Permittivity Function Research Articles

Influence of linear permittivity on thermally-induced nonlinear optical properties of aluminum-doped zinc oxide thin films: the visible range

In this study, the influence of the linear permittivity on the thermally-induced nonlinear optical properties of aluminum-doped zinc oxide thin films was investigated in the visible range, namely at 405, 532, and 650 nm. The strength of the nonlinear response in the films at these wavelengths represented by the thermal nonlinear index of refraction ( n 2 t h ) and the absorption coefficients (β) magnitudes followed dispersive changes in the films’ permittivity function. These changes were dominantly scattering events within the films, which strongly influenced the nonlinear absorption behavior alternating between saturable absorber and reverse saturable absorber trend. In this research, the results and qualitative description of this relationship are presented.

A Ground Penetrating Radar Imaging Approach for a Heterogeneous Subsoil With a Vertical Permittivity Gradient

The article presents an imaging approach for ground penetrating radar prospecting over a heterogeneous background soil characterized by a dielectric permittivity variation along depth. The proposed approach is based on a linear model of the electromagnetic scattering phenomenon, where the soil inhomogeneity in the reference scenario is accounted for by introducing an equivalent permittivity function. Such a function notably simplifies the computation of the kernel of the relevant linear integral equation to be inverted. Then, the data inversion is carried out in a regularized way by resorting to the truncated singular value decomposition scheme. A procedure for estimating the equivalent permittivity function, typically unknown in practical situations, is also proposed. Reconstruction results achieved from full-wave simulated data and real data collected in a controlled test site are provided to demonstrate the effectiveness and the reliability of the proposed imaging approach.

Recognition of healthy and cancerous breast cells: Sensing the differences by dielectric spectroscopy.

The response of human cells to applied electrical signals depends on the cellular health status, because it is influenced by the composition and structure of the main cellular components. Therefore, electrical impedance-based techniques can be considered as sensitive tools to investigate healthy or disease state at cellular level. The goal of this study is to show that different types of in vitro cellular lines, related to different health status, can be differentiated using impedance spectra analysis. Three different types of human breast cell line, corresponding to healthy, cancerous, and metastatic adenocarcinoma cells, were measured by means of electrical impedance spectroscopy. By modeling the investigated cells with proper resistive and capacitive circuital elements, the magnitude of the cell electrical components and spectra of real and imaginary part of dielectric permittivity were obtained. The latter were subsequently examined with a commonly adopted mathematical model, in order to estimate the values of specific dielectric parameters for the three different cellular lines. The relative variation of cellular capacitance with respect to that of the culture medium, estimated at 100Hz, has a larger value for the two types of cancerous cells with respect to the noncancerous type. Furthermore, the ratio between the real and imaginary part of the dielectric permittivity function has larger values for metastatic cells with respect to the normal and nonmetastatic ones. Therefore, the mentioned relative capacitance allows to discriminate between normal and cancerous cells, whereas the results obtained for the dielectric function can discriminate between metastatic and nonmetastatic cells. This study can be considered as an exploratory investigation of evaluating in vitro the health status of humans cells using selected electrical impedance parameters as potential markers. The obtained results highlight that a standard cultureware system, provided with interdigitated electrodes and appropriate impedance parameters, that is, cellular capacitance and the ratio between the imaginary and real part of cellular dielectric function, can be used to discriminate between healthy and cancerous breast cell lines, as well as different malignancy degrees.

Effect of Carrier Diffusion on the Optical Property in Si–In–Zn–O/Ag/Si–In–Zn–O Optical Media

Si–In–Zn–O (SIZO)/Ag/Si–In–Zn–O (SIZO) (totally, SAS) multilayered oxide–metal–oxide (OMO) structure has been fabricated and analyzed. Amorphous oxide semiconductor has been uniquely adopted in this study. Different from a metal–dielectric composite multilayer system, carrier diffusion occurred at the semiconductor–metal interface resulting in a complicated electric field distribution in a semiconductor–metal composite multilayer. This phenomenon causes the distortion of bulk permittivity function, therefore mismatching could be found which is confirmed by epsilon-zero-points of samples with different volume filling fraction. Carrier concentration distribution in a SAS was carefully analyzed by introducing Poisson’s electrostatic equation. Further discussion on the distortion of bulk permittivity function in SAS multilayers has been conducted and, carrier diffusion model was introduced to analyze the redistribution of electric field. Carrier concentration dependency of frequency of transmitted light has been investigated and established with a correction parameter related with the total thickness of the samples. It is expected that this research would not only provide a solution to correct the distorted bulk permittivity function of semiconductor–metal multilayer system, but also reveal a potentially promising method for designing a carrier concentration controllable meta-material, such as low-emissivity coating, or low-loss plasmonic for an optical integrated circuits.

A Vertical Combo Spacer to Optimize Electrothermal Characteristics of 7-nm Nanosheet Gate-All-Around Transistor

In this article, the impact of self-heating effect (SHE) on nanosheet gate-all-around (GAA) transistor with a vertical combo spacer and different underlap/overlap channels is studied by the 3-D TCAD simulation. To achieve high authoritative evidences, the ${I}_{\text {d}}$ – ${V}_{\text {g}}$ characteristic with SHE is calibrated with the experimental data. First, the change of electrical characteristic introduced by different dielectrics of a single- ${k}$ spacer is investigated, and the results show that the current of ON-state ( ${I}_{ \mathrm{\scriptscriptstyle ON}}$ ) is a power function of relative permittivity, whereas the OFF-state ( ${I}_{ \mathrm{\scriptscriptstyle OFF}}$ ) exhibits a linear dependence. Second, a novel vertically wrapped combo spacer is proposed to achieve a compromise between thermal characteristic and electrical performance for the first time. The electrothermal characteristics of the combo spacer under different underlap/overlap channels are also studied, and the results showed that the combo spacer composed of inner Si3N4 and outer HfO2 has the highest ${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ but smaller thermal resistance and lower lattice temperature compared with other different combinations. At last, a CMOS inverter with Si3N4/HfO2 combo spacer is demonstrated for its improvement in propagation delay.

Coupled wave method with modified boundary conditions for diffraction grating calculations

The Fourier modal method for grating diffraction calculations is reformulated to improve its numerical performance, which is then studied on a rectangular aluminium grating. The Fourier coefficients of the rectangular permittivity function are calculated by the discrete Fourier transform from equidistant sample points rather than from the Fourier integral, which partially suppresses the Gibbs phenomenon. The continuous field components are treated in the Fourier space analogously to the conventional algorithm, whereas the discontinuous components are calculated in the direct space. The lateral component of the electric field, which is discontinuous inside the periodic medium but continuous on horizontal interfaces, is used for the boundary conditions in the direct space, which improves the convergence of diffraction efficiencies and considerably suppresses field fluctuations in the vicinity of sharp corners.

Dielectric metamaterials with hexagonal lattice

We consider all-dielectric photonic structures with electric response consist of dielectric rods arranged in a hexagonal lattice. We construct gap map as a function of rod permittivity for a constant filling factor by analyzing photonic band diagrams. A near-boundary phase with a strong spatial dispersion is found, whereas in the case of a square lattice this phase does not exist. We observe ε-near zero modes in a metamaterial phase, which do not depend on a lattice orientation and a structure boundary.

Complimentary split ring resonator sensor with high sensitivity based on material characterization

A new model of microwave planar sensor established on the complementary split ring resonator (CSRR) as well as an air hole in substrate of the structure is introduced for a precise measurement of materials permittivity. The hole is filled into substrate of the planar microstrip line. The CSRR structure with hole is selected for the sensitivity analysis, the result is established to hold over quite sensitive compared with CSRR structure without hole and thus evidence to be more suitable for the sensor design. The sensor in the form of CSRRs operating at a 1.74–3.4 GHz band is explained. At resonance, it is found that the electric field produced straight the plane of CSRR being highly sensitive for the characterization of sample resident with the sensor. The minimum transmission frequency of sensor shifts from 3.4 to 1.74 GHz as the sample permittivity varies from 1 to 10. A numerical model is introduced here for the computation of the system resolution as a function of resonance frequency and sample permittivity using electromagnetic simulator. It is found that the proposed sensor provides 35% increment in sensitivity more than conventional sensor for same permittivity of the sample under test.

Exchange Process in the Dielectric Loss of Molecular and Macromolecular Ionic Conductors in the Interfacial Layers Formed by Electrode Polarization Effects.

Here we report a first analytical approach to determine the spectral dependence of the complex permittivity function of molecular and macromolecular ionic conductors in the interfacial layers formed by electrode polarization effects. We show that a previous model of electrode polarization effects that was successfully applied for describing the dielectric behavior of ionic liquids ( Serghei, A.; Tress, M.; Sangoro, J. R.; Kremer, F. Electrode polarization and charge transport at solid interfaces. Phys. Rev. B 2009 , 80 , 184301 ) can be now generalized and applied for polymer/ionic liquid blends as well as for poly(ionic liquid)s. The determined dielectric function of the interfacial layers reveals a dramatic change in the charge transport process manifested by a large decrease in conductivity. Our approach brings the first evidence for a relaxation peak detected in the dielectric loss of the interfaces, which is attributed to an exchange process between the interface and the bulk. This study gives new insights into the mechanism of charge transport at interfaces and could thus contribute to a better correlation between the dielectric properties of ion conducting materials and their electrochemical behavior at interfaces.

Combining isolated scatterers into a dimer by strong optical coupling

We analyze the transition between different coupling regimes of two dielectric rods, which occurs at a critical distance between them. The hallmark of strong coupling regime is the peak splitting effect observed in spectra. Here we comprehensively evaluate the critical distance as a function of the rod permittivity using a number of different approaches. The scattering spectra of the two rods in dependence on the distance demonstrate the weak to strong coupling transition. We start the analysis by introducing a region of a tidal energy flux around a single isolated rod (the region is related to the near field) and demonstrate that its effective radius corresponds to the critical distance obtained from the scattering spectra. Next, we study the eigenfrequencies of the dimer as functions of distance by 'diagonalizing' the coupled multipole matrix. In order to find an analytical formula for the critical distance, we consider the problem under several approximations, which yield similar results.

Bandlimited Distortionless Material Design by an Approximation of the Heaviside Condition

The distortionless propagation of signals in a medium offers a way to preserve the signal integrity. There exists a condition for distortionless propagation on a transmission line known as the Heaviside condition. This paper proposes the use of the Heaviside condition to characterize and design magneto-dielectric materials that provide distortionless propagation in a specified finite frequency band. Plane wave propagation in a magneto-dielectric material is modeled by a transmission line model, thereby assuming transverse electromagnetic mode propagation. Then, the Heaviside condition is employed to derive the frequency-dependent permittivity and permeability functions of the material in rational form, so they satisfy the condition in a specified frequency interval. A procedure to design such materials is described. A numerical example of the design process is provided and an illustration of the effectiveness of modeled material in fulfilling the Heaviside condition in a specified frequency interval both in the time and frequency domains is given, indicating the validity of the approximation. The design procedure is as such a suitable preliminary design guide for deriving a realizable description of a magnetodielectric, exhibiting the distortionless property in the desired frequency interval, with certain specified requirements put on the loss, or the permeability and permittivity values satisfied. The obtained results may initiate further investigations into the bandwidth restrictions of the approximation, on closed-form design solutions, and the practical realization of such materials.

A Novel and Systematic Approach to Inhomogeneous Dielectric Lens Design Based on Curved Ray Geometrical Optics and Particle Swarm Optimization

A numerical synthesis algorithm is presented to design inhomogeneous 3-D-printed lenses for any aperture field and, hence, beam pattern. The algorithm is based on geometrical optics (GO), a numerical method for wave propagation in inhomogeneous media, particle swarm optimization, and a global stochastic optimization technique. The approach allows the synthesis of either optimal geometry with known constant permittivity (shape only), optimal nonconstant permittivity with known geometry (material only), or optimal geometry and nonconstant permittivity (shape and material). The presented approach is validated against the analytic test case of the Maxwell fish eye and is shown to provide excellent agreement. A spherical lens is optimized for nonconstant permittivity function and is shown to recover the permittivity of the Luneburg lens. Instructions on how to fabricate the resultant inhomogeneous lenses via 3-D-printing techniques is given. Examples of optimum inhomogeneous lenses synthesized with our approach are provided along with the full-wave simulation verification. A 30 cm inhomogeneous lens is fabricated via 3-D-printing and measured in the UCLA’s plane bipolar near-field measurement range and compared with the results of the GO algorithm.

비균일 지하에 묻혀있는 유전체 충진 비금속관에 의한 지표투과레이다 응답의 특성 변화

The variation of ground-penetrating radar(GPR) signal characteristics from dielectric-filled nonmetallic pipes buried in inhomogeneous ground are compared through a numerical simulation. The relative permittivity distribution of the ground is generated by using the continuous random media(CRM) technique. As a function of the relative permittivity of the material filling the nonmetallic pipe buried in the ground media, GPR signals are simulated by using the finite-difference time-domain(FDTD) method. We show that, unlike the case for homogeneous ground, the distortion characteristics of the reflected waves caused by the front convex surface and the rear concave surface of the pipe buried in inhomogeneous ground are different depending on the permittivity contrast between the inside and outside of the pipe.

Bi-gyrotropic impact upon high-performance transverse magneto-optical Kerr effect in a superlens

Abstract In this letter, we study the transverse magneto-optical Kerr effect (TMOKE) in a bi-gyrotropic superlens, and its dependence on the losses of both permittivity and permeability functions, which is a determining factor for the existence of the TMOKE. We found extreme values for this effect for both p- and s-polarized waves, and in particular the conditions under which these extreme values occur for a wide-range of the angle of incidence.

An auxiliary field approach for computing optical resonances in dispersive media

We report on an auxiliary field approach for solving nonlinear eigenvalue problems occurring in nano-optical systems with material dispersion. The material dispersion can be described by a rational function for the frequency-dependent permittivity, e.g., by a Drude-Lorentz model or a rational function fit to measured material data. The approach is applied to compute plasmonic resonances of a metallic grating.

Optical Property–Composition Correlation in Noble Metal Alloy Nanoparticles Studied with EELS

Noble metals are currently the most common building blocks in plasmonics and thus define the available range of optical properties. Their alloying provides a viable strategy to engineer new materials with a tunable range of optical responses. Despite this attractive prospect, the link between composition and optical properties of many noble metal alloys is still not well understood. Here, electron energy-loss spectroscopy is employed to systematically study AuAg and AuPd nanoparticles of varying compositions. The localized surface plasmons, the bulk plasmons, and the permittivity functions of these two sets of alloys are investigated as functions of their composition. In the case of the more widely studied AuAg alloy system, good agreement is found with previous experimental and theoretical studies. The results on the less scrutinized AuPd system provide highly valuable experimental data that complements other experimental investigations and supports the development of theoretical models.

Phase sensitive measurement of the wavelength dependence of the complex permittivity of a thin gold film using surface plasmon resonance

We report on a new method for measuring the wavelength dependence of the complex permittivity of a thin gold film of a surface plasmon resonance (SPR) structure comprising a gold-coated SF10 slide with an adhesion film of chromium attached to an SF10 glass prism. The method is based on spectral interferometry and utilizes a setup with a birefringent crystal and the SPR structure in the Kretschmann configuration, in which channeled spectra are recorded and from them, the phase functions of the SPR for air at different angles of incidence are retrieved. The SPR phenomenon is manifested as an abrupt phase change with respect to the reference phase difference for the interference resolved with the SF10 glass prism alone. The phase changes for different angles of incidence are processed in the vicinity of the resonance wavelengths to obtain the real and imaginary parts of the complex permittivity in a wavelength range from 530 to 850 nm or equivalently, the parameters of a modified Drude-Lorentz model. This research, to the best of the authors’ knowledge, is the first demonstration of spectral interferometry-based measurement of the complex permittivity function of a thin metal film, which is important from the point of view of material characterization directly performed in the Kretschmann configuration.

Dual Notch Microwave Sensors Based on Complementary Metamaterial Resonators

In this paper, three dual notch microwave sensors are presented based on a microstrip transmission line and complementary metamaterial resonators. The main aim of this paper is to compare the constitutive parameters and sensitivity of all three dual notch sensors which are based on complementary symmetric split ring resonator (CS-SRR), complementary asymmetric split ring resonator (CAS-SRR) and complementary bisymmetric split ring resonator (CBS-SRR). The main motivation beyond the presented work is to use dual notches to estimate the relative permittivity of material under test (MUT). Electromagnetic simulation elucidates the origin of dual mode resonance of all the three resonators. Sensitivity analysis is performed on each sensor by using fifteen MUTs with relative permittivity ranges from 1.006 to 16.5 and constant dimensions 10 mm × 10 mm × 1 mm. To verify the concept, a sensor is fabricated and its response is measured using a vector network analyzer (AV3672). Using curve fitting technique the shift in the resonance frequencies of the fabricated sensor due to interaction with MUT is presented as a function of permittivity. Simulated, measured and formulated results are in good agreement with each other.

Microwave Treatment of Ultramafic Nickel Ores: Heating Behavior, Mineralogy, and Comminution Effects

Ultramafic nickel ores are difficult to process because they contain serpentine, an anisotropic mineral with a nonspherical morphology and multiple pH-dependent surface charges. Dehydroxylation of serpentine in ultramafic nickel ores by microwave treatment is proposed to improve the processability of these ores. Upon heating, serpentine is converted to olivine, an isotropic mineral that is benign in mineral processing circuits. The microwave heating of two ultramafic nickel ores is explored in this paper, as well as effects on mineralogy and grindability. The first ore was sourced from the Okanogan nickel deposit in Washington State, USA, while the second ore was obtained from the Vale-owned Pipe deposit located in the Thomson Nickel Belt in Manitoba, Canada. The ultramafic nickel ores were found to heat well upon exposure to microwave radiation and the heating behaviors were a function of the imaginary permittivities. The temperatures achieved during microwave treatment were sufficient to dehydroxylate serpentine, and the serpentine content in ultramafic nickel ores was reduced by 63–84%. The grindability of ore with consistent texture (OK ore) improved dramatically with microwave treatment, whereas the grindability of ore with inconsistent texture (Pipe ore) was found to decrease. Pentlandite liberation and specific surface area improved for both ores with microwave treatment. Ultimately, microwave pretreatment did not decrease the energy required for grinding under the conditions studied. However, energy savings may be realized when overall process improvements are considered (e.g., grinding, rheology, flotation, material handling, dewatering and tailings treatment).

Bi2O3–TiO2–Nd2O3 lead‐free material for microwave device applications

AbstractLead‐free Bi2O3–TiO2–Nd2O3 system and its potential application for microwave devices applications were studied. The samples were synthesized using the melt quenching method. According to the X‐Ray Diffraction analysis, the samples are polycrystalline with three different crystal phases. Measurements of the dielectric complex permittivity function were made at 2.7 GHz, using a resonant cavity and the small perturbation theory. The values of the dielectric permittivity of the prepared materials were compared with the commercial ones, and we conclude that these new lead‐free materials have a good potential to replace lead‐containing devices for microwave frequency applications.