Four-probe Resistivity Measurements Research Articles

Optoelectronic and electrochemical properties of nickel oxide (NiO) films deposited by DC reactive magnetron sputtering

Abstract Nickel oxide (NiO) thin films were deposited onto glass substrates by the DC reactive magnetron sputtering technique. The as-deposited films were post-annealed in air at 450–500 °C for 5 h. The effect of annealing on the structural, microstructural, electrical and optical properties were studied by X-ray diffraction (XRD), atomic force microscope (AFM), four-probe resistivity measurement and UV-vis spectrophotometer. XRD studies indicated cubic structure with a lattice parameter of 0.4193 nm. The band gap of the films was found to be 3.58 eV. Fourier transform infrared (FTIR) studies indicated a broad spectrum centered at 451.6 cm −1 . Photoluminescence studies exhibited room temperature emission at 440 nm. Cyclic voltammetry studies in 1 M KOH solution revealed the electrochromic nature of the NiO films prepared in the present study.

Optical and electrical properties of indium tin oxide nanofibers prepared by electrospinning

Indium tin oxide (ITO) nanofibers were successfully prepared via an electrospinning method, followed byannealing at 400 °C. Mixed solutions of ITO nanoparticle sol and polyethylene oxide (PEO) were used asprecursors of the nanofibers. The PEO decomposed during annealing to yield ITO fibers.The fibers were characterized by scanning electron microscopy (SEM), x-ray diffraction(XRD), thermo-gravimetric/differential thermal analysis (TG/DTA), UV–visspectrophotometry and four-probe resistivity measurements. The diameter of the preparedfibers was controlled by adjusting the flow rate and the applied electric current.In2O3 crystallized in the ITO nanofibers with a crystallite size of 27 nm. The opticaltransmittance in the visible region approached 90% in films deposited for 5 min, confirmingthat the nanofiber film is still transparent in the optical region. The sheet resistance of thenanofiber film was linearly dependent on the inverse of the deposition time and on thePEO/ITO ratio.

Electrical properties of carbon nanotube FETs

The electrical properties of carbon nanotube FETs (CNTFETs) have been studied in detail. The conduction type of the CNTFETs was dependent on the work function of the contact metal, which suggests that Fermi level pinning at the metal/nanotube interface does not happen. Based on the two-probe and four-probe resistance measurements, it was shown that the carrier transport at the contact is explained by the edge contact model even in the diffusive regime. The chemical doping using F4TCNQ was effective to reduce not only the channel resistance but also the contact resistance. It has also been shown that the surface potential measurement based on the electrostatic force detection in the scanning probe microscopy was effective in studying the behavior of the CNTFETs such as the transient behavior and the effect of the defects. Finally, in the CNTFETs fabricated using plasma-enhanced (PE) CVD-grown nanotubes, most of the drain current could be modulated by the gate voltage with little non-depletable drain current suggesting the preferential growth of the nanotubes with semiconducting behavior.

Electrical Resistivity of Tetramethyltetratelluronaphtalene Crystal at Very High Pressures Examination of the Condition of Metallization of π Molecular Crystal

Four-probe resistivity measurements were performed on the TMTTeN crystal by using a diamond anvil high-pressure cell up to 30 GPa. The crystal could not be metallized though the room-temperature resistivity decreased to a very small value (1.5 x 10-3 Omega cm). Although single-component molecular metals are composed of molecules, the pressure-induced metallization of a single-component pi molecular crystal while maintaining the initial molecular structure appears to be very difficult.

Effect of Gold Adsorption on the Conductive Properties of Cyclo-octasulfur Microcrystals

The formation of gold crystallites on the surface of S8 promotes diffusion of electrons and determines the conductive properties of the shell-core nanosystems. Conducting probe atomic microscopy and four-probe resistance measurements confirmed that Au/S8 shell-core systems exhibit electrical conductivity on the micro- as well as on the nanoscale in contrast to non-covered S8 crystals, which are insulating. The conductivity of Au/S8 systems on the microscale was measured to be 10+/-1 S cm(-1). In XPS measurements, a single peak at 163.6 eV was observed for bulk S8 whereas an additional peak corresponding to a binding energy of 161.4 eV appeared for S8 adsorbed on a Au substrate. This is interpreted to mean that a chemical reaction has taken place. A process which results in adsorption of uniform gold nanolayers on needle shaped or fibrous S8 crystallites is under investigation.

Effect of tensile and compressive strains on the transport properties of SmNiO3 layers epitaxially grown on (001) SrTiO3 and LaAlO3 substrates

This paper deals with the role of epitaxial strain on the structure and electronic transport properties of metastable SmNiO3 layers grown by metal-organic chemical vapor deposition onto SrTiO3 and LaAlO3 substrates. The characterization of these layers is carried out by high resolution x-ray diffraction and four-probe resistivity measurements. It is found that the SmNiO3 phase is stabilized by in-plane compressive strain whereas in-plane tensile strain induces the creation of oxygen vacancies that induces an annihilation of the metal-insulator transition and a huge increase of the resistivity.

Unusual devitrification behaviour in rapidly solidified Ti 45Zr 38Ni 17 alloy

In this study, Ti 45Zr 38Ni 17 ribbons have been elaborated using planar flow casting method ( v quenching = 10 6 K s −1). The rapidly quenched samples, displaying a dispersion of nanoscaled β phase particles in an amorphous matrix, have been extensively characterised using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Devitrification behaviour, investigated by four-probe resistivity measurements and differential scanning calorimetry as well as high resolution TEM analysis, revealed the formation of nanometric quasicrystals (QC) during the first exothermic phase transformation as well as the precipitation of omega domains inside β particles. On the basis of these data, it has been noticed that nanoscaled β metastable particles had adopted the same temperature dependence as β metastable bulk. Furthermore, particular orientation relationships have been observed for QCs in the vicinity of β particles which have suggested probable influence of crystalline structure on the QCs growth, although the presence of such peculiar materials after annealing treatment could be mainly explained by an icosahedral short-range order prevailing in Ti–Zr–Ni melt and favouring their nucleation.

Numerical assessment of the methods of measurement of the electrical resistance in carbonfiber reinforced cement

Carbon fiber reinforced cement is a smart material due to its sensing ability, which is basedon piezoresistivity. A finite element model for simulating the measurement of electricalresistance in this material is provided. The measured four-probe resistance decreases withincreasing distance between the adjacent voltage and current contacts. For a beam of size320 × 40 × 40 mm3, the minimum distance for accurate four-probe resistivity measurement is 5 mmfor surface contacts (at the end surfaces), 5 mm for loop contacts (around theperimeter) and 40 mm for line contacts (on one surface). The two-probe resistivityis most inaccurate for the line contacts. For loop contacts, the two-proberesistivity is accurate when the aspect ratio exceeds 8, and the four-proberesistivity is accurate when the aspect ratio exceeds 1.5. For a column of size426 × 92 × 76 mm3,the minimum distance between the adjacent current and voltage contacts for accurate four-proberesistivity measurement is 50 mm for loop contacts and 400 mm for line contacts. For a slab of size9.75 × 4.88 × 0.30 m3, the minimum distance for accurate four-probe resistivity measurement along the 9.75 mlength is 250 mm for line contacts.

Crystallization mechanism in Sb:Te thin films

The aim of this work is to study the mechanism of crystallization in Sb:Te thin films using differential scanning calorimetry (DSC), four-probe resistivity and X-ray diffraction (XRD) measurements. The DSC showed that the Sb 70+ x Te 30− x films with x in the range of −3⩽ x⩽3 show one exothermic reaction at 110 °C, whereas the films with x in the range of 3⩽ x⩽13 present an additional one at about 70 °C. XRD measurements and Rietveld analysis have shown that the first exothermal peak can be associated to the formation of crystalline Sb and the second to the process of transformation of the Sb and the remaining material into a more stable Sb 2 n Te 3 crystalline phase. Appearance of additional Sb phase decreases the crystallization temperature of Sb 70+ x Te 30− x films. These structural transformations are also observed in the four-probe resistivity measurements: a one-step crystallization process in the Sb 70+ x Te 30− x films with x in the range of −3⩽ x⩽3and a two-steps crystallization process in films with x in the range of 3⩽ x⩽13. The results of this investigation have shown that the amorphous-to-crystalline phase transformation in eutectic Sb:Te depended on the films composition.

Structure and Physical Properties of Ternary Uranium Transition‐Metal Antimonides U3MSb5 (M: Zr, Hf, Nb).

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Micromemory Effects Involved during Martensitic Transformation in Ni-Rich NiTi Alloy

In the present study, interrupted mechanical cycles are performed to observe ‘micromemory effect’ for the Ni-rich (Ni51.0at%-Ti) Ni-Ti Shape Memory Alloy (SMA) with different strain rates. In addition, the tensile test is coupled with the four-probe electrical resistivity (ER) measurements. Coupled measurements of stress-strain and electrical resistivity for mechanical cycling (with SIM) have not yet been reported in the literature. The behaviour of the alloy during the interrupted cycles is discussed on the basis of the ER profile

Structure and thermoelectric properties of the ordered skutterudite CoGe 1.5Te 1.5

The skutterudite-related material CoGe 1.5Te 1.5 has been synthesised and structurally characterised by powder neutron diffraction. Analysis of the high-resolution powder neutron diffraction data indicates that the structure of CoGe 1.5Te 1.5 retains the a + a + a + tilt system of the ideal skutterudite structure, while the anions are ordered in layers perpendicular to the [111] direction of the skutterudite unit cell. This anion ordering results in a lowering of the symmetry from cubic to rhombohedral (space group R 3 ¯ , a=12.3270(5) and c=15.102(1) Å at 293 K). The electrical transport properties have been investigated using four-probe resistivity and Seebeck coefficient measurements. The temperature dependence of the electrical resistivity and the magnitude of the Seebeck coefficient indicate that CoGe 1.5Te 1.5 is an n-type semiconductor.

In Search of Benzene-like Sn66-: Synthesis of Na4CaSn6 with Interconnected Cyclohexane-like Sn66-

The title compound was synthesized in an attempt to produce stacked benzene-like Sn6(6-) rings separated by alkaline-earth cations in analogy with the recently reported stacks of aromatic cyclopentadienyl-like Sn5(6-) in Na8BaSn6 (in addition to isolated Sn4- anions). The resulting compound, synthesized from a stoichiometric mixture of the elements at high temperature, has the "correct" stoichiometry with six tin atoms and six positive charges. However, the rings of Sn6(6-) are puckered into chair-type cyclohexanes that are interconnected into isolated cylindrical tubes stuffed with Ca2+ between the rings. Such tubes, if fused to each other, form the hexagonal diamond structure. The new compound is electronically balanced according to magnetic and four-probe resistivity measurements. Reported are also the synthesis and properties of Na10EuSn12 and Na10YbSn12 which are isostructural with the known Na10CaSn12.

The contribution of grain boundary and defects to the resistivity in the ferromagnetic state of polycrystalline manganites

In the present study we report the precise resistivity measurements for the polycrystalline bulk sample as well as highly oriented thin-films of La 0.8Ca 0.2MnO 3. The poly crystalline sample was prepared by standard solid-state reaction route and the oriented thin film was prepared by pulsed laser deposition (PLD). The phase purity of these samples was confirmed by X-ray diffraction and the back-scattered electron imaging using scanning electron microscopy (SEM). The oxygen stoichiometry analysis was done by iodimetry titration. The resistivities of these samples were carried out with four-probe resistivity measurement setup. The observed temperature dependence of resistivity data for both the samples was fitted using the polaron model. We have found that polaronic model fits well with the experimental data of both polycrystalline and single crystal samples. A new phenomenological model is proposed and used to estimate contribution to the resistivity due to grain boundary in the ferromagnetic state of polycrystalline manganites and it has been shown that the scattering of electrons from the grain boundary (grain surface) is a function of temperature and controlled by the effective grain resistance at that temperature.

Structure and physical properties of ternary uranium transition-metal antimonides U 3MSb 5 (M = Zr, Hf, Nb)

The ternary uranium transition-metal antimonides U 3MSb 5 (M = Zr, Hf, Nb) were prepared by arc-melting reactions followed by annealing at 800 °C, or by use of a Sn flux. These compounds extend the previously known series U 3MSb 5 (M = Ti, V, Cr, Mn) and RE 3MSb 5 (RE = La, Ce, Pr, Nd, Sm; M = Ti, Zr, Hf, Nb). The crystal structures of U 3MSb 5 were determined by single-crystal X-ray diffraction data (Pearson symbol hP18, hexagonal, space group P6 3/ mcm, Z = 2; U 3ZrSb 5, a = 9.2223(3) Å, c = 6.1690(2) Å; U 3HfSb 5, a = 9.2084(4) Å, c = 6.1629(3) Å; U 3NbSb 5, a = 9.1378(4) Å, c = 6.0909(6) Å). U 3TaSb 5 has also been identified in microcrystalline form ( a = 9.233(3) Å, c = 6.142(3) Å). Four-probe electrical resistivity measurements on single crystals and dc magnetic susceptibility measurements on powders indicated prominent transitions that are attributed to ferromagnetic ordering. The Curie temperatures, T C, located from ac magnetic susceptibility curves, are 135 K for U 3ZrSb 5, 141 K for U 3HfSb 5, and 107 K for U 3NbSb 5.

Structural, optical and electronic properties of nanocrystalline TiN films

Nanocrystalline titanium nitride thin films have been deposited by reactive dc magnetron sputtering inpure N2, Ar–N2 and He–N2 gas mixtures. The influence of the nature of the sputtering gas on the structural, opticaland the electronic properties of the nanocrystalline TiN films has been studied. Structuralproperties were investigated by using x-ray diffraction and an atomic force microscope,optical ones by using a UV–visible spectrophotometer and electronic propertiesby means of dc four-probe resistivity measurements. The films deposited in anHe–N2 gas mixture exhibited a strong (111) texture, while for those deposited in anAr–N2 mixture under identical conditions, the texture of the films changed from (111) to (200).

STRUCTURAL AND ELECTRICAL PROPERTIES OF DIAMOND-LIKE CARBON THIN FILMS PREPARED IN INERT GAS CONDITION

The effects of ambient helium gas pressure on the optical, structural and electrical properties of the diamond-like carbon thin films from camphoric carbon soot target, deposited by pulsed laser deposition have been studied. Optical gap and electrical resistivity are found to increase initially at low ambient pressure of 0.008 Torr. With further increase in ambient pressure up to 2.6 Torr, optical gap and electrical resistivity are found to decrease. The films are characterized for their structural properties using different spectroscopic techniques such as, XPS, Raman, and FTIR spectroscopy, and surface morphological techniques like SEM and AFM, and their electrical properties using four-probe resistance measurement.

SEMICONDUCTING AMORPHOUS CAMPHORIC CARBON NITRIDE THIN FILMS

Amorphous carbon nitride ( a-CN x) films have been deposited by pulsed laser deposition at 0.8 Torr nitrogen gas ambient with varying substrate temperature from 20 to 500°C. The effects of the substrate temperature and ambient nitrogen gas pressure on the surface morphology, composition, nitrogen content, structure, and electrical properties of the a-CN x thin films have been investigated. The deposited a-CN x films were characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Fourier transform infrared (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-Visible transmittance, and four-probe resistance measurement. It is found that the amorphous structure of a-CN x films can be changed by the substrate temperature (ST) and the a-CN x films with high nitrogen content have relatively high electrical resistivity. Also, graphitization is found to cause the reduction of nitrogen content and changes in the bonding structure of nitrogen atoms in the films.

Simultaneous electrical and X-ray diffraction studies on neodymium metal to 152 GPa

Using designer diamond anvils and angle dispersive X-ray diffraction technique at a synchrotron source, we have performed simultaneous electrical and structural studies on neodymium metal to 152 GPa in a diamond anvil cell. Four-probe electrical resistance measurement shows a 38% decrease in the electrical resistivity, associated with the delocalization of the 4f-shell electrons, starting at 100 GPa up to a final pressure of 152 GPa. The continuous decrease in electrical resistivity is consistent with the observation of a gradual phase transition to α-U structure in this pressure range. The (1 1 1) diffraction peak of α-U structure first appears at 100 GPa and increases in intensity with increasing pressure to 152 GPa. This increase in intensity is attributed to an increasing volume fraction of α-U phase and an increase in structural y-parameter from 0.07 at 118 GPa to 0.095 at 152 GPa. In contrast to the abrupt pressure-induced f-electron transition seen in cerium and praseodymium, the continuous evolution of α-U structure and electrical resistivity in neodymium confirms the gradual nature of 4f delocalization process in this element.

Structure and Physical Properties of Ternary Rare-Earth Cobalt Bismuth Intermetallics (RE)12Co5Bi (RE = Y, Gd, Tb, Dy, Ho, Er, Tm)

The rare-earth intermetallic compounds (RE)12Co5Bi (RE = Y, Gd, Tb, Dy, Ho, Er, Tm) were prepared by arc-melting and annealing at 600 degrees C. These compounds extend the previously known (RE)6M2+xX1-x (M = Co, Ni; X = Ga, In, Sn, Pb) series with the Ho6Co2Ga-type structure to X = Bi. The crystal structure of Ho12Co5Bi was refined by the Rietveld method from powder X-ray diffraction data obtained using synchrotron radiation (Pearson symbol oI36, orthorhombic, space group Immm, Z = 2, a = 9.37598(14) A, b = 9.37871(14) A, c = 9.85465(13) A). Unlike other Ho6Co2Ga-type compounds, the 2a site in Ho12Co5Bi is exclusively occupied by Co atoms. Four-probe electrical resistivity measurements on sintered polycrystalline samples of (RE)12Co5Bi indicated metallic behavior. Magnetic measurements revealed behavior ranging from frequency-dependent maxima in the ac susceptibility for Y12Co5Bi to possible ferrimagnetic ordering for Gd12Co5Bi to antiferromagnetic ordering with metamagnetic transitions for the remaining compounds. As confirmed by band structure calculations using Y12Co5Bi as a model compound, Y-Y and Y-Co interactions are the most important bonding components, but matrix effects are likely responsible for anomalously short Co-Co contacts in the structure.