Multilayered Dielectric Material Research Articles

Accurate Estimation without Calibration of the Complex Relative Permittivity of Multilayer Dielectric Material based on the Finite Integration Technique

In this paper, a simple and effective solution is proposed to accurately estimate the complex relative permittivity of individual layers and multilayers of dielectric material samples from the S-parameters measured by two waveguide cells having equal or different lengths filled with the same vacuum/empty material without having to calibrate before performing experiments. The measurement system is set up by modeling using the Computer Simulation Technology (CST) software. In the modeling, a single layer/multilayer material sample is placed in the X-band rectangular waveguide and it has two ports used for the electromagnetic wave supply and measurement of S-parameters. From the S-parameters measured, the complex relative permittivity of individual layers and the multilayers of the material samples are estimated by the proposed method. The known single-layer and multilayer materials such as Garlock, Bakelite, and Teflon have different dielectric constants and thicknesses. The results show that the complex relative permittivity of the samples matches the measured and calculated values of S-parameters in the frequency range of 8.2GHz to 12.4GHz.

Computer simulation of reflectance due to dielectric mirror

The present work is calculating the reflectance due to stacked multilayer dielectric material. The calculation is based on the analysis of the characteristic matrix of an arrangement of n layers, each containing parameters that dealing with reflection (reflective index, optical thickness, wavelength of incident wave, angle of incident wave). The implication of this calculation on a dielectric mirror is pointed out. For certain arrangement of dielectric layers with a particular thickness, maximum reflectance can be obtained. In this work, FORTRAN program has been written to obtain the product of matrices. Calculation of reflectance and transmittance which are particularly needed in this context have been obtained.

Multinozzle 3D Printing of Multilayer and Thin Flexible Electronics

Multilayer flexible electronics have broad applications in the fields of sensors, biomedicine, flexible displays, etc. The existing multilayer flexible electronic manufacturing methods are complicated and usually require multiprocess and multiequipment combinations for processing; especially, it is difficult to achieve integrated manufacturing. The increase in the overall thickness of multilayer flexible electronics also limits its flexibility, stretchability, and spatial density. Herein, a method for integrated multinozzle 3D printing of multilayer flexible electronics with thin structures is proposed and a new strategy for interlayer interconnection is presented. Printing high‐viscosity stretchable silver paste on the edge of the multilayer dielectric material and avoiding microholes and vertically printed conductive micropillar structures in traditional interlayer interconnection wires are discussed. The influences of process parameters on the fabrication of multilayer and thin flexible electronics are explored, and the minimum layer thickness for the fabrication of multilayer circuits is determined. A five‐layer flexible pressure sensor and two flexible electromagnetic actuators with different coils are fabricated, and the related performance tests of the two devices are carried out. The test results demonstrate that the proposed fabrication method of flexible electronics provides a high‐efficiency, low‐cost, and simple manufacture solution for the fabrication of multilayer and thin flexible electronics.

A new method to solve the neutron transport problem of spherical structure

The Boltzmann equation is an integro-differential equation representing a wide range of transport and radiative transfer problems. In this paper, we propose to use the half boundary method (HBM) in the spherical coordinate system for deriving accurate and robust numerical solutions of the Boltzmann transport equation for neutron transport problem, respectively for vacuum boundary conditions, reflection boundary conditions and multilayer dielectric materials, yielding the recursive equation of the angular neutron flux by discretizing the transport equation's space and angle variables. The relationship between any point and the boundary point is derived and the particle flux distribution is obtained. Compared to traditional discrete ordinate method, the HBM uses no inverse matrix, which increases the degree of discretion, significantly reducing the computation expenses in the solution process. Finally, the HBM results are compared to those of the Monte Carlo method, proving the proposed method's feasibility, high accuracy and applicability.

Evaluating the Accuracy of Reconstruction of the Electrical and Geometric Parameters of Multilayer Dielectric Coatings by a Multifrequency Radio-Wave Method for Slow Surface Electromagnetic Waves

One of the most important problems in the diagnostics of multilayer dielectric materials and coatings is the development of methods for quantitative interpretation of the results of monitoring the electrical and geometric parameters of these materials. Results are presented from a study of the potential informativeness of a multifrequency radio-wave method for slow surface electromagnetic waves for reconstruction of the electrical and geometric parameters of multilayer dielectric coatings. A simulation model is shown for evaluating the accuracy of reconstructing the electrical and geometric parameters of multilayer dielectric coatings. The model takes into account the electrical and geometric parameters of the coating, the level of noise in the measurement data, and the measurement bandwidth. Simulation modeling and experimental test data for the reconstruction of the relative dielectric constants and thicknesses of one- and two-layer equal-thickness dielectric coatings based on polymethyl methacrylate, ftoroplast (teflon) F-4D, and RO3010 for different values of the mean square deviation of the noise level in the measured attenuation coefficients for the field of a slow surface electromagnetic wave. The accuracy of the reconstruction of the geometric and electrical parameters of the layers is found to decrease as the number of estimated parameters and the noise level increase, as well as when the dielectric constant and thickness of the layers are reduced. Experimental data confirm the adequacy of the simulation model developed here. This model can be used for a specific measurement complex employing a multifrequency radio-wave technique for slow surface electromagnetic waves to estimate quantitatively the potential possible accuracy of reconstructing the geometric and electrical parameters of multilayer dielectric materials and coatings. A simulation model and experimental study of a multilayer dielectric coating show that for a measurement bandwidth of 1 GHz the errors in estimating the dielectric constants and thicknesses of the layers do not exceed 10% with a confidence coefficient of 0.95 for a mean square deviation of 0.003–0.004 in the noise level.

Control of defects in the multilayer dielectric materials and coatings in the microwave range

The development of modern engineering is inextricably linked with the development of the new types of multilayer dielectric materials. Existing radio wave methods for monitoring interlayer defects in such materials exhibit low accuracy in reconstructing the geometric parameters of defects. The results of studying extended interlayer defects in the three-layer coating consisting of polymethyl methacrylate, F-4D PTFE, and semi-hard rubber by the method of surface electromagnetic waves are presented. The method is based on the solution of inverse problems in the reconstruction of the geometric parameters of extended interlayer defects of special multilayer materials and coatings from the frequency dependence of the attenuation coefficient of the field of a slow surface electromagnetic wave. Unlike the methods that make use from the complex reflection coefficient we proposed to increase the accuracy of the reconstruction of the geometric parameters of extended interlayer defects taking into account the linear frequency dependence of the attenuation coefficient as well as reducing the number of fixed measurement frequencies. Moreover, the determination procedure is rather simple, since only the field strength of the surface electromagnetic wave is measured, and there is no need for phase measurements. Experimental data obtained on a multifrequency measuring complex in the range of 10 – 11 GHz were used for reconstruction of the interlayer defects in the coating under study. The developed method provided a relative error of thickness estimation below 10%. The proposed method approach can be used in studying multilayer dielectric coatings on the metal for detection of delamination in the lack of glue or poor adhesion between the layers. The developed method is also suitable for control of the defects in semiconductors, ferrite and composite materials.

Influence of modifying coatings on dielectric permittivity of ceramic materials with composite coatings

The results of research of features of modification of aluminosilicate ceramics by suspension of fluoroplastic, aluminophosphate binder (AFS), non-aqueous compositions of polyurethane components, are presented. Samples of aluminosilicate ceramics for research were obtained by technological methods, including batch preparation operations, sample pressing, pre-annealing and sintering at a temperature of 1200–1350 °C. Polydisperse powders of aluminosilicates obtained by grinding waste of porcelain production (porcelain ware, GOST 28390-89); low-melting clay raw materials were selected as initial components. Modification of surface of aluminosilicate materials was carried out by impregnation of aqueous compositions based on a suspension of fluoroplastic and aluminophosphate binder (AFS), non-aqueous compositions of polyurethane components used in the preparation of polyurethane foam and 5 % solution of polyethylene hydrosiloxane in toluene with the formation of composite coatings on the surface of ceramic materials. It is shown that the application of organic film coatings (based on polyurethane, aluminophosphate binder and a suspension of fluoroplastic-4D, polyethylene hydrosiloxane) leads to formation of a multilayer dielectric material in which there are interface surfaces separating areas with different dielectric properties. In the presence of an external electric field, conditions are created for migration polarization between the crystalline phase of the substrate and the amorphous phase of the coating, due to the redistribution of free charges in the volume of the composite. Moreover, the chemical interaction of AFS with ceramics leads to the smoothing of the surface relief of the aluminosilicate base and the overgrowth of deep pores. Composite “aluminosilicate – AFS-fluoroplastic coating” differs from other materials, primarily in that aluminophosphate binder coating chemically reacts with the ceramic base. The impurity ions introduced during coating application, its composite structure, as well as the heterogeneity of the interface determine the pronounced frequency dependence ε and tgδ, as well as large dielectric losses of the composite in comparison with the original aluminosilicate material.

Evaluation of the accuracy of reconstruction of the electrophysical and geometric parameters of multilayer dielectric coatings by the multi-frequency radio wave method of a slow surface electromagnetic waves

One of the most important diagnostic problems multilayer dielectric materials and coatings is the development of methods for quantitative interpretation of the checkout results their electrophysical and geometric parameters. The results of a study of the potential informativeness of the multi-frequency radio wave method of surface electromagnetic waves during reconstruction of the electrophysical and geometric parameters of multilayer dielectric coatings are presented. The simulation model is presented that makes it possible to evaluate of the accuracy of reconstruction of the electrophysical and geometric parameters of multilayer dielectric coatings. The model takes into account the values of the electrophysical and geometric parameters of the coating, the noise level in the measurement data and the measurement bandwidth. The results of simulation and experimental investigations of reconstruction of the structure of relative permittivitties and thicknesses of single-layer and double-layer dielectric coatings with different thicknesses, with different values of the standard deviation (RMS) of the noise level in the measured attenuation coefficients of the surface slow electromagnetic wave are presented. Coatings based on the following materials were investigated: polymethyl methacrylate, F-4D PTFE, RO3010. The accuracy of reconstruction of the electrophysical parameters of the layers decreases with an increase in the number of evaluated parameters and an increase in the noise level. The accuracy of the estimates of the electrophysical parameters of the layers also decreases with a decrease in their relative permittivity and thickness. The results of experimental studies confirm the adequacy of the developed simulation model. The presented model allows for a specific measuring complex that implements the multi-frequency radio wave method of surface electromagnetic waves, to quantify the potential possibilities for the accuracy of reconstruction of the electrophysical and geometric parameters of multilayer dielectric materials and coatings. Experimental investigations and simulation results of a multilayer dielectric coating demonstrated the theoretical capabilities gained relative error permittivity and thickness of the individual layers with relative error not greater than 10 %, with a measurement bandwidth of 1 GHz and RMS of noise level 0,003–0,004.

A Molecular Dynamics Study on Polycaprolactone -Metal Oxide Interactions

In order to realize the macroscopic features of a number of chemically bonded multi-layer dielectric and composite materials, interactions of metal oxide surfaces, polymer surface atoms, and near-surface atoms are very beneficial. The simulation study of polymer-metal oxides interfaces is of great importance in investigating the adhesion and miscibility features of these systems that are inherently challenging to obtain experimentally or for which there is no experimental data, even if some low data exist, they are not reliable. Polycaprolactone (PCL) is biocompatible, biodegradable, non-toxic and hydrophobic polyester that has been used in tissue engineering, such as a bioactive implant. Hence, the molecular dynamics simulations of PCL are carried out to investigate its surface interaction with metal oxides as ZnO, CuO, Fe2O3, NiO and SiO2. The force field of COMPASS is applied to simulations in order to compute interfacial and solubility parameters. Molecular dynamics approach to investigate the interaction and adsorption manner of PCL with metal oxides. Whereas investigations are useful in exploring polymer composites. Much better adhesion is achieved by the calculations between the PCL oligomer and the metal oxides under investigation. The negative values of interaction energy have to be forecasted despite the presence of acid-base or hydrogen-bonding interactions.

Reconstruction of The Structure of the Electrophysical Parameters of Multilayer Dielectric Materials and Coatings from The Frequency Dependence of the Attenuation Coefficient of the Field of a Surface Electromagnetic Wave

A new radio-wave method of reconstruction of the relative permittivities and thicknesses of multilayer materials and coatings is proposed. The method is based on the solution of inverse problems in the reconstructionof the structure of the electrophysical parameters of special multilayer materials and coatings from the frequency dependence of the attenuation coefficient of the field of a slow surface electromagnetic wave. The principal differences of the new method from well-known radio wave methods of determining the electrophysical parameters of multilayer materials are demonstrated. In contrast to methods that involve an informative parameter – the complex reflection coefficient – the proposed method yields an increase in the precision and reliability of the reconstruction of the structure of the relative permittivitties and thicknesses. Improved precision and reliability is achieved by taking into account the linear dependence of the attenuation coefficient on frequency as well as reducing the number of fixed measurement frequencies. The results of experimental studies that confirm the linear dependence of the attenuation coefficient of the field of a surface electromagnetic wave on frequency as well as a decrease in the number of fixed measurement frequencies are presented. The method implements a simple measurement procedure, since only the values of the field strength of the surface electromagnetic wave are measured and there is no need for phase measurements in the method. Reconstruction of the permittivity of a three-layer coating consisting of polymethyl methacrylate, F-4D PTFE, and semi-hard rubber with precision acceptable for practical applications is realized with the use of experimental results of measurements in a multifrequency measurement complex in the range 9–10 GHz by means of the new method. Experimental investigations of a multilayer dielectric coating demonstrated the theoretical capabilities gained with measurement of the relative permittivity and thickness of the individual layers with relative error not greater than 8 and 6%, respectively.

Multiple compound Tamm waves with Uller–Zenneck wave characteristics guided by dissipative dielectric defect in periodic multilayered isotropic dielectric material

A canonical problem configured in three different arrangements of periodic multilayered isotropic dielectric material layers with a dissipative dielectric defect, to guide multiple compound Tamm waves with Uller–Zenneck wave characteristics, was formulated and solved. The numerical solutions showed multiple Tamm waves guided at a fixed wavelength along the dissipative defect with same polarization state. These waves propagate with different phase speeds, different propagation distances, different field localizations, and different field profiles. The results identified excitation of symmetric and anti-symmetric solutions of p-polarized Tamm waves and p- and s-polarized waveguide modes. The high phase speed solutions ceased to exist beyond a certain limit of dissipative dielectric defect thickness, but the low phase speed solutions were computed for a wide range of dissipative dielectric defect thickness. The Tamm waves were compounded when the thickness of defect is very small and transmuted into waveguide modes for increasing thickness of dissipative dielectric defect because most of the energy is then strongly confined to the dissipative dielectric defect. The excitation of multiple Tamm waves and waveguide modes at a given dissipative dielectric defect thickness and fixed wavelength can be considered for multi-channel optical communication and sensing applications.

Reconstruction of the structure electrophysical parameters of multilayer dielectric materials and coatings according to the frequency dependence of the attenuation coefficient of the field of surface electromagnetic wave

Reconstruction of the structure electrophysical parameters of multilayer dielectric materials and coatings according to the frequency dependence of the attenuation coefficient of the field of surface electromagnetic wave

Bilayer Dielectrics for RRAM Devices

To implement low power and highly reliable resistive random-access memory (RRAM) devices, suitable multi-layer dielectric materials are required. This consists of a switching layer, the oxygen vacancy medium, to form the filament and an oxygen vacancy deficient layer, such as Al2O3 to control the filament rupture. This work explores several different bilayer structures using different dielectrics, electrode materials and processing conditions to reduce power consumption during forming, set and reset operations and to enhance endurance with a large Roff/Ron value for RRAM application. Several transition metal dielectrics (HfAlO2 or HfZrO2) were used as the switching layer on a thin Al2O3. By comparing the forming voltage values, Roff/Ron values and both set and reset power consumption, optimized performance was derived.

The Talbot effect in a metamaterial

The effect of anisotropy and spatial dispersion of a metamaterial on the Talbot effect may be engineered in principle. This has profound implications for applications of the Talbot effect such as the design of a multimode interference coupler (MMI). The paper describes how a metamaterial can suppress the modal phase error which otherwise limits the scaling of MMI port dimension. A binary multilayer dielectric material described by the Kronig–Penney model is shown to provide a close approximation to the required dispersion relation. Results of simulations of a multi-slotted waveguide MMI engineered to provide a polarising beam splitter function are given as an example of the method.

Signatures of thermal hysteresis in Tamm-wave propagation

We numerically solved the boundary-value problem for Tamm waves (which may also be classified as Uller-Zenneck waves here) guided by the planar interface of a homogeneous isotropic dissipative dielectric (HIDD) material and a periodically multilayered isotropic dielectric material. The HIDD material was chosen to be VO${}_2$ which, at optical wavelengths, has a temperature-dependent refractive index with a hysteresis feature, i.e., the temperature-dependence of its refractive index varies depending upon whether the temperature is increasing or decreasing. A numerical code was implemented to extract solutions of the dispersion equation at a fixed wavelength for both $p$- and $s$-polarization states over the temperature range [50,80] degrees. A multitude of Tamm waves of both linear polarization states were found, demonstrating a clear demarcation of the heating and cooling phases in terms of wavenumbers and propagation distances. Thereby, the signatures of thermal hysteresis in Tamm-wave propagation were revealed.

Periodicity effects on compound waves guided by a thin metal slab sandwiched between two periodically nonhomogeneous dielectric materials

Surface-plasmon-polariton waves can be compounded when a sufficiently thin metal layer is sandwiched between two half spaces filled with dissimilar periodically nonhomogeneous dielectric materials. We solved the boundary-value problem for compound waves guided by a layer of a homogeneous and isotropic metal sandwiched between a structurally chiral material (SCM) and a periodically multilayered isotropic dielectric (PMLID) material. We found that the periodicities of the PMLID material and the SCM are crucial to excite a multiplicity of compound guided waves arising from strong coupling between the two interfaces.

Multifunctional Hybrid Multilayer Gate Dielectrics with Tunable Surface Energy for Ultralow-Power Organic and Amorphous Oxide Thin-Film Transistors.

For large-area, printable, and flexible electronic applications using advanced semiconductors, novel dielectric materials with excellent capacitance, insulating property, thermal stability, and mechanical flexibility need to be developed to achieve high-performance, ultralow-voltage operation of thin-film transistors (TFTs). In this work, we first report on the facile fabrication of multifunctional hybrid multilayer gate dielectrics with tunable surface energy via a low-temperature solution-process to produce ultralow-voltage organic and amorphous oxide TFTs. The hybrid multilayer dielectric materials are constructed by iteratively stacking bifunctional phosphonic acid-based self-assembled monolayers combined with ultrathin high-k oxide layers. The nanoscopic thickness-controllable hybrid dielectrics exhibit the superior capacitance (up to 970 nF/cm2), insulating property (leakage current densities <10-7 A/cm2), and thermal stability (up to 300 °C) as well as smooth surfaces (root-mean-square roughness <0.35 nm). In addition, the surface energy of the hybrid multilayer dielectrics are easily changed by switching between mono- and bifunctional phosphonic acid-based self-assembled monolayers for compatible fabrication with both organic and amorphous oxide semiconductors. Consequently, the hybrid multilayer dielectrics integrated into TFTs reveal their excellent dielectric functions to achieve high-performance, ultralow-voltage operation (< ± 2 V) for both organic and amorphous oxide TFTs. Because of the easily tunable surface energy, the multifunctional hybrid multilayer dielectrics can also be adapted for various organic and inorganic semiconductors, and metal gates in other device configurations, thus allowing diverse advanced electronic applications including ultralow-power and large-area electronic devices.

Compound guided waves that mix characteristics of surface-plasmon-polariton, Tamm, Dyakonov–Tamm, and Uller–Zenneck waves

Solutions of the boundary-value problem for electromagnetic waves guided by a layer of a homogeneous and isotropic (metal or dielectric) material sandwiched between a structurally chiral material (SCM) and a periodically multi-layered isotropic dielectric (PMLID) material were numerically obtained and analyzed. If the sandwiched layer is sufficiently thick, the two bimaterial interfaces decouple from each other, and each interface may guide one or more electromagnetic surface waves (ESWs) by itself. Depending on the constitution of the two materials that partner to form an interface, the ESWs can be classified as surface-plasmon-polarition (SPP) waves, Tamm waves, Dyakonov-Tamm waves, or Uller-Zenneck waves. When the sandwiched layer is sufficiently thin, the ESWs for single bimaterial interfaces coalesce to form compound guided waves (CGWs). The phase speeds, propagation distances, and spatial profiles of the electromagnetic fields of CGWs are different from those of the ESWs. The energy of a CGW is distributed in both the SCM and the PMLID material, if the sandwiched layer is sufficiently thin. Some CGWs require the sandwiched layer to have a minimum thickness. Indeed, the coupling between the two faces of the sandwiched layer is affected by the ratio of the thickness of the sandwiched layer to the skin depth in that material and the rates at which the fields of the ESWs guided individually by the two interfaces decay away from their respective guiding interfaces.

Broadband Thin-Film Transmission-Line Characterization for Accurate High-Frequency Measurements of On-Wafer Components

A high-frequency fine-pitched (i.e., very narrow line width) thin-film transmission line (TL) characterization technique is presented. A new dielectric permittivity determination technique for thin-film TL structures is developed. Multi-layered mixed dielectric materials are then accurately characterized in a broad frequency band, to be followed by the TL characterization. For experiments, various lengths of TL and extra patterns were designed and fabricated by using both a ${\hbox{0.18-}}\mu{\hbox{m}}$ SK Hynix CMOS process and ${\hbox{0.13-}}\mu{\hbox{m}}$ Samsung CMOS process. S-parameters for the test patterns were measured by using a vector network analyzer from 10 MHz to 50 GHz. It is shown that not only the inherent de-embedding problems associated with wafer-level high-frequency characterizations can be conveniently eliminated, but also the frequency-variant characteristic impedance of a thin-film TL can be readily determined using the proposed technique. It can be exploited for accurate high-frequency wafer-level component characterizations including miniaturized transistors, frequency-variant interconnect lines, and other circuit components.

Buffer layer between a planar optical concentrator and a solar cell

The effect of inserting a buffer layer between a periodically multilayered isotropic dielectric (PMLID) material acting as a planar optical concentrator and a photovoltaic solar cell was theoretically investigated. The substitution of the photovoltaic material by a cheaper dielectric material in a large area of the structure could reduce the fabrication costs without significantly reducing the efficiency of the solar cell. Both crystalline silicon (c-Si) and gallium arsenide (GaAs) were considered as the photovoltaic material. We found that the buffer layer can act as an antireflection coating at the interface of the PMLID and the photovoltaic materials, and the structure increases the spectrally averaged electron-hole pair density by 36% for c-Si and 38% for GaAs compared to the structure without buffer layer. Numerical evidence indicates that the optimal structure is robust with respect to small changes in the grating profile.