Four-probe Resistivity Research Articles

Synthesis, crystal structure, resistivity, and electronic structure of the U(V) quaternary polyselenide Ba8PdU2Se12(Se2)2

A new quaternary uranium(V) selenide, Ba8PdU2Se12(Se2)2, has been synthesized by reaction of elements at 1173K. A single-crystal X-ray diffraction study shows that the compound crystallizes in a new structure type with two formula units in space group D2h12–Pnnm of the orthorhombic crystal system with cell constants of a=9.490(1), b=12.240(2), and c=13.780(3)Å. Its crystal structure consists of PdU2Se1212- units where U atoms are coordinated to six Se atoms in octahedral geometry and Pd atoms are coordinated to four Se atoms in square-planar geometry. These PdU2Se1212- units are separated by Ba to result in a salt-like crystal structure. This compound also contains Se22- dimers that are part of Ba coordination polyhedra. The formula charge balances as (Ba2+)8(Pd2+)(U5+)2(Se2−)12(Se22-)2. Theoretical calculations predict antiferromagnetic semiconducting behavior for this compound with a band gap of 1.6eV. Temperature-dependent four-probe resistivity measurements on single crystal confirm the semiconducting nature with an activation energy of 0.18(1)eV.

Electrical properties of single CuO nanowires for device fabrication: Diodes and field effect transistors

High aspect ratio CuO nanowires are synthesized by a simple and scalable method, thermal oxidation in air. The structural, morphological, optical, and electrical properties of the semiconducting nanowires were studied. Au-Ti/CuO nanowire and Pt/CuO nanowire electrical contacts were investigated. A dominant Schottky mechanism was evidenced in the Au-Ti/CuO nanowire junction and an ohmic behavior was observed for the Pt/CuO nanowire junction. The Pt/CuO nanowire/Pt structure allows the measurements of the intrinsic transport properties of the single CuO nanowires. It was found that an activation mechanism describes the behavior at higher temperatures, while a nearest neighbor hopping transport mechanism is characteristic at low temperatures. This was also confirmed by four-probe resistivity measurements on the single CuO nanowires. By changing the metal/semiconductor interface, devices such as Schottky diodes and field effect transistors based on single CuO p-type nanowire semiconductor channel are obtained. These devices are suitable for being used in various electronic circuits where their size related properties can be exploited.

Effect of swift heavy ion (SHI) irradiation on transparent conducting oxide electrodes for dye-sensitized solar cell applications

Transparent conducting oxides (TCOs) are used as electrodes in dye-sensitized solar cells (DSSCs) because of their properties such as high transmittance and low resistivity. In the present work, the effects of swift heavy ion (SHI) irradiation on various types of TCOs are presented. The objective of this study is to investigate the effect of SHI on TCOs. For the present study, three different types of TCOs are considered, namely, (a) FTO (fluorine-doped tin oxide, SnO2:F) on a Nippon glass substrate, (b) ITO (indium tin oxide, In2O3:Sn) coated on polyethylene terephthalate (PET) on a Corning glass substrate, and (c) ITO on a Corning glass substrate. These films are irradiated with 120MeV Ag+9 ions at fluences ranging from 3.0×1011ions/cm2 to 3.0×1013ions/cm2. The structural, morphological, optical and electrical properties are studied via X-ray diffraction (XRD), atomic force microscopy (AFM), UV–Vis absorption spectroscopy and four-probe resistivity measurements, respectively. The ITO-PET electrode is found to exhibit superior conductivity and transmittance properties in comparison with the others after irradiation and, therefore, to be the most suitable for solar cell applications.

RESISTIVITY MEASUREMENT TECHNIQUES FOR COMPOSITE MATERIALS

In this article, the theoretical concepts and the experimental techniques for measurements of the volume and surface resistivity of carbon fibre reinforced polymer (CFRP) composite materials have been explained. The purpose of these measurements is to investigate the potential of composite materials as lightning arrestors for an aircraft. In particular, the AC resistivity method and the Delta mode of measurement have been described in detail. A few measurements were carried out using an indigenously designed and fabricated collinear four-probe resistivity measurement tool, for which factors dependent on the dimensions of the samples have to be incorporated, as per the ASTM F390-11 standards. The validity of the two-probe and four-probe methods is also analyzed, along with techniques to minimize errors in measurements. Conductivity measurements on uni-directional laminates have been made in the longitudinal (fibre) direction as well as perpendicular to it, indicating a marked difference in the relative magnitudes. When investigating the potential of materials as lightning arrestors, a very high surface conductivity is desired so that lightning currents (even of the order of kA) pass along the exterior of the aircraft, without penetrating the underlying structure. The effects of the addition of copper nanotubes (CNT) and copper mesh have also been studied. The instruments involved in these experiments have been automated based on the IEEE – 488.2 protocols. The software to program them was developed using Labview. Measurements have also been performed on standard samples to test the accuracy of the data. Currents ranging from 0.1 to 100mA were passed, to deduce the current-dependency of the surface resistivity of these materials.

Influence of Sputtering Power on the Structure, Optical and Electric Properties of Cu<sub>3</sub>N Films

The Cu3N films were deposited successfully by reactive direct current magnetron sputtering, the films were comprehensively and systematically characterized by X-ray diffraction analyzer (XRD), UV-Visible spectrophotometer, four-probe resistance tester and other instruments. Results showed that under low deposition power (80W~100W), crystal orientation increased, which is attributed to higher energy under higher power. When sputtering power exceeded the value, excessive energy led to anti-sputtering hindering the process of further nucleation and growth of films. The transmittance of the films deposited under 100W reached the peak value of 78% on the scope of near-infrared light, and optical band gap (Eg) of 1.35ev. The resistivity of Cu3N films increased from 9.68×102Ω.cm to 2.12×103Ω.cm with increasing in sputtering power up to 100W.

Radio‐frequency transport Electromagnetic Properties of chemical vapour deposition graphene from direct current to 110 MHz

We report measurement of the radio-frequency (RF) transport electromagnetic properties of chemical vapour deposition (CVD) graphene over the DC to 110 MHz frequency range at room temperature. Graphene on Si/SiO2 substrate was mounted in a shielded four terminal-pair (4TP) adaptor which enabled direct connection to a calibrated precision impedance analyser for measurements. Good agreement is observed for the DC four-probe resistance and the 4TP resistance at 40 Hz, both yielding R ~ 104 {\Omega}. In general the apparent graphene channel electromagnetic properties are found to be strongly influenced by the substrate parasitic capacitance and resistance, particularly for high-frequencies f > 1 MHz. A phenomenological lumped-parameter equivalent circuit model is presented which matches the frequency response of the graphene 4TP impedance device over approximately seven decades of the frequency range of the applied transport alternating current. Based on this model, it is shown for the first time, that the intrinsic graphene channel resistance of the 4TP device is frequency-independent (i.e. dissipationless) with RG ~ 105 {\Omega} or sheet resistance of approximately 182 {\Omega} / sq. The parasitic substrate impedance of the device is found shunt RG with RP ~ 2.2 {\Omega} in series with CP ~ 600 pF. These results suggest that our new RF 4TP method is in good agreement with the conventional DC four-probe method for measuring the intrinsic sheet resistance of single-atom thick materials and could potentially open up new applications in RF electronics, AC quantum Hall effect metrology and sensors based on graphene 4TP devices operating over broad range of frequencies.

Interplay between snake and quantum edge states in a graphene Hall bar with a pn-junction

The magneto- and Hall resistance of a locally gated cross shaped graphene Hall bar is calculated. The edge of the top gate is placed diagonally across the center of the Hall cross. Four-probe resistance is calculated using the Landauer-Büttiker formalism, while the transmission coefficients are obtained using the non-equilibrium Green's function approach. The interplay between transport due to edge channels and snake states is investigated. When two edge channels are occupied, we predict oscillations in the Hall and the bend resistance as function of the magnetic field, which are a consequence of quantum interference between the occupied snake states.

The effects of specimen parameters on the resistivity of concrete

The nondestructive Wenner four-probe resistivity measurement is often used to evaluate the durability of concrete onsite owing to its merits of easy operation and instant results. However, the factors influencing the measurements are not clear. In this study, the influencing factors, including the specimen shape, size, measuring probe spacings, cover thickness, and moisture contents, are thus discussed. Results showed that a correction coefficient K, associated with the ratios of specimen length and diameter to the probe spacing should be applied to the resistivity measurements of the cylindrical specimens. Among all the factors, the moisture content had the highest impact on the measurement. When the specimen was oven-dried or air-dried at 40% RH, the measurements were unstable. On the other hand, the resistivities of the specimens at saturated surface dry (SSD) or wet were about the same. However, when the specimens were air-dried at 80% RH, the resistivities were increased by 6.9–8 times. In contrast, no correction was required for the resistivity measurements of the prismatic specimens as long as the applied currents did not pass through the reinforcements.

Two-Dimensional CoS Nanosheets Used for High-Performance Organic–Inorganic Hybrid Solar Cells

Poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) is one of the most popular hole-transporting materials in organic–Si hybrid solar cells. However, the inferior sheet resistance and the low work function of the PEDOT:PSS layer hinder the power conversion efficiency (PCE) of the devices. Here, two-dimensional cobalt sulfide (CoS) nanosheets with a low sheet resistance and higher work function are blended into the PEDOT:PSS films in order to enhance the device performance. By tuning the morphology and concentration of CoS nanosheets in the PEDOT:PSS films, a lower recombination rate at the organic–inorganic interfaces and improved hole-transporting ability can be achieved simultaneously, yielding a PCE of 11.2% under simulated air mass 1.5 solar irradiation at 100 mW cm–2. The scanning Kelvin probe microscopy, the ultraviolet photoelectron spectroscopy, four-probe sheet resistance measurement, and the transient electrical output characterization were used to study the origin of performance...

Microstructural and elasto-plastic material parameters identification by inverse finite elements method of Ti(1 − x)AlxN (0 < x < 1) sputtered thin films from Berkovich nano-indentation experiments

The mechanical properties of Ti(1−x)AlxN (0<x<1) films of different thicknesses deposited by r.f. reactive magnetron sputtering on Si <100> and high speed steel substrates have been investigated. The as-deposited coatings have been characterized by X-ray diffraction, atomic force microscopy, four-probe electric resistivity method, mechanical deflection of cantilever beams and Berkovich nano-indentation tests associated with inverse finite elements analysis. The coatings with x<0.58–0.59 present a cubic structure whereas for x>0.7 a hexagonal structure is observed. Between these two compositions cubic and hexagonal structures coexist. The roughness depends on the film thickness and on the Al content and a minimum associated to a very fine microstructure is clearly observed in the two-phase coatings. The electric resistivity sharply increases as soon as the hcp structure appears (x~0.6). The mean residual stresses are compressive, except for the AlN coating, and present a minimum at the neighborhood of x~0.64 where a mixed structure is observed.The indentation modulus M<hkl> and the Berkovich hardness HB<hkl> greatly depend on the Al content and a progressive decreasing has been observed for 0.58<x<0.7. For the M<hkl> evolution, a simple model taking into account the stiffness coefficients of TiN and AlN structures, the mean residual stress level and the variations of the lattice parameters in the two structure domains is proposed.Knowing the elastic properties of these films, inverse finite elements analysis of the indentation curves considering a simple isotropic linear elasto-plastic behavior allows, as a function of the composition, the yield stress σY and the linear hardening coefficient Hp⁎ to be estimated. σY and Hp⁎ are in the ranges 4.2 to 6.8GPa and 60 to 400GPa, respectively. The maximum value of Hp⁎/σY which characterizes the ability of these coatings to exhibit plastic strain hardening is maximum for x=0.5 and 0.6. The quality of the estimation was discussed through a practical identifiability study and quantified using an identifiability index. Tip radius and elasticity of the Berkovich indenter are two very relevant parameters to improve identifiability and correctly extract the plastic parameters of the behavior law. Scratch crack propagation resistance shows an evolution similar to those of Hp⁎/σY.

Microwave absorption and radiation from large-area multilayer CVD graphene

Here we experimentally study the microwave absorption and near-field radiation behavior of monolayer and few-layer, large-area CVD graphene in the C and X bands. Artificial stacking of CVD graphene reduces the sheet resistance, as verified by non-contact microwave cavity measurements and four-probe DC resistivity. The multilayer stacked graphene exhibits increased absorption determined by the total sheet resistance. The underlying mechanism could enable us to apply nanoscale graphene sheets as optically transparent radar absorbers. Near-field radiation measurements show that our present few-layer graphene patches with sheet resistance more than 600Ω/sq exhibit no distinctive microwave resonance and radiate less electromagnetic power with increasing layers; however, our theoretical prediction suggests that for samples to be practical as microwave antennas, doped multilayer graphene with sheet resistance less than 10Ω/sq is required.

Nanocrystalline Nickel Ferrite Reinforced Conducting Polyaniline Nanocomposites

Nanocrystalline nickel ferrite (NiFe2O4) powder of crystallite size ~20 nm was synthesized by refluxing method. Electrically conductive polyaniline-nickel ferrite (PANI/NiFe2O4) nanocomposites have been synthesized by an in-situ polymerization of aniline monomer in the presence of as-prepared NiFe2O4 in different weight percentage (5%, 10%, and 15%). These nanocomposites were subsequently characterized for morphological, crystalline, structural, electrical and magnetic properties by Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Four Probe Resistivity (FPR) and Vibrating Sample Magnetometer (VSM). Existence of NiFe2O4 in the nanocomposites was confirmed by XRD, FTIR and TEM analysis. The change in morphology with crystallite size ? 50 nm was observed for the nanocomposites clearly indicate the coating of PANI on NiFe2O4 . Nanocomposites showed increase in saturation magnetization as compared to that of PANI and increase in electrical conductivity as compared to that of NiFe2O4 indicating the synergistic effect of individual components. The saturation magnetization drastically increased as nickel ferrite content changed from 5 to 15% in nanocomposites. The conductivity of nanocomposites increased with temperature, exhibiting typical semiconductor behavior. The nanocomposites show semiconducting and ferromagnetic behaviour. The electrical conductivity of nanocomposites decreased from 1.089 to 0.268 S/cm, but saturation magnetization increased from 0.97 to 2.803 emu/g, when ferrite content changed from 5 to 15 wt%, indicates such nanocomposites are good for electromagnetic devices.

A single-component molecular superconductor.

The pressure dependence of the resistivities of a single-component molecular conductor, [Ni(hfdt)2] (hfdt = bis(trifluoromethyl)tetrathiafulvalenedithiolate) with semiconducting properties at ambient pressure was examined. The four-probe resistivity measurements were performed up to ∼10 GPa using a diamond anvil cell. The low-temperature insulating phase was suppressed above 7.5 GPa and the resistivity dropped, indicating the superconducting transition occurred around 7.5-8.7 GPa with a maximum Tc (onset temperature) of 5.5 K. The high-pressure crystal and electronic band structures were derived by the first-principle calculations at 6-11 GPa. The crystal was found to retain the semiconducting band structure up to 6 GPa. But the electron and hole Fermi surfaces appear at 8 GPa. These results of the calculations agree well with the observation that the pressure-induced superconducting phase of [Ni(hfdt)2] appeared just above the critical pressure where the low-temperature insulating phase was suppressed.

Synthesis of PPy–silver nanocomposites via in situ oxidative polymerization

Silver nanoparticles were synthesized by chemical reduction method. The surface of silver nanoparticles (SNPs) was modified using polyvinylpyrrolidone to make them more compatible with pyrrole. Surface-modified SNPs were dispersed in pyrrole and polymerized via in situ oxidative polymerization technique. The molar ratio of monomer unit to initiator and dopant was 1:1:1 and the weight percent of SNPs in polymer matrix was varied from 1 to 10. The properties of polypyrrole–silver nanocomposites have been characterized using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscope, transmission electron microscope, thermo-gravimetric analysis and four-probe resistivity meter. All these characterizations indicate that the polypyrrole–silver nanocomposite is successfully synthesized via in situ oxidative polymerization and electrical extent shows suitable conductivity.

Improved electrochemical performance of LiNi0.5Mn1.5O4 as cathode of lithium ion battery by Co and Cr co-doping

Three samples, LiNi0.5Mn1.5O4, LiNi0.4Mn1.4Co0.2O4, and LiNi0.4Mn1.4Cr0.15Co0.05O4, were prepared by sol–gel method and characterized by powder X-ray diffraction, Fourier transformed infrared spectroscope, scanning electron microscopy, Brunauer–Emmett–Teller surface area, four-probe resistance, cyclic voltammetry, electrochemical impedance spectroscopy, and charge–discharge test. It is found that the co-doped sample LiNi0.4Mn1.4Cr0.15Co0.05O4 exhibits an improved performance compared with the Co-doped sample LiNi0.4Mn1.4Co0.2O4 and the undoped sample LiNi0.5Mn1.5O4, especially at elevated temperature. At 25 °C, the discharge capacity of LiNi0.4Mn1.4Cr0.15Co0.05O4 is 130 mAh g−1 at 0.1 C and 103 mAh g−1 at 10 C. At an elevated temperature (55 °C), its 1 C discharge capacity is 136 mAh g−1 and maintains 95.6 % of its initial capacity after 100 cycles. Compared with the reported results of LiNi0.4Mn1.4Co0.2O4 and LiNi0.475Mn1.475Co0.05O4, the co-doped sample LiNi0.4Mn1.4Cr0.15Co0.05O4, with least content of Co, 0.05, possesses not only the high C-rate capacity but also the structural stability. The mechanism on the electrochemical performance improvement of LiNi0.5Mn1.5O4 by the co-doping was discussed.

Ultrasmooth metal nanolayers for plasmonic applications: surface roughness and specific resistivity.

The future of plasmonic devices depends on effective reduction of losses of surface plasmon-polariton waves propagating along metal-dielectric interfaces. Energy dissipation is caused by resistive heating at the skin-deep-thick outer layer of metal and scattering of surface waves on rough metal-dielectric interfaces. Fabrication of noble metal nanolayers with a smooth surface still remains a challenge. In this paper, Ag layers of 10, 30, and 50 nm thickness deposited directly on fused-silica substrates and with a 1 nm wetting layer of Ge, Ti, and Ni are examined using an atomic-force microscope and four-probe resistivity measurements. In the case of all three wetting layers, the specific resistivity of silver film decreases as the thickness increases. The smallest, equal 0.4 nm root mean squared roughness of Ag surface of 10 nm thickness is achieved for Ge interlayer; however, due to Ge segregation the specific resistivity of silver film in Ag/Ge/SiO₂ structures is about twice higher than that in Ag/Ti/SiO₂ and Ag/Ni/SiO₂ sandwiches.

Investigation of the properties of In doped NiO films

NiO and Indium doped (3, 5, 8 and 10at%) NiO thin films were produced on glass substrates at 400°C by airbrush spraying method using a solution of nickel nitrate hexahydrate. The effect of Indium (In) concentration on the structural, optical and transport properties of NiO thin films was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), spectral transmittance and linear four-probe resistivity. From The X-ray diffraction pattern, it is observed that pure, 3% and 5at% In doped NiO films have a cubic structure, but 8 and 10at% doped films have an amorphous structure. Optical measurements show that the band gap energies of the films vary with indium concentrations. Moreover, It has been observed that the doping of NiO films with In increases the electrical resistivity.

Sintering Temperature Effect on the Structural and Electrical Transport Properties of Nanophasic Nd&lt;sub&gt;0.7&lt;/sub&gt;Sr&lt;sub&gt;0.3&lt;/sub&gt;MnO&lt;sub&gt;3&lt;/sub&gt; Manganite

A systematic investigation of neodymium-based manganite, Nd0.7Sr0.3MnO3, was undertaken with a view to understand the influence of sintering temperature on various physical properties. The materials were prepared by the a soft chemical approach of co-precipitation method by sintering at four different temperatures starting from 700 to 1000 °C, with an interval of 100 °C. X-ray diffraction (XRD), transmission electron microscopy (TEM) and D. C. four-probe resistivity were employed to study the crystal structure, average particle size and electrical property respectively. Analysis of XRD patterns shows that all the samples exhibit single phase orthorhombic crystal structure. We followed William-son Hall approach to calculate the lattice stain (ε).These materials were found to exhibit different metal-insulator transition temperature (TMI) for the different sintering temperature. The value of TMIincreases, as the sintering temperature increases, whereas ε decreases. TEM results show that with the increment of sintering temperature, the particle size of the NSMO samples also increases, which plays a key role on electrical transport. To understand the conduction mechanism in metallic and insulating regions of resistivity, various theoretical models are discussed in this communication.

Junction Effect on Transport Properties of a Single Si Nanowire Metal–Semiconductor–Metal Device

We report measurements of electrical transport properties and impedance spectroscopy studies on a single Si nanowire (diameter ~ 50 nm) metal-semiconductor-metal device, fabricated using electron beam deposited Pt. The temperature-dependent four-probe resistivity of the nanowire exhibits freezing of carriers below 30 K, while at higher temperature, it resembles the temperature variation seen in bulk doped crystals. The device shows reproducible nonlinear and asymmetric current-voltage ( I-V) characteristics which were quantitatively analyzed and were found to arise from unequal Schottky-type barriers at the two ends which also showed temperature dependence. The measured contact resistance is bias as well as temperature dependent and reduces as the bias is increased.

Sub-micron ZnO:N particles fabricated by low voltage electrical discharge lithography on Zn3N2 sputtered films

This work analyzes the morphological, compositional and electrical modification of zinc nitride (Zn3N2) films through arc discharges produced by biasing a metal tip at a micrometric distance of the surface. Polycrystalline nitride layers are prepared by radio-frequency magnetron sputtering from a pure Zn target on glass substrates using N2 as working gas. Film properties after arc discharges are investigated by using scanning electron microscopy (SEM), ion beam analysis (IBA) techniques and four-probe resistivity measurements. Electrical discharge lithography performed at low bias voltages reveals as an effective mechanism to reduce resistivity by electrical breakdown of the thin oxide layer formed on top of the nitride. At higher voltages, electrical discharges along the scan increase nitride resistivity due to the severe modification of the structural properties. Additionally, compositional analysis reveals that nitrogen leaves the structure being replaced by ambient oxygen. This characteristic behavior leads to the formation of facetted submicron ZnO crystals whose size depends on the original Zn3N2 grain size and the probe voltage used. The excess of zinc forms self-assembled microstructures along the scan edge.