Electrical Material Parameters Research Articles

Development of high-precision hardware and software tools for automated determination of the characteristics of thermoelectric devices

In this work, a high-accuracy setup was developed for the characterization of thermoelectric devices in the temperature range of 300-900 K. The output parameters of the thermoelectric devices, including the thermoelectric efficiency Z, Seebeck coefficient S, and internal resistance r, were measured. A technique, block diagram, and computer tools for automated measurement and preliminary processing of experimental data were developed for automated studies of the properties of semiconductor materials and thermoelectric power conversion modules. The developed tools were shown to have high efficiency. The complexity of the process of measuring the main electrical parameters of semiconductor materials was significantly reduced, and the accuracy of the obtained results was increased.

Development of a Wire Mesh Composite Material for Aerospace Applications

The electrical conductivity of Fiber-Reinforced Polymers (FRPs) may be used to reduce the dangers of lightning strikes, radar radiation, and aerial radio frequency transmitters. Metal Matrix Composites (MMCs) were created to guard against Electromagnetic Interference (EMI) in the aircraft's electric and electrical systems. High-Intensity Radiated Field Protection (HIRFP) aircrafts are required to be manufactured from a metal matrix consisting of Al6061, Al2O3, and Fly Ash (FA) to keep up with the ever-increasing needs of industry. The current work considered three MMC combinations. MMC1 is AL6061+10% and Al2O3+5% FA, MMC2 consists of AL6061+15 and Al2O3+5% FA, and MMC3 of AL6061+20% and Al2O3+5% FA. These MMCs made the shielding more effective at different percentages. The material electrical properties were interpreted based on experiments. Analytical approaches include the testing of the electrical parameters of materials to measure the shielding effectiveness. The calculated shielding efficiencies MMC1-55.7dB, MMC2-57.2dB, and MMC3-59.1dB allow the composites to be employed in aircrafts. This indicates that, for specific applications like HIRFPs, the constructed MMCs perform well.

Electromagnetic Shielding Analysis of Planar Materials Using ASTM D4935 Standard Fixture

In this article, analytic models are proposed for electromagnetic shielding analysis of planar materials using the ASTM D4935 standard fixture typically employed to measure far-field shielding effectiveness (SE). The fixture with an inserted planar material is divided into two coaxial line sections and one material section that are modeled as lossless and lossy transmission lines (TLs), respectively. Using the ABCD parameters of TLs, the far-field SEs of planar materials are analytically derived and calculated. In order to analyze the case where the conductive materials are coated on insulating substrates, contact impedances are considered at the inner and outer conductors of the flanged coaxial fixture. The proposed high-frequency model can accurately predict the absorption loss especially in the high-frequency where the skin depth of the material becomes smaller than its thickness. Low-frequency and lumped models are also derived by approximation of the high-frequency model. In addition, correction factors are introduced to remove the SE error in the low-frequency range due to the attached insulating substrates of the conducting materials. For verification, the proposed models are compared with the theoretical plane-wave SE and the measurement results presented in other literatures. They show a good agreement with each other. Lastly, an influence of the errors in the thicknesses and electrical parameters of actual materials on the analytic SE models is analyzed.

Measurement of complex permittivity of liquids in the frequency range 100-1000MHz by using a re-entrant cavity.

For many liquid materials and biological media, their complex permittivity varies with frequency in the P-band (100-1000MHz). In this paper, a re-entrant coaxial cavity resonance test system with intensive multi-frequency points testing capability is designed for the P-band to realize the test of the complex permittivity of P-band materials. For this system, a test algorithm has been written, and on the basis of this system, a perturbation block has been designed, using stepper motors to control the up and down movement of the perturbation block to achieve frequency tunability of the cavity, enabling more P-band frequency test data to be obtained. The experimental results show that the system is suitable for testing the electrical parameters of P-band biological media and liquid materials and for testing solid materials in aerospace, electromagnetic shielding, and other fields where there is a great demand for P-band testing.

(Electronics and Photonics Division Award) The Impact of Defects on the Performance of Semiconductor Devices and Materials

Since the early days of the semiconductor industry, defect control has been key to the successful development of devices and circuits. It requires a thorough understanding of their formation and the impact on the electrical material parameters. This has only been possible by the invention of powerful structural, chemical and electrical characterization tools, with the device itself perhaps as the most sensitive probe. This evolution was paralleled by the development of ab initio calculation methods, based on Density Functional Theory and more recently, also TCAD tools allowing more and more refined modelling of the impact of defects on the electrical characteristics of devices.The implementation of other materials than Si and SiO2 in CMOS through the hetero-epitaxial growth on a silicon substrate for example, has renewed the interest in defect engineering during the last two decades, leading to single-defect analysis methods like Random Telegraph Noise (RTN) [1] or novel growth schemes like Aspect Ratio Trapping (ART) [2] for the removal of extended defects from the device active regions.In this presentation, some state-of-the-art analysis techniques will be highlighted, including Deep Level Transient Spectroscopy (DLTS) [3], Generation-Recombination (GR) noise and RTN spectroscopy [1,4] and p-n diode lifetime analysis [5]. These methods will be applied to several case studies. As shown in Fig. 1, threading extended defects impact the recombination lifetime of lowly-doped n-type In0.47Ga0.53As starting from a density of a few 107 cm-2. Likewise, it will be demonstrated that the GR noise observed in GaN-on-Si MOSHEMTs (Fig. 2) most likely originates from threading dislocations [6]. It is concluded that when hetero-epitaxial layers can be grown with a sufficiently low defect density, their impact will be more on the variability of the electrical parameters rather than on the effective values. In addition, the position of the defect with respect to strategic nodes like a p-n junction or depletion region largely determines its electrical impact, as has been validated by TCAD simulations.

Lumped Element Model of Spherical Cells Exposed to an External Electric Field

A lumped element model for cells is proposed, giving an overview of the general electrical behavior (e.g., in terms of current distribution within different cell layers) of a cell exposed to an external electric field. The aim is to provide a model which is easily adaptable to different cell types and cell sizes such that it can be used in the frame of different studies where cells are exposed to electric fields, e.g., <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Tumor Treating Fields</i> , operating at frequencies around 200 kHz. Originating from the usual model of a spherical cell, an electric lumped element model is derived under consideration of the electric field distribution within a cell. Possible simplifications of the model are suggested, which are justified by consideration of electrical material properties. Lumped element parameters of the model are approximated with formulas containing only cell dimensional parameters and electrical material parameters. The lumped element model is validated on the basis of a glioblastoma cell model with two different nuclei sizes. The proposed lumped element model with the according formulas for the lumped element parameters is easily adaptable to different cell types and cell sizes. It leads to a sufficient approximation of the general electrical behavior of cells in terms of current distribution and general frequency behavior in frequency ranges up to several hundreds of megahertz. The model is an easy to handle electrical description of a biological cell.

Longitudinal size effects on electrical and actuation behaviors of ionic polymer-metal composite

The structural characteristics of ionic polymer-metal composite (IPMC) were analyzed, and the effects of IPMC length ranging from 1 to 5 cm (with a width of 0.5 cm) were evaluated in terms of electrical parameters and actuation behavior. It has been concluded that the electrical parameters of IPMC materials (including capacitance, electrode resistance in thickness-direction, and internal resistance) decrease, and the bending strain of the setpoint increases as the length increases. The simulation of the current response of IPMC to 2 V DC voltage shows that the error between simulated peak current using 1 cm-IPMC parameters and the measured value is 8.23 times higher than that of 5 cm-IPMC. The strain of the set point on 5 cm-IPMC sample is 5.65 times bigger than that of the 1 cm-IPMC sample.

Electrical characteristics of wire-to-wire dielectric barrier discharges

A wire-to-wire dielectric barrier discharge (DBD) is a novel method of plasma generation that has been demonstrated as an effective ion source for electroaerodynamic ion propulsion devices. A wire-to-wire DBD comprises two parallel wires spaced less than a millimeter apart: an insulated high voltage wire forms the encapsulated electrode and a thin uninsulated wire forms the exposed electrode. This electrode arrangement is lightweight, simple to manufacture, and has low aerodynamic drag; these properties make it suitable for ion generation in atmospheric ion propulsion and other potential applications. We performed a parametric experimental exploration of this type of plasma source using a sinusoidal driving signal, measuring power draw and discharge characteristics over a range of electrical, geometric, and dielectric material parameters. We find that it has similar electrical characteristics to volume DBDs. We provide a model for predicting the power draw to within 0.9 W m−1 with a correlation of r 2 = 0.99 between model and experiments.

Anisotropic transport properties of graphene-based conductor materials

We analyzed nanographite-based materials in a combined study including experimental analysis via 4-point probe STM and simulation to provide a complete picture of microscopic and macroscopic properties of the material. The two- and three-dimensional transport regimes were determined and evaluated regarding the anisotropy of the conductivity. The experimental results yield the full macroscopic conductivity tensor. Microstructural simulations are used to map those macroscopic properties to the microscopic building blocks of the sample. By combining those two, we present a coherent and comprehensive description of the electrical material parameters across several length scales.

Features for the design of a specialized information-measuring system for the study of thermoelectric properties of semiconductors

Methods for studying thermoelectric parameters of semiconductors that are optimal for the implementation of software and hardware have been analyzed and selected. It is based on the Harman method and its modifications, adapted for pulse measurements, which are convenient to implement on a modern element base. An important advantage of these methods is the absence of the need for accurate measurements of heat fluxes, which greatly simplifies and reduces the time for conducting experimental research. The required operating ranges for the voltage 10 µV–1 V, for the current 10 µA–300 mA and the element base performance at the processing level of 40–200 million samples per second have been determined. Structural and electrical circuits, as well as software for a specialized computer system for studying thermoelectric parameters of both bulk and thin-film thermoelectric materials, and express analysis of the operational characteristics of finished modules have been developed. It has been shown that the proposed scheme copes well with the task. And the use of FPGA and 32-bit microcontrollers provide sufficient processing speed up to 200 MSPS and the necessary synchronization modes for the implementation of the Harman pulse method even when studying films of nanometer thickness. Experimental studies of both bulk thermoelectric modules based on Bi2Te3 and thin-film thermoelectric material based on PbTe have been carried out. The effectiveness of the developed tools and techniques has been shown, which made it possible to more than halve the time for sample preparation and experiment. Based on the presented models, all the main thermoelectric and operational parameters have been determined, in particular, electrical conductivity, Seebeck coefficient, thermal conductivity, thermoelectric figure of merit. As a result of the development of specialized computer tools, it was possible to reduce the labor intensity of the process of measuring the main electrical and operational parameters of semiconductor thermoelectric materials and energy conversion modules based on them, as well as to automate the process of defects identification of thermoelectric modules. The labor intensity of the research process has decreased not only due to the automation of the measurement process, but also due to an optimized technique that allows research on a sample of one configuration, since the manufacture and preparation of samples are the most laborious

Investigation of Complex Permittivity/Conductivity Distribution by Electrical Tomography

The electrical tomography technology is a multi-phase flow detection technology. This technology has the advantages of non-radiation, non-invasive and visualization, can be widely used in traditional energy field and new energy field. The permittivity and conductivity, as the basic electrical parameters of material, are closely related to the distribution of material in multiphase flow. However, in the actual multiphase flow, due to the non-uniform distribution of permittivity and conductivity in time and space, the accuracy and validity of measuring instruments are challenged. The main target of this research is to investigate the application of electrical capacitance tomography (ECT), electrical resistance tomography with voltage excitation (ERTv) and electrical resistance tomography with current excitation (ERTc) on the multiphase flow with complex permittivity and conductivity distribution. The final objective based on the above research is to provide suitable tomography modual for different multiphase flow process. The experimental results show that ECT is suitable for measuring dry gas-solid fluids. ERTv is better for measuring high water content gas-solid fluids and low conductivity gas-liquid fluids, while ERTc is better for measuring continuous phase conductivity gas-liquid fluids.

Application of Circuit Modeling in the Study of Spark Formation During Electroerosion Treatment

Electrical discharge machining (EDM) of a workpiece is a complex, fast-flowing process characterized by alternating (intermittent) states: short circuit, idle and spark formation. The discontinuity of the EDM process means that the processing is carried out in single pulses, which are formed by a special pulse generator. The parameters of the generator pulses can be divided into time and electrical. The time period and duration of the pulses, as well as the difference between these two parameters (the “silence” interval), are considered temporary. The electric ones include the amplitude value of the voltage, the maximum permissible current, and the polarity of the pulses. in addition, depending on the device of the generator, the pulses can be composite, for example, have an igniting pulse with a higher voltage and a lower current than the main (working) pulse. In this work, we have developed a interelectrode gap model that allows not only to obtain values of electrical parameters, but also to evaluate and to optimize the electrical parameters of materials being processed with known electrical properties. The key advantage of this model is its modularity, which allows to add new functional blocks, which describe external and internal influences, for example, the concentration of erosion products, uneven electrical conductivity of the workpiece, and others, without changing its structure.

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.

Multi-method characterization approach to facilitate a strategy to design mechanical and electrical properties of sintered copper

Advanced die application materials, utilizing pressure-less sintered copper, show great prospects regarding cost effectiveness, power density, withstanding high switching speeds and temperature loading for novel eco-friendly and high efficiency semiconductors. In general, to preserve high reliability in combination with electrical functionality the design of elastic as well as electrical material parameters is of great importance. Here, we present a multi-method characterization approach to understand the impact of the morphology on the elastic as well as electrical behavior, which facilitates a strategy to design the relevant material parameters by tuning the morphology. Nano-SEM/FIB tomography and SEM/EBSD are applied to probe the morphology of three representative copper films. Nanoindentation and 4-point probe are used to extract the elastic modulus and specific electrical resistivity, respectively. The evaluated material parameters are compared with modeling results using the analyzed image data as an input. For the crucial image analysis, we develop a validated objective image analysis workflow. We obtain a quantified insight about the effect of the heterogeneous morphologies on the elastic modulus and specific electrical resistivity, thereby delivering important information about the necessary homogeneous copper morphology- and nano-scale pore-design. The strategy shall provide design guidelines to ensure reliable and high-performance die attachments.

Methods of computer tools development for measuring and analysis of electrical properties of semiconductor films

The method is presented and computer tools of automated measurement of electrical parameters and experimental data processing are developed, taking into account models for describing physical processes that determine the operating characteristics of semiconductor material. The possibility of automated investigation of the quality and ohmicity of contacts is realized, which significantly improves the reliability of the data obtained.Methods and features of software processing of automated research results are considered using the models that allow taking into account the effect of surface, structure and thickness of the sample on the electrical properties of semiconductor films.Experimental studies of a series of n-PbTe thin films are carried out and the efficiency of the developed tools and methods of processing scientific data using the described methods of experimental data analysis is shown. Based on the simulation, the electrical parameters of the surface layers were determined and the effect of the surface and grain boundary mechanisms of charge carrier scattering on the electrical parameters of the films was separated. The surface mobility of the charge carriers is approximately 3 times less than the mobility in the bulk material, which indicates the dominance of the diffuse scattering of charge carriers on the surface of the thin-film samples despite the high reflectance coefficient (0.4). Taking into account the effect of the surface and the boundaries of the grains, it is possible to choose the technological modes and duration of spraying to obtain a semiconductor material with the desired properties.As a result of using the developed tools, it was possible to significantly reduce the complexity of the process of measuring the basic electrical parameters of semiconductor materials, processing the experimental results, to improve the accuracy of the results obtained

A Stochastic Finite-Difference Time-Domain (FDTD) Method for Assessing Material and Geometric Uncertainties in Rectangular Objects

The uncertainties present in a variety of electromagnetic (EM) problems may have important effects on the output parameters of interest. Unfortunately, deterministic schemes are not applicable in such cases, as they only utilize the nominal value of each random variable. In this work, a two-dimensional (2D) finite-difference time-domain (FDTD) algorithm is presented, which is suitable for assessing randomness in the electrical properties, as well as in the dimensions of orthogonal objects. The proposed technique is based on the stochastic FDTD method and manages to extract the mean and the standard deviation of the involved field quantities in one realization. This approach is applied to three test cases, where uncertainty exists in the electrical and geometrical parameters of various materials. The numerical results demonstrate the validity of our scheme, as similar outcomes are extracted compared to the Monte Carlo (MC) algorithm.

Homodyne vector network analysis as a tool for the real-time measurement of electrical material parameter distributions in the field

Abstract The spatial distribution of electrical material parameters (e. g. permittivity and conductivity) can be a valuable indicator of the state of a chemical process or the condition of the processing system. Unfortunately, there are very few measurement systems that could handle this task in the field at low cost and with small shape factors. A potential solution currently under research for the determination of material parameter distributions is based on electromagnetic resonances inside chemical reactors. In the laboratory, vector network analyzers (VNA) and personal computers are used, which is expensive. This contribution reports on an application-specific stand-alone homodyne VNA with integrated data processing as an effort to transfer the laboratory-proven method to the field. The quality of the approach, validated by comparison with commercial VNAs, is shown to suffice for typical field applications.

Theoretical and Experimental Study on Electrical Contact Resistance of Metal Bolt Joints

As a kind of fixed connection, bolt joints are widely used in engineering. In this paper, the analytic equations of the contact resistance under different situations are deduced by approximating the Gaussian distribution and the asperity deformation process based on the Greenwood–Williamson model. The equations explicitly describe the theoretical dependences of contact resistance on mechanical and electrical parameters of materials, surface topographic features, and the property of the surface oxidation film. The characteristic curves of contact resistance versus contact pressure for brass, copper, and their silver-coated counterparts are measured by using a specially designed bolted-joints structure. The experimental results are consistent with the theoretical model, indicating that, in the log–log plot, the contact resistance depends linearly on contact pressure with a slope ranging from −0.5 to −1. The analytic equations and experimental observations of contact resistance revealed in this paper can be used as a guidance for electrical contact engineering.

Investigation of undoped and Tb-doped ZnO films on Al2O3 substrate by infrared reflection method

Undoped and Tb-doped ZnO thin polycrystalline films grown on Al2O3 substrate by magnetron sputtering approach were investigated using external infrared reflection in the spectral range from 50 to 5000 cm−1. The modelling of the IR reflection spectra was performed for absorbing film on semi-infinite substrate. For undoped ZnO film, the single oscillator model was used. Theoretical calculations were found to be in good agreement with the experimental results. The free carrier concentration, mobility and specific conductivity of electrons in ZnO films on Al2O3 substrates with E→⊥c→ orientation were determined. It was found that sheet resistance of the films investigated was much higher than that obtained from IR reflection spectra, which was ascribed to the presence of high resistive spaces between ZnO columns. In this case, IR reflection method is suitable for analysing the electrical parameters of textured materials when planar conductivity gives the incorrect results. Apparent effect of Tb doping on ZnO conductivity was not observed in the films investigated.

Application of acoustic waves to estimate mechanical and electrical parameters of ceramic materials obtained by sintering

Abstract The paper proposes an algorithm for estimating the physical parameters of piezoceramic materials obtained by the sintering technology. The task of analyzing the state of such materials is a modern actual material science problem. The efficiency of application of methods of acoustic microscopic flaw detection for the analysis of the structure of roller materials, determination of their density and porosity, optimization of annealing temperatures is demonstrated. It is shown that the measurement of a number of acoustic characteristics of piezoceramics allows us to determine the values of its electrical characteristics. To obtain the extreme values of the parameters, the methods of solving optimization problems are applied.