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Two-Dimensional Fluorine Distribution in a Heavily Distorted Perovskite Nickel Oxyfluoride Revealed by First-Principles Calculation
摘要： Most perovskite oxyfluorides synthesized to date have cubic structures, wherein fluorine atoms tend to reside at every oxygen site randomly. In this theoretical study, we show a two-dimensional fluorine arrangement in a perovskite nickel oxyfluoride (NdNiO2F) with a large orthorhombic distortion. The site selectivity in the perovskite lattice is due to the orthorhombicity, which stabilizes the two-dimensional cis configurations with shorter Ni?O and longer Ni?F bonds to minimize the electrostatic energy. The electronic structure of NdNiO2F is characterized by its large octahedral rotation and the higher electronegativity of fluorine than oxygen. We also observed how the anion arrangement was affected by the biaxial strain by modeling epitaxial strained thin film on substrate and found that the 2D cis structure remains the most stable. However, the orientation of the two-dimensional structure containing F depends on the magnitude of the biaxial strain. Our findings suggest that fluorine doping in orthorhombic perovskite oxides effectively yields oxyfluorides with anisotropic anion ordering.
关键词： electronic structure,orthorhombic distortion,perovskite oxyfluorides,two-dimensional fluorine arrangement,biaxial strain
更新于2025-09-12 10:27:22
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Laser Preparing Tunable Wrinkles on the Surface of PDMS with Assistance of Pre-strain Stress
摘要： Micro directional wrinkles are widely used to functionalize the surface inside micro chips. In this paper, a nano-second laser, with the assistance of pre-strain stress, was applied to prepare tunable wrinkles on the surface of PDMS (polydimethylsiloxane). Experiments were carried out to investigate the impact of the pre-strain stress and the laser fluence on the wrinkles, like the direction and the wavelength. It was noticed that wrinkles prepared in the process grown vertically to the direction of the pre-strain stress. The wrinkles wavelength increased from about 500nm to 2.5μm when the power shifted from 5W to 8W. And strengthening the pre-strain stress sharply reduced the wavelength at the beginning then the trend was slowed down and some cracks were observed. And the end, a model was proposed to tune the pattern of wrinkles by precisely control pre-strain stress and the laser power. With that, several pattern of wrinkles was prepared.
关键词： Pre-strain,bio-application,surface modification,wrinkles,PDMS
更新于2025-09-12 10:27:22
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Extracellular biosynthesis of cadmium sulphide quantum dot using cell-free extract of Pseudomonas chlororaphis CHR05 and its antibacterial activity
摘要： For the ?rst time a novel aquatic bacterium belonging to strain of Pseudomonas chlororaphis was developed for the synthesis of cadmium sul?de quantum dots. The cadmium sulfate solution incubated with cell-free extract (CFE) of P. chlororaphis strain CHR05 to generate cadmium sul?de nanoparticles (CdSNps) which were characterized with combined spectroscopy and microscopy analyses. The preliminary con?rmation on the formation of CdSNps was done by UV–vis and ?uorescence analyses with the absorption and emission spectra at 435 and 475 nm, respectively. EDX pattern shows that the CdSNps are composed of the elementals Cd and S. Also, XRD analysis of the puri?ed nanoparticles con?rmed the formation of CdSNps. FE-SEM, TEM, and DLS analyzed the size and morphology of the CdSNps. The biosynthesis of CdSNps with the strategy of cell free extract was investigated under optimum conditions. After 24 h of incubation, the results showed that the novel isolated strain can produce spherical CdSNps with an average size of 6.7 ± 2.4 nm, after exposure to CdSO4 solution (2.5 mM) at pH 7.5 and 30 °C. The antibacterial activity CdSNps against some Gram-positive and -negative bacteria were determined using agar well di?usion method and microplate method which has growth-inhibitory e?ect all on tested bacteria.
关键词： CdSNps,Cell-free extract,P. chlororaphis strain CHR05,Antibacterial activity
更新于2025-09-12 10:27:22
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Optical Fiber Strain Measurements and Numerical Modeling of Load Tests on Grouted Anchors
摘要： This paper reports on the behavior of a grouted anchor instrumented with a fiber optic strain sensor in the grout body along the entire anchor length. During load tests up to the estimated pull-out capacity, the strain measurements indicate that a delamination occurs in the tendon bond length between the steel tendons and the grout body. The upper delaminated part of the grout body is under compression, whereas the lower bonded part of the grout body is under tension. This delamination gradually progresses as the anchor load increases. Furthermore, a significant part of the load is transferred from the anchor to the soil in the tendon free length. The anchor behavior is further modeled with a one-dimensional finite-element model that includes the steel tendons and the grout body, where an interface damage model is used to account for possible delamination of the interface. The numerical model confirms that the observed compressive and tensile strains in the grout can be related to a delamination of the steel strands in the tendon bond length. The experiment and numerical modeling demonstrate how optical fiber measurements in the grout body can be used, in operational conditions, to assess the anchor behavior, the mobilization of the soil resistance, and the estimation of the remaining anchor capacity.
关键词： soil resistance,fiber optic strain sensor,grouted anchor,delamination,finite-element model
更新于2025-09-12 10:27:22
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Strain-Related Degradation of GaN-Based Blue Laser Diodes
摘要： Degradation of GaN-based laser diodes (LDs) is studied using Electroluminescence (EL) and Transmission Electron Microscopy (TEM). The slope efficiency decrease is observed in addition to threshold current increase. Further studies on the optical loss and microstructures of the LDs indicate that the reduction of the slope efficiency is attributed to the increase of optical loss (from 14.2 cm-1 to 24.2 cm-1) and decrease of injection current efficiency induced by the defect generation around the waveguide and cladding layers. Injection current induced blue-shift of the spontaneous EL peak reduced after > 3000 hrs operation, which is ascribed to the compensation of Quantum-Confined Stark Effect (QCSE) caused by partial strain relaxation near the active region.
关键词： Spectroscopy,Degradation,Strain relaxation,Semiconductor lasers,Linewidth
更新于2025-09-12 10:27:22
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Sensing characteristics of long period grating by writing directly in SMF-28 based on 800?nm femtosecond laser pulses
摘要： A long period grating is fabricated in standard SMF-28 ?bers without hydrogen loading by adopting point-by-point direct writing based on femtosecond laser pulses with 800 nm wavelength and 100 fs pulse width. Its sensing characteristics is investigated and the sensing sensitivities to temperature, external refractive index (RI) and strain are systematically examined as well. The experimental results show that the sensing sensitivity of the long period grating to temperature, RI and strain is about 124 pm/°C with a linearity of 0.989 within temperature ranging from 20 °C to 800 °C, ?582.5 nm/RIU (refractive index unit) with a linearity of 0.998 in the RI ranging from 1.342 to 1.380, and ?9.45 × 10-4 dB/με with a linearity of 0.98 in the strain ranging from 0 to 2925 με, respectively. The high sensitivity of prepared LPG will have potential application values in sensing measurement of multi-parameters and in the ?eld of high temperature and harsh environments detection.
关键词： Refractive index (RI),Long Period Gratings (LPGs),Femtosecond laser,Strain sensing,Temperature sensitivity
更新于2025-09-12 10:27:22
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Strain-induced control of a pillar cavity-GaAs single quantum dot photon source
摘要： Herein, we present the calculated strain-induced control of single GaAs/AlGaAs quantum dots (QDs) integrated into semiconductor micropillar cavities. We show precise energy control of individual single GaAs QD excitons under multi-modal stress fields of tailored micropillar optomechanical resonators. Further, using a three-dimensional envelope-function model, we evaluated the quantum mechanical correction in the QD band structures depending on their geometrical shape asymmetries and, more interestingly, on the practical degree of Al interdiffusion. Our theoretical calculations provide the practical quantum error margins, obtained by evaluating Al-interdiffused QDs that were engineered through a front-edge droplet epitaxy technique, for tuning engineered QD single-photon sources, facilitating a scalable on-chip integration of QD entangled photons.
关键词： single-photon sources,quantum dots,micropillar cavities,strain-induced control,quantum computation
更新于2025-09-12 10:27:22
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High Power Quantum Cascade Laser at λ 5.1 <i>μ</i> m Based on Low Strain Compensation Design
摘要： We demonstrate the development of a high performance quantum cascade laser at (cid:2) ～ 5(cid:3)1 (cid:4)m with low strain-balanced structure using a double-phonon resonant design approach. The wafer was grown by solid source molecular beam epitaxy and fabricated with buried heterostructure waveguides. A high output power up to 1.5 W is obtained at 288 K with a high wall plug ef?ciency of 8.5% for devices with stripe dimension of 5 mm × 10 (cid:4)m. The characteristic temperatures, T 1, are 114 K and 198 K respectively.
关键词： High Power Laser,Strain-Compensation,Quantum Cascade Laser
更新于2025-09-12 10:27:22
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Nanomachining-enabled strain manipulation of magnetic anisotropy in the free-standing GaMnAs nanostructures
摘要： Strain perturbs atomic ordering in solids, with far-reaching consequences from an increased carrier mobility to localization in Si, stabilization of electric dipoles and nanomechanical transistor action in oxides, to the manipulation of spins without applying magnetic fields in n-GaAs. In GaMnAs, a carrier-mediated ferromagnetic semiconductor, relativistic spin-orbit interactions – highly strain-dependent magnetic interactions – play a crucial role in determining the magnetic anisotropy (MA) and anisotropic magnetoresistance (AMR). Strain modifies the MA and AMR in a nanomachined GaMnAs structure as measured by the anomalous Hall effect (AHE) and the planar Hall effect (PHE). Here, we report an MA modification by strain relaxation in an isolated GaMnAs Hall bar structure and by applying a range of local strains via fabricating asymmetrically mechanically buckled GaMnAs micro-Hall bar structures. in the AHe and pHe measurements, we observe a reduction in the in-plane MA and an enhancement in the out-of-plane MA as the compressive strain due to the lattice mismatch relaxes in the suspended structure. The functionality of such mechanical manipulation, as well as the two-level mechanical state and the corresponding AHe responses, is demonstrated by a fully scalable binary mechanical memory element in a GaMnAs single Hall cross structure.
关键词： strain,GaMnAs,magnetic anisotropy,planar Hall effect,anomalous Hall effect
更新于2025-09-12 10:27:22
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Tuning the electron band structure of graphene for optoelectronics
摘要： Graphene, a conjugated sp2 carbon sheet arranged in a two-dimensional honeycomb-like lattice, shows the unique electronic structure in which conical shaped π-electron conduction and valence bands meet at the Dirac point. The properties of graphene are largely controlled by the Fermi level and the density of π-electron states, which can be used for tuning graphene to specific optoelectronic and electrochemical applications. We report a computational study of the electron states and electrochemical response towards I?/I3 redox mediator used in dye sensitized solar cells. We consider the influence of lattice deformations and magnetic field combined with covalently bonded moieties and charged ions on the heterogeneous electron transfer kinetics.
关键词： uniaxial strain,density of electron states,graphene,heterogeneous electron transfer,Landau levels
更新于2025-09-12 10:27:22