Resistance Measurement Technique Research Articles

Single-walled carbon nanotube networks in conductive composite materials.

Electrically conductive composite materials can be used for a wide range of applications because they combine the advantages of a specific polymeric material (e.g., thermal and mechanical properties) with the electrical properties of conductive filler particles. However, the overall electrical behaviour of these composite materials is usually much below the potential of the conductive fillers, mainly because by mixing two different components, new interfaces and interphases are created, changing the properties and behaviours of both. Our goal is to characterize and understand the nature and influence of these interfaces on the electrical properties of composite materials. We have improved a technique based on the use of sodium carboxymethyl cellulose (CMC) to disperse single-walled carbon nanotubes (SWCNTs) in water, followed by coating glass substrates, and drying and removing the CMC with a nitric acid treatment. We used electron microscopy and atomic force microscopy techniques to characterize the SWCNT films, and developed an in situ resistance measurement technique to analyse the influence of both the individual components and the mixture of an epoxy/amine system on the electrical behaviour of the SWCNTs. The results showed that impregnating a SWCNT network with a polymer is not the only factor that affects the film resistance; air exposure, temperature, physical and chemical properties of the individual polymer components, and also the formation of a polymeric network, can all have an influence on the macroscopic electrical properties of the initial SWCNT network. These results emphasize the importance of understanding the effects that each of the components can have on each other before trying to prepare an efficient polymer composite material.

A multi‐point electrical resistance measurement system for characterization of foam drainage regime and stability

Foam drainage regimes are significantly associated with the nature of the hydrodynamic resistance in foam structure. A multi‐point electrical resistance measurement technique has been applied for characterization of the drainage regimes and quantifying stability within standing foams. The capacity of the technique was confirmed by the estimation of macroscopic drainage rates for aqueous foams stabilized with sodium dodecyl sulfate. The drainage of sodium dodecylbenzenesulfonate, a commercial form of linear alkylbenzene sulfonate that is the most frequently used in household detergents was studied in detail by two complementary methods (forced and free drainage). The experimental data could be fitted using a power‐law with an exponent of 1/3 for forced drainage and of 1.0 for free drainage. These data indicate the following drainage behavior: mobile bubble surfaces, causing plug‐like flow within Plateau borders, thus dissipation mainly occurs inside the nodes. This research introduced an accurate method for quantifying foam stability that can be assessed by variations of real‐time measured foam heights that incorporate the evolution of the liquid content. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3143–3150, 2014

Electrochemical behavior of silver thin films interfaced with yttria-stabilized zirconia

Thin silver films (100–800 nm) were deposited by physical vapor deposition (PVD) on yttria-stabilized zirconia solid electrolyte. The electric percolation as a function of the film thickness was studied during deposition and annealing using a two-electrode in-situ resistance measurement technique. Electrical percolation was achieved in as-deposited films greater than 5.4 ± 0.4 nm; however, thermal treatment (550 °C in air) resulted in film dewetting for Ag films as thick as 500 nm and formation of electronically isolated Ag nanoparticles, as was confirmed by SEM and XPS. In thermally treated samples, stable electronic conductivity associated with a continuous percolated network was only observed in samples greater than 600 nm in thickness. The effect of polarization on the electrochemical reactions at the three-phase (electrode-gas-electrolyte) and two-phase (electrode-electrolyte) boundaries of the electrode was investigated by solid electrolyte cyclic voltammetry (SECV) at 350 °C and PO2 = 6 kPa. With the application of positive potential, silver oxide (Ag2O) was found to form along the three-phase boundary and then extends within the bulk of the electrode with increasing anodic potentials. By changing the hold time at positive potential, passivating oxide layers are formed which results in a shift in favor of the oxygen evolution reaction at the working electrode. This oxide forms according to a logarithmic rate expression with thick oxides being associated with decrease in current efficiency for subsequent oxide formation.

Acoustic impedance rhinometry (AIR): a technique for monitoring dynamic changes in nasal congestion

We describe a simple and inexpensive method for monitoring nasal air flow resistance using measurement of the small-signal acoustic input impedance of the nasal passage, similar to the audiological measurement of ear drum compliance with acoustic tympanometry. The method requires generation of a fixed sinusoidal volume–velocity stimulus using ear-bud speakers, and an electret microphone to monitor the resultant pressure fluctuation in the nasal passage. Both are coupled to the nose via high impedance silastic tubing and a small plastic nose insert. The acoustic impedance is monitored in real-time using a laptop soundcard and custom-written software developed in LabView 7.0 (National Instruments). The compact, lightweight equipment and fast time resolution lends the technique to research into the small and rapid reflexive changes in nasal resistance caused by environmental and local neurological influences. The acoustic impedance rhinometry technique has the potential to be developed for use in a clinical setting, where the need exists for a simple and inexpensive objective nasal resistance measurement technique.

Evaluation of the corrosion behavior of the polyester-coated galvanized steel subjected to SO2 gas under different relative humidities

Evaluation of the corrosion behaviour of the polyester-coated galvanized steels exposed to different relative humidities was utilized using electrochemical impedance spectroscopy (EIS), anodic polarization curves and linear polarization resistance (LPR) measurement techniques. The samples were exposed to SO2 gas in laboratory conditions that was adjusted to various relative humidities. The results obtained from current-potential curves indicate that, corrosion current density of polyester-coated samples increases as the relative humidity increases in SO2 containing medium. The EIS results showed that polyester-coated samples exposed to relative humidity (RH) of 70% experienced defect-free coating, whereas the samples significantly lost their protection behaviour under relative humidities of 80, 90 and 100%.

Fabrication of Porous Noble Metal Thin-Film Electrode by Reactive Magnetron Sputtering

Porous platinum films have been fabricated by reactive sputtering combined with subsequent thermal annealing. Using the SEM, XRD, XPS, and polarization resistance measurement techniques, the microstructural development of the film and its resultant electrochemical properties have been characterized. Pore evolution was understood as a result of the thermal grooving of platinum during annealing process. We demonstrated that crystallization should be followed by agglomeration for the evolution of porous microstructures. Furthermore, reaction sputtering affected the adhesion enhancement between the film and substrate compared to the film deposited by non-reactive sputtering. The polarization resistance of the porous platinum film was five times lower than that of the dense platinum film. At 600 degrees C the resistance of the porous film was 5.67 omega x cm2, and that of the dense film was 38 omega x cm2.

Polyaniline–CuO hybrid nanocomposites: synthesis, structural, morphological, optical and electrical transport studies

Thin films of semiconducting polyaniline (PANi) nanofibers reinforced with copper oxide (CuO) nanoparticles (NPs) were prepared on glass substrate using spin coating technique. Polyaniline (PANi) have been synthesized by chemical oxidative polymerization method with monomer aniline in presence of (NH4)2S2O8 as an oxidant at 0 °C. The copper oxide (CuO) nanoparticles were synthesized by sol–gel method. Physical properties of nanocomposite (NCs) films were characterized and analyzed by X-ray diffraction, Scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, UV–vis spectroscopy, Two probe resistivity measurement technique and Thermo-emf measurement. Structural analysis showed that the crystal structure of CuO is not disturbed in the PANi–CuO hybrid nanocomposite. Surface morphology study shows the uniform distribution of CuO nanoparticles in PANi matrix. FTIR and UV–Visible studies confirm the presence of polyaniline in emeraldine base form in the composites and suggest incorporation of CuO in polymer. Two probe electrical resistivity measurements of nanocomposites (NCs) film revealed that the resistivity of PANi increases with increasing content of CuO NPs.

Difficulties in Characterizing High-Resistivity Silicon

High-resistivity silicon (HRS) plays an important role in modern telecommunication IC chips and HR Czochralski (CZ) crystals are gaining more importance. During our study of CZ-HRS wafers, both bulk and Silicon-On-Insulator (SOI), we observed it is not easy to use traditional characterization techniques such as capacitance-voltage (C-V) or resistivity measurement techniques on HRS. During C-V measurements using a Schottky contact directly on HRSOI film we observed a bias spreading effect, where the capacitance was much higher than that due to the gate area. Effects of various factors such as frequency, contact size, light, temperature, and annealing are discussed. The challenges in accurate resistivity measurement using four-point probe, Hall method, and C-V profile are highlighted and a new approach using Impedance Spectroscopy to extract resistivity is discussed.

A traceable technique to calibrate dc current shunts and resistors in the range from 10 μΩ to 10 mΩ

A traceable to dc resistance and dc voltage National Standards measurement technique to calibrate dc current shunts and resistors in the range from 10μΩ to 10mΩ has been developed at National Institute of Metrological Research (INRIM) in addition to the primary reference system for low value resistors calibration. This technique is applicable in secondary and industrial metrological laboratories. It is based on a volt-amperometric method, to compare an unknown shunt with a standard one in 1:1 or 1:10 ratios. In the setup are involved: a dc current calibrator and a current generator to supply currents respectively up to 100A and up to 1200A, with a switch to reverse the current, two 7 1/2 digit nanovoltmeters (nVs) for the acquisition of the voltage on the standard and under calibration shunts and two Tinsley 100μΩ and 1mΩ standard shunts kept in mineral oil and with a cooling system. An optional variation in the procedure that can reduce the measurement uncertainties is discussed. The 2σ relative capabilities of the technique span from 6.0×10−6to 4.6×10−4. Compatibility results with the INRIM reference measurement system for low value resistors calibration are also given.

Intrinsic domain-wall resistivity in half-metallic manganite thin films

Deciphering the intrinsic magnetic domain-wall (DW) resistivity of manganite materials by typical low-field magnetoresistance measurement is flawed due to the addition of different galvanomagnetic effects such as, colossal magnetoresistance, Lorentz force magnetoresistance, and anisotropic magnetoresistance (AMR). In this paper, by taking the advantage of rotational anisotropy and the stable rotation of the DW planes in half-metallic manganite La${}_{0.7}$Sr${}_{0.3}$MnO${}_{3}$ film, we deploy a remanent state resistance measurement technique to exclude all the field-dependent spurious effects from the intrinsic DW resistivity. To further refine its magnitude, we calculate the remanent state DW AMR by exploiting the three-dimensional micromagnetic simulation, which reveals a comparable but opposite contribution to the positive DW resistivity. From these results, we estimate the intrinsic DW resistance-area product in La${}_{0.7}$Sr${}_{0.3}$MnO${}_{3}$ to be $1.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}\phantom{\rule{0.16em}{0ex}}\ensuremath{\Omega}\ifmmode\cdot\else\textperiodcentered\fi{}{\mathrm{m}}^{2}$.

Non-destructive investigation of corrosion current density in steel reinforced concrete by artificial neural networks

Corrosion of the steel reinforcement in concrete is an important problem for the civil engineering. Inspection techniques are needed to assess the corrosion in order to protect and repair concrete structures. Many studies were performed to establish a series of corrosion rate assessment methods. A method of providing a direct evaluation of the corrosion rate by corrosion current density measurement is Linear Polarisation Resistance (LPR). The main drawback is that it requires a localised breakout of the concrete cover. The corrosion of the steel reinforcement is monitored by measuring the resistivity of the concrete. The purpose of this paper is to use the resistivity four-probe method and galvanostatic resistivity measurement together with neural networks to assess the corrosion rate of steel in concrete without a direct connection to the reinforcement. Three parameters determined by two non-destructive resistivity methods together with the air temperature were employed as input variables, and corrosion current density, predicted by the destructive LPR method, acted as the output variable. The results shows that it is possible to predict corrosion current density in steel reinforced concrete by using the model based on artificial neural networks on the basis of parameters determined by two non-destructive resistivity measurement techniques.

EFFECT OF SURFACTANTS ON THE SIZE, COLOR, PHOTOLUMINESCENCE AND RESISTIVITY OF INDIUM TIN OXIDE NANOPARTICLES PREPARED BY CO-PRECIPITATION METHOD

Indium tin oxide (ITO) nanoparticles were synthesized by co-precipitation method using ammonia as a precipitator in absence/presence of various surfactants (LABS and Triton X-100). The synthesized nanoparticles were investigated by scanning electron microscopy, resistance measurement, photoluminescence (PL) spectroscopy and X-ray diffractometry (XRD) techniques. The XRD patterns of nanoparticles were also studied by Rietveld refinement method for calculation of crystallite size, micro-strain and lattice parameter. The results indicate that by application of LABS and Triton X-100 as surfactant the particle size was increased. Two luminescence bands were observed in PL spectra of ITO nanoparticles with the excitation energy lower than their band gaps. It was found that the ratios of luminescence bands have relation with resistances and colors of ITO nanoparticles. In addition, the band structure of ITO nanoparticles was described considering the obtained results.

Effect of nitrogen flow rate on the properties of TiN film deposited by e beam evaporation technique

In this work, titanium nitride (TiN) films have been deposited by e beam evaporation technique on Si/SiO2 (100) substrates at room temperature. The influence of nitrogen flow rate (N2=0, 4, 6, 8 and 10sccm (standard cubic centimeter per minute)) on the structural, morphological and electrical properties of the TiN films has been studied. The deposited TiN films have been characterized using X-ray diffraction (XRD), XPS (X-ray photoelectron spectroscopy), FESEM (Field emission scanning electron microscopy) and four-point probe resistivity measurement techniques. XRD patterns reveal FCC symmetry of the film with (111) preferred orientations for Ti film (N2=0sccm) and (200) preferred orientations for TiN film (N2=4, 6, 8 and 10sccm), respectively. The lattice parameters for TiN films are found to increase from 4.237Å to 4.239Å with the increase in nitrogen flow rate. The presence of different phases such as TiN, TiON and TiO2 were confirmed by XPS analysis. The FESEM images of the TiN films showed a smooth morphology with columnar grain structures. The grain size of the TiN films was found to increase as the nitrogen flow rate was increased from 4 to 10sccm. The electrical resistivity measurement showed that the resistivity of the film decreased from 333μΩcm to 111μΩcm on increasing nitrogen flow rate from 4 to10sccm.

High-Pressure Electrical Transport Behavior in WO3

The high-pressure electrical transport behavior of microcrystalline tungsten trioxides (WO3) was investigated by direct current electrical resistivity measurement and alternate current impedance spectrum techniques in a diamond anvil cell up to 35.5 GPa. Discontinuous changes of electrical resistivity occurred during the pressure induced structure phase transitions at 1.8, 21.2, and 30.4 GPa. The irreversible resistivity reveals that the structure phase transition is not reversible. In addition, the abnormal changes of bulk resistance and transport activation energy at about 3 and 10 GPa are related to the isostructural phase transition reported by previous Raman study. The temperature induced resistivity change indicates that WO3 is a semiconductor from ambient pressure to 25.3 GPa.

Some aspects of thermal resistance measurement technique for IMPATT and light-emitting diodes

Some aspects of measuring the thermal resistance to a constant heat flow at a p-n junction–package region in IMPATT and light-emitting diodes are considered. We propose a method of studying the thermal resistance of high-power light-emitting diodes. This method makes it possible to increase accuracy of measuring the thermal resistance by determining the temperature at a linear section of the voltage−temperature curve. A possibility to measure the thermal resistance of IMPATT diodes by using the pulse I-V curves is shown. This enables one to simplify calculations and increase accuracy of measuring the thermal resistance.

Kinetics of large B clusters in crystalline and preamorphized silicon

We present an extended model for B clustering in crystalline or in preamorphized Si and with validity under conditions below and above the equilibrium solid solubility limit of B in Si. This model includes boron-interstitial clusters (BICs) with BnIm configurations—complexes with n B atoms and m Si interstitials—larger (n > 4), and eventually more stable, than those included in previous models. In crystalline Si, the formation and dissolution pathways into large BICs configurations require high B concentration and depend on the flux of Si interstitials. In the presence of high Si interstitial flux, large BICs with a relatively large number of interstitials (m ≥ n) are formed, dissolving under relatively low thermal budgets. On the contrary, for low Si interstitial flux large BICs with few interstitials (m ≪ n) can form, which are more stable than small BICs, and whose complete dissolution requires very intense thermal budgets. We have also investigated the kinetics of large BICs in preamorphized Si, both experimentally and theoretically. B was implanted at a high-dose into preamorphized Si, and the B precipitation was studied by transmission electron microscopy and by sheet resistance and Hall measurement techniques. A simplified model for B clustering and redistribution in amorphous Si is proposed, including the experimental value for the B diffusivity in amorphous Si and the energetics of BICs. Our model suggests that B2, B3I, B4I and B4I2 clusters are the most energetically favored configurations, with relative abundance depending on B concentration. After recrystallization, thermal anneals up to 1100 °C evidence that BICs evolve under very low flux of Si interstitials under the particular experimental conditions considered. Simulations indicate that for very high B concentrations and low Si interstitial flux a significant fraction of the initial small BICs evolves into larger and very stable BIC configurations that survive even after intense thermal budgets, as confirmed by energy filtered transmission electron microscopy analyses. The correlation between simulations and Hall measurements on these samples suggest that hole mobility is significantly degraded by the presence of a high concentration of BICs.

Synthesis of nanostructured Cu xS thin films by chemical route at room temperature and investigation of their size dependent physical properties

Nanostructured semiconductors show very interesting physical properties than bulk crystal due to size effects that arises because of quantum confinement of the electronic states. Using cupric acetate and sodium thiosulphate as cationic and anionic precursor, nanostructured Cu 2S thin films were successfully prepared at room temperature by chemical bath deposition technique. By varying the deposition time from 9 to 24 h, the Cu 2S films of thickness 70–233 nm were prepared. The different characterization methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), optical absorption and electrical resistivity measurement techniques were used to investigate size dependent properties of Cu 2S thin films. As thickness increases, the hexagonal covellite phase of CuS observed at thickness 70 nm gets converted to monoclinic chalcosite phase of Cu 2S. The resistivity and activation energy is found to be thickness dependent. The optical band-gap energy increases from 2.48 to 2.90 eV as thickness decreases from 233 to 70 nm. The influence of film thickness on carrier concentration, mobility and thermo-emf is reported.

Relation between conductance, photoluminescence bands and structure of ITO nanoparticles prepared by various chemical methods

To study the relation between conductance, photoluminescence bands and structure of indium tin oxide (ITO), nano- and microparticles of ITO were synthesised using various methods, including hydrothermal, oxalate precursor decomposition and Pechini type sol–gel combustion methods. The resultant powders were analysed by X-ray diffraction (XRD), resistance measurement, photoluminescence (PL) spectroscopy and scanning electron microscopy techniques. The crystallographic and microstructural parameters of samples were refined from the XRD patterns utilising Rietveld method. Two PL bands were observed in 475 and 560 nm and it was found that the low-energy PL band intensity presents direct relation with conductivity of samples while the other one shows inverse relation. Pechini samples demonstrated the highest conductivity and low-energy PL band intensity, while hydrothermal sample has low conductivity. It was suggested that the low-energy PL band is the characteristics of excitons trapped in oxygen vacancy while the high-energy PL band is attributed to the excitons trapped in other defects centre. The colour of samples and data resulted from XRD pattern refinement were also validated. According to the refinement results and Popa's model, all samples show anisotropic micro-strain and crystallite size. It was also deduced that hydrothermal sample was textured in the 〈111〉 direction.

Electrical Resistance Measurement Techniques for Metal Hydrides under High-Pressure H2 Conditions & Electrical Transport and Structural Properties of FeHx

We present the newly developed electrical resistance measurement technique for metal hydrides compressed in high-pressure H2 and the first successful in-situ simultaneous measurements of electrical resistance and X-ray diffraction of FeH at high pressures and low temperatures. The electrical resistivity ρ showed a sharp increase with the formation of iron-hydride FeHx (x∼1) at 3.5 GPa. The e′-phase of FeH was found to be metallic up to 25.5 GPa. The ρ vs. T curves up to 16.5 GPa approximately follow Fermi-liquid law below 25 K. However, T5 was found to be better fitting at 25.5 GPa. This change can be related to the previously reported ferromagnetism collapse at corresponding pressures.

Investigation of humidity sensing properties of ZnS nanowires synthesized by vapor liquid solid (VLS) technique

Zinc sulfide (ZnS) nanostructures were synthesized by vapor–liquid–solid (VLS) method which is based on thermal evaporation. The morphology, chemical composition and crystal structure of ZnS nanostructures were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses. The results of these studies revealed that wurtzite ZnS nanowires with diameters in range of 50–400 nm are obtained. In order to investigate the humidity sensing capability, quartz crystal microbalance (QCM) and electrical resistance measurement techniques were carried out at different relative humidity (RH) conditions between 33% and 100% RH at room temperature. QCM results show that the oscillating frequency of ZnS nanowires loaded on QCM crystal decreases in range of 33–84% RH, but increases at 90% and 100% RH. The sensitivity of ZnS nanowires-based sensor ( R air/ R RH) increases over 1000 times from 33% to 100% RH. These experimental results show that ZnS nanowires have a great potential for humidity sensing applications at room temperature.