High Precision Electrical Resistance Research Articles

The kinetics of structural relaxation of bulk and ribbon glassy Pd 40Cu 30N 10P 20 monitored by resistance and density measurements

Density and in situ high precision electrical resistance measurements on bulk and ribbon glassy Pd 40Cu 30Ni 10P 20 in the initial state, after cold rolling and quenching from the supercooled liquid state are performed. Three relaxation stages resulting in different signs of the electrical resistance relaxation are determined. It is shown that the resistance change upon structural relaxation is predominantly controlled by the resistivity relaxation while the volume change has a minor effect on the resistance. Cold rolling has a complex impact on the electrical relaxation similar to the effect of plastic deformation on the dislocation anelasticity in crystals. Quenching of fully relaxed samples from the supercooled liquid state recovers structural relaxation and the amount of the resistance relaxation can be several times bigger than that in the initial state. It is concluded that relaxation of the electrical resistance as dependent on different conditions (bulk/ribbon samples, thermocycling, rolling and the parameters of quenching from the supercooled liquid state) is rather complex but it is unlikely that the degree of the relaxation is governed by the amount of the free volume. This conclusion agrees with the established fact of equal density of initial glassy and crystallized bulk samples and earlier findings of nearly equal shear viscosity of bulk and ribbon samples different by four orders of magnitude in the production quenching rate.

Electric Charge Transport Anomalies in Holmium and Thulium Thin Films at Low Temperatures

High-precision electrical resistance measurements were performed on holmium and thulium bulk and thin-film samples in the temperature range from 4.2 K up to room temperature. A “knee-like” resistance anomaly near the Neel temperature was observed in Ho bulk and thin-film samples. The X-ray diffraction of Ho films revealed diffraction peaks coming from the h.c.p. structure of Ho and those from holmium dihydride. Unexpected resistance anomalies were observed for thulium thin films in the temperature region below ≈ 60 K and near ≈ 170 K. The crystal structure study revealed diffraction peak originating only from the Tm h.c.p. crystal structure.

WEAK-LOCALIZATION EFFECT IN SINGLE CRYSTAL TaN(001) FILMS

We here report the manifestation of weak localization effects in the electrical resistivity of TaN (001) films grown on MgO (001) substrates by a pulsed laser deposition technique. These films were characterized by X-ray diffraction and Rutherford backscattering. High precision electrical resistivity measurements were performed on these films in the temperature range 12–300 K. A careful analysis of data showed these films to lie in the weakly localized regime with negative temperature coefficient of resistivity throughout the whole temperature range of study. A crossover from 2D localization at lower temperatures to 3D localization at higher temperatures was observed.

Low temperature electrical transport in La 1− xNd xNiO 3− δ

We have investigated low temperature electrical transport in La 1− x Nd x NiO 3− δ perovskite oxide samples. Samples were prepared by a sol–gel method and were characterized by X-ray diffraction and chemical methods. High precision electrical resistivity, magnetoresistance (MR) and electron tunneling conductance measurements were performed. Crystal structure investigations showed a phase transition from rhombohedral to orthorhombic phase at x=0.4. In the orthorhombic phase Ni–O–Ni bond angle was found to depend very sensitively on the value of x; as the value of x increases Ni–O–Ni bond angle decreases resulting in the tilting of NiO 6 octahedra. A Correlation between the Ni–O–Ni bond angle and electrical transport has been observed. The analysis of the electrical resistivity data showed the presence of disorder driven quantum correction effects, namely e–e interactions and weak localization, in the system. A dip in the tunneling density of states and negative MR also suggest the presence of e–e interaction and weak localization effects in the system.

Single Crystal TaN Thin Films on TiN/Si Heterostructure

AbstractWe have successfully grown epitaxial cubic (B1-NaCl structure) tantalum nitride films on Si (100) and (111) substrate using a pulsed laser deposition technique. A thin layer of titanium nitride was used as a buffer medium. We characterized these films using X-ray diffraction, high resolution transmission electron microscopy and scanning transmission electron microscopy (Zcontrast). X-ray diffraction and high-resolution transmission electron microscopy confirmed the single crystalline nature of these films with cubic-on-cubic epitaxy. The epitaxial relations follow TaN(100)//TiN(100)//Si(100) on Si(100) and TaN(111)//TiN(111)//Si(111) on Si(111). We observed sharp interfaces of TaN/TiN and TiN/Si without any indication of interfacial reaction. Rutherford backscattering experiments showed these films to be slightly nitrogen deficient (TaN0.95). High precision electrical resistivity measurements showed excellent metallic nature of these films. We also tried to deposit TaN directly on silicon, the films were found to be polycrystalline. In our method, TiN plays a key role in facilitating the epitaxial growth of TaN. This method exploits the concept of lattice matching epitaxy between TaN and TiN and domain matching epitaxy between TiN and Si. We studied the diffusion barrier properties of these films by growing a thin layer of copper on the top and subsequently annealing the films at 500°C and 600°C in vacuum. Cu diffusion layer was about 2nm after 600°C annealing for 30min. This work explores a promising way to grow high quality TaN diffusion barrier on silicon for copper interconnection.

Enhanced electron–electron interaction, weak localization and electron–magnon scattering contributions to electrical resistivity in Fe- and Co-based metallic glass wires

An extensive analysis of high-precision electrical resistivity ( ρ) data taken on Fe- and Co- based metallic glass wires over the temperature range 10 K⩽ T⩽300 K and discussion of the results, so obtained, in terms of the existing theoretical models identifies enhanced electron–electron interaction (EEI), weak localization (WL) and electron–magnon (EM) scattering as the main mechanisms governing the temperature dependence of ρ in these systems and determines their relative magnitudes accurately. Out of the inelastic processes that destroy phase coherence, inelastic electron–phonon scattering turns out to be the most effective one and its dephasing action persists to temperatures as high as 300 K. While EEI and WL effects are basically responsible for the negative temperature coefficient of resistivity (TCR), EM scattering accounts for the positive TCR. The observed resistivity minima are thus an outcome of these competing contributions to ρ( T).

Unusual electrical resistivity anomalies of thulium thin films at low temperatures

High precision electrical resistance measurements were performed in the temperature range from 4.2 K up to room temperature on a pure thulium bulk sample with a high residual resistivity ratio, RRR=146, and on thulium thin films in the thickness interval from 25 to 115 nm. The observed size-effect of the electrical resistivity is in accordance with theory and it is without resistivity vs. thickness anomalies. The typical “hump-backed” anomaly in the resistivity vs. temperature dependence was observed for the Tm bulk sample near the Néel temperature. In contrast, unexpected resistivity vs. temperature anomalies were observed for thulium thin films in the low temperature region below ∼60 K and near ∼170 K. A crystal structure study using X-ray diffraction revealed that these thin films were single phase with the Tm hcp crystal structure and with preferential orientation of crystallites.

Crystallization characterisics in the Fe [sbnd]Si [sbnd]B glassy ribbon system

The kinetics of crystallization of Fe 80Si xB 20 − x (with x = 2, 4, 6, 8, 10) and Fe 75Si 15B 10 glassy ribbons was examined using differential scanning calorimetry and high precision electrical resistivity measurements. The main crystallization parameters are presented. The corresponding structure of the materials was observed using transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. The mechanism of crystallization is described in terms of the local ordering (cluster) model.

High-resolution digital temperature logging in areas with significant convective heat transfer

The Marmara region of northwestern Turkey is characterized by frequent manifestations of anomalously high temperature gradients in the underground, thermal springs, and steaming grounds. Within an interdisciplinary project, our research group measured temperature profiles in many drillholes in this region, using a digital temperature logging tool. Temperatures are measured by a PT 100 sensor; the 2 km wireline and its winch are mounted on a trailer; the data acquisition system is freely movable, weighs about 40 kg, and is transported by jeep along with a 4.7 kW power generator. This system consists of a controlling unit for the winch drive, a high-precision electrical resistance meter with a sensitivity of 100 ppm Ω and a 286 MS-DOS PC as the recording unit. All parts of the equipment are commercially available. The depth interval between two measurements is 10 cm and maximumlogging speed is 5 m/min. Using this temperature tool we were able to detect convection cells in a borehole in northern Switzerland. These cells, about 1 m in length, have a temperature amplitude range of about 0.01–0.04°C. Repeated measurements of boreholes in Switzerland and in northwestern Turkey show, for the entire length of the wells, a maximum difference of 0.05–0.1°C. The measured temperature profiles show different distortions (nonlinearity) as a result of the strong influence of groundwater circulation. The observations are checked for constancy in time (repeated measurements after one year). Using different models of groundwater movement, local heat flow can be calculated even from such disturbed temperature logs. These models are presented and discussed with respect to their reliability.

Hydrogen in niobium under pressure

By means of electrotransport and high precision electrical resistance measurements we studied the influence of hydrostatic pressure (up to 2.2 GPa) on the diffusion coefficient and some related properties of hydrogen in niobium. The hydrogen-to-niobium ratio was varied from 0.002 to 0.05 and the temperature from −80 to 160 °C. At atmospheric pressure the results for the diffusion coefficient are in accordance with the results from the Gorsky effect and quasi-elastic neutron scattering experiments. Even within the high precision of our measurements no change in the diffusion coefficient could be observed under hydrostatic pressure. This is in contradiction to theoretical predictions. Electrotransport measurements also provide information on the effective charge Z∗ of the screened proton in niobium. Below 20 °C, Z∗ increases rapidly with decreasing temperature. High pressure does not change Z∗ and its temperature dependence. This must be due to a negligible influence of high pressure on the electronic structure of hydrogen in niobium. The specific electrical resistivity change due to dissolved hydrogen is not altered as a function of pressure. From this it is concluded that the lattice distortions due to hydrogen in niobium are not changed by high pressure.

Hydrogen in niobium under pressure

By means of electrotransport and high precision electrical resistance measurements we studied the influence of hydrostatic pressure (up to 2.2 GPa) on the diffusion coefficient and some related properties of hydrogen in niobium. The hydrogen-to-niobium ratio was varied from 0.002 to 0.05 and the temperature from −80 to 160 °C. At atmospheric pressure the results for the diffusion coefficient are in accordance with the results from the Gorsky effect and quasi-elastic neutron scattering experiments. Even within the high precision of our measurements no change in the diffusion coefficient could be observed under hydrostatic pressure. This is in contradiction to theoretical predictions. Electrotransport measurements also provide information on the effective charge Z ∗ of the screened proton in niobium. Below 20 °C, Z ∗ increases rapidly with decreasing temperature. High pressure does not change Z ∗ and its temperature dependence. This must be due to a negligible influence of high pressure on the electronic structure of hydrogen in niobium. The specific electrical resistivity change due to dissolved hydrogen is not altered as a function of pressure. From this it is concluded that the lattice distortions due to hydrogen in niobium are not changed by high pressure.

On the Temperature Hysteresis of Dysprosium Electrical Resistance near Phase Transitions

High precision electrical resistance measurements of pure dysprosium were performed in the temperature range from 4.2 K to 300 K on cooling and warming. We have observed the electrical resistance temperature hysteresis at the order-order transition due to existence of the mixed spiral - ferromagnetic phase and that at order-disorder transition, caused by a new intermediate “vortex” magnetic structure.

Influence of plastic deformations on the electron-electron and electron-phonon interactions in K and K(Rb) samples

High precision electrical resistivity measurements were made on potassium samples, including a dilute alloy at temperatures between 0.9 and 4.2K. These samples were annealed and deformed by twisting at or below 4.2K in stages, in order to generate controlled amounts of dislocations. The resulting enhancement of the electron-electron and electron-phonon terms is analysed in the light of recent theories based on the anisotropy of electron-dislocation scattering. Difficulties in interpretation in connection with recent measurements below 1K by another group are discussed. Some metallurgical aspects are considered.

Study of multilayer surface oxidation of platinum by electrical resistance technique

Multilayer surface oxidation of polycrystalline Pt wire is studied for the first time at moderate oxygen pressures using a high precision electrical resistance technique. The dependence of the oxidation rate on pressure, temperature, and time is investigated. Oxide films of up to 90 nm thickness are grown, and the temperature region for rapid dissociation of the oxide is identified. The dissociation pressure-temperature relationship for the oxide is determined in the region 450–600°C, yielding high precision values for the heat of decomposition and entropy change. A two zone model for the electrical resistance is developed and shown to agree qualitatively with the experimental results. The oxide is identified as the β phase of PtO 2 on the basis of its heat of decomposition, electron diffraction pattern, and acid solubility properties.

High-precision electrical resistivity of Tb, Dy, and Ho single crystals between 1 and 4 K

The electrical resistivity of Tb, Dy, and Ho single crystals has been investigated with a precision of one in 5×104 in the temperature range 1–4 K and in magnetic fields up to 60 kOe. In Tb and Dy, in zero field, the change in resistance is about 0.3%. The resistance vs. temperature curve shows a point of inflection at around 3.5 K, with a more rapid decrease in resistance below this temperature. In a magnetic field, the latter part shows a gradual reduction as field increases. On the basis of the present result and previously published specific heat results, the source of this resistivity has been suggested to be the scattering of the conduction electrons by the rare earth ions in the oxide environment. The Ho crystals show a slightly stronger temperature dependence (∼0.4%) but no anomalous component. These results have been discussed on the basis of the spin-wave and phonon scattering. The phonon resistivity of Dy and Ho can be described by aT3 law.

Critical Behavior at the Metal-Nonmetal Transition in Tetrathiafulvalene-Tetracyanoquinodimethane (TTF-TCNQ)

We present the results of high-precision electrical resistivity measurements in the vicinity of the metal-nonmetal transition in TTF-TCNQ. We find a sharp negative divergence in the derivative of the resistivity, $\frac{{R}^{\ensuremath{-}1}\mathrm{dR}}{\mathrm{dT}}$, which suggests the existence of a second-order phase transition at about 53 K. A critical-exponent analysis of this divergence implies that the onset of long-range order occurs with a classical exponent (i.e., $\ensuremath{\beta}=\frac{1}{2}$) within a three-dimensional region which extends to approximately $\frac{|T\ensuremath{-}{T}_{c}|}{{T}_{c}}=t={10}^{\ensuremath{-}1}$.

Evaluation of selected refractories as high temperature thermophysical property calibration materials

Twenty-two materials were screened as candidates for high temperature thermophysical property reference standards. Of these five (alumina, thoria, tungsten and two graphites) were selected for an initial field test program involving six laboratories in the U.S. Thermal conductivity and thermal diffusivity data and physical-chemical stability results on these materials in the temperature range from 500 to 2700°K are presented. Two of the materials, tungsten and an isotropic graphite, were selected for more detailed evaluation in an expanded international measurement program which involved 18 laboratories, 9 in Europe and 9 in the U.S. It was concluded with some qualifications which are described that the thermal conductivity and thermal diffusivity of the graphite were known within ± 10 per cent and ± 6 per cent respectively while for the tungsten the corresponding inaccuracy bound for both properties was ± 5 per cent. Although greater data scatter was observed among the tungsten results, the uncertainty estimates in the thermophysical properties were reduced using high precision electrical resistivity data. The experimental results on graphite and tungsten were found to be consistent based on theoretical considerations. Specific recommendations are given for further experimental and analytical studies with these two calibration materials.

Critical Exponent of Phase Separation in Metallic Binary Liquids

The first detailed study of the critical exponent of phase separation, ${\ensuremath{\beta}}_{\mathrm{BM}}$, in a metallic binary liquid is reported. High-precision electrical resistivity measurements made on a Ga-Hg mixture of critical composition allowed the determination of ${\ensuremath{\beta}}_{\mathrm{BM}}$, which was found to be 0.335 \ifmmode\pm\else\textpm\fi{} 0.005 in the reduced temperature interval ${10}^{\ensuremath{-}4}l~\ensuremath{\epsilon}l~{10}^{\ensuremath{-}2}$.

The interaction between indium atoms and vacancies in dilute aluminium-indium alloys

Abstract The effect of very small additions of indium on the decay of quenched-in vacancies at 0°c in aluminium is studied by high precision electrical resistivity measurements. The extent of the observed resistivity decrease in the alloy on ageing with respect to that in pure aluminium is used as a measure of the strength of binding between indium atoms and vacancies. Good agreement between the values for -B In-v (0·18 ± 0·01 ev), is obtained in the solute concentration range where the Lomer expression can be used with confidence. A further value of B In-v (0·17(4) ev) is deduced from electron micrographs of the dislocation loop structure in material that had been quenched and then aged at room temperature. It is suggested that all values bo regarded as a minimum, and that the true magnitude of B In-v lies in the range 0·18-0·21 ev. The discrepancy between this and previous values presented in the literature is discussed.