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Input Impedance and Efficiency Analysis of Graphene-Based Plasmonic Nanoantenna Using Theory of Characteristic Modes
摘要： In this letter, the input impedance and radiation efficiency analysis of graphene-based plasmonic nano-antenna (GPNA) is presented utilizing the theory of characteristic mode (CM). The total input impedance and radiation efficiency values at various feed positions are accurately and efficiently obtained as the superposition of natural characteristic modes. Furthermore, the modal input impedances and the radiation efficiencies are also provided for in-depth understanding of the GPNA. This work provides a new perspective to analyze the GPNA and can be easily applied to the design and optimization of other lossy plasmonic antennas with complicated geometries.
关键词： input impedance,nano-antenna,characteristic mode (CM),plasmonic,graphene
更新于2025-09-11 14:15:04
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A Compact Impedance Model of Plasmonic Nanoshell for Metamaterial Applications
摘要： Recent research in plasmonics demonstrated merging different materials and shapes to form complex geometries with improved optical response. One of the most extensively used nanostructure is the coated nanosphere (nanoshell), which finds its application in diverse fields of medical, science and engineering. In this paper, we propose a compact impedance model of metallic core nanoshell. The model is based on time-varying approach by solving full dipole equation for the metallic core and impedance of the dielectric shell is derived using near-field components of the dipole field. The expressions for the absorption and scattering cross-sectional areas, and their behavior with change in the dielectric function are derived for the first time for nanoshell using voltages, currents and circuit elements, with their equivalence compared with exact solution. Additionally, the effects of changes in nanoshell parameters (dielectric constants, thickness of shell layer and radii of core) on the resonance frequency predicted by the proposed impedance model are analyzed. The simplified impedance model is based on parallel resonance circuit and contributes to the better understanding the behavior of nanoshell and facilitate cost-effectiveness solution for the next generation nanoshell based metamaterials.
关键词： nanophotonics,coated sphere,impedance model,metamaterial,plasmonics,Nanoshell,nanocircuit,dipole
更新于2025-09-11 14:15:04
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Nanoparticulate Metal Oxide Top Electrode Interface Modification Improves the Thermal Stability of Inverted Perovskite Photovoltaics
摘要： Solution processed γ-Fe2O3 nanoparticles via the solvothermal colloidal synthesis in conjunction with ligand-exchange method are used for interface modification of the top electrode in inverted perovskite solar cells. In comparison to more conventional top electrodes such as PC(70)BM/Al and PC(70)BM/AZO/Al, we show that incorporation of a γ-Fe2O3 provides an alternative solution processed top electrode (PC(70)BM/γ-Fe2O3/Al) that not only results in comparable power conversion efficiencies but also improved thermal stability of inverted perovskite photovoltaics. The origin of improved stability of inverted perovskite solar cells incorporating PC(70)BM/ γ-Fe2O3/Al under accelerated heat lifetime conditions is attributed to the acidic surface nature of γ-Fe2O3 and reduced charge trapped density within PC(70)BM/ γ-Fe2O3/Al top electrode interfaces.
关键词： nanoparticulate metal oxides,accelerated lifetime,electrodes,thermal stability,degradation mechanisms,interfaces,inverted perovskites solar cells,impedance spectroscopy,charge traps density
更新于2025-09-11 14:15:04
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[IEEE 2018 5th International Conference on Systems and Informatics (ICSAI) - Nanjing (2018.11.10-2018.11.12)] 2018 5th International Conference on Systems and Informatics (ICSAI) - Modeling of Multilayer Graphene at Terahertz with Vector Fitting Method
摘要： Graphene is a promising carbon nanomaterial, and multilayer graphene are more interesting than the monolayer one. The dispersion of multilayer graphene at terahertz (THz) leads to difficulties in transient electromagnetic simulation, e.g. the time domain integral equation (TDIE) method. This paper aims to achieve accurate fitting of multilayer graphene dispersive surface conductivity/impedance over ultra wideband THz frequencies. Graphene surface conductivity/impedance at THz is calculated by the Kubo formula. Thereafter, the surface conductivity and impedance is approximated by vector fitting method with expansions of several pairs of poles and residues. Numerical results are provided to validate the proposed method. Multilayer graphene time domain surface impedance which is used in the impedance boundary condition (IBC) for TDIE can be obtained readily by the inverse Fourier transform of its frequency domain counterpart.
关键词： terahertz,vector fitting,impedance,multilayer graphene
更新于2025-09-11 14:15:04
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Photovoltaic, photo-impedance, and photo-capacitance effects of the flexible (111) BiFeO <sub/>3</sub> film
摘要： Ferroelectric polarization allows a depolarization electric field to separate electron-hole pairs excited by lights, and thus, the photovoltaic properties of ABO3-type films on a hard SrTiO3 or Si substrate have been extensively studied recently. However, there are a few reports on the photocapacitance and photoimpedance of these oxide films, especially on flexible substrates. In this work, the strong photovoltaic, giant photocapacitance, and photoimpedance effects were observed in the flexible (111) BiFeO3 films with natural downward polarization. The flexible mica/SrRuO3/BiFeO3/Au cells show a maximum photovoltaic efficiency at 150 °C, a 95.5% decrease in photoimpedance effects, and a 316% increase in photocapacitance effects under 405-nm-wavelength light illumination at 25 °C. Most importantly, these properties do not show obvious degradation when the device is bent to 3 mm radius for 104 times. This work is of vital importance for us to develop new flexible photoelectronic devices.
关键词： photo-capacitance,photovoltaic,flexible,photo-impedance,BiFeO3 film
更新于2025-09-11 14:15:04
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Design of Substrate Integrated Gap Waveguide and Their Transitions to Microstrip Line, for Millimeter-Wave Applications
摘要： This paper offers an approximate, but very convenient and accurate, manner to find the desired strip width for substrate integrated gap waveguide (SIGW) with a given characteristic impedance and the conductor and dielectric attenuation constants, without any complicated manual calculations or time-consuming full-wave simulation and optimization iterations. Moreover, the investigation of the transition between SIGW and microstrip lines will prove that an additional transition structure, such as a conventional microstrip taper, is not required any more at millimeter-wave frequencies for the desired transmission performance. This is a useful feature in circuit design and compactness. Both of the above works will be of great help to realize future feeding networks for SIGW antenna arrays or other types of cost-effective SIGW passive components at high frequencies. Two SIGW prototypes, working at Ka and V bands, are fabricated and offer experimental verifications, which present good agreement with the simulation results.
关键词： 5G,characteristic impedance,Gap waveguide,transition,attenuation constant,millimeter waves
更新于2025-09-11 14:15:04
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Stripline beam position monitor for X-ray free electron laser of Pohang Accelerator Laboratory
摘要： Beam position monitors (BPMs) are important instruments even in the case of an X-ray free-electron laser (XFEL). Pohang Accelerator Laboratory (PAL) finished the construction of an XFEL (PAL-XFEL) in 2015, and new stripline BPMs were installed in PAL-XFEL. New BPMs were designed to have a strong signal and a high resolution. In addition, the impedance matching was considered to reduce a signal reflection. These features of the BPM design were confirmed with a simulation study as well. Fabricated BPMs were tested by using a wire test stand. Two-dimensional position errors and offsets were measured to select best BPMs for PAL-XFEL. Finally, a real beam test was tried to check the BPM performance and a better resolution than the requirement was obtained.
关键词： stripline BPM,X-ray free-electron laser,Beam position monitors,impedance matching,PAL-XFEL
更新于2025-09-11 14:15:04
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A PWM based readout circuit for optical sensors with adaptive frequency control
摘要： This paper proposes a pulse-width modulation-based readout circuit for optical sensors which adopts adaptive frequency control technique to enhance input dynamic range of current sensing systems. The proposed readout circuit is designed and fabricated using a 65 nm CMOS process. The readout IC achieves 100 dB of dynamic range in current sensing system by adaptively controlling the frequency of operating clock.
关键词： photodiode,current to PWM converter,trans-impedance amplifier,pulse-width modulation,CMOS,optical sensor
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - Atlanta, GA, USA (2019.7.7-2019.7.12)] 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - Modulating Surface Impdances of Surface Plasmon Polaritons for Leaky Wave Plasmonic Nanoantennas
摘要： Plasmonic nanoantennas offer unusual optical properties and constitute a fundamental building block for plasmonic devices. In this paper, we propose to modulate the surface impedances of surface plasmon polaritons for directional leaky wave emission from hybrid plasmonic waveguides. Simulation results indicate that the proposed nanoantenna presents a wide-angle beam scanning of over 90° with a peak directivity of 19 dBi.
关键词： impedance modulation,leaky wave,nanoantenna,plasmonic
更新于2025-09-11 14:15:04
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A Novel CMUTs-based Resonant Biochemical Sensor Using Electrospinning Technology
摘要： A novel CMUTs-based resonant biochemical sensor was presented to detect SO2 with a sensitive polymer electrospinning technology. The electrospinning technology was proposed as an innovative functionalization method to fabricate nano reticular polymer fibers with the diameters of 50 nm~500 nm on the movable plates of the CMUTs. The surface topography of electrospun nanofibers and the impedance properties of functionalized CMUTs were characterized. The CMUTs-based resonant biochemical sensor was packaged to detect SO2 in the experiments. Its resonant frequency shifts varied against the variation of SO2 concentration. The influences of the mixed gas flow rate were also analyzed. These showed the proposed sensor had good volume sensitivity and frequency stability.
关键词： volume sensitivity,electrospinning technology,impedance characteristics,CMUTs-based resonant biochemical sensor,frequency shift
更新于2025-09-11 14:15:04