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A facile method for direct bonding of single-crystalline SiC to Si, SiO2, and glass using VUV irradiation
摘要： Single-crystalline silicon carbide is an attractive material for power electronics. However, it is difficult to achieve the direct bonding of SiC to conventional Si-based materials (e.g., Si, SiO2, and glass) due to the large mismatch in coefficients of thermal expansion and lattice constants. To solve the bottleneck, we present a facile direct bonding method using vacuum ultraviolet (VUV) surface irradiation for a robust combination of SiC to Si, SiO2, and glass at low temperatures (≤ 200 oC). The mechanisms behind the VUV-irradiated bonding of SiC to Si-based materials were also investigated. According to surface characterizations, VUV irradiation can lead to smooth and hydrophilic surfaces, which are beneficial for direct bonding in humid air. The tight and defect-free SiC/Si, SiC/SiO2 and SiC/glass bonding interfaces were confirmed by transmission electron microscopy. In particular, the enriched carbon transition layers were formed on the side of silicon carbide because of the oxidation and sputtering of Si atoms during VUV irradiation. This will possibly improve the bonding interfaces and contribute to the enhanced bonding strengths. Moreover, the SiC/glass bonded pair exhibited relatively high optical transparency in the UV-Vis range. Therefore, the direct bonding of single-crystalline SiC and heterostructure Si-based materials offers great potentials for high-performance power electronics, as well as micro/nanofluidic devices.
关键词： direct bonding,vacuum ultraviolet,interface,silicon carbide
更新于2025-09-23 15:21:21
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Indirect predissociation of highly excited singlet states of N <sub/><b>2</b> </sub>
摘要： Indirect predissociation of the b(cid:2) 1(cid:1)+u (v = 20) level of N2 is studied experimentally by vacuum-ultraviolet photoabsorption employing synchrotron radiation and a Fourier-transform spectrometer, and interpreted with the aid of a quantitative model of interacting 1(cid:2)u and 1(cid:1)+u, bound and unbound states which solves the coupled Schr?dinger equation. An observed rotationally-localised peak in the b(cid:2)(20) predissociation linewidths is identi?ed by the model as arising from an interaction with a strongly predissociated and unobserved bound level of the mixed c3 1(cid:2)u and o3 1(cid:2)u Rydberg states. This leads to the dissociation of b(cid:2)(20) into the continuum of the b 1(cid:2)u valence state. The residual observed predissociation of b(cid:2) 1(cid:1)+u (v = 20) apart from the rotationally-localised peak cannot be explained by a mechanism of 1(cid:2)u and 1(cid:1)+u interaction, and must involve states of higher multiplicity.
关键词： Fourier-transform spectrometer,coupled Schr?dinger equation,vacuum-ultraviolet photoabsorption,N2,Indirect predissociation,synchrotron radiation
更新于2025-09-23 15:21:01
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Infrared + vacuum ultraviolet two-color ionization spectroscopy of neutral metal complexes based on a tunable vacuum ultraviolet free-electron laser
摘要： This paper describes an experimental technique for studying neutral metal complexes using infrared + vacuum ultraviolet (IR+VUV) two-color ionization spectroscopy based on a tunable VUV free-electron laser (VUV-FEL). The preliminary IR spectroscopy results of mass-selected nickel tetracarbonyl are reported in this work. The results demonstrate that the tunable VUV-FEL light allows the selective ionization of a given neutral cluster free of confinement along with the recording of well-resolved IR spectra. As the ionization energies of many neutral clusters are accessible by a broadly tunable VUV-FEL (50–150 nm) and near-threshold ionization can be readily achieved, the proposed experimental method offers unique possibilities for the size-specific study of a wide variety of confinement-free neutral clusters.
关键词： infrared,vacuum ultraviolet,tunable VUV free-electron laser,two-color ionization spectroscopy,neutral metal complexes
更新于2025-09-23 15:19:57
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Study on Irradiation Effect of Mid-Infrared Free Electron Laser on Hen Egg-White Lysozyme by Using Terahertz-Time Domain Spectroscopy and Synchrotron-Radiation Vacuum-Ultraviolet Circular-Dichroism Spectroscopy
摘要： Mid-infrared free-electron laser (MIR-FEL) is potentially applicable for tissue ablation and dissociation of pathological peptide aggregates in medicine. However, it is still poorly understood how the MIR-FEL irradiation influences on functional proteins such as enzymes. In the current study, the effect of MIR-FEL on both aggregate and non-aggregate (= native) states of hen egg-white lysozyme (HEWL) as a representative enzyme has been investigated. Absorption intensity at terahertz region (0.3–1.2 THz, 10–40 cm?1) of the aggregate of HEWL was lower than that of the native HEWL, but the former was increased nearly to the same level with the latter after the MIR-FEL irradiation tuned to 6 μm that corresponds to carbonyl stretching vibrational mode of amide bonds (amide I). This indicates that the aggregate of HEWL was converted to the native state by the irradiation. On the other hand, synchrotron-radiation vacuum-ultraviolet circular-dichroism spectroscopy showed that protein conformation of the native HEWL, which was rich in α-helix, was little changed after the MIR-FEL irradiation under the same condition with the case of the aggregate of HEWL. Furthermore, the enzymatic hydrolysis activity of the native HEWL against bacterial glycan was not remarkably decreased by the irradiation. Therefore, it can be estimated that the native structure of HEWL is little damaged although the aggregate state can be easily dissociated by the resonant excitation at amide bonds.
关键词： Vacuum-ultraviolet circular-dichroism spectroscopy,Mid-infrared free-electron laser,Protein aggregate,Terahertz-time domain spectroscopy
更新于2025-09-19 17:13:59
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Experimental and theoretical investigations on high power vacuum-ultraviolet laser at 165?nm by eighth-harmonic generation in KBBF
摘要： A high power nanosecond (ns) vacuum-ultraviolet (VUV) laser at 165 nm was demonstrated by means of a frequency-octupled 1319 nm Nd:YAG laser with a thick KBe2BO3F2 crystal. A 6.8 mW maximum output power at 165 nm was attained in the experiment, which is to our knowledge the highest power for all solid state lasers below 170 nm. The 165 nm output power versus the 330 nm pump power was simulated. The calculated result was well consistent with experimental data. Meanwhile, the dependence of 165 nm output power on the KBBF effective length was investigated theoretically. It was found that the thickness of KBBF crystal used in our experiment is close to the optimal thickness, which allows to creating the high VUV output power. We used the simulation further to analyze the pulse width, beam quality factor and beam spatial intensity profile of the generated 165 nm radiation.
关键词： Eight-harmonic generation,Vacuum-ultraviolet laser,KBBF
更新于2025-09-12 10:27:22
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Vacuum ultraviolet laser induced breakdown spectroscopy for detecting sulphur in thermally aged transformer insulation material
摘要： Spatially resolved and temporally integrated vacuum ultraviolet laser induced breakdown spectroscopy (VUV LIBS) was used for contaminant analysis in thermally aged oil impregnated pressboard (OIP) insulation material from high voltage transformers. The signature of copper sulphide contamination was obtained through detection of Cu and S emission lines. The plasma emission also contained highly ionized Oxygen and Carbon emission lines. S emissions were found to be strong in the VUV region in contrast to the UV-VIS region. The concentration of sulphur was found to increase with the duration of ageing of the OIP material.
关键词： copper sulphide,laser induced breakdown spectroscopy,Oil impregnated pressboard,vacuum ultraviolet,VUV,LIBS
更新于2025-09-11 14:15:04
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A soft x-ray-ultraviolet (SUV) beamline and diffractometer for resonant elastic scattering and ultraviolet-vacuum ultraviolet reflectance at the Singapore synchrotron light source
摘要： A new beamline and a six-circle UHV diffractometer have been constructed at the Singapore Synchrotron Light Source with a broad energy coverage from 3.5 to 1500 eV. The beamline is optimized for ultraviolet-vacuum-ultraviolet optical reflectivity and resonant soft X-ray scattering with medium energy resolution over a broad energy range, achieved by using a self-focusing monochromator consisting of a plane mirror and three variable line spacing gratings. The unique character of the diffractometer comprises 4-circles in the vertical plane and 2-circles in the horizontal plane. Thirteen motions are available inside the UHV chamber with a base pressure of 1 × 10?9 mbar. Two sample holders working independently over a temperature range of 37 K–400 K are controlled by a closed-cycle cryostat, while the bottom holder inside a high field compact pulsed magnet is available for measurements requiring a magnetic field.
关键词： ultraviolet-vacuum ultraviolet reflectance,soft x-ray-ultraviolet beamline,resonant elastic scattering,diffractometer,Singapore synchrotron light source
更新于2025-09-10 09:29:36
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crystal structure on the stability of polymer composites exposed to vacuum ultraviolet radiation
摘要： Vacuum ultraviolet (VUV) radiation produced by the Sun in the space environment can cause degradation to thermoregulating coatings producing changes in optical, mechanical, and chemical properties. These effects are particularly important for polymers. The purpose of this study was to study the effect of VUV radiation on polymeric composites based on polyalkaneimide. Amorphous and crystalline SiO2 were used as the filler. A comparative characterization of physico-mechanical properties of composites is presented depending on the polymorphic structure of the filler being introduced. According to the microhardness of the surface of composites with amorphous and crystalline SiO2, an optimum filler content of 60–65 wt% is established. The exposure of VUV radiation to polymeric composites with SiO2 leads to a mass loss and a change in their near-surface layers, which leads to a deterioration in the optical properties. At an elevated temperature (125oC), the mass loss of all composites with amorphous crystalline SiO2 does not exceed 1.33%, and with crystalline SiO2, the maximum mass loss is 0.52%. The mass loss of composites with crystalline SiO2 of all compositions did not exceed the allowable value for spacecraft products of 1%. For high-filled (50 wt% filler or more) composites with amorphous SiO2, mass loss after VUV treatment is more than 1%, which does not allow them to be used in outer space. The change in the main optical characteristics of thermoregulating coatings after VUV treatment was studied. The smoothing of the surface of composites after VUV treatment is established.
关键词： Spacecraft coverings,Deep vacuum,Optical characteristics,Gas evolution,Vacuum ultraviolet,Cosmic radiation
更新于2025-09-10 09:29:36
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[Advances in Experimental Medicine and Biology] Glycobiophysics Volume 1104 || Synchrotron-Radiation Vacuum-Ultraviolet Circular-Dichroism Spectroscopy for Characterizing the Structure of Saccharides
摘要： Circular-dichroism (CD) spectroscopy is a powerful tool for analyzing the structures of chiral molecules and biomolecules. The development of CD instruments using synchrotron radiation has greatly expanded the utility of this method by extending the spectra to the vacuum-ultraviolet (VUV) region below 190 nm and thereby yielding information that is unobtainable by conventional CD instruments. This technique is especially advantageous for monitoring the structure of saccharides that contain hydroxy and acetal groups with high-energy transitions in the VUV region. Combining VUVCD spectra with theoretical calculations provides new insight into the contributions of anomeric hydroxy groups and rotational isomers of hydroxymethyl groups to the dynamics, intramolecular hydrogen bonds, and hydration of saccharides in aqueous solution.
关键词： Glycoprotein,Hydration,Circular dichroism,Synchrotron radiation,Time-dependent density functional theory,Molecular dynamics simulation,Saccharide,Intramolecular hydrogen bond,Solution structure,Structural dynamics,Vacuum ultraviolet,Glycosaminoglycan
更新于2025-09-10 09:29:36
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Anapole Resonances Facilitated by High Index Contrast between Substrate and Dielectric Nanodisk Enhance Vacuum Ultraviolet Generation
摘要： Anapole modes are known to be excited only in high-index nanoparticles. Here we show that the nanodisks made of dielectric materials with much lower refractive indices, such as LiNbO3, can generate anapole modes, provided that they are supported by metallic or near-zero-index substrate. The important parameter for exciting anapole mode is the index contrast between nanodisk and substrate, rather than the refractive index of the nanodisk. We numerically demonstrate highly efficient coherent generation of vacuum ultraviolet with the efficiency higher than 10-2 % based on the second-harmonic generation via the excitation of anapole modes in LiNbO3 nanodisks supported by aluminum substrate. Highly efficient vacuum ultraviolet nanosource proposed in this work can find important applications for spectroscopic and sensing purposes at the nanoscale.
关键词： Second-harmonic generation (SHG),Anapole mode,Refractive index,Nanodisks,Vacuum ultraviolet (VUV)
更新于2025-09-09 09:28:46