Measurements Of Electrical Properties Research Articles

Sub-10nm spatial resolution for electrical properties measurements using bimodal excitation in electric force microscopy.

We demonstrate that under ambient and humidity-controlled conditions, operation of bimodal excitation single-scan electric force microscopy with no electrical feedback loop increases the spatial resolution of surface electrical property measurements down to the 5nm limit. This technical improvement is featured on epitaxial graphene layers on SiC, which is used as a model sample. The experimental conditions developed to achieve such resolution are discussed and linked to the stable imaging achieved using the proposed method. The application of the herein reported method is achieved without the need to apply DC bias voltages, which benefits specimens that are highly sensitive to polarization. Besides, it allows the simultaneous parallel acquisition of surface electrical properties (such as contact potential difference) at the same scanning rate as in amplitude modulation atomic force microscopy (AFM) topography measurements. This makes it attractive for applications in high scanning speed AFM experiments in various fields for material screening and metrology of semiconductor systems.

Integrated magnetotelluric and petrological analysis of felsic magma reservoirs: Insights from Ethiopian rift volcanoes

Geophysical and petrological probes are key to understanding the structure and the thermochemical state of active magmatic systems. Recent advances in laboratory analyses, field investigations and numerical methods have allowed increasingly complex data-constraint models with new insights into magma plumbing systems and melt evolution. However, there is still a need for methods to quantitatively link geophysical and petrological observables for a more consistent description of magmatic processes at both micro- and macro-scales. Whilst modern geophysical studies provide detailed 3-D subsurface images that help to characterize magma reservoirs by relating state variables with physical material properties, constraints from on-site petrological analyses and thermodynamic modelling of melt evolution are at best incorporated qualitatively. Here, we combine modelling of phase equilibria in cooling magma and laboratory measurements of electrical properties of melt to derive the evolution of electrical conductivity in a crystallizing silicic magmatic system. We apply this framework to 3-D electrical conductivity images from magnetotelluric studies of two volcanoes in the Ethiopian Rift. The presented approach enables us to constrain key variables such as melt content, temperature and magmatic volatile abundance at depth. Our study shows that accounting for magmatic volatiles as an independent phase is crucial for understanding electrical conductivity structures in magma reservoirs at an advanced state of crystallization. Furthermore, our results deepen the understanding of the mechanisms behind volcanic unrest and help assess the long-term potential of hydrothermal reservoirs for geothermal energy production.

Lead-Free BiFeO3-BaTiO3 Ceramics with High Curie Temperature: Fine Compositional Tuning across the Phase Boundary for High Piezoelectric Charge and Strain Coefficients

BiFeO3-BaTiO3 is a promising high-temperature piezoelectric ceramic that possesses both good electromechanical properties and a Curie temperature (TC). Here, the piezoelectric charge constants (d33) and strain coefficients (d*33) of (1 - x)BiFeO3-xBaTiO3 (BF-xBT; 0.20 ≤ x ≤ 0.50) lead-free piezoelectrics were investigated at room temperature. The results showed a maximum d33 of 225 pC/N in the BF-0.30BT ceramic and a maximum d*33 of 405 pm/V in the BF-0.35BT ceramic, with TCs of 503 and 415 °C, respectively. To better understand the performance enhancement mechanisms, a phase diagram was established using the results of XRD, piezoresponse force microscopy, TEM, and electrical property measurements. The superb d33 of the BF-0.30BT ceramic arose because of its location in the optimum point in the morphotropic phase boundary, low oxygen vacancy (VO··) concentration, and domain heterogeneity. The superior d*33 of the BF-0.35BT ceramic was attributed to a weak relaxor behavior between coexisting macrodomains and polar nanoregions. The presented strategy provides guidelines for designing high-temperature BF-BT ceramics for different applications.

Rapid detection of catechins during black tea fermentation based on electrical properties and chemometrics

Catechins are important to evaluate the quality of black tea. In this study, a quantitative prediction model was established based on the measurement of electrical properties and a chemometrics method to detect the catechin content in fermented black tea. The effects of different preprocessing, variable screening methods, and nonlinear algorithms on the model were studied. Results show that the electrical parameters most sensitive to catechin content are equivalent parallel capacitance, loss factor, and reactance mainly at low frequencies (0.05–0.1 kHz). Normalization processing (Zscore), variable combinations' population analysis and the iterative retained information variable algorithm (VCPA-IRIV), and the nonlinear intelligent algorithm random forest (RF) can all effectively improve the performance of a catechin prediction model. In the VCPA-IRIV-RF model, the number of introduced variables was reduced from 162 to 9 with a compression ratio of 94.5%; the root mean square error of prediction and the root mean square error of validation of this model were only 0.269 and 0.214, respectively. The predictive correlation coefficient, correlation coefficient of calibration, and residual predictive deviation increased to 0.988, 0.994, and 5.47, respectively, indicating the good performance of the model. The rapid and nondestructive determination of catechin content in black tea fermentation using a method to detect the electrical properties seems to be practical.

Aging Modeling of Low-Voltage Cables Subjected to Radio-Chemical Aging

This article presents the development and application of a modelling approach based on quantities obtained from mechanical and electrical tests to assess the aging of low voltage cable insulation for nuclear applications. In order to obtain experimental data needed for the establishing of the models, accelerated aging is performed on coaxial cables. The first part of this paper focuses on the development of a predictive modelling for mechanical properties; this allows the evaluation of the Dose to Equivalent Damage (DED) as a function of the aging stress (dose rate). However, the use of mechanical tests for cable aging assessment presents some problems, being such tests destructive for the insulation and potentially affected by local defects. The novelty of this work lays on the introduction of a new model, allowing the definition of the end-of-life point in terms of electrical non-destructive tests. The second part of this article presents the development of aging modelling of cable insulation and correlation with experimental data obtained at different stresses, which allow the estimation of the expected life of the cable under test to be derived from diagnostic measurements of electrical properties like, e.g, tan δ. Finally, the application of the proposed life model to two typical real-condition nuclear environments is presented and discussed.

Moisture sensitive electrical property measurement in concrete slab with step graded antenna

The step graded antenna is designed for the measurement of electrical property inside the concrete samples. This paper designs, simulates and fabricates the single band microstrip antenna at the frequency of 2.76 GHz. The simulated results are compared and analysed with measured results for the designed antenna. It has been noted that the measured and simulated values corresponding to reflection coeffcieints results in offset of 0.02 GHz. The designed antenna is tested on two different composition of concrete samples. The disparity in the reflectivity of both the samples is observed due to the variance in the composition of the concrete structure. The operating frequency of the proposed antenna changes from 2.76 to 2.72 GHz when applied to both concrete samples. Thus the designed antenna can be used for the soil moisture content measurement for structural health monitoring.

Fast picking strategy and electrical properties measurement of carbon nanotubes

Fast picking strategy and electrical properties measurement of carbon nanotubes

Study of Solar Radiation Effect on Radio Signal Using Plasma Antenna

Plasma antenna can be formed by energizing glass tubes which are filled with neutral gases. It works similarly as metal antenna where it can transmit and receive wireless signal. This study aims to investigate the effect of weather focused on solar radiation towards the performance of plasma antenna represented by signal strength. Fluorescent lamp was set as plasma because it used ionized gas as its conducting element instead of metal. Execution of electrical properties measurements need to be done first, in order to obtain discharge current and voltage values, that need to be used into Glomac programming for the generation of electron temperature and electron density. Next, calculations of the plasma properties was performed to derive the value of plasma and collision frequencies. The plasma properties are important parameters to design and simulate plasma antenna using Computer Simulation Technology (CST). Antenna parameters in terms of return loss, gain, directivity and radiation pattern can be simulated using CST. Signal strength experiment was conducted to evaluate plasma antenna performance in terms of its capability to capture the signals and analyse the effect of solar radiation on that particular moment through the rate of power level over time versus solar radiation data. It was observed at the highest solar radiation rate which is 920 V/m, the power level recorded is the lowest value at-172.93 dBm. Therefore, the signal strength received by the plasma antenna shows remarkable changes under the influence of solar radiation.

Preparation and Properties of SBR Composites Containing Graphene Nanoplatelets Modified with Pyridinium Derivative.

The goal of this work was to study the effect of graphene nanoplatelets (GnPs) modified with ionic liquid (IL) on properties of styrene–butadiene rubber (SBR) composites. GnPs were decorated with IL or were modified in bulk directly during rubber mix preparation. The ionic liquid used was 1-butyl-4-methylpyridinium tetrafluoroborate (BMPFB). The textural properties were studied to confirm surface modification of GnPs with BMPFB. In these investigations, the impact of the concentration of GnPs and the effect of the method of GnPs’ modification with IL on elastomers properties are described. Some thermal measurements (e.g., differential scanning calorimetry and thermogravimetry) were conducted to characterize the thermal stability or the vulcanization process of the investigated samples. Complementary experimental techniques were used to investigate the properties of the obtained elastomers, specifically tensile testing, and electrical and barrier property measurements. The deposition of IL on the GnPs’ surface positively influenced the mechanical and barrier properties of elastomers. However, samples containing graphene nanoplatelets modified from solution were characterized by less electrical conductivity. SEM analysis was additionally performed to investigate GnPs’ dispersion within SBR composites.

Femtosecond Charge Transfer Dynamics in Monomolecular Films in the Context of Molecular Electronics.

A key issue of molecular electronics (ME) is the correlation between the molecular structure and the charge transport properties of the molecular framework. Accordingly, a variety of model and potentially useful molecular systems are designed, to prove a particular function or correlation or to build a prototype device. These studies usually involve the measurements of the static electric conductance properties of individual molecules and their assembles on solid supports. At the same time, information about the dynamics of the charge transport (CT) and transfer in such systems, complementary in the context of ME and of a scientific value on its own, is quite scarce. Among other means, this drawback can be resolved by resonant Auger electron spectroscopy (RAES) in combination with core hole clock (CHC) approach, as described in this Account. The RAES-CHC scheme was applied to a variety of aliphatic and aromatic self-assembled monolayers (SAMs), adsorbed on Au(111) over the thiolate and selenolate docking groups. Electron transfer (ET) from a suitable terminal tail group to the substrate, across the molecular framework, was monitored, triggered by resonant excitation of this group (nitrile in most cases) by narrow-band X-ray radiation. This resulted in the quantitative data for the characteristic ET time, τET, in the femtosecond domain, with the time window ranging from ∼1 fs to ∼120 fs. The derived τET exhibit an exponential dependence on the molecular length, mimicking the behavior of the static conductance and suggesting a common physical basis behind the static CT and ET dynamics. The dynamic decay factors, βET, for the alkyl, oligophenyl, and acene molecular "wires" correlate well with the analogous parameters for the static CT. Both τET and βET values exhibit a distinct dependence on the character of the involved molecular orbital (MO), demonstrating that the efficiency and rate of the CT in molecular assemblies can be controlled by resonant injection of the charge carriers into specific MOs. This dependence as well as a lack of correlation between the molecular tilt and τET represent strong arguments in favor of the generally accepted model of CT across the molecular framework ("through-bond") in contrast to "through-space" tunneling. Comparison of the SAMs with thiolate and selenolate docking groups suggests that the use of selenolate instead of thiolate does not give any gain in terms of ET dynamics or molecular conductance. Whereas a certain difference in the efficiency of the electronic coupling of thiolate and selenolate to the substrate cannot be completely excluded, this difference is certainly too small to affect the performance of the entire molecule to a noticeable extent. The efficient electronic coupling of the thiolate docking group to the substrate was verified and the decoupling of the electronic subsystems of the substrate and π-conjugated segment by introduction of methylene group into the backbone was demonstrated. No correlation between the molecular dipole or fluorine substitution pattern (at the side positions) and the ET efficiency was recorded. Several representative examples for the resonantly addressable tail groups are given, and perspectives for future research in the context of ET dynamics in molecular assemblies are discussed.

Electrochemical Characterization of Pr(A)MnO3 Perovskites As Oxygen Electrodes for Solid Oxide Fuel-Assisted Electrolysis Cells

Long-term degradation remains the main issue for the viability of solid oxide electrolysis cell (SOEC) technology as a practical hydrogen production system. The major specific degradation mechanism in SOECs relates to delamination phenomena at or near electrolyte/anode interface. The principle of so-called fuel-assisted electrolysis is to supply the carbon-containing species which can react with oxygen at the anode side thus bringing down the oxygen chemical potential at the electrolyte/anode interface and improving its stability. The present work is aimed at the characterization of PrMnO3-based perovskites for potential application as anodes in solid oxide fuel-assisted electrolysis cells.Pr0.6-x A0.4MnO3 ±δ (A = Sr, Ca; x = 0 and 0.05) powders were synthesized by glycine-nitrate combustion technique. The characterization included XRD, SEM/EDS, XPS, dilatometry and thermogravimetry, measurements of electrical properties, and determination of oxygen nonstoichiometry by coulometric titration. XRD analysis confirmed the formation of solid solutions with orthorhombic perovskite-like structure. Pr0.6-x A0.4MnO3 ±δ exhibit negligible variations of oxygen content with temperature and oxygen partial pressure under oxidizing conditions, while reducing p(O2) below 10-4 atm results in a progressive oxygen losses from the lattice and reduction of variable-valence cations. The low-p(O2) stability boundary of the perovskite phase at 800°C corresponds to ~10-17-3×10-16 atm; the stability domain is wider for Ca-substituted compositions and narrows with introduction of A-site vacancies. Dilatometric studies confirmed a good thermomechanical compatibility with common solid electrolytes. The electrical conductivity of Pr0.6-x A0.4MnO3 ±δ ceramics is p-type electronic and decreases with reducing p(O2), but still exceeds 40-50 S/cm under oxygen chemical potentials anticipated for the oxygen electrode operation conditions at 800°C. The electrochemical performance of Pr0.6-x A0.4MnO3 ±δ porous electrode layers was evaluated in contact with yttria-stabilized zirconia solid electrolyte using symmetrical cell configuration as function of relevant parameters (electrode fabrication conditions, with and without ceria-based interface layers, modifications via impregnations by praseodymia or gadolinia-doped ceria).

Performance Evaluation of Current Leads for a 5 Tesla Electromagnetic Properties Measurement System

The development of the Electromagnetic Property Measurement System is underway at the Korea Basic Science Institute. The Electromagnetic Property Measurement System is used for electrical, thermal, and magnetic specimen property measurements in variable magnetic fields and temperatures with a low-temperature superconducting magnet. To activate low-temperature superconducting magnet that operates with liquid helium, we propose the use of vapor-cooled current leads. The low-temperature superconducting magnet is connected to the power supply at room temperature through a pair of current leads. Accordingly, heat inflows through the current leads and represents one of the major contributory factors of the entire heat inflow. Therefore, design optimization and evaluation of the current leads is necessary to minimize heat and liquid helium consumption. Vapor-cooled, and hybrid current leads were designed and fabricated, and testing in liquid helium cryostat was conducted. The low-temperature superconducting magnet was charged with electrical current up to the operating level, and the liquid helium boil-off rate was measured with respect to the supplied electrical current level. The performances of the two current leads were accessed based on the thermal load and boil-off rate of the liquid helium. The experimental and analyzed liquid helium boil-off rates associated with the current leads were in close agreement.

Study of Heat Treatment Effect in MnCoGe Compound on Stucture and Electric Properties

A comprehension about magnetic refrigeration which develops strong materials as the refrigerant will be explained and develop in this project. Magnetic refrigeration comes from magnetocaloric effect (MCE) which is magnetic material known as refrigerant that react with a magnetic and demagnetic field. Refrigerant plays the roll in control the performance of magnetic refrigerator. One of interesting refrigerant is MnCoGe compound which found very favourable in produce high value of MCE. From this point of view, the process of producing of MnCoGe using ball milling treatment and heat treatment had been studied. Variable of temperature in heat treatment process and following by cooling down to room temperature have been implemented in order to produce good structure of MnCoGe compound. Furthermore, from structure properties measurement found this compound produce three type of structures which are hexagonal, orthorhombic and mix structure (hexagonal and orthorhombic). Based on the different temperature of heat treatment, it indicate for 1500o C and 1200o C treatment are dominant to the hexagonal structure type, then for 1000o C dominant to the orthorhombic structure and lastly for 1100o C dominant to mix structure. Electric properties measurement found the frequency play the role in change the structure as well as in 1000o C compound was found below 5M Hz frequency show the hexagonal structure and when increasing above 5M Hz the pattern change to orthorhombic structure respectively. Moreover, for the permittivity measurement it gives the information about conductivity and tan delta value. Systematically at 1000o C compound found this material is more to conductor behavior compare others compound. Therefore, when the temperature is increased to 1100o C, 1200o C and 1500o C then the conductivity value decreasing and its resistivity value become increasing.

Screening piezoelectricity in determination of flexoelectric coefficient at nanoscale

Piezoelectricity usually accompanies with flexoelectricity in polar materials which is the linear response of polarization to a strain gradient. Therefore, it is difficult to eliminate piezoelectric effect in determination of pure flexoelectric response. In this work, we propose an analytical method to characterize the flexoelectric coefficient quantitatively at nanoscale in piezoelectric materials by screening piezoelectricity. Our results show that the flexoelectricity reduces the nanopillar stiffness while the piezoelectricity enhances it. With precise design of the shape of the nanopillars and measurement of their stiffness difference, the flexoelectric coefficient can be obtained with the piezoelectric contribution eliminated completely. This approach avoids the measurement of electrical properties with dynamic load, which helps to reduce the challenge of flexoelectric characterization at nanoscale. Our work suggests an alternative strategy for quantitative characterization of flexoelectric properties and design of flexoelectric devices at nanoscale.

Synthesis of Semiconducting 2H-Phase WTe2 Nanosheets with Large Positive Magnetoresistance.

Tungsten ditelluride (WTe2) is provoking immense interest because of its unique electronic properties, but studies about its semiconducting hexagonal (2H) phase are quite rare. Herein, we report the synthesis of semiconducting 2H WTe2 nanosheets with large positive magnetoresistance, for the first time, by a simple lithium-intercalation-assisted exfoliation strategy. Systematic characterizations including high-resolution transmission electron microscopy, X-ray diffraction, and Raman and X-ray photoelectron spectroscopies provide clear evidence to distinguish the structure of 2H WTe2 nanosheets from the orthorhombic (Td) phase bulk counterpart. The corresponding electronic phase transition from metal to semiconductor is also confirmed by density of states calculation, optical absorption, and electrical transport property measurements. Besides, the 2H WTe2 nanosheets exhibit large positive magnetoresistance with values of up to 29.5% (10 K) and 16.2% (300 K) at 9 T. Overall, these findings open up a promising avenue into the exploration of WTe2-based materials in the semiconductor field.

An approach to alternative post-deposition treatment in CdTe thin films for solar cell application

Abstract In this study, preliminary investigation of different post-deposition treatments using materials such as cadmium chloride (CdCl2), magnesium chloride (MgCl2), copper chloride (CuCl2), and silver nitrate (AgNO3) has been reported for close-spaced sublimation (CSS) grown cadmium telluride (CdTe) thin films. The treatment of CdTe thin films was conducted in open air at 390 °C. Treated CdTe thin films were then exposed to different characterization tools to explore the effects of treatment on the structural and optoelectronic properties of CdTe films. Hall effect measurement was executed for electrical properties measurement as well as X-ray diffraction (XRD) analysis was utilized for the detection of structural parameters. The energy band gap was obtained at approximately 1.47 eV for all the treated films. CuCl2 treated CdTe films exhibited a higher carrier concentration of 1015 cm−3 than other treatments. The impact of Cu diffusion during CuCl2 treatment was suggested as an effect of doping during recrystallization. The average grain sizes changed moderately in the range 4–7 μm for different post-deposition treatments. The optimized results can provide an indication for other materials to be used as the alternative post-deposition treatment to conventional CdCl2.

Assessing the Performance and Transport Properties of Concrete using Electrical Property Measurements

Assessing the Performance and Transport Properties of Concrete using Electrical Property Measurements

Phase diagram for Bi-site La-doped BiFeO3[sbnd]BaTiO3 lead-free piezoelectric ceramics

Three different series of lead-free ceramics, i.e., (1-y)Bi1.03(1-x)LaxFeO3–yBaTiO3 (y = 0.27, x = 0.00–0.12), (y = 0.30, x = 0.00–0.10), and (y = 0.33, x = 0.00–0.08) are prepared via a conventional solid-state reaction with water quenching. From X-ray diffraction and electrical property measurements, two morphotropic phase boundaries (MPBs) are discovered in all three ceramic systems. The first MPB (MPB-I) appeared between rhombohedral and tetragonal phases, whereas the second MPB (MPB-II) appeared between tetragonal and cubic-like phases. The highest direct piezoelectric coefficients (d33 = 201, 274, and 268 pC/N) are mainly attributed to the typical MPB-I of the rhombohedral and tetragonal phases. However, the highest converse piezoelectric coefficients (d33∗ = 490, 500, and 570 pm/V with Curie temperature > 330 °C) are obtained for compositions near to the MPB-II. A significant enhancement in the dielectric constant at low temperature is associated with the local structural heterogeneity by La3+ doping, which serves as an origin for a high piezoelectric strain response. Based on the crystal structure as well as on the dielectric, ferroelectric, and piezoelectric properties, a phase diagram is constructed for La-doped BiFeO3BaTiO3 ceramics. This phase diagram reveals the relationship between piezoelectric performance and crystal structure.

Assessment of Soil Electrical Properties in Selected Agricultural Soils of Puchuncaví, Central Chile

Abstract Precision agriculture requires a wide sampling procedure to determine the spatial variability of soil properties for adequate assessment of soil state and appropriate recommendations. Electrical geophysical methods (i.e. vertical electrical resistivity sounding) allow performing rapid measurement of soil electrical properties directly from the soil surface to any depth without any mechanical disturbance of soil cover. Soil electrical properties are linked with many soil properties and could improve the quality and spatial coverage of soil surveys. The results obtained in our study using vertical electrical resistivity sounding confirmed the hypothesis of a high correlation between electrical resistivity and such soil properties as carbon and nitrogen content and silt content. The highest correlation (r > 0.9) was found for electrical resistivity and carbon content. It was also confirmed that significant correlations between electrical resistivity and soil properties are found mainly when soil properties are highly ranged. Perspectives for the applied method lie at the relationship between electrical resistivity and soil properties, such as texture class, clay content, carbon content, and cation exchange capacity. The results obtained in this work could be useful for complex precision agriculture, creating maps of agricultural soils, adequate methods of plant growth, and other issues of precision and conventional agriculture.

Verification of topological magnetic properties of patterned ferromagnetic films

Topological order of magnetic films shows promise due to its unconventional electromagnetic transport effects, but the discontinuity and the miniaturization of patterned magnetic films impose a limit on research of topological properties. In this article, a technique is proposed, the application of which improves the ease of electrical measurement in sub-micrometer-sized magnetic thin film elements. To obtain the topological Hall resistivity of the discretized magnetic textures, a ferromagnetic bilayer film was fabricated into specific geometries. Micromagnetic simulations are presented that demonstrate the topological spin distribution in an exchange coupled patterned ferromagnetic film. Experiments are performed on FePt/FeNi bilayered films that are formed with square arrays of FeNi disks on top of a continuous FePt film in a topological spin distribution. The observation of topological Hall effect was made in the FePt/FeNi film without a nanoscale Hall-bar device. The technique presented facilitates the electrical property measurement even in nanometer elements and offers a pathway for promoting spintronics applications.