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过滤筛选
- 2018
- arbitrary coupling coefficients
- Dielectric resonator
- filtering
- coupler
- filtering balun
- dual-band
- dual-mode dielectric resonator (DR)
- Electronic Science and Technology
- Nantong University
- Sun Yat-Sen University
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Manipulation of Magnetic Dipole Emission from Eu <sup>3+</sup> with Mie-Resonant Dielectric Metasurfaces
摘要： Mie-resonant high-index dielectric nanoparticles and metasurfaces have been suggested as a viable platform for enhancing both electric and magnetic dipole transitions of fluorescent emitters. While the enhancement of the electric dipole transitions by such dielectric nanoparticles has been demonstrated experimentally, the case of magnetic-dipole transitions remains largely unexplored. Here, we study the enhancement of spontaneous emission of Eu3+ ions, featuring both electric and magnetic-dominated dipole transitions, by dielectric metasurfaces composed of Mie-resonant silicon nanocylinders. By coating the metasurfaces with a layer of an Eu3+ doped polymer, we observe an enhancement of the Eu3+ emission associated with the electric (at 610 nm) and magnetic-dominated (at 590 nm) dipole transitions. The enhancement factor depends systematically on the spectral proximity of the atomic transitions to the Mie resonances as well as their multipolar order, which is controlled by the nanocylinder radius. Importantly, the branching ratio of emission via the electric or magnetic transition channel can be modified by carefully designing the metasurface, where the magnetic dipole transition is enhanced more than the electric transition for cylinders with radii of about 130 nm. We confirm our observations by numerical simulations based on the reciprocity principle. Our results open new opportunities for bright nanoscale light sources based on magnetic transitions.
关键词： Purcell enhancement,Dielectric metasurfaces,Mie resonances,Magnetic dipole emission
更新于2025-09-23 15:23:52
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Enhancement of local electromagnetic fields by periodic optical resonators
摘要： The periodically profiled metasurfaces of silicon and of the same surfaces coated with a thin layer of silver are experimentally investigated to improve the signal-to-noise ratio in the observation of Raman light scattering from molecular compounds. The noise in this case is the unavoidable background molecular luminescence. Our experimental and computer simulation data demonstrate an anomalous optical response due to the excitation of metal-dielectric surface resonances. An enhanced Raman scattering signal is observed from 5,5'-dithiobis(2-nitrobenzoic) acid (DTNB) organic molecules deposited on the metasurface. The proposed metasurface provides a significant enhancement of the RS signal in comparison with the luminescence signal and is an efficient substrate for realising giant Raman scattering of light.
关键词： silicon,metasurface,dielectric resonators,nanostructures,plasmon resonance,giant Raman scattering of light
更新于2025-09-23 15:23:52
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Structural and dielectric properties of prepared PbS and PbTe nanomaterials
摘要： In this work, PbS and PbTe nanomaterials with various morphologies were synthesized by a hydrothermal method. The structural properties were investigated by using X-ray diffraction (XRD) and corresponding scanning electron microscopy together with their EDX analysis. Both the PbS and PbTe nanomaterials possess good polycrystalline structure. The crystallite size, determined from the XRD data, of PbS is 5 nm whereas the corresponding value of PbTe is 2.69 nm. SEM micrographs reveal that the prepared PbS nanomaterial has star-shaped structures, micro-flowers, some cubes, and semi-dendrites, whereas PbTe has semi-flower structures. Additionally, the dielectric properties have been studied in a broad frequency range from 0.1 Hz up to 1 MHz at temperatures from 298–423 K. The real and imaginary parts of the complex dielectric constant ε' and ε'' of PbTe are comparatively higher than those of PbS. Moreover, the dielectric data were analyzed on the basis of the electric modulus.
关键词： electric modulus,PbS,EDX,PbTe,dielectric properties,SEM
更新于2025-09-23 15:23:52
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Effect of potassium and magnesium codoping on the dielectric properties of BST powders
摘要： K and Mg codoped BST powders were prepared by a sol-gel method, and the effect of doped concentration on the dielectric performances was studied. For comparison, pure, Mg doped and K doped BST powders were studied. XRD shows all powders reveal complete diffraction peaks and ABO3 cubic perovskite polycrystalline structures. Compared to the pure BST powder, Mg doped BST powder shows a little weaker crystallization, 5%～15% K doped BST powders exhibit stronger crystallization, and the crystallization is getting stronger with increasing K doped concentrations from 2% to 15%. BST powder shows lattice parameter of 3.963 ?A, Mg doping corresponds to 3.963 ?A, 2%～20% K doping correspond to 3.963 ?A～3.967 ?A, and Mg and K codoping make lattice parameters increase from 3.967 ?A to 3.974 ?A. Mg2+ ion and K+ ion show acceptor doped mechanisms, Mg doping makes grains refine, and K doping makes grains grow. Pure BST powder and Mg doped BST powder show uniform grains with unclear grain boundaries, K doped BST powders can obtain uniform and dispersive grains with clear grain boundaries, but Mg and K codoping makes the uniformity and dispersity of the powders getting worse. Compared to pure BST powder, Mg doped BST powder shows smaller but more stable dielectric constant and dielectric loss, K doped powders tend to reveal larger and less stable dielectric constants and dielectric losses. Mg and K codoped BST powders show less than 35 dielectric constants, and lower than 0.02 dielectric losses. Dielectric properties are strongly dependent on the crystallization, doped mechanism and morphology. Mg doped and 2% Mg 2% K and 2% Mg 5% K codoped BST powders show low and stable dielectric constants and dielectric losses, thus can meet the requirements for tunable microwave applications and other applications.
关键词： dielectric property,codoping,Mg,K,BST powder
更新于2025-09-23 15:23:52
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A method for alleviating the effect of pinhole defects in inter-metal dielectric films
摘要： As the insulation layers between two metal layers, inter-metal dielectric (IMD) films are widely used in integrated circuits (IC) and micro-electromechanical-systems (MEMS) devices. Commonly used IMD materials, such as silicon dioxide and silicon nitride, can be deposited on the metal surface using either physical vapor deposition (PVD) or chemical vapor deposition (CVD). However, due to the imperfections of deposition processes and surface cleanliness, defect-free of an IMD film cannot be guaranteed. As a common defect of an IMD film, pinhole is a tiny via of IMD film that can result in failures of short-circuit or current leakage between two metal layers and therefore decrease the fabrication yield. Reported methods for healing the pinhole defect require light-transmitting substrate, suspended structures, high-temperature annealing processes and none of them is universal. Therefore, we propose a metal etching method that uses metal etchants to etch the underlying metals through the pinholes of the IMD film. The etched area is reasonably larger than the pinhole; therefore, although the following upper metal deposition fills the pinhole, there is no electrical connection between the lower and upper metal features through the pinhole. Results of a series of experiments prove that the proposed method is feasible, valid, operable and reliable. Therefore, the proposed method is promising to be used for many IMD-based applications for either discovering pinholes or healing pinhole induced defects.
关键词： defect healing,thin film,inter-metal dielectric,pinhole,metal etching
更新于2025-09-23 15:23:52
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The sintering behavior and physical properties of Li <sub/>2</sub> CO <sub/>3</sub> -doped Bi <sub/>0.5</sub> (Na <sub/>0.8</sub> K <sub/>0.2</sub> ) <sub/>0.5</sub> TiO <sub/>3</sub> lead-free ceramics
摘要： In this study, Li2CO3-doped Bi0.5(Na0.8K0.2)0.5TiO3 (BNKT) ceramics were fabricated via the conventional solid-state reaction using ultrasound waves for preliminary milling. The milling time was shortened from 20 h to 1 h with ball milling. The phase structure of BNKT investigated by X-ray diffraction showed a single perovskite phase. With increasing Li2CO3 content, the phase structure of the ceramics changed from rhombohedral to tetragonal. At a sintering temperature of 1 100 8C and Li2CO3 content of 0.4 wt.%, the best physical properties of the ceramics, such as density (q), 5.9 g cm–3; electromechanical coupling factors (kp), 0.32; (kt), 0.29; remanent polarization (Pr), 12.0 lC cm–2; dielectric constant (er), 1 191; and highest dielectric constant (emax), 5 800, were obtained.
关键词： Lead-free ceramics,Electromechanical coupling factor,BNKT,Sintering temperature,Dielectric constant
更新于2025-09-23 15:23:52
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Photolithographic Patterning of Cytop with Limited Contact Angle Degradation
摘要： Cytop is a commercially available amorphous fluoropolymer with excellent characteristics including electric insulation, water and oil repellency, chemical resistance, and moisture-proof property, making it an attractive material as hydrophobic layers in electrowetting-on-dielectric (EWOD) devices. However, its highly hydrophobic surface makes it difficult for photoresists to be directly coated on the surface. To pattern Cytop, plasma treatment prior to applying photoresists is required to promote the adhesion between the photoresist and the Cytop coating. This approach inevitably causes hydrophobicity loss in the final EWOD devices. Thus, a damage-reduced recipe for Cytop patterning is urgently needed. In this paper, we first characterized the damage caused by two categories of surface treatment methods: plasma treatment and metal treatment. Parameters such as plasma gas source (Ar/O2), plasma treatment time (0–600 s), metal target (Al/Cu/Cr/Au), metal deposition process (magnetron sputtering or e-beam evaporation) were varied. Film thickness, wettability, and roughness were quantified by ellipsometry measurements, contact angle measurements, and atom force microscope (AFM), respectively. We then evaluated the effectiveness of annealing in damage reduction. Experimental results show that: (1) annealing is necessary in restoring hydrophobicity as well as smoothing surfaces; (2) specified film thickness can be obtained by controlling plasma treatment time; (3) “Ar/O2 plasma treatment + an AZ5214 soft mask + annealing” is a feasible recipe; (4) “an Al/Cu/Cr/Au hard mask + annealing” is feasible as well.
关键词： Cytop,electrowetting-on-dielectric (EWOD),annealing,patterning,microfluidics
更新于2025-09-23 15:23:52
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Hybrid bilayer gate dielectric-based organic thin film transistors
摘要： Organic thin film transistors (OTFTs) are key building blocks for flexible, low cost electronics systems. They provide a viable alternative for silicon-based electronics with added advantages of low cost and flexibility. However, few issues like high-operating voltage, low-switching speed, high-leakage current and reliability are still a challenge. The overall performance of an OTFT depends on organic semiconductors and gate dielectric interface. In this paper, we review the current status and trends in the choice of dielectric layer for OTFTs. As a starting point, the performance parameters of an OTFT and their dependence on the dielectric layer are briefly discussed. A variety of dielectric materials which includes high-k inorganic, organic, surface coated inorganics and nanocomposites are also presented. The advantages and drawbacks of each of these materials are discussed in detail. We reviewed the latest developments in the dielectric materials especially, self-assembled monolayers (SAMs), hybrid bilayers and nanocomposites. SAM-based OTFTs offer several advantages but shift in the threshold voltage remains a concern. Nanocomposites are a latest addition to the dielectric materials, which offer advantages like solution processing and improved dielectric constant but have a rough surface. A hybrid bilayer that incorporates the inorganic dielectric as a base layer and a thin polymer layer over it to improve the surface properties offers several desirable characteristics over the other choices. Hence, we propose that hybrid bilayer gate dielectrics shall play a pivotal role in improving the OTFT performance.
关键词： low-k organic,high-k inorganic,Organic thin film transistor,self-assembled monolayer,gate dielectric,hybrid bilayer
更新于2025-09-23 15:23:52
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Effect of processing conditions on (Ba1-xCax)(Ti0.9Sn0.1)O3 lead-free ceramics for the enhancement of structural, humidity sensing and dielectric properties
摘要： The present study reports detailed guidelines for the preparation of high-quality perovskite (Ba1-xCax)(Ti0.9Sn0.1)O3 (BCTS) (x = 0.0–0.1) lead-free ceramics by solid state reaction. The compositions (x = 0.0–0.04) exhibit orthorhombic–tetragonal phase transition (TO-T), except x ≥ 0.06 that shows a pure tetragonal structure phase which conformed by X-ray diffraction (XRD). The microstructure and purity of the sintered ceramics were examined using scanning electron microscope equipped with an energy dispersive spectrometer (SEM-EDS). Some pores existing in the grain boundary were observed at high concentrations of Ca content. Field emission scanning electron microscope (FE-SEM) was used to examine the morphology of sensing film of the calcined powder and it was prepared as a humidity sensor using screen-printing technique. All the compositions exhibited poor sensitivity toward the humidity sensing in the range of 0–98% RH at room temperature. Hot-stage microscope (HSM) has been used to investigate the sintering curve of the pure calcined powder and it was found that the suitable sintering temperature for obtaining a fully dense microstructure is 1400 °C. The highest values of permittivity (εr = 46,515, at 10 kHz) and piezoelectric coefficient (d33 = 510 pC/N) were achieved in the composition x = 0.02. The difference between alumina and platinum crucibles for the processing of the powders has been introduced, and by the aid of dispersive spectrometer analysis and it was indicated that use of alumina crucibles leads to the undesired presence of Al in the ceramics, which can be prevented by using a capped platinum crucibles.
关键词： Lead-free ceramics,Humidity sensing,Phase formation,Processing,Dielectric properties
更新于2025-09-23 15:23:52
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High quality factor cold sintered Li2MoO4BaFe12O19 composites for microwave applications
摘要： Ceramics-ceramic composites (1-x)Li2MoO4-xBaFe12O19 (LMO-BF12, 0.00≤x≤0.15) have been cold sintered at 120oC and their structure and properties characterized. X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed that compositions were dual phase and had a dense microstructure. Composites in the xBF12-(1-x)LMO (0.0≤x≤0.15) series resonated at MW frequencies (~6GHz) with 5.6≤e r≤5.8 and Qf =16,000-22,000 GHz, despite the black colour of compositions with x > 0. The permeability of the composites was measured in the X band (~8 GHz) and showed an increase from 0.94 (x=0.05) to 1.02 (x=0.15). Finite element modelling revealed that the volume fraction of BF12 dictates the conductivity of the material, with a percolation threshold at 10 vol.% BF12 but changes in e r as a function of x were readily explained using a series mixing model. In summary, these composites are considered suitable for the fabrication of dual mode or enhanced bandwidth microstrip patch antennas.
关键词： Finite element modeling (FEM),Composite,Cold sintering process,Dielectric,Ceramic material
更新于2025-09-23 15:23:52