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Detecting Water in the Atmosphere of HR 8799 c with <i>L</i> -band High-dispersion Spectroscopy Aided by Adaptive Optics
摘要： High-dispersion spectroscopy of brown dwarfs and exoplanets enables exciting science cases, e.g., mapping surface inhomogeneity and measuring spin rate. Here, we present L-band observations of HR 8799 c using Keck NIRSPEC (R = 15,000) in adaptive optics (AO) mode (NIRSPAO). We search for molecular species (H2O and CH4) in the atmosphere of HR 8799 c with a template-matching method, which involves cross-correlation between reduced spectra and a template spectrum. We detect H2O but not CH4, which suggests disequilibrium chemistry in the atmosphere of HR 8799 c, and this is consistent with previous findings. We conduct planet signal injection simulations to estimate the sensitivity of our AO-aided high-dispersion spectroscopy observations. We conclude that 10?4 contrast can be reached in the L band. The sensitivity is mainly limited by the accuracy of line list used in modeling spectra and detector noise. The latter will be alleviated by the NIRSPEC upgrade.
关键词： planets and satellites: atmospheres,planetary systems,methods: observational,planets and satellites: composition,techniques: spectroscopic,techniques: high angular resolution
更新于2025-09-23 15:21:21
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Selected properties of laser cladding coatings shaped using Flow drill technology
摘要： The paper presents the investigations of selected chemical and mechanical properties as well as macro- and microstructure of materials formed using thermal drilling process (Flow drill). The aim of this study was to determine the microstructure of the coatings produced using laser cladding with powder technology. The coatings were produced on the low-carbon steel using 1 kW disc laser. After modification of surface, the thermal drilling process was applied. To produce all coatings, the pure copper powder was used. In this study the laser power equal of 500, 700 and 900 W were used. The microstructure, chemical composition (EDS) and microhardness were investigation. It was found that the surface modification of low carbon steel and next conducted thermal drilling process caused change the surface properties on the hole flange. It was found that surface modification of steel using laser cladding with cooper powder and next Flow drill process contributes to the change in microhardness and chemical composition on hole flange.
关键词： microhardness,microstructure,laser cladding,chemical composition,Flow drill technology
更新于2025-09-23 15:21:21
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Electric field strength-dependent accuracy of TiAlN thin film composition measurements by laser-assisted atom probe tomography
摘要： Accurate quantification of absolute concentrations represents a major challenge for atom probe tomography (APT) since the field evaporation process is affected significantly by the measurement parameters. In the present work we investigate systematically the effect of laser pulse parameters on the accuracy of laser-assisted APT for a TiAlN thin film previously quantified by ion beam analysis, combining Rutherford backscattering spectrometry and time-of-flight elastic recoil detection analysis. The electric field strength is estimated from the Al2+/Al+ charge state ratio for all systematically varied measurement parameters. Subsequently, the absolute concentrations from laser-assisted APT are compared to ion beam analysis data. An increase of the electric field strength from approximately 25–28 V nm?1 improves the accuracy of absolute concentrations measured by laser-assisted APT from 11.4 to 4.1 at% for N, from 8.8 to 3.0 at% for Al and from 2.8 to 0.9 at% for Ti. Our data emphasize that the measurement accuracy of laser-assisted APT for TiAlN is governed by the electric field strength. It is shown that the smallest compositional discrepancies between ion beam analysis and APT are obtained for the maximum electric field strength of approximately 28 V nm?1 at 10 pJ laser pulse energy. This can be rationalized by considering the enhanced ionization of neutral fragments caused by the increased electric field strength.
关键词： accuracy,chemical composition,atom probe tomography,TiAlN,electric field strength
更新于2025-09-23 15:21:01
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A Guide to Small-Scale Energy Harvesting Techniques || Quest for Lead-Free Perovskite-Based Solar Cells
摘要： Today, the perovskite solar cells (PSCs) are showing excellent potentials in terms of simple processing, abundance of materials, and architectural integration, as well as very promising device’s power conversion efficiencies (PCEs), rocketed from 3.8% in 2009 to 23.3% in 2018. However, the toxic lead (Pb) element containing the chemical composition of typically used organic-inorganic halide perovskites hinders the practical applications of PSCs. This chapter starts with a general discussion on the perovskite crystal structure along with the serious efforts focused on Pb replacement in these devices. Section 2 will elaborate the fundamental features of tin (Sn)-based perovskites together with their performance in the PSCs. Other alternative elements, such as copper (Cu), germanium (Ge), bismuth (Bi), and antimony (Sb), will be discussed in Section 3. The end will summarize the challenges and opportunities based on the chapter contents.
关键词： stability,lead-free perovskites,chemical composition,toxicity
更新于2025-09-23 15:21:01
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Numerical analysis of earth-abundant Cu2ZnSn(SxSe1-x)4 solar cells based on Spectroscopic Ellipsometry results by using SCAPS-1D
摘要： Mixed chalcogenide CZTSSe with earth abundant elements, inexpensive, environmental-friendly and impressive photovoltaic performance is a promising absorber material for kesterite thin film solar cells of third generation. In this work, a numerical simulation of p-CZTSSe/n-CdS heterojunction solar cells have been presented using one dimensional Solar Capacitance Simulator. The influence of composition, absorber thickness, defect density and working temperature on Voc, Jsc, FF and power conversion efficiency has been investigated. The optimized cell shows 23.16% efficiency with a Voc ~ 0.724 V corresponding to 40% of the ratio.
关键词： Composition and Spectroscopic Ellipsometry,Absorption coefficient,CZTSSe,Thin film solar cell,Third generation,SCAPS,Efficiency
更新于2025-09-23 15:21:01
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A Review: Crystal Growth for High-Performance All-inorganic Perovskite Solar Cells
摘要： Recently, halide perovskites have become one of the most promising materials for solar cells owing to their outstanding photoelectric performance. Among them, metal halide all-inorganic perovskites (CsPbX3; where X denotes a halogen) show superior thermal and light stability. In particular, the power conversion efficiency (PCE) of perovskite solar cells (pero-SCs) based on a CsPbX3 active layer has shown a steady increase from 2.7% to 19.03% with the improvement of the CsPbX3 crystal quality. In this review, we summarize methodologies that have been employed for controlling the growth of all-inorganic perovskite films so far, including precursor solution deposition, substrate modification, composition doping, and surface engineering. Furthermore, we discuss the effect of perovskite crystal characteristics on defects and perovskite film morphology, both of which are closely related to device performance. Finally, conclusions and perspectives are presented along with useful guidelines for developing all-inorganic pero-SCs with high PCE and robust stability.
关键词： light stability,halide perovskites,precursor solution deposition,all-inorganic perovskites,surface engineering,substrate modification,thermal stability,power conversion efficiency,CsPbX3,composition doping,solar cells,crystal growth
更新于2025-09-23 15:21:01
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Role of shell composition and morphology in achieving single-emitter photostability for green-emitting a??gianta?? quantum dots
摘要： The use of the varied chemical reactivity of precursors to drive the production of a desired nanocrystal architecture has become a common method to grow thick-shell graded alloy quantum dots (QDs) with robust optical properties. Conclusions on their behavior assume the ideal chemical gradation and uniform particle composition. Here, advanced analytical electron microscopy (high-resolution scanning transmission electron microscopy coupled with energy dispersive spectroscopy) is used to confirm the nature and extent of compositional gradation and these data are compared with performance behavior obtained from single-nanocrystal spectroscopy to elucidate structure, chemical-composition, and optical-property correlations. Specifically, the evolution of the chemical structure and single-nanocrystal luminescence was determined for a time-series of graded-alloy “CdZnSSe/ZnS” core/shell QDs prepared in a single-pot reaction. In a separate step, thick (～6 monolayers) to giant (>14 monolayers) shells of ZnS were added to the alloyed QDs via a successive ionic layer adsorption and reaction (SILAR) process, and the impact of this shell on the optical performance was also assessed. By determining the degree of alloying for each component element on a per-particle basis, we observe that the actual product from the single-pot reaction is less “graded” in Cd and more so in Se than anticipated, with Se extending throughout the structure. The latter suggests much slower Se reaction kinetics than expected or an ability of Se to diffuse away from the initially nucleated core. It was also found that the subsequent growth of thick phase-pure ZnS shells by the SILAR method was required to significantly reduce blinking and photobleaching. However, correlated single-nanocrystal optical characterization and electron microscopy further revealed that these beneficial properties are only achieved if the thick ZnS shell is complete and without large lattice discontinuities. In this way, we identify the necessary structural design features that are required for ideal light emission properties in these green-visible emitting QDs.
关键词： green-emitting,photostability,quantum dots,morphology,giant quantum dots,shell composition
更新于2025-09-23 15:21:01
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Role of Sb on the vertical-alignment of type-II strain-coupled InAs/GaAsSb multi quantum dots structures
摘要： The implementation of GaAs0.8Sb0.2 as CL to obtain type-II strain-coupled InAs MQD structures has been examined and compared to similar structures without Sb or without strain coupling. First, it has been demonstrated that capping with GaAsSb prevents the formation of In-rich agglomerations that hampered the QD formation as it has been observed in the sample without Sb. Instead, it promotes the vertical alignment (VA) of almost all QDs with a high density of QD columns. Second, there is a preferential Sb accumulation over the dots together with an undulation of the growth front, contrary to the observed in the uncoupled structure. In case of a deficient covering of GaAsSb, as occurs for giant QDs, In-rich agglomerations may develop. Each VAQD column consists of a sequence of alternating quantum blocks of pyramid-shaped In(Ga)As separated by GaAsSb blocks that rest over them. These Sb-rich blocks are not homogeneous accumulating around the pyramidal apex like a collar. Between the columns, there is an impoverishment of In and Sb compared to the uncoupled sample. These columns can behave as self-aligned nanowires with type II band alignment between self-assembled InAs and GaAsSb quantum blocks that opens new opportunities for novel devices.
关键词： GaAsSb capping layer,III-V semiconductors alloys,Transmission electron microscopy,Composition distribution,Vertical aligned quantum dots
更新于2025-09-23 15:21:01
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Fully Doctor-bladed efficient perovskite solar cells in ambient condition via composition engineering
摘要： It is very meaningful to develop large-scale, low-cost technology for fabricating efficient perovskite solar cells (PSCs) to accelerate their commercialization. Doctor-blading is one of important scalable technologies for processing PSCs, but the power conversion efficiencies (PCEs) of fully doctor-bladed PSCs, including electron transport layer, perovskite layer and hole transport layer, are still lag far behind the PSCs fabricated via conventional spin-coating technology, especially fabricated in ambient condition. Herein, highly efficient planar heterojunction PSCs with a structure of ITO/SnO2/FAxMA(1-x)PbIyBr(3-y)/Spiro-OMeTAD/Ag are achieved by fully doctor-blading technique in ambient condition, in which high-quality perovskite films with low trap-density are fabricated via two-step sequential deposition with a low temperature process by simultaneously introducing composition engineering and additive-doping technology. Organic cation is added into the PbI2 precursor to reduce the uneven distribution of nucleation sites in the perovskite films during doctor-blading process and promote the uniform growth of perovskite grain. Moreover, 2,3,5,6-tetrafluoro-7,7,8,8-tetra-cyanoquinodimethane (F4-TCNQ) acted as the doping additive is employed into perovskite, resulting in healing the perovskite grain boundary and reducing trap-density accordingly. As a result, the doctor-bladed PSCs fabricated in ambient condition exhibit the champion PCE of 18% and a stabilized efficiency of 17.7%. Furthermore, PSCs fabricated via fully doctor-blading in ambient condition achieve the PCE of 17.0% with negligible hysteresis. This work provides an important strategy for scalable fabrication of efficient PSCs in ambient condition and potentially accelerates the commercialization.
关键词： Doctor-blading,Additive,Composition engineering,Perovskite solar cell
更新于2025-09-23 15:21:01
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Determination of the isotopic composition of enriched materials using laser ablation molecular isotopic spectrometry: partial least squares and multivariate curve resolution for the determination of 15N content in enriched urea
摘要： A quantitative analytical method based on laser ablation molecular isotopic spectrometry (LAMIS) and multivariate analysis was developed and evaluated for the determination of the isotopic composition of enriched materials. The method consists preparing a concentrated solution of the enriched material, using small quantities of a sample (125 mg), and ensuring the economic efficiency of the analysis. Standard solutions of known isotopic contents are prepared by employing mixtures of urea highly enriched in 15N and urea of natural isotopic ratio and analyzed by mass spectrometry. A small volume (30 μL) of these solutions is delivered to a filter paper disc (3 cm diameter). After drying, the disc, offering a homogeneously distributed analyte, is presented to a LAMIS equipment to acquire the vibronic emission spectra containing information about the isotopologues of interest. To illustrate the proposed method, the content of 15N is determined in enriched samples of urea. In this case, each spectrum is normalized by the intensity of emission of the CN isotopologues for the electronic (Δν = 0) emission band at 387.1 nm, ensuring better accuracy. Selected regions and single wavelengths of the vibronic emission spectrum (Δν = + 1 or ? 1) related to CN species were employed to construct multivariate partial least squares (PLS) and univariate regression models to predict the isotopic content of new samples. Besides, the LAMIS data set was evaluated by multivariate curve resolution (MCR) algorithm. The best MCR and PLS models presented similar results regarding the accuracy to determine 15N content in enriched urea. MCR is capable of identifying spectral interferences and minimizing its effect. The results show that the proposed method based on LAMIS and PLS or MCR multivariate analysis can determine the 15N content in the range 5–50% with a root mean square error of prediction (RMSEP) respectively equal to 0.5 or 0.7% (m/m) in comparison with reference results obtained by mass spectrometry.
关键词： 15N determination in enriched urea,Laser ablation molecular isotopic spectrometry (LAMIS),Isotopic composition of enriched materials,Partial least squares,Multivariate regression,Multivariate curve resolution (MCR)
更新于2025-09-23 15:19:57