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Ultra-broad bandgap metal-insulator-metal waveguide filter with symmetrical stubs and defects
摘要： An ultra-broad bandgap plasmonic based ?lter that consists of a metal-insulator-metal waveguide with symmetrical stubs and defects is designed and investigated for the ?rst time. A tunable wide bandgap can be achieved by introducing the defects into the stubs and a larger bandgap width about 1.35 times compared to its counterpart without defects is acquired. It is found that both the defects and number of periods play the crucial roles to a?ect the bandgap performance, which is attributed to the change of e?ective refractive index and plasmon resonance modes in the proposed structure. The proposed plasmonic ?lter has potential to be a promising alternative structure to realize in integrated optical circuits for optical trapping and tunable devices.
关键词： Integrated optical circuits,Ultra-broad bandgap,Defects,Metal-insulator-metal waveguide,Plasmonic based ?lter
更新于2025-09-23 15:19:57
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Changes in the Photoluminescence of Monolayer and Bilayer Molybdenum Disulfide during Laser Irradiation
摘要： Various postsynthesis processes for transition metal dichalcogenides have been attempted to control the layer number and defect concentration, on which electrical and optical properties strongly depend. In this work, we monitored changes in the photoluminescence (PL) of molybdenum disulfide (MoS2) until laser irradiation generated defects on the sample flake and completely etched it away. Higher laser power was required to etch bilayer MoS2 compared to monolayer MoS2. When the laser power was 270 μW with a full width at half-maximum of 1.8 μm on bilayer MoS2, the change in PL intensity over time showed a double maximum during laser irradiation due to a layer-by-layer etching of the flake. When the laser power was increased to 405 μW, however, both layers of bilayer MoS2 were etched all at once, which resulted in a single maximum in the change of PL intensity over time, as in the case of monolayer MoS2. The dependence of the etching pattern for bilayer MoS2 on laser power was also reflected in position changes of both exciton and trion PL peaks. The subtle changes in the PL spectra of MoS2 as a result of laser irradiation found here are discussed in terms of PL quantum efficiency, conversion between trions and excitons, mean interatomic spacing, and the screening of Coulomb interaction.
关键词： photoluminescence,defects,etching,laser irradiation,molybdenum disulfide
更新于2025-09-23 15:19:57
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Dielectric Response of ZnTea??Ti/Al Schottky Junctions with CdTe Quantum Dots Studied by Impedance Spectroscopy
摘要： The electrical properties of ZnTe–Ti/Al Schottky junctions were investigated by the impedance spectroscopy (IS) method. Current-voltage (I-V) and capacitance-voltage (C-V) measurements were also performed. The studied samples were the CdTe quantum dot structures embedded in ZnTe matrix and a reference ZnTe sample without quantum dots. C-V characteristics confirmed the presence of quantum dots (QDs) in the structures. Electric modulus and impedance data were analyzed. IS studies proved that long-range conductivity governs the relaxation processes in the junctions. For both samples, the data were fitted with a simple RC circuit composed of a depletion layer capacitance in parallel with bulk resistance and a series resistance of contacts. The activation energy of the relaxation process observed for the reference sample obtained from the Arrhenius plot of the resistance, imaginary impedance, and electric modulus equals 0.4 eV at zero bias. For the quantum dot sample, the value of activation energy determined with the help of the same methods equals 0.2 eV. In conclusion, it was assumed that the relaxation processes for the reference sample are attributed to the trap present in ZnTe host material, whereas those observed for the QD structure are assigned to the deep level associated with defects located close to the QDs created during their growth.
关键词： quantum dots,defects,impedance spectroscopy,CdTe,ZnTe
更新于2025-09-23 15:19:57
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Antia??Counterfeiting Microstructures Induced by Ultrashort Laser Pulses
摘要： Ultrashort pulsed laser enables selective ablation of metal films on glass substrates, ripple formation on metal surface, and defect generation inside functional glass, etc. Correspondingly, direct writing of computer-generated holograms (CGHs), ripple rendered structure color, and defect featured photostimulated luminescence can be realized. Due to the feature of small size or invisibility, these induced microstructures can be used for anti-counterfeiting.
关键词： ultrashort laser pulses,computer-generated holograms,defects,anti-counterfeiting microstructures,ripples
更新于2025-09-23 15:19:57
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Probing a novel heat source model and adaptive remeshing technique to simulate laser powder bed fusion with experimental validation
摘要： A finite element method based three-dimensional heat transfer model with adaptive remeshing is presented to simulate the building of multiple tracks and layers in laser powder bed fusion of metallic powders with enhanced computational competence. A dimensional analysis is undertaken to define the heat source dimensions as function of laser parameters and properties of alloy powder. The computational model is used to calculate the melt pool cross sections for multiple combinations of laser power and scanning velocities considering multi-track-multi-layer builds of SS316L powder. The computed results are verified extensively with the corresponding experimentally measured ones. The model is utilized further to examine its ability to predict defects such as melt track discontinuity and incomplete fusion between neighboring tracks and layers. Overall, the adaptive remeshing and the proposed heat source expression could significantly enhance the model competence by reducing the computational time and memory while maintaining the accuracy of results in simulating laser powder bed fusion of multiple tracks and layers.
关键词： Selective laser melting (SLM),Pool dimensions,Adaptive remeshing,Laser powder bed fusion (L-PBF),Melt pool defects,SS316L alloy
更新于2025-09-23 15:19:57
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On symmetry of rare-earth scandium borate RESc3(BO3)4 (RE = Ce, Nd) laser crystals
摘要： Symmetry, structural features, and point defects in the Czochralski-grown single crystals with the initial compositions CeSc3(BO3)4 (CSB-1.0) and Nd1.25Sc2.75(BO3)4 (NSB-1.25) are studied by the full-profile Rietveld method on synchrotron X-ray powder data. The space group P321 is first established and confirmed for CSB-1.0 and NSB-1.25 crystals, respectively. The features of synchrotron diffraction patterns that distinguish the space group Р321 from the R32 one are given. The site occupancies in both structures are refined and resulted in the stoichiometric composition for CeSc3(BO3)4, which coincides with the nominal composition, and the composition [Nd0.455(1)Sc0.045(39)(1)]Nd0.500(2)Sc3(BO3)4 ((Nd0.955Sc0.045(39))Sc3(BO3)4), which differs from the initial Nd1.25Sc2.75(BO3)4 one, with partial occurrence of Sc ions in one of the trigonal-prismatic sites. An analysis of literature data on single crystals with the general formula RESc3(BO3)4 (RE ? Ce, Pr, Nd) together with the results of present study of powdered single crystals gives reason to exclude a crystallization of these compounds and solid solutions based on them in the space group R32. The correlation between the refined compositions of RESc3(BO3)4 crystals (RE ? La, Ce, Pr, Nd), having a specific space group, and compositions of initial charge is given.
关键词： Crystal structure,Czochralski technique,Optical materials,Point defects,Synchrotron radiation
更新于2025-09-23 15:19:57
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Ion Implantation - Research and Application || MeV Electron Irradiation of Ion-Implanted Si-SiO2 Structures
摘要： The effect of (10–25) MeV electron irradiation on Si‐SiO2 structures implanted with different ions (Ar, Si, O, B, and P) has been investigated by different methods, such as deep‐level transient spectroscopy (DLTS), thermo‐stimulated current (TSCM), Rutherford backscattering (RBS), and soft X‐ray emission spectroscopy (SXES). It has been shown that in double‐treated Si‐SiO2 structures, the defect generation by high‐energy electrons depends significantly on the location of preliminary implanted ions relative to the Si‐SiO2 interface as well as on the type (n‐ or p‐Si) of silicon wafer. SiO2 surface roughness changes, induced by ion implantation and high‐energy electron irradiation of Si‐SiO2 structures, are observed by the atomic force microscopy (AFM). Si nanoclusters in SiO2 of ion‐implanted Si‐SiO2 structures generated by MeV electron irradiation is also discussed.
关键词： ion implantation,Si nanoclusters,MeV electron irradiation,Si‐SiO2 structures,radiation defects
更新于2025-09-23 15:19:57
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Silica/polycaprolactone Nanofiber Scaffold Variants for Human Periosteal Cell Growth
摘要： Polycaprolactone (PCL) nanofiber scaffolds with attached cadaveric human periosteum or its cells were investigated in this study as a tissue-engineering approach to repair non-union injuries of bone. Addition of silica nanoparticles (silica or nSiO2) to PCL scaffolds was examined for effects on the growth of human periosteal cells in vitro and in vivo. Electrospun PCL nanofiber (nanoPCL) scaffolds were fabricated with different silica content (0, 0.5 and 1.0 wt%) and utilized as substrates on which periosteal cells were seeded. Human periosteal cell growth analyzed in vitro over 21 days with a PrestoBlue? viability assay increased as a function of culture time on each of the three different silica/nanoPCL scaffolds. Cadaveric periosteum attached to nanoPCL scaffolds with or without silica was wrapped around allograft bone and implanted for 10 or 20 weeks in athymic (nude) mice. Histological and immunohistochemical analyses of these experiments in vivo confirmed the presence of viable cells populating the constructs after their retrieval from host mice. Osterix, a marker for osteoblasts, increased in retrieved constructs over time and indicated remodeling of the underlying allograft bone. Summary results suggest that silica/nanoPCL scaffolds may be utilized as substrates for periosteal cell and tissue expansion to augment and support clinical applications for treatment and healing of bone defects, including segmental bone injuries and non-unions.
关键词： nanoPCL,bone defects,silica,Periosteum,tissue engineering
更新于2025-09-23 15:19:57
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RBS/C, XRR, and XRD Studies of Damage Buildup in Er‐Implanted ZnO
摘要： Accumulation and transformation of defects formed in bulk ZnO crystals at room temperature upon 300 keV Er ions bombardment have been thoroughly examined using complementary techniques: Rutherford Backscattering Spectrometry in ion Channeling mode (RBS/C), X-Ray Reflectivity (XRR), and X-Ray Diffraction (XRD). Evaluation of RBS/C spectra has been performed using Monte Carlo (MC) simulations (McChasy software). Two defect types have been indicated: point defects (randomly displaced atoms, RDA) and extended ones (edge dislocations, DIS). Depth-distributions of RDA and DIS turned out to be shifted toward deeper regions of ZnO crystals (relative to Er-ions range) while DIS are localized even deeper than RDA. The MC simulations reveal three regions of defects accumulation separated by two regions of rapid defects transformation occurring at a certain critical Er fluence. Strain, suggested to be a driving force of defect transformation, has been determined using simulations of the XRD profiles based on the dynamical theory of X-ray diffraction (MROX software). The presented research can help to better understand the interaction between impurity Er ions and ZnO target atoms during the implantation process. Hence, implantation conditions, for example, for luminescence purpose may now be more efficiently chosen based on the results discussed.
关键词： Monte Carlo simulations,defects analysis,X-ray reflectivity,ion channeling,dynamical theory of X-ray diffraction
更新于2025-09-23 15:19:57
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Comparative study of radiation defect dynamics in 3C-SiC by X-ray diffraction, Raman scattering, and ion channeling
摘要： At moderately elevated temperatures, radiation defects in SiC exhibit pronounced dynamic annealing, which remains poorly understood. Here, we study 3C-SiC bombarded at 100°C with pulsed beams of 500 keV Ar ions. Radiation damage is monitored by a combination of X-ray diffraction, Raman scattering, and ion channeling. Similar damage buildup behavior but with different defect relaxation time constants, ranging from ～1 to ～6 ms, is observed for the different types of lattice defects probed by these techniques. A correlation between relaxation times and the nature of the defects is proposed. These results reveal additional complexity of radiation defect dynamics in SiC and demonstrate that results of different defect characterization techniques are needed for a better understanding of dynamic annealing processes in solids.
关键词： X-ray diffraction,Ion channeling,Raman scattering,Dynamic annealing,Radiation defects,3C-SiC
更新于2025-09-23 15:19:57