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Characterization of Si and SiC detectors for laser-generated plasma monitoring in short wavelength range
摘要： Silicon carbide detectors were employed to characterize the plasma produced by laser interaction with a double stream gas-pu? target source. A 10 Hz repetition rate Nd:YAG laser (1064 nm wavelength, 0.69 J pulse energy and 3 ns pulse duration) was employed to irradiate di?erent gas-pu? targets (Argon, Xenon and Sulfur hexa?uoride), at di?erent pressures (1–10 bar), emitting plasma radiation in di?erent wavelength ranges (ultraviolet, extreme ultraviolet and soft X-rays). The emission produced by the laser radiation was properly ?ltered (employing Titanium, Aluminium, Zirconium and Calcium ?uoride ?lters), to narrow down the broad-band emission of the generated plasma. The SiC detectors’ signals were compared with a calibrated traditional silicon detector evaluating their di?erences, i.e. taking into account the plasma stability, the time trace pro?le and the characteristics of the gas-pu? target source. The obtained results, which will be presented and discussed, allow to improve the geometry and con?guration of the SiC detectors avoiding saturation and charge recombination e?ects and getting a better proportionality to the energy and ?uence of the detected radiations.
关键词： X-ray detectors,Radiation monitoring,Detectors for UV, visible and IR photons,Plasma generation (laser-produced, RF, x ray-produced)
更新于2025-09-23 15:21:01
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The effect of Zn3N2 phase decomposition on the properties of highly-doped ZnO: Al, N films
摘要： Study of Al-N simultaneous doping and thermal annealing influence on the properties of ZnO films is very important for achievement as p-type conductivity in the films as for improvement the performance of ZnO-based ultraviolet detectors. Highly-doped ZnO:Al,N films containing the Zn3N2 phase (ZnO:Al,N-Zn3N2) were grown on Si substrates by magnetron sputtering using a layer-by-layer growth technique. Our work presents a comparative study of the structure, optical and electronic properties of highly-doped as-grown and annealed ZnO:Al,N films. It was shown that the thermal annealing of ZnO:Al,N-Zn3N2 film at atmospheric conditions allows to decompose the Zn3N2 phase. The features of this phenomena on the properties of ZnO:Al,N films were investigated and discussed in detail by using X-ray diffraction, energy dispersive X-ray analysis, Raman scattering, photoluminescence, X-ray photoelectron spectroscopy and X-ray emission spectroscopy.
关键词： Radio-frequency magnetron sputtering,Zinc oxide,Nitrogen-aluminum doping,Photoluminescence,X-ray photoelectron spectroscopy,Thin films,X-ray diffraction,Raman scattering
更新于2025-09-23 15:21:01
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Thermal stability study of transition metal perovskite sulfides
摘要： Transition metal perovskite chalcogenides, a class of materials with rich tunability in functionalities, are gaining increased attention as candidate materials for renewable energy applications. Perovskite oxides are considered excellent n-type thermoelectric materials. Compared to oxide counterparts, we expect the chalcogenides to possess more favorable thermoelectric properties such as lower lattice thermal conductivity and smaller band gap, making them promising material candidates for high temperature thermoelectrics. Thus, it is necessary to study the thermal properties of these materials in detail, especially thermal stability, to evaluate their potential. In this work, we report the synthesis and thermal stability study of five compounds, a-SrZrS3, b-SrZrS3, BaZrS3, Ba2ZrS4, and Ba3Zr2S7. These materials cover several structural types including distorted perovskite, needle-like, and Ruddlesden–Popper phases. Differential scanning calorimeter and thermogravimetric analysis measurements were performed up to 1200 °C in air. Structural and chemical characterizations such as X-ray diffraction, Raman spectroscopy, and energy dispersive analytical X-ray spectroscopy were performed on all the samples before and after the heat treatment to understand the oxidation process. Our studies show that perovskite chalcogenides possess excellent thermal stability in air at least up to 550 °C.
关键词： differential scanning calorimeter,thermoelectric materials,Transition metal perovskite chalcogenides,thermal stability,thermogravimetric analysis,Raman spectroscopy,Ruddlesden–Popper phases,X-ray diffraction,energy dispersive analytical X-ray spectroscopy
更新于2025-09-23 15:21:01
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Enhancement in the performance of nanostructured CuOa??ZnO solar cells by band alignment
摘要： In this study, we investigated the effect of cobalt doping on band alignment and the performance of nanostructured ZnO/CuO heterojunction solar cells. ZnO nanorods and CuO nanostructures were fabricated by a low-temperature and cost-effective chemical bath deposition technique. The band offsets between Zn1?xCoxO (x = 0, 0.05, 0.10, 0.15, and 0.20) and CuO nanostructures were estimated using X-ray photoelectron spectroscopy and it was observed that the reduction of the conduction band offset with CuO. This also results in an enhancement in the open-circuit voltage. It was demonstrated that an optimal amount of cobalt doping could effectively passivate the ZnO related defects, resulting in a suitable conduction band offset, suppressing interface recombination, and enhancing conductivity and mobility. The capacitance–voltage analysis demonstrated the effectiveness of cobalt doping on enhancing the depletion width and built-in potential. Through impedance spectroscopy analysis, it was shown that recombination resistance increased up to 10% cobalt doping, thus decreased charge recombination at the interface. Further, it was demonstrated that the insertion of a thin layer of molybdenum oxide (MoO3) between the active layer (CuO) and the gold electrode hinders the formation of a Schottky junction and improved charge extraction at the interface. The ZnO/CuO solar cells with 10% cobalt doped ZnO and 20 nm thick MoO3 buffer layer achieved the best power conversion efficiency of 2.11%. Our results demonstrate the crucial role of the band alignment on the performance of the ZnO/CuO heterojunction solar cells and could pave the way for further progress on improving conversion efficiency in oxide-based heterojunction solar cells.
关键词： nanostructured,solar cells,X-ray photoelectron spectroscopy,power conversion efficiency,molybdenum oxide,chemical bath deposition,band alignment,CuO–ZnO,cobalt doping
更新于2025-09-23 15:21:01
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Dynamic Laser Absorptance Measured in a Geometrically Characterized Stainless-Steel Powder Layer
摘要： The relationship between real powder distributions and optical coupling is a critical building block for developing a deeper physical understanding of laser-additive manufacturing and for creating more reliable and accurate models for predictable manufacturing. Laser-light absorption by a metal powder is distinctly different from that of a solid material, as it is impacted by additional parameters, such as particle size, shape distribution, and packing. Here, we use x-ray computed tomography to experimentally determine these parameters in a thinly spread austenitic stainless-steel powder on a metal substrate, and we combine these results with optical absorptance measurements during a 1 ms stationary laser-light exposure to simulate the additive-manufacturing process. Within the thinly spread powder layer, the particle volume fraction changes continuously from near zero at the powder surface to a peak value of 0.72 at a depth of 235 μm, with the most rapid increase taking place in the first 100 μm. The relationship between this particle volume fraction gradient and optical absorptance is investigated using an analytical model, which shows that depth-averaged absorptance measurements can measure the predicted average value, but will fail to capture local effects that result from a changing powder density. The time-averaged absorptance remains at levels between 0.67 and 0.80 across a two orders of magnitude range in laser power, which is significantly higher than that observed in solid stainless-steel experiments. The dynamic behavior of the absorptance, however, reveals physical phenomena, including oxidation, melting, and vapor cavity (keyhole) formation, as well as quantifying the effect of these on the absorbed energy.
关键词： keyhole formation,laser-additive manufacturing,stainless-steel powder,x-ray computed tomography,optical coupling,optical absorptance,particle volume fraction
更新于2025-09-23 15:21:01
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[IEEE 2020 International SAUPEC/RobMech/PRASA Conference - Cape Town, South Africa (2020.1.29-2020.1.31)] 2020 International SAUPEC/RobMech/PRASA Conference - Thin film photovoltaic module characterisation based in indoor and outdoor methods
摘要： This paper is the fifth in a series of articles on the basic physics of light yield nonproportionality in scintillators. Here, we compare and contrast the nonproportionality as registered by gamma rays and high-energy electrons. As has been noted in the past, these two types of data have different curve shapes (for plots of the light yield against electron or gamma energy). Herein, we show how the experimental gamma nonproportionality curve can be calculated from the electron response by accounting for the distribution of high energy electrons created by the gamma photon via the photoelectric interaction. Similarly, we measure and model the gamma-induced resolution as a function of energy and compare this data to predictions from our model. The utility of the model is explored using data acquired with the scintillators (Eu), GYGAG(Ce) and CsI(Na).
关键词： Gamma ray detectors,solid scintillation detectors,luminescence
更新于2025-09-23 15:21:01
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Correlations between thermal history and keyhole porosity in laser powder bed fusion
摘要： Additive manufacturing has the potential to revolutionize the production of metallic components as it yields near net shape parts with complex geometries and minimizes waste. At the present day, additively manufactured components face qualification and certification challenges due to the difficulty in controlling defects. This has driven a significant research effort aimed at better understanding and improving processing controls – yielding a plethora of in-situ measurements aimed at correlating defects with material quality metrics of interest. In this work, we develop machine-learning methods to learn correlations between thermal history and subsurface porosity for a variety of print conditions in laser powder bed fusion. Un-normalized surface temperatures (in the form of black-body radiances) are obtained using high-speed infrared imaging and porosity formation is observed in the sample cross-section through synchrotron x-ray imaging. To demonstrate the predictive power of these features, we present four statistical machine-learning models that correlate temperature histories to subsurface porosity formation in laser fused Ti-6Al-4V powder.
关键词： in-situ measurement,keyhole porosity,machine learning,laser powder bed fusion,x-ray imaging
更新于2025-09-23 15:21:01
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Growth of high purity zone-refined Boron Carbide single crystals by Laser Diode Floating Zone method
摘要： We report the growth of 4 mm diameter x 50 mm long Boron Carbide (B4C) with large single crystal regions using a Laser Diode Floating Zone (LDFZ) method at varying growth rates of 5-20 mm/hr. These materials were grown using polycrystalline B4C as a seed. Microstructural characterization shows the presence of a significant number of twinning-boundaries along the growth direction ([001]h) oriented in the (1210)h plane. At faster growth rates >10 mm/hr, the crystal orientation was reproducible, suggesting a twin-plane mediated growth mechanism. On the contrary, at slower growth rates <10 mm/hr the crystal orientation was not reproducible, suggesting a critical rate for twin-plane mediated growth to dominate. Zone refinement of these crystals led to a significant reduction of trace impurities to better than 99.999 wt % purity, at the expense of increased twinning. Powder x-ray diffraction confirms that the bulk is rhombohedral B4C, consistent with the microstructural analysis. The X-ray reciprocal space maps reveal the growth direction to be close to the [001]h direction, and the corresponding ω-rocking curve width is ~530arcsec. The rocking curve consisted of 3 distinct peaks, indicating in-plane mosaicism, consistent with the twinning observed. Berkovich nano-indentation of the key (001)h plane showed 41 ± 1 GPa hardness, with a Young’s modulus of 520 ± 14 GPa, comparable to literature reports.
关键词： A2. Single crystal growth,A1. Defects,A1. X-ray diffraction,A1. Characterization,A2. Growth from melt
更新于2025-09-23 15:21:01
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<i>In situ</i> structural kinetics of picosecond laser-induced heating and fragmentation of colloidal gold spheres
摘要： Fragmentation of colloidal 54 nm gold nanoparticles by picosecond laser pulses is recorded by time-resolved X-ray scattering, giving access to structural dynamics down to a 80 ps resolution. Lattice temperature and energy dissipation have been quantified to verify that the maximum applied fluence of 1800 J m?2 heats up the particles close to boiling. Already within 30 ns, particles with significantly lower particle sizes of 2 to 3 nm are detected, which hints towards an ultrafast process either by a thermal phase explosion or Coulomb instability. An arrested growth is observed on a microsecond time scale resulting in a final particle size of 3–4 nm with high yield. In this context, the fragmentation in a NaCl/NaOH solution seems to limit growth by electrostatic stabilization of fragments, whereas it does not modify the initial product sizes. The laser-induced fragmentation process is identified as a single-step, instantaneous reaction.
关键词： Coulomb instability,fragmentation,thermal phase explosion,time-resolved X-ray scattering,picosecond laser pulses,gold nanoparticles
更新于2025-09-23 15:21:01
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Growth and investigation on novel single crystal of ?2-cyclodextrin 2, 4-dinitrophenylhydrazine for optical sensors applications
摘要： Nonlinear optical (NLO) 2, 4-Dinitrophenylhydrazine (DNPH) single crystal was grown by slow evaporation solution growth method at ambient temperature. The characterization of Powder X – Ray diffraction peaks was con?rmed the new crystalline system. Fourier transform infrared spectroscopic analysis (FTIR) was used to the identi?cation of various functional groups present in the grown crystal. The range of optical transmittance exhibited by the grown bCD-DNPH crystal was investigated by UV Visible – NIR spectral analysis. The lower cut off wavelength of the grown crystal is observed at 270 nm. The SEM ?gures are recorded in different magni?cation. It is clear that the surface of the grown crystal appears very smooth although it has pots and microcrystal on the surface. The grain boundaries are clearly seen which shows the perfect growth of the crystal. The weight percentage (wt %) of C, N and O as obtained from EDAX analysis is in concurrent with the theoretical values. The SHG ef?ciency of the grown crystal was determined.
关键词： Optical properties,X-ray diffraction,Crystal growth
更新于2025-09-23 15:21:01