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The Effects of Laser Parameters and the Ablation Mechanism in Laser Ablation of C/SiC Composite
摘要： The e?ects of laser parameters and the ablation mechanism in laser ablation of a carbon ?ber reinforced silicon carbide (C/SiC) composite are investigated in the present study. Six di?erent power densities are provided, as well as six levels of pulse numbers, and then ablation experiments are conducted for the C/SiC composite, induced by a pulsed laser. Based on the experimental results, the characteristics of surface morphology and ablation behavior are discussed. It is revealed that the surface morphology of the C/SiC composite under laser irradiation usually includes three regions: the center region, the transition region, and the border region. With the increase of laser power density, the ablation of the center region becomes severe, surface cracks occur, and more spherical SiC particles are found in the transition region. As for scenarios involving multiple pulses, the damage occurs in the center region at low power density limits, within the ?rst two layers below the surface. However, if the power density is relatively high, an ablation pit occurs in the center region when the pulse number is larger than 50. Meanwhile, the transition region and the border region diminish with increase of the pulse number. It is noted that both the power density and pulse number have noticeable e?ects on surface morphology and ablation behavior during laser ablation, which is helpful for material design and performance evaluation of C/SiC composites.
关键词： Surface morphology,C/SiC composite,Ablation mechanism,Laser ablation,Scanning electron microscopy (SEM)
更新于2025-09-12 10:27:22
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Measurement and Evaluation of Local Surface Temperature Induced by Irradiation of Nanoscaled or Microscaled Electron Beams
摘要： Electron beams (e-beams) have been applied as detecting probes and clean energy sources in many applications. In this work, we investigated several approaches for measurement and estimation of the range and distribution of local temperatures on a subject surface under irradiation of nano-microscale e-beams. We showed that a high-intensity e-beam with current density of 105-6 A/cm2 could result in vaporization of solid Si and Au materials in seconds, with a local surface temperature higher than 3000 K. With a lower beam intensity to 103-4 A/cm2, e-beams could introduce local surface temperature in the range of 1000–2000 K shortly, causing local melting in metallic nanowires and Cr, Pt, and Pd thin films, and phase transition in metallic Mg-B films. We demonstrated that thin film thermocouples on a freestanding Si3N4 window were capable of detecting peaked local surface temperatures up to 2000 K and stable, and temperatures in a lower range with a high precision. We discussed the distribution of surface temperatures under e-beams, thermal dissipation of thick substrate, and a small converting ratio from the high kinetic energy of e-beam to the surface heat. The results may offer some clues for novel applications of e-beams.
关键词： Vaporization,Local temperature,Nanoscale thermometry,Transmission electron microscopy,Thin film thermocouple,Energy converting,Electron beam,Scanning electron microscopy,Melting point
更新于2025-09-11 14:15:04
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Micron-Sized Constrictions Fabricated Using the Femtosecond Laser Technique on YBCO Thin Films
摘要： In this paper, I report on the fabrication of micron-sized constrictions in YBCO thin films using the femtosecond laser technique. The constrictions are S-shaped superconducting weak links fabricated on YBCO thin films. The constrictions show a measurable superconducting current flowing through them. Current-voltage (I–V) characteristics were used to determine the critical current IC of the constrictions at 77 K. The width of the constrictions was determined at the narrowest point using SEM (scanning electron microscope). Three micron-sized constrictions were fabricated with a width of 2.88 μm, 1.72 μm, and 1.69 μm and a length of 5 μm. Based on the width and length of these constrictions in relation to the coherence length (ξ) of the YBCO, these constrictions should conduct supercurrent by Abrikosov vortices. The SEM images show that the femtosecond laser heats the samples beyond the geometric boundary, damaging some of the superconductive phases of the YBCO constrictions. As a result, the constrictions conduct current by one-dimensional depairing.
关键词： Atomic force microscope (AFM),Abrikosov vortices,Flux pinning,YBCO thin film,Lasers,Critical currents,Scanning electron microscopy (SEM)
更新于2025-09-11 14:15:04
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<i>In-Situ</i> Observation for Formations of Gold Micrometer-Sized Particles in Liquid Phase Using Atmospheric Scanning Electron Microscopy (ASEM)
摘要： In this report, we present a novel method to produce micrometer-sized gold particles by dissolving and recovering gold from a dimethyl sulfoxide/hydrochloric acid (DMSO/HCl) solution containing copper (II) chloride (CuCl2) and sodium chloride (NaCl). It was reported that spherical or confeito-like particles can be formed depending on the concentrations of dissolved gold and Cl? ions in the solution. In this paper, in-situ observation of gold particle formation in the solution phase was conducted using atmospheric scanning electron microscopy (ASEM). An electron-permeable window made of a pressure-resistant silicon nitride (Si3N4) film (100 nm-thick), was set at the bottom of the open ASEM sample dish, which facilitated the projection of electron beams from underneath the sample. This structure of ASEM enabled us to observe dynamic phenomena in liquid or gas phase under atmospheric pressure in real time. It was found during the in-situ observation that all of the particles formed were confeito-like in shape, which was different from the expected particle morphology.
关键词： gold,in-situ observation,atmospheric scanning electron microscopy (ASEM),particle formation
更新于2025-09-11 14:12:44
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Determination of Sulfite in Botanical Medicine Using Headspace Thin-Film Microextraction and Surface Enhanced Raman Spectrometry
摘要： A facile method using headspace thin-film microextraction (HS-TFME) coupled with surface enhanced Raman spectrometry (SERS) has been developed for the determination of sulfite in traditional Chinese herbal medicine. The extraction substrate was synthesized by depositing urchin-like ZnO micron particles on glass sheets using chemical liquid phase deposition. Under the optimal conditions, the intensity of the SERS signal at 630–640 cm?1 provided a good linear relationship with the concentration of sulfite from 25 to 400 mg/kg, and the linear correlation coefficient (R) was 0.996 with a detection limit of 6 mg/kg. The method was employed for the determination of sulfite in herbal medicines, and the results were confirmed by a traditional distillation-titration method. Therefore, this developed HS-TFME-SERS method may play an important role in the rapid, simple, and selective determination of sulfite residues in Chinese herbal medicine and become a potentially universal method for this analyte in various solid samples.
关键词： Headspace thin-film microextraction (HS-TFME),scanning electron microscopy (SEM),X-ray diffraction (XRD),surface enhanced Raman spectrometry (SERS),transmission electron microscopy (TEM)
更新于2025-09-10 09:29:36
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From EBIC images to qualitative minority carrier diffusion length maps
摘要： A novel method is presented with the aim to perform minority carrier di?usion length map on cross-sectional samples. The method is based on one Electron-Beam Induced Current (EBIC) acquisition and on the analyze of the EBIC signal slope variation on each scanned points. This method is applied on a pinned photodiode array realized on a low doped silicon epitaxy, and the electron di?usion length map which is extracted is in good accordance with our expectation taking into account the doping distribution of the device. A TCAD simulation also con?rms quantitatively the measured di?usion length map. Advantages and drawbacks of this method are discussed in this study.
关键词： CMOS image sensors,CMOS,Scanning electron microscopy (SEM),Simulation,Electron-beam-induced current (EBIC),Deep submicron process,Solid-state image sensor,Semiconductor material measurements
更新于2025-09-10 09:29:36
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Influence of a Surface Finishing Method on Light Collection Behaviour of PWO Scintillator Crystals
摘要： In the ?eld of scintillators, high scintillation and light production performance require high-quality crystals. Although the composition and structure of crystals are fundamental in this direction, their ultimate optical performance is strongly dependent on the surface ?nishing treatment. This paper compares two surface ?nishing methods in terms of the ?nal structural condition of the surface and the relative light yield performances. The ?rst polishing method is the conventional “Mechanical Diamond Polishing” (MDP) technique. The second polishing technique is a method applied in the electronics industry which is envisaged for ?nishing the surface treatment of scintillator crystals. This method, named “Chemical Mechanical Polishing” (CMP), is ef?cient in terms of the cost and material removal rate and is expected to produce low perturbed surface layers, with a possible improvement of the internal re?ectivity and, in turn, the light collection ef?ciency. The two methods have been applied to a lead tungstate PbWO4 (PWO) single crystal due to the wide diffusion of this material in high energy physics (CERN, PANDA project) and diagnostic medical applications. The light yield (LY) values of both the MDP and CMP treated crystals were measured by using the facilities at CERN while their surface structure was investigated by Scanning Electron Microscopy (SEM) and Grazing Incidence X-ray Diffraction (GID). We present here the corresponding optical results and their relationship with the processing conditions and subsurface structure.
关键词： light yield,scintillator crystals,polishing techniques,scanning electron microscopy,grazing incidence X-ray diffraction
更新于2025-09-10 09:29:36
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Synthesis of Ge1?xSnx Alloy Thin Films by Rapid Thermal Annealing of Sputtered Ge/Sn/Ge Layers on Si Substrates
摘要： In this work, nanocrystalline Ge1?xSnx alloy formation from a rapid thermal annealed Ge/Sn/Ge multilayer has been presented. The multilayer was magnetron sputtered onto the Silicon substrate. This was followed by annealing the layers by rapid thermal annealing, at temperatures of 300 ?C, 350 ?C, 400 ?C, and 450 ?C, for 10 s. Then, the effect of thermal annealing on the morphological, structural, and optical characteristics of the synthesized Ge1?xSnx alloys were investigated. The nanocrystalline Ge1?xSnx formation was revealed by high-resolution X-ray diffraction (HR-XRD) measurements, which showed the orientation of (111). Raman results showed that phonon intensities of the Ge-Ge vibrations were improved with an increase in the annealing temperature. The results evidently showed that raising the annealing temperature led to improvements in the crystalline quality of the layers. It was demonstrated that Ge-Sn solid-phase mixing had occurred at a low temperature of 400 ?C, which led to the creation of a Ge1?xSnx alloy. In addition, spectral photo-responsivity of a fabricated Ge1?xSnx metal-semiconductor-metal (MSM) photodetector exhibited its extending wavelength into the near-infrared region (820 nm).
关键词： Raman spectroscopy,Ge-Sn,thin films,sputtering,semiconductors,nanocrystalline,X-ray diffraction,scanning electron microscopy
更新于2025-09-10 09:29:36
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Assessment of tegumental damage to Schistosoma mansoni and S. haematobium after in vitro exposure to ferrocenyl, ruthenocenyl and benzyl derivatives of oxamniquine using scanning electron microscopy
摘要： Schistosomiasis is one of the most harmful parasitic diseases worldwide, praziquantel being the only drug in widespread use to treat it. We recently demonstrated that ferrocenyl, ruthenocenyl and benzyl derivatives of oxamniquine (Fc-OXA, Rc-OXA and Bn-OXA) are promising antischistosomal drug candidates. In this study we assessed the tegumental damage of these three derivatives of oxamniquine using scanning electron microscopy. Adult Schistosoma mansoni and S. haematobium were exposed to a concentration of 100 μM of each drug and incubated for 4–120 h, according to their onset of action and activity. While on S. mansoni the fastest acting compound was Fc-OXA, which revealed high activity after 4 h of incubation, on S. haematobium, Rc-OXA revealed the quickest onset, being lethal on all males within 24 h. In both species studied, the three derivatives showed the same patterns of tegumental damage consisting of blebs, sloughing and tegument rupturing all over the body. Additionally, on S. mansoni distinct patterns of tegumental damage were observed for each of the compounds: tissue ruptures in the gynaecophoric canal for Fc-OXA, loss of spines for Rc-OXA and oral sucker rupture for Bn-OXA. Our study confirmed that Fc-OXA, Rc-OXA and Bn-OXA are promising broad spectrum antischistosomal drug candidates. All derivatives show fast in vitro activity against S. mansoni and S. haematobium while validating the previous finding that the parent drug oxamniquine is less active in vitro under the conditions described. This work sets the base for further studies on the identification of a lead oxamniquine derivative, with the aim of identifying a molecule with the potential to become a new drug for human use.
关键词： Schistosoma haematobium,Scanning electron microscopy,Schistosomiasis,Oxamniquine,Schistosoma mansoni,Organometallic derivatives
更新于2025-09-10 09:29:36
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Morphological, Luminescence and Gas Adsorption Studies of Pb(II)-MOFs
摘要： In this study, we describe the synthesis of four Lead based organic frameworks (1 – 4) using 2,5-thiophenedicarboxylic acid (H2TDC) and 4-mercaptobenzoic acid (H2MBA) as organic linkers. Lead nitrate and Lead acetate were used as source of Pb +2 ions. The morphological and other structural aspects of these MOFs were subsequently established on the basis of Fourier transform infrared spectroscopy (FTIR), 1H NMR, Scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and powder X-ray diffraction technique. Brunauer-Emmett-Teller (BET) studies of these MOFs (1 – 4) revealed more promising adsorption of N2 gas by MOF 1 (surface area, 3699 m2/g) followed by 3 (surface area, 742 m2/g), 4 (surface area, 382 m2/g), 2 (surface area, 318 m2/g). Moreover, these MOFs (1 ? 4) have been investigated for their luminescence activity assigned to ligand-to-metal charge transfer (LMCT).
关键词： Lead,Scanning Electron Microscopy,luminescence,Bidentate Ligand,Metal organic frameworks
更新于2025-09-10 09:29:36