz, et al., J. Chem. Phys., 2016, 145, 244304] has been helpful to set up a methodological and computational protocol which shall be used for predicting the atmospheric absorption and photolysis properties of several Hg compounds present in the atmospheric cycle of Hg.
关键词： semi-classical approach,quantum-chemical computations,Earth's atmosphere,UV-vis spectrum,spin-orbit coupling,mercury halides,absorption cross sections
更新于2025-09-19 17:15:36