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Comparison of Sensitive Volumes Associated with Ion-and Laser-Induced Charge Collection in an Epitaxial Silicon Diode
摘要： A sensitive volume is developed using pulsed laser-induced collected charge for two bias conditions in an epitaxial silicon diode. These sensitive volumes show good agreement with absorption laser-induced collected charge at a variety of focal positions and pulse energies. When compared to ion-induced collected charge, the laser-based sensitive volume over predicts the experimental collected charge at low bias and agrees at high bias. A sensitive volume based on ion-induced collected charge adequately describes the ion experimental results at both biases. Differences in the amount of potential modulation explain the differences between the ion- and laser-based sensitive volumes at the lower bias. Truncation of potential modulation by the highly doped substrate at the higher bias results in similar sensitive volumes.
关键词： single-event transients,two-photon absorption,sensitive volume,single-event effects,Pulsed laser
更新于2025-09-12 10:27:22
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Applications of Laser Ablation - Thin Film Deposition, Nanomaterial Synthesis and Surface Modification || Concurrent Multi-Target Laser Ablation for Making Nano-Composite Films
摘要： New method of using laser ablation for film deposition that can be called as concurrent multi-beam multi-target matrix-assisted pulsed laser evaporation and pulsed laser deposition (MBMT-MAPLE/PLD) is described. Practical MBMT-MAPLE/PLD system built at Dillard University has three separate laser beams, three targets and the remotely controlled plume overlapping mechanism that provides even mixing of the target materials during their deposition on the substrate. The system accommodates MAPLE targets in the form of polymer solutions frozen with flowing liquid nitrogen. The feasibility of the method was demonstrated when it was used for making polymer nano-composite films with two inorganic additives: upconversion fluorescent phosphor NaYF4:Yb3+, Er3+ and aluminum-doped ZnO (AZO). Three laser beams, an infrared 1064-nm beam for the MAPLE and two 532-nm beams for the PLD targets, were concurrently used in the process. The fabricated nano-composite films were characterized using X-ray diffraction, scanning electron microscopy (SEM), optical fluorescent spectroscopy, and the measurement of the quantum efficiency (QE) of the upconversion fluorescence. The size of the inorganic nanoparticles varied in the range 10–200 nm. The AZO additive increased QE by 1.6 times. The conclusion was made on the feasibility of MBMT-MAPLE/PLD method for making multi-component nano-composite films for various applications.
关键词： matrix-assisted pulsed laser evaporation,polymer nano-composite films,pulsed laser deposition,laser ablation
更新于2025-09-11 14:15:04
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Chemical Structure of EVA Films Obtained by Pulsed Electron Beam and Pulse Laser Ablation
摘要： Poly(ethylene-co-vinyl acetate) (EVA) films were deposited for the first time using physical methods. The chemical structure of the films obtained using two techniques, pulsed electron beam deposition (PED) and pulsed laser deposition (PLD), was studied by attenuated total reflection Fourier infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Whilst significant molecular degradation of the EVA films was observed for the PLD method, the original macromolecular structure was only partially degraded when the PED technique was used, emphasizing the superiority of the PED method over PLD for structurally complex polymers such as EVA. Optical and scanning electron microscopic observations revealed compact and smooth EVA films deposited by pulsed electron beam ablation as opposed to heterogeneous films with many different sized particulates obtained by PLD.
关键词： chemical structure analysis,poly(ethylene-co-vinyl acetate),pulsed laser deposition,pulsed electron beam deposition
更新于2025-09-11 14:15:04
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[Laser Institute of America ICALEO? 2015: 34th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - Atlanta, Georgia, USA (October 18–22, 2015)] International Congress on Applications of Lasers & Electro-Optics - Comparison between ps- and μs-laser radiation for drilling holes for force transmission elements in CFRP-preforms
摘要： Current lightweight strategies in automobile, aerospace and wind energy applications include composite structures consisting of metal and fiber reinforced plastics for minimum weight, maximum force transmission and high material efficiency. Therefore, economic and technological beneficial material processing for the integration of force transmission elements such as inserts are crucial for these high performance materials. Current state of the art of machining carbon fiber reinforced material is to drill or mill the work piece after the consolidation process. Conventional mechanical and water jet processes lead to high tool wear and often non-repairable defects in the work piece such as delamination, fiber pullout, cracks in matrix and fibers, and deformation. Laser processing of the consolidated material can prevent force induced defects but leads to degradation of the matrix and leaves freestanding fibers inside the drilling hole which can damage the protective surface of subsequently inserted force transmission elements. This is especially critical for lifetime and performance during operation of the structural part. One solution is to drill the so called preform, prior to the infusion process, insert force transmission elements and subsequently infuse the preform with resin. Ultra sonic excited cutting knifes are not applicable for cutting hole diameters of a few millimeters with high aspect ratios. Punching as well as water jet cutting drop out due to force induced interaction with the textile or necessity of a subsequent drying process. Laser material processing could be an adequate solution to circumvent the above mentioned issues. Within this work, non-crimp carbon fiber (NCF) layers are investigated regarding laser processing via ultra-short pulsed and microsecond (fiber laser) radiation. The influence of different process parameters such as scanning speed, repetition rate and laser power are being evaluated regarding geometrical and materialographical quality such as conicity, textile swelling and heat affected zone (HAZ). The temperature distribution during laser processing is important for the estimation of when and where the knitting yarn, which keeps the carbon fiber plies together, disintegrates. Without the knitting yarn swelling occurs which is not desired for subsequent process steps.
关键词： force transmission elements,CFRP-preforms,microsecond laser,ultra-short pulsed laser,laser drilling
更新于2025-09-11 14:15:04
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[Laser Institute of America ICALEO? 2015: 34th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - Atlanta, Georgia, USA (October 18–22, 2015)] International Congress on Applications of Lasers & Electro-Optics - Rapid direct laser writing of microfluidic device on siloxane molds for microreplication
摘要： Microfluidic devices are usually made by replication with PDMS (polydimethylsiloxane) from masters produced using MEMS microfabrication technology. PDMS is the material of choice for pattern transfer due to its flexibility, chemical stability, and low surface energy. Creating functional microfluidic devices that integrate manipulation components (i.e., micro-filters or mixers) using MEMS technology is a costly and time consuming operation. This limits the ability to test design variants through agile, rapid prototyping of the device. Direct PDMS fabrication is an attractive alternative which require a direct writing technology. This work demonstrates direct structuring of PDMS with picoseconds pulsed laser, used for rapid creation of a mould for replication of the devices themselves. The main hindrance found in PDMS direct writing is the generation of decomposed layers which limits the further processing and compromises surface quality. The first results demonstrated that a microfluidic device with integrated functional microfeatures can be effectively fabricated without the formation of decomposed PDMS by carefully optimising the laser parameters and machining strategy. Complete 3x3mm microfluidic devices (with the integration of multistage filter components) were thus fabricated in under 2 minutes with lateral resolution down to 10μm. Hence, an optimized set of parameters allows fast rapid prototyping of microfluidic devices for development and proof of new concepts, using ultrafast lasers.
关键词： microfluidic devices,picoseconds pulsed laser,direct laser writing,rapid prototyping,PDMS
更新于2025-09-11 14:15:04
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Synthesis of gold nanoparticles by pulsed laser-assisted reduction of aqueous gold precursor
摘要： In this paper, colloidal gold nanoparticles (GNPs) were synthesized by Nd:YAG (λ = 1064 nm) pulsed laser-assisted reduction (PLAR) of aqueous [AuCl4]?. In this process, during laser ablation of a Mo target in DI water, a [AuCl4]? precursor solution was being added dropwise in situ. UV–Vis absorption spectra showed distinct plasmonic absorption bands at 209 and 530 nm corresponding to Mo nanoparticles (NPs) and GNPs, respectively. Furthermore, no significant conversion for [AuCl4]? was found when it was added to aged Mo NPs or when it was irradiated in the lack of the Mo target. Using transmission electron microscope (TEM) images, it was found that precursor concentration and laser-ablation time can affect the population or size of GNPs. In PLAR with a small amount of KI solution in water, the GNPs size increases to ~ 50 nm via an iodine-induced particle fusion mechanism. The reduction mechanism was discussed based on metastable species intercation, producing the cavitation bubble during laser ablation.
关键词： Mo target,Nd:YAG laser,TEM,UV–Vis absorption,Pulsed laser-assisted reduction,Gold nanoparticles,KI solution
更新于2025-09-11 14:15:04
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Impact of lattice defects on water oxidation properties in SnNb <sub/>2</sub> O <sub/>6</sub> photoanode prepared by pulsed-laser deposition method
摘要： SnNb2O6 is one of the promising photoanode materials for photoelectrochemical water splitting. We prepared the SnNb2O6 thin-film photoanode with various Sn/Nb ratios by a pulsed-laser deposition method and investigated impacts of lattice defects in the SnNb2O6 photoanode on the water oxidation property. Photoelectrochemical measurements and Raman spectroscopy analyses for the SnNb2O6 photoanodes presented that the water oxidation property can be improved by suppressing the formation of the acceptor site caused by the substitution of Sn4+ for the Nb5+ site in the crystal lattice of SnNb2O6. This study provides material’s design strategy based on defect chemistry to realize an efficient SnNb2O6 photoanode used for the photoelectrochemical cell, which can operate without an external bias.
关键词： lattice defects,photoanode,water oxidation,pulsed-laser deposition,SnNb2O6
更新于2025-09-11 14:15:04
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Uniform and smooth molybdenum film produced through picosecond pulsed laser deposition
摘要： An approach to achieve uniform and smooth molybdenum (Mo) ?lm on a BK7 glass plate at room temperature is proposed through picosecond pulsed laser deposition, with the pulsed laser radiating the target along a linear track. A numerical model is established to analyze the in?uence of linear scanning offsets on the thickness homogeneity of the deposited thin ?lm. Through an appropriate choice of radiation intensity and scanning parameters, a uniform and smooth layer of Mo thin ?lm is prepared with its maximum thickness variation and root-mean-square roughness better than 5% and 1.2 nm, respectively.
关键词： picosecond pulsed laser deposition,smooth,numerical model,molybdenum film,uniform
更新于2025-09-11 14:15:04
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Propagation Kinetics of Isoprene Radical Homopolymerization Derived from Pulsed Laser Initiated Polymerizations
摘要： The propagation kinetics of isoprene radical polymerizations in bulk and in solution are investigated via pulsed laser initiated polymerizations and subsequent polymer analyses via size-exclusion chromatography, the PLP-SEC method. Because of low polymerization rate and high volatility of isoprene, the polymerizations are carried out at elevated pressure ranging from 134 to 1320 bar. The temperatures are varied between 55 and 105 °C. PLP-SEC yields activation parameters of kp (Arrhenius parameters and activation volume) over a wide temperature and pressure range that allow for the calculation of kp at technically relevant ambient pressure conditions. The kp values determined are very low, e.g., 99 L mol?1 s?1 at 50 °C, which is even lower than the corresponding value for styrene polymerizations. The presence of a polar solvent results in a slight increase of kp compared to the bulk system. The kp values reported are important for determining rate coefficients of other elemental reactions from coupled parameters as well as for modeling isoprene free-radical polymerizations and reversible deactivation radical polymerization with respect to tailored polymer properties and optimizing the polymerization processes.
关键词： polyisoprene,radical polymerization,kinetics,pulsed laser initiated polymerization
更新于2025-09-11 14:15:04
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[IEEE 2018 10th International Conference on Advanced Infocomm Technology (ICAIT) - Stockholm, Sweden (2018.8.12-2018.8.15)] 2018 10th International Conference on Advanced Infocomm Technology (ICAIT) - Mode-locked Fiber Laser Based on ZnO Nanoparticles as a Saturable Absorber
摘要： A mode-locked fiber laser based on ZnO nanoparticles as a saturable absorber is developed. ZnO nanoparticles deposited on a side-polished fiber function as a proper saturable absorber in the near infrared range. Mode-locking of pulses is verified through the Fourier transform analysis which characterizes the longitudinal modes of ring cavity. Stable optical pulses of less than 1-ns (resolution-limited) pulse-width are generated at 1064 nm.
关键词： ZnO nanoparticles,pulsed laser,side-polished fiber,saturable absorber,mode-locked
更新于2025-09-11 14:15:04