Evolution Of Electrical Resistance Research Articles

Effects of salt freeze-thaw cycles and cyclic loading on the piezoresistive properties of carbon nanofibers mortar

This paper aims to investigate the evolution of electrical resistance and piezoresistivity of carbon nanofibers (CNFs) mortar with freeze-thaw cycles in solutions containing 0%, 1.5% and 3.0% NaCl. Two temperature ranges selected for the freeze-thaw cycles are −10 °C to 10 °C and −20 °C to 20 °C respectively. Four groups of cement mortars with water to cement ratios (w/c) of 0.5, 0.45, 0.4 and 0.35 were prepared by incorporating 2.25% CNFs by cement volume. Additionally, cyclic loading damage was applied to selected samples before exposure to freeze-thaw cycles. Experimental results showed that the strain-sensing sensitivity and linearity of CNFs mortar with low w/c ratios were decreased by the freeze-thaw cycles under temperature of −10 °C to 10 °C. However, the samples with high w/c ratios exhibited an opposite tendency with freeze-thaw cycles. The higher concentration of NaCl solution induced the worse degradation of sensitivity and linearity of low w/c ratio samples. The salt freeze-thaw cycles under temperature of −20 °C to 20 °C resulted in the obvious degradation of piezoresistivity for all the samples. Moreover, the cyclic loading history before freeze-thaw cycles debased the sensitivity and linearity of strain-sensing property of CNFs mortars. Therefore, negative effects from both mechanical loading and freeze-thaw environment should be fully considered for the field application of this type of self-sensing material.

Fretting studies on electroplated brass contacts

This article describes frictional and electrical contact behaviors of electroplated brass under fretting conditions. Fretting tests using a crossed cylinder configuration are conducted. Cylindrical-type specimens are made of tin-plated and gold-plated brass. The ratio of the maximum tangential force to normal force is calculated. The ratio is 0.85 for the self-mated tin-plated brass and 0.55–0.6 for the self-mated gold-plated brass. The results show that the evolution of the dimensionless electrical resistance can be described with a Kachanov-type damage form. Two parameters, the electrical resistance rate constant and electrical resistance exponent, are determined to describe the evolution of the electrical resistance. The results also reveal that the rate constant is affected by the test temperature.

Pressure-induced structural evolution, optical and electronic transitions of nontoxic organometal halide perovskite-based methylammonium tin chloride

Hybrid solar cells with organometal halide perovskites have already reached a power conversion efficiency exceeding 22.1%, but their toxic lead component remains a serious concern. Hence, the replacement of lead with nontoxic alternatives, such as tin, has attracted increasing interest. This study investigates the structural and optoelectronic properties of nontoxic perovskite methylammonium tin chloride (MASnCl3, MA: CH3NH3) under pressure. The synchrotron X-ray diffraction experiment shows that the sample transforms from the monoclinic to the triclinic phase and then amorphizes. The tilting and distortion of [SnCl6]4− octahedra are mainly responsible for the bandgap decreasing below 1.0 GPa. Upon further compression, an additional optical absorption peak appears, which is ascribed to the conduction band splitting of the triclinic MASnCl3. The high pressure behavior of MA cations indicates that the interaction between MA cations and [SnCl6]4− octahedra is strengthened. The pressure-induced electrical resistance evolution of MASnCl3 coincides with the structural changes. The intrinsic properties and the stability of nontoxic Sn-based hybrid perovskites provide better understanding and insights into their potential applications in photovoltaics.

The electro-mechanical behavior of conductive filler reinforced polymer composite undergone large deformation: A combined numerical-analytical study

Abstract The electro-mechanical performance of flexible strain sensors under large deformation is of great concern due to their applications in measuring large strain. In this paper, we develop a combined numerical-analytical approach to study the electro-mechanical behavior of conductive filler reinforced polymer composite under uniaxial tensile load. This developed approach couples the displacement field of the microstructure and the evolution of the micro circuit. A 2D micromechanical representative volume element model is used to simulate the deformation and strain field in the composite, taking into consideration the random distribution of conductive aggregates and the hyperelastic mechanical properties of the polymer matrix. We then predict the evolution of electrical resistance using the tunneling conduction theory and transfer-matrix approach, based on the strain distribution of the material under various tensile deformations. The numerical results agree well with experimental results in terms of different material parameters and tensile conditions. This suggests the developed model is capable of predicting the nonlinear electro-mechanical response of the studied material under large deformation and revealing the effect of particle mass fraction on the electro-mechanical performance. The present approach can be served as a useful tool in the design and improvement of conductive filler-polymer composites for flexible strain sensor application.

Electrical Resistance Evolution of Cu Redistribution Layer Electroplated on a Si Interposer

The changes in electrical and microstructural properties of electroplated Cu films on a Si-interposer substrate were investigated. When Cu films were exposed in an air environment after electroplating on SiO2/Si-substrate as a Si interposer, the resistance increased slightly until 7 days with a uniform distribution of it, and then increased very rapidly after 19 days with broader resistance distribution than those of the initial 7 days. It took 129 days to have much broader resistance distribution than that of 19 days. Secondary ion mass spectroscopy, X-ray photoelectron spectroscopy, and thin film X-ray diffraction demonstrated that the increase in electrical resistance of electroplated Cu films can be significantly influenced by the chlorine redistribution of impurity in electroplated Cu film to the surface of it, by the oxidation behavior on the surface of electroplated Cu film in an air environment, and the microstructural changes of electroplated Cu film with time, respectively. These phenomena can be explained by the ionic neutrality behavior due to the oxidation on the surface of electroplated Cu film and the microstructural changes with time at room temperature caused by recrystallization of electroplated Cu film. This study will be helpful in understanding the necessity of passivating or encapsulating the electroplated Cu film and will also give guidance to the 3-D integration of stacking many chips on a Si interposer.

Microstructure and electrical resistance evolution during sintering of a Ag nanoparticle paste

Silver nanoparticle pastes are promising materials for high temperature interconnection particularly above 400 °C. Reliability is a major concern in interconnection and it mainly depends on the behavior under the stress induced by thermal cycling. The joint microstructure is then a crucial parameter for reliability and determines the electrical, mechanical and thermal properties. Here, an investigation procedure is proposed to describe the microstructure of a joint and to monitor its evolution in real-time during the sintering. Combining electron and x-ray diffraction with electrical resistance measurement and secondary ion mass spectroscopy, our method is used on a sample made out of a home-made silver nanoparticle paste. The influence of the chemical composition of the paste on the microstructure is discussed as well as the compatibility of the paste for oxide interconnection.

Comment on: “Isothermal nature of the B2–B19′ martensitic transformation in a Ti–51.2 Ni (at.%) alloy”

Fukuda et al. published a paper (Scripta Mater. 68 (2013) 984–987) in which they claimed to be able to determine the isothermal nature of the martensitic transformation in a Ti–Ni alloy. They analyzed the evolution of electrical resistance during isothermal holding stages and concluded that the variations were a consequence of the isothermal transition between austenite and martensite. In the following we will demonstrate that the discussed data do not allow the interpretation presented and that the isothermal nature is not proved.

Effects of Electromigration on the Creep and Thermal Fatigue Behavior of Sn58Bi Solder Joints

Electromigration (EM), creep, and thermal fatigue (TF) are the most important aspects of the reliability of electronic solder joints, the failure mechanisms of which used to be investigated separately. However, current, mechanical loading, and temperature fluctuation usually co-exist under real service conditions, especially as the magnitude of current density is increasing with joint miniaturization. The importance of EM can no longer be simply ignored when analyzing the creep and TF behavior of a solder joint. The published literature reports that current density substantially changes creep rate, but the intrinsic mechanism is still unclear. Hence, the purpose of this study was to investigate the effects of EM on the creep and TF behavior of Sn58Bi solder joints by analyzing the evolution of electrical resistance and microstructure. The results indicated that EM shortens the lifetime of creep or TF of Sn58Bi solder joints. During creep, EM delays or suppresses the cracking and deforming process, so fracture occurs at the cathode interface. During TF, EM suppresses the cracking process and changes the interfacial structure.

Real-time monitoring of the silicidation process of tungsten filaments at high temperature used as catalysers for silane decomposition

The scope of this work is the systematic study of the silicidation process affecting tungsten filaments at high temperature (1900 °C) used for silane decomposition in the hot-wire chemical vapour deposition technique (HWCVD). The correlation between the electrical resistance evolution of the filaments, Rfil(t), and the different stages of the their silicidation process is exposed. Said stages correspond to: the rapid formation of two WSi2 fronts at the cold ends of the filaments and their further propagation towards the middle of the filaments; and, regarding the hot central portion of the filaments: an initial stage of silicon dissolution into the tungsten bulk, with a random duration for as-manufactured filaments, followed by the inhomogeneous nucleation of W5Si3 (which is later replaced by WSi2) and its further growth towards the filaments core. An electrical model is used to obtain real-time information about the current status of the filaments silicidation process by simply monitoring their Rfil(t) evolution during the HWCVD process. It is shown that implementing an annealing pre-treatment to the filaments leads to a clearly repetitive trend in the monitored Rfil(t) signatures. The influence of hydrogen dilution of silane on the filaments silicidation process is also discussed.

Oxidation of RuAl and NiAl Thin Films: Evolution of Surface Morphology and Electrical Resistance

RuAl and NiAl thin films on SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Si were oxidized, and the results were compared to those from aluminum, ruthenium, and nickel films. Both aluminides are more oxidation resistant than nickel, aluminum, and ruthenium, and they form an outer layer of alumina after oxidation to 850 °C. The depth profiles differ for NiAl and RuAl, with alternating layers of alumina and a Ru-rich phase forming on RuAl, while a more complex structure forms on NiAl due to reaction with the substrate. The surface of RuAl after oxidation remains fairly smooth and reflective, whereas NiAl has a hazy appearance. However, the surface morphology changes at a slightly lower temperature in the case of RuAl (~ 500°C) . Both films remain conductive even after the surface begins to show signs of oxidation, with the NiAl remaining conductive to a higher temperature (after 1 h at 850 °C) than RuAl. The results show that NiAl and RuAl films can be used in an oxidizing atmosphere up to ~ 500°C (at least 1 h) for applications requiring a smooth reflective surface and to higher temperatures when the surface quality is less important but conductivity needs to be maintained (~ 800°C for RuAl and ~ 850°C for NiAl).

Introduction of an exponential formulation to quantify the electrical endurance of micro-contacts enduring fretting wear: Application to Sn, Ag and Au coatings

Abstract The massive use of electronic control in automotive, plane and energy systems requires the extensive application of in board low current electrical connectors. Subjected to vibrations, the electrical contacts endure severe fretting wear damage (i.e. wear of contacts induced by oscillating small amplitude displacements). One consequence of this fretting wear damage is that oxide debris are formed and maintained within the interface, decaying the electrical transmission of information. To prevent this critical damage, various soft and thin electrolytic coatings like Sn, Ag and Au layers are usually applied. In order to better understand the damage processes and provide a quantitative strategy to select the coating palliatives, an original approach coupling representative experiments and analytical models is introduced. Using a representative micro-fretting system, the electrical resistance evolution is shown to be mainly controlled by the applied displacement and sliding condition. It is confirmed that below a threshold displacement amplitude, related to a stabilised partial slip condition, the electrical endurance is infinite. Above this threshold, when full gross slip conditions are running, a finite endurance behaviour is observed. The electrical endurance is then controlled by the interfacial oxide debris layer formation and the nature of the coating. For non-noble coatings, like Sn, the electrical failure comes about as soon as an oxide debris layer, the so-called “third body” is trapped within the interface, while the endurance of noble and semi-noble materials (i.e. Au, Ag), which is significantly greater, is controlled by the progressive decrease of noble element concentrations in the third body layer and the related increase of its current resistivity. Finally, simple and basic exponential formulations are introduced to rationalise the global electrical endurance of “connector like” micro-contacts subjected to fretting wear. Using this formulation, an endurance ratio is developed to compare the endurance performance of the different coating palliatives.

Nitrogen plasma-based ion implantation of poly(tetrafluoroethylene): Effect of the main parameters on the surface properties

The surface of poly(tetrafluoroethylene) (PTFE or Teflon) was treated by nitrogen plasma-based ion implantation. Accelerating voltages between 15 and 30 kV, fluences between 1 × 10 17 and 3 × 10 17 cm −2 and fluence rates between 3 × 10 13 and 7 × 10 13 cm −2 s −1 were applied. The effects of these main parameters were examined on the evolution of surface chemical composition, mean roughness, abrasive wear, wettability and surface electrical resistance. The aim was to obtain relationships, enabling to control the surface properties examined. The F/C atomic ratio determined by XPS strongly decreased, correlating inversely with voltage. The mean surface roughness characterized by topography measurements, increased, correlating directly with fluence and inversely with voltage. The wear volume obtained by multipass scratch tests did not show clear relationship with the main process parameters, however, it increased upon treatment with the increase of surface roughness and O/C atomic ratio. The water contact angle increased at low voltages and high fluences, due to preferential increase of roughness, and decreased at high voltages and low fluences, owing to intense defluorination and incorporation of N and O. The electrical resistance of the PBII-treated surfaces decreased by several orders of magnitude, showing a significant inverse correlation with fluence. It continued to decrease for samples exposed to air, primarily after treatments performed with low fluences, due to post-treatment type oxidation.

Electrical Resistance Evolution During a Small Scale Two-phase Electrolysis

During two-phase electrolysis for hydrogen, aluminium or fluor production, there are bubbles which are created at electrodes which imply a great hydrodynamic acceleration in the normal earthgravity field and then a quite important electrical properties and electrochemical processes disturbance. This disturbance can lead to the modification of the local current density and to anode effects for example. There is few works concerning the local modelling of electrochemical processes during a two-phase electrolysis process. There are also few local experimental measurements in term of chemical composition, temperature or current density which will allow the numerical calculations validation. Nevertheless, effects like the anode effect, particularly expensive on the point of the process efficiency, should need a better understanding.

Real-time evolution of electrical resistance in cracking concrete

The aim of this paper is to present a real-time relation between the evolution of the electrical resistance and the crack width opening in a saturated concrete sample. The splitting (Brazilian) test has been enhanced and adapted so that the monitoring of a single crack opening and the electrical resistance of the specimen are possible. The experimental results showed that the electrical resistance is constant before the peak (when no crack is observed) and decreases only when the peak of load is reached and when a crack is initiated. No threshold value and no delay between the crack opening and the resistance evolution have been observed, even in the case of a breathing crack. The evolution of the electrical conductance has then been modeled by taking into account the (simplified) morphology of the crack and assuming a constant value for the electrolyte conductivity. The model and the experimental conductance through a traversing crack have proved to be in good agreement.

Pressure induced structural transitionsin CoSi2

Results of diamond anvil cell based electrical resistance and x-raydiffraction measurements under pressure at room temperature onCoSi2 are reported. The evolution of electrical resistance and x-ray powder diffraction patternsconfirms two structural transitions near 0.4 and 13 GPa. There is small isostructural (0.71%)volume collapse near 20 GPa. The diffraction lines gradually broaden with increasingpressure. A disorder that involves breaking of Co–Si and Si–Si bonds and occupancy ofvacant sites, which results in an intermediate bonding topology between that ofCaF2 andadamantine structures, is suggested to be responsible for this behaviour. This could be a general featurefor CaF2 structured materials (with directional bonding nature) because of the presence of orderedvacancies and a competing adamantine structure.

Hopf bifurcation, bistability, and onset of current-induced surface wave propagation on void surfaces in metallic thin films

We analyze the electromigration-induced stable wave propagation on surfaces of voids in metallic thin films based on self-consistent numerical simulations of current-driven surface morphological evolution according to a fully nonlinear continuum model. The void surface morphological response is studied for single-crystalline films with twofold and fourfold symmetry of surface diffusional anisotropy, characteristic of <1 1 0>- and <1 0 0>-oriented film planes in face-centered cubic (fcc) metals, respectively, and the effects of the electric-field strength, the surface diffusional anisotropy strength, and the void size are examined. Variation of the above parameters past critical values is found to cause transitions from stable steady to stable oscillatory morphological responses on voids migrating along the films at constant speed; these transitions are the result of Hopf bifurcation at the corresponding critical points. For every bifurcation parameter, the nature of the Hopf bifurcation is determined by the symmetry of the surface diffusional anisotropy on the film plane: the bifurcation is supercritical for fourfold symmetry and subcritical for twofold symmetry. The amplitude and frequency of the void surface oscillations are calculated as a function of the bifurcation parameters and the corresponding bifurcation diagrams are constructed. Our simulations reveal hysteresis phenomena and bistability in both cases of Hopf bifurcation, i.e., for both twofold and fourfold symmetry. For twofold symmetry, i.e., for subcritical Hopf bifurcations, the transitions are between a stable steady state and a stable time-periodic state. For fourfold symmetry, i.e., for supercritical Hopf bifurcations, the transitions may also be between two stable steady states; one of the two steady states bifurcates (upon further variation of the bifurcation parameter) to a time-periodic state at the corresponding Hopf point. The film’s electrical resistance evolution reflecting the void’s morphological evolution is monitored in the regime of oscillatory void morphological response and it is found to be in good agreement with experimental measurements in accelerated electromigration testing.

Modification of the Pet-Membrane/Solution Interface: Effect on Electrical Parameters

Electrochemical characterization of a symmetric track-etched polyethylenthereftalate (PET) membrane in contact with KCl solutions at different concentrations was carried out by measuring impedance spectroscopy (IS) and membrane potential (MP), which allow the estimation of membrane electrical resistance and ion transport numbers, respectively. IS measurements permit us the characterization of membranes in “working conditions” (in contact with electrolyte solutions) and the determination of electrical parameters for the membrane and the membrane/solution interface (resistance, capacitance and Warburg impedance) by analyzing the impedance plots and using equivalent circuits as models. The non-reproducibility of membrane potential values for two series of measurements and the asymmetry of the impedance curves show the modification of the membrane/aqueous solution interface. This point was confirmed by the time evolution of the membrane system electrical resistance and the increase of nitrogen content obtained from X-ray photoelectron spectroscopy (XPS) analysis for dry and PET samples maintained in water for different periods of time, and the results indicate an increase in nitrogen content, which is attributed to bacterial presence on the membrane surfaces. These results seem to indicate modification of the PETmembrane/solution interface due to fouling and the possibility of its determination by electrical measurements.

Current-driven interactions between voids in metallic interconnect lines and their effects on line electrical resistance

We present a theoretical analysis based on self-consistent numerical simulations of current-driven interactions between voids in metallic thin-film interconnects and the resulting void migration, morphological evolution, and coalescence phenomena. The analysis reveals the complex nature of electromigration-induced void-void interactions, and their implications for the evolution of interconnect line electrical resistance. Most importantly, it is demonstrated that current-driven void-void interaction effects, such as void coalescence, can cause sudden changes in the interconnect line electrical resistance, in qualitative agreement with observations in accelerated electromigration testing experiments.

Experimental data about mechanical behaviour during compression tests for various matted fibres

A specific experimental device has been set up to test compressive mechanical behaviour of an assembly of fibres. Simple compression, as well as cyclic loading experiments and relaxation tests were performed. The experimental set up also allows to record the evolution of the mat fibre electrical resistance while testing. Experimental results are presented for a variety of fibrous materials. Despite the very different nature of each of these individual fibres, it appears that the mats exhibit a very similar mechanical behaviour. This common behaviour has been observed during monotonic single compression tests, as well as during cyclic or relaxation experiments. These experimental results are discussed in terms of different parameters such as the intrinsic mechanical properties of individual fibres and moreover the tangle intrinsic parameters (effect of fibre length, effect of geometrical position of fibres in the sample, fibre surface modifications...). The influence of the contact points between fibres is discussed in regard of the electric resistivity measurements.

Effects of electromigration-induced void dynamics on the evolution of electrical resistance in metallic interconnect lines

The effects of void dynamics under electromigration conditions on the electrical resistance evolution in metallic thin-film interconnects are examined based on self-consistent dynamical simulations. Changes in the interconnect line resistance are found to depend strongly on electromigration-induced void morphological changes and are explained on the basis of void extension across the linewidth and void surface area evolution at constant void volume. The void morphological evolution may lead to stable steady or time-periodic line resistance response or to abrupt resistance increase associated with failure. Our computational results imply that electrical resistance increases should not be attributed only to void formation or void growth and that electrical resistance oscillations are not due to alternating defect generation and annihilation. The results are in excellent agreement with analytical scaling theories and qualitatively consistent with a large set of experimental electrical resistance measurements.