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- impedance spectroscopy
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- Ba0.97La0.02Ti1-xNb4x/5O3
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- electric conductivity
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- South Ural State University
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Transfer and approximation of the impedance for time-harmonic Maxwell’s system in a planar domain with thin contrasted multi-layers
摘要： We consider the diffraction of time-harmonic electromagnetic waves by a perfectly conducting planar obstacle, coated by thin contrasted multi-layers of dielectric materials. A partial Fourier transform is used to derive an impedance condition that links the tangential components of the electric and magnetic fields, and transfers the boundary condition from the obstacle’s face to the other face of dielectric multi-layers. We first determine the exact formula and construct approximations of the impedance condition for one dielectric thin layer; after that, we extend the obtained result to multi-layers.
关键词： scattering,thin dielectric layers,Time-harmonic Maxwell’s system,impedance operator
更新于2025-09-23 15:21:21
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Structural, Electrical and Morphological Properties of Materials Type Sillenite Phase Bi12TiO20
摘要： This work reports the investigation of the ternary system Bi2O3–TiO2–MgO. Some compositions have been synthesized by solid state reaction at 800?°C and characterized by powder X-ray diffraction. The doping of (α-Bi2O3) allowed us to stabilize three compositions isotype of sillenite structure phase with formulas Bi0.9 Ti0.1 O1.55, Bi0,9 Ti0,05Mg0,05 O1,5, and Bi0.8 Mg0.1 Ti0.1 O1.5. The structural resolution of the synthesized materials was performed using Rietveld method by means of FullProf program. It crystallizes in the cubic system. The space group I23 and lattice parameter a = 10.1723(2) ?. The morphological proprieties of the synthesized compositions have been investigated by means of scanning electron microscopy (SEM). Sintered samples showed a dense and uniform microstructure. The density of sintered samples obtained is nearly 92% of the theoretical density. Various impedance model including capacity and Warburg impedances have been used to interpret the Nyquist representations of electrical analyses. The highest conductivity is observed for Bi0.9 Ti0.1 O1.55 (σ = 1.39E?07 at 600?°C).
关键词： Electrical Impedance,SEM,Spectroscopy,X-ray diffraction,Sillenite
更新于2025-09-23 15:21:21
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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Impedance Matching of Dipole Antennas by Metal Rod and Disk Placing
摘要： It has been researched experimentally and theoretically the impedance-matching possibility of dipole antenna with a coaxial feeder circuit. It has been made in case of a symmetrical dipole antenna placed parallel to a flat perfectly conducting screen by two bracket. It has been chosen a metal pins and discs of small electrical sizes as impedance-matching elements, which actually are placed between the dipole and the screen. Their dimensions and position relative to the dipole can be changed within certain small limits. The configuration and all dimensions of the tuned antenna has been entered into a computer for the calculation of the directivity patterns and dependence of the VSWR antenna on frequency. It is proved that such tuning elements allow to ensure good impedance-matching of the antenna and the feeder circuit, and also that practically does not affect on its directivity pattern.
关键词： near field region,dipole antenna,impedance matching,directivity pattern,flat screen
更新于2025-09-23 15:21:21
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Effect of pH Values on the Structural, Optical and Electrical Properties of SnO2 Nanostructures
摘要： In the present work, we have synthesized the SnO2 nanostructures via precipitation method under optimal conditions at different pH values (3, 7 and 11) and studied the effect of different pH values on the structural, optical and electrical properties. The prepared samples are characterized by XRD, FESEM, TEM, PL, UV–Visible, FTIR spectroscopy and EIS measurements. XRD analysis reveals the tetragonal crystal structure for the prepared SnO2 nanostructures. TEM images show that the morphology of SnO2 nanostructures changed from spherical to hexagonal as pH values increased from 3 to 11. The deconvoluted PL spectra show various defects present in the synthesized samples that act as luminescent centers. The absorption spectra revealed that the maximum optical band-gap is obtained for SnO2 nanostructures synthesized using acidic solutions. The FTIR spectrum verifies the presence of stretching vibration mode of O-Sn-O bond and, stretching and bending bonds of O-H bonds in the prepared samples. A detailed exploration on frequency and temperature dependent impedance properties of SnO2 nanostructures has been done with the change in pH values.
关键词： Impedance spectroscopy,SnO2,PL,TEM,pH values,Nanostructures,FESEM
更新于2025-09-23 15:21:21
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Exploiting lateral current flow due to doped layers in semiconductor devices having crossbar electrodes
摘要： Organic electronic devices such as light-emitting diodes, solar cells or rectifying diodes normally have a sandwich layer architecture stacked between the electrodes in a crossbar layout. Often however, the side effects of operating the devices in such an arrangement are either ignored or give rise to misinterpretations regarding the device performance or layer quality. For the sake of simplicity, device currents are typically assumed to exclusively flow in the direction vertical to the substrate, even though the conductivity of doped organic layers is high and gives rise to significant lateral current flows. Here, we study the vertical and lateral charge up along the n-doped and the p-doped layers as well as the resulting capacitance increase of charging the intrinsic layer outside the active area. We observe that controlling such lateral charging by structuring the doped layers can reduce the leakage current dramatically. We employ impedance spectroscopy to investigate the lateral charging responsibility for the capacitance increase at low frequencies. Modeling of the devices by a distributed RC circuit model yields information about the thickness, the conductivity, and the corresponding activation energy of both, the n-doped and the p-doped layers, simultaneously. We demonstrate that the capacitive effects from lateral charging can easily be misinterpreted as trap states in capacitance frequency characteristics. However, correct analysis with the proposed model actually yields rich and detailed post-fabrication information which can be utilized in device failure and degradation tests. Moreover, our results will aid the design and characterization of new electronic devices where lateral charge flow is part of the device concept.
关键词： Parasitic current,Leakage current,Impedance spectroscopy,Crossbar electrodes,Lateral current flow,Organic light-emitting diode,Capacitance,Organic solar cell,Structuring
更新于2025-09-23 15:21:21
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Miniature dual-band bandpass filter using modified quarter-wavelength SIRs with controllable passbands
摘要： A modified quarter-wavelength (λ/4) stepped-impedance resonator (SIR) is proposed to design a miniature dual-band bandpass filter (BPF). The proposed λ/4 SIR has two individually controllable resonances for constructing dual passbands. Moreover, two independent geometrical parameters are adopted to realize individual adjustment of the coupling strengths between two adjacent λ/4 SIRs at the dual passbands. As a result, both the center frequencies and bandwidths of the two passbands of the filter can be individually designed. Furthermore, multiple transmission zeros are created by the introduced source-load coupling, which improve highly the selectivity of both passbands. The dual-band BPF is designed at 2.35GHz and 5.8GHz, and its simulated and measured responses are presented and show good agreement.
关键词： stepped-impedance resonator,controllable passbands,miniature,dual-band bandpass filter
更新于2025-09-23 15:21:21
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Reflection coefficient of HfO <sub/>2</sub> -based RRAM in different resistance states
摘要： Impedance spectra of multiple resistive states in a stable-switching Resistive Random-Access Memory device based on a stack of Ru/HfO2/Zr/W was studied in this work. Using these observations, re?ection-coef?cients were extracted for different resistive states. Clear changes in the re?ection coef?cient for different resistive states were observed. The device in a low resistive state showed a signi?cantly higher re?ection coef?cient compared to its high resistive state. An increasing trend in the re?ection coef?cient was observed as the device state was gradually recon?gured towards lower resistances. Maximum frequency for re?ection increased with the decrease in the device area. The physics behind this observation is attributed to the interplay of oxygen ion transport among the interfacial layer, conductive ?lament, and HfO2-?lm.
关键词： resistive states,impedance spectra,HfO2,RRAM,reflection coefficient
更新于2025-09-23 15:21:21
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Hierarchically structured metamaterials with simultaneously negative mass density and Young’s modulus by using dynamic homogenization
摘要： We propose one-dimensional hierarchical metamaterials (HMMs) that have simultaneously negative mass density and Young’s modulus in the sense of effective properties. Frequency-dependent effective properties of the HMMs are evaluated by using a dynamic homogenization theory. By considering three necessary conditions for dynamic homogenizability, we verify that our proposed HMMs can have physically meaningful double negativity, whereas the conventional periodic structures cannot. In addition, HMMs yield the broader ranges of the frequency and the effective properties for double negativity due to the large number of geometrical parameters. By exploring all the possible effective properties of HMMs, we discuss whether we can design metamaterials with the opposite sign of material properties in nature, ultimately aiming at perfect impedance matching.
关键词： dynamic homogenization,double negativity,impedance matching,hierarchical metamaterials
更新于2025-09-23 15:21:21
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[IEEE 2019 IEEE International Autumn Meeting on Power, Electronics and Computing (ROPEC) - Ixtapa, Mexico (2019.11.13-2019.11.15)] 2019 IEEE International Autumn Meeting on Power, Electronics and Computing (ROPEC) - Electrical characteristics of ternary solar cells based on PTB7:PCBM:ICBA
摘要： Multivariable dynamic ankle mechanical impedance in two coupled degrees-of-freedom (DOFs) was quanti?ed when muscles were active. Measurements were performed at ?ve different target activation levels of tibialis anterior and soleus, from 10% to 30% of maximum voluntary contraction (MVC) with increments of 5% MVC. Interestingly, several ankle behaviors characterized in our previous study of the relaxed ankle were observed with muscles active: ankle mechanical impedance in joint coordinates showed responses largely consistent with a second-order system consisting of inertia, viscosity, and stiffness; stiffness was greater in the sagittal plane than in the frontal plane at all activation conditions for all subjects; and the coupling between dorsi?exion–plantar?exion and inversion–eversion was small—the two DOF measurements were well explained by a strictly diagonal impedance matrix. In general, ankle stiffness increased linearly with muscle activation in all directions in the 2-D space formed by the sagittal and frontal planes, but more in the sagittal than in the frontal plane, resulting in an accentuated “peanut shape.” This characterization of young healthy subjects’ ankle mechanical impedance with active muscles will serve as a baseline to investigate pathophysiological ankle behaviors of biomechanically and/or neurologically impaired patients.
关键词： stiffness anisotropy,Ankle joint,ankle stiffness,impedance structure,human ankle,ankle joint stiffness,multivariable stiffness,multivariable impedance
更新于2025-09-23 15:21:01
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Graphene disks for frequency control of terahertz waves in broadband applications
摘要： The terahertz (THz) gap lying between the microwave and optical parts of the electromagnetic spectrum has attracted immense attention due to its applications between radiofrequency (RF)/microwave and photonic systems. A structure consisting of a graphene sheet sandwiched between two graphene disks is introduced herein to control the reflection, absorption, and transmission of THz waves. The proposed metamaterial structures are designed analytically using transmission line theory. Also, the dimensions of the structure and the electrical gating of the graphene are optimized utilizing a genetic algorithm. The structure is simulated using two different methods: (1) a circuit model based on transmission line theory and (2) commercial full-wave software based on the finite element method, which are verified by the agreement between their results. Finally, the proposed method is used to design a THz filter and THz wave absorber, which are in great demand for application in modulators, sensors, detectors, and imaging systems.
关键词： Resonator,Circuit method,Coupling effect,Graphene,Genetic algorithm,Absorber design,Impedance matching
更新于2025-09-23 15:21:01