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- 实验方案
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Photoluminescence Properties of Yb and Ag Co-Doped Ta<sub>2</sub>O<sub>5</sub> Thin Films
摘要： We prepared ytterbium and silver co-doped tantalum-oxide (Ta2O5:Yb,Ag) thin films using a simple co-sputtering method and evaluated photoluminescence (PL) properties of the films after annealing. We found that a PL peak at a wavelength of 980 nm due to Yb3+ can be strongly enhanced by Ag doping. From X-ray diffraction measurements, we found that Ag2Ta8O21 and orthorhombic Ta2O5 crystalline phases are very important in order to enhance the 980-nm peak observed from our Ta2O5:Yb,Ag thin films. Because of the human-body transmittability of the 980-nm wavelength, such films are applicable to a novel real-time X-ray dosimeter system.
关键词： Yb,Ag,co-sputtering,Ta2O5,photoluminescence,X-ray diffraction
更新于2025-09-19 17:15:36
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Ultra-narrow band perfect metamaterial absorber based on dielectric-metal periodic configuration
摘要： The ultra-narrow band perfect metamaterial absorber (PMA) based on dielectric-metal periodic configuration for near infrared spectral region is proposed. The PMA consists of a dielectric resonant structure and a metal substrate. Two design examples show that the proposed PMAs are able to exhibit nonpolarizing absorption peaks at normal and oblique incidences respectively. Moreover, the absorption spectra of the PMA for oblique incidence are insensitive to the incident angle under TE polarized light illumination. But this PMA exhibits a large spectral shift by rotating the angle of incidence under TM polarized light illumination. Then a PMA sample for oblique incidence is fabricated through thin-film deposition and electron beam lithography patterning. Finally, the reflection spectra of the fabricated PMA sample are measured. The absorption spectra obtained by subtracting the measured reflection spectra from incident spectra are consistent with the theory. Thus the novel characteristics of the ultra-narrow band PMA based on dielectric-metal periodic configuration are experimentally demonstrated.
关键词： Ultra-narrow band,Nonpolarizing absorption,Perfect metamaterial absorber,Tunable spectrum,Diffraction grating
更新于2025-09-19 17:15:36
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Dynamics of the photoinduced insulator-to-metal transition in a nickelate film
摘要： Material properties can be controlled via strain, pressure, chemical composition, or dimensionality. Nickelates are particularly susceptible due to their strong variations of the electronic and magnetic properties on such external stimuli. Here, we analyze the photoinduced dynamics in a single crystalline NdNiO3 film upon excitation across the electronic gap. Using time-resolved reflectivity and resonant x-ray diffraction, we show that the pump pulse induces an insulator-to-metal transition, accompanied by the melting of the charge order. Finally, we compare our results with similar studies in manganites and show that the same model can be used to describe the dynamics in nickelates, hinting towards a unified description of these photoinduced electronic ordering phase transitions.
关键词： resonant x-ray diffraction,nickelate,insulator-to-metal transition,charge order,photoinduced dynamics,time-resolved reflectivity
更新于2025-09-19 17:15:36
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Wave diffraction by a half-screen with Nth order generalized sheet transition conditions
摘要： The scattering of plane waves by a half-plane with Nth order transition conditions is investigated. First of all, the reflection and transmission conditions of the transmissive surface are evaluated by using the generalized sheet transmission boundary conditions. The scattered geometrical optics fields are determined from the total geometrical optics and incident waves. The diffracted field is obtained by using a relation between the scattered geometrical optics and diffracted waves. The behaviors of the total, total geometric optics and diffracted fields are analyzed numerically.
关键词： Metasurfaces,Diffraction theory,Generalized sheet boundary conditions
更新于2025-09-19 17:15:36
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Generation of pure Laguerre-Gaussian vector beams on the higher-order Poincaré sphere by hollow Gaussian beams through dielectric metasurfaces
摘要： It is a longstanding challenge for the extracavity generation of vector beams (VBs) to have pure Laguerre-Gaussian (LG) modes due to diffraction. Here we propose theoretically and realize experimentally the generation of pure LG VBs by using hollow Gaussian beams (HGBs) through q-plates. A general expression for the VB generated by the HGB with arbitrary polarization is derived. It is found that when the order of the HGB is two times the topological charge of the q-plate, the VB possesses a pure LG mode and that any desired polarization distribution on the higher-order Poincaré sphere can be realized by tuning the incident polarization. Further we implement the q-plates with dielectric metasurfaces and experimentally verify the theoretical results. The generated pure LG VB may find applications in the situations where high mode purity is required.
关键词： Vector beam,Laguerre-Gaussian mode,Diffraction,Metasurfaces,Pancharatnam-Berry phase,Hollow Gaussian beam
更新于2025-09-19 17:15:36
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Tilted-pulse-front space-time wave packets
摘要： Tilted-pulse-front pulses, which are produced via dispersive devices that introduce angular dispersion, are useful in many areas of nonlinear optics. Such pulses typically have large transverse cross sections and propagate for limited distances to offset the impact of diffractive space-time coupling that leads to spectral walk-off. Here we show that sculpting the spatio-temporal spectral profile of a pulsed plane wave enables the synthesis of propagation-invariant wave packets endowed with a tilted intensity pulse front with respect to the propagation axis. These wave packets are based on new elementary propagation-invariant wave-packet solutions to the wave equation obtained by a complexification of the space and time degrees of freedom.
关键词： Propagation-invariant pulses,Tilted-front-pulses,Diffraction-free,Space-time wave packets
更新于2025-09-19 17:15:36
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Surface microstructural characteristics and hardness of Cr-coated Zr702 sheet processed by pulsed laser
摘要： Microstructural characteristics and hardness of Cr-coated Zr702 sheet after the laser surface treatment (LST) were characterized and investigated by combined use of electron backscatter diffraction, electron channeling contrast imaging, energy dispersive spectrometry and hardness measurement. Results show that after the LST processing at 100 W, three zones with different microstructural characteristics are presented from the surface to the matrix: melted zone (MZ), solid-state phase transformation zone (SSPTZ) and matrix. Surface alloying with Cr occurs in the MZ, leading to the formation of a large number of discontinuous netlike ZrCr2 Laves phases. The SSPTZ is comprised of untransformed bulk α grains with internal substructures and fine martensitic plates. The appearance of such substructures can be attributed to dislocation movements induced by thermal stresses while the martensitic plates result from rapid β→α transformation induced by the pulsed laser. Hardness measurements show that the LST can remarkably increase surface hardness (by ~110%) of the Cr-coated Zr702 sheet, which can be ascribed to strengthening/hardening effects by solid solution of Cr, the formation of dense second phases and significant grain refinement.
关键词： Electron backscatter diffraction,Microstructure,Hardness,Laves phase,Zr702 sheet,Laser surface processing
更新于2025-09-19 17:13:59
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Eco-friendly synthesis of regioregular poly(3-hexylthiophene) by direct arylation polymerization: Analysis of the properties that determine its performance in BHJ solar cells
摘要： A series of regioregular poly(3-hexylthiophenes) (rr-P3HTs) was synthetized by optimizing an eco-friendly Direct Arylation Polymerization (DArP) method, using as novel strategy, a gradual catalyst addition and temperature reaction increase improving P3HT quality. The polymers were analyzed and tested in organic solar cells (OSCs) in order to correlate the P3HTs properties with the power conversion efficiency (PCE). Results revealed that the best PCEs (3.6 and 3.4 %) were reached with P3HTs of the highest RR (94 and 93 % HT), with the lowest molecular weight (5.1 and 4.9 kDa) and, as X-ray diffraction in films and 2D-GIWAXS results endorse, with an edge-on orientation over the substrate, the largest size crystal and the highest Bragg’s peaks, this latter feature could be the most effective reason to obtain the best PCEs. Theoretical calculations helped to understand how specific P3HT crystalline arrangements in the active layer favors the PCE.
关键词： X-ray diffraction,Poly(3-hexylthiophene),organic solar cells,eco-friendly direct heteroarylation polymerization
更新于2025-09-19 17:13:59
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GaAs1-Sb /GaAs single quantum well for long wavelength photonic devices
摘要： Carrier dynamics in GaAs1-xSbx/GaAs single quantum well (SQW) is investigated in this report. With Sb incorporation (x = 0.352, 0.405), the photoluminescence (PL) emission peaks exhibit characteristics of GaAs1-xSbx in low temperature and GaAs above 200 K. In power dependent PL, the intensities reveal sublinear power relationship as localized and free excitons are involved at 10 K. The power exponent is in agreement with the degree of localization energy present in SQW and carrier kinetics for various recombination mechanisms are also discussed by deriving respective rate equations.
关键词： X-ray diffraction,Gallium Arsenic-antimonide,Photoluminescence,Heterostructure,SQW
更新于2025-09-19 17:13:59
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Deposition of p-type Al doped PbS thin films for heterostructure solar cell device using feasible nebulizer spray pyrolysis technique
摘要： Doping of metal atoms with PbS thin films can make significant influence on the structural and electron transport properties which makes it suitable for photovoltaic and other device applications. The objective of the present work is to study the structural, morphological, optical and electrical properties of PbS:Al thin films as a function of different Al doping percentage. PbS and Al doped PbS thin films were deposited using Nebulizer Spray Pyrolysis (NSP) on soda lime glass substrates by varying Al doping level from 0 wt% to 8 wt%. Polycrystalline nature with face centered cubic crystal structure was noticed for all the prepared films from XRD pattern. The orientation along (200) plane was observed for all the prepared films. From AFM analysis, the observed surface roughness values were considerably decreased on increasing the Al doping concentration. The calculated optical band gap values exhibits increasing trend and shifted from 1.54 eV to 1.66 eV on increasing Al doping concentration. The electrical resistivity value of the PbS:Al thin films were reduced from 3.08 ? 103 to 1.63 ? 103 Ωcm with raise in Al doping level. The solar cell efficiency for FTO/n-CdS/p-PbS:Al structure constructed from 6% of Al doped PbS film was about 0.44%.
关键词： SEM/AFM,Hall effect measurement,PbS:Al structure,UV visible,Solar cell,X-ray diffraction
更新于2025-09-19 17:13:59