DC Measurement Techniques Research Articles

Phenylalanine-Assisted Conductivity Enhancement in PEDOT:PSS Films.

Biological materials such as amino acids are attractive due to their smaller environmental footprint, ease of functionalization, and potential for creating biocompatible surfaces for devices. Here, we report the facile assembly and characterization of highly conductive films of composites of phenylalanine, one of the essential amino acids, and PEDOT:PSS, a commonly used conducting polymer. We have observed that introducing aromatic amino acid phenylalanine into PEDOT:PSS to form composite films can improve the conductivity of the films by up to a factor of 230 compared to the conductivity of pristine PEDOT:PSS film. In addition, the conductivity of the composite films can be tuned by varying the amount of phenylalanine in PEDOT:PSS. Using DC and AC measurement techniques, we have determined that the conduction in the highly conductive composite films thus created is due to improvement in the electron transport efficiency compared to the charge transport in pure PEDOT:PSS films. Using SEM and AFM, we demonstrate that this could be due to the phase separation of PSS chains from PEDOT:PSS globules which can create efficient charge transport pathways. Fabricating composites of bioderived amino acids with conducting polymers using facile techniques such as the one we report here opens up opportunities for the development of low-cost biocompatible and biodegradable electronic materials with desired electronic properties.

Densification, morphological and transport properties of functional La1–xBaxYbO3–δ ceramic materials

The effective operation of protonic ceramic electrochemical cells requires the design of electrolytes having not only high ionic conductivity, but also excellent stability with respect to carbonisation. In the present work, the La-based oxides (La1–xBaxYbO3–δ, 0.03 ≤ x ≤ 0.10) are proposed as a possible alternative to the convenient Ba(Ce,Zr)O3-based electrolytes due to their high chemical stability. It was discovered that Ba-doping results in a deterioration of sintering behaviour; as a result, the relative density decreases and open porosity appears (for x = 0.10). A thorough analysis of transport properties by means of AC and DC measurement techniques enables a selection of the La0.97Ba0.03YbO3–δ sample, which demonstrates the highest conductivity compared with those samples where x = 0.5 and 0.10. Due to its excellent densification behaviour, stability and ionic conductivity, La0.97Ba0.03YbO3–δ can be considered as a promising proton-conducting electrolyte in the La-based family.

Research on DC resistivity for an arbitrarily anisotropic earth using circular scanning measurement

This paper presents a 3D forward modelling algorithm with an adaptive finite-element method based on unstructured grids that when used with a circular scanning DC measurement technique can provide an indication of anisotropy in a layered earth. The accuracy of this algorithm is checked against 1D semi-analytical solutions for an arbitrarily anisotropic earth. This anisotropy produces a measurement paradox, results are dependent on the physical relationship between DC transmitter and receiver. To resolve this paradox, a circular scanning measurement technique has been suggested. Through analysing the response of typical anisotropic models, we study the characteristics of apparent resistivity related to the electrically anisotropic media and identification of underground electrical anisotropy. The results of numerical experiments shows the effectiveness of our algorithm and the analysis will be helpful to the interpretation of anisotropic DC resistivity data. Key words: numerical modelling, unstructured grids

Nano-second time resolved investigations on thermal implications of high-field transport through MWCNTs

The high-current carrying capacity of Multi-walled Carbon Nanotubes (MWCNTs) is the central idea behind their possible applications as interconnects. Joule-heating due to transport of high current through constricted quasi-1D electron channel results in various temperature-driven phenomena. Two such phenomena are current annealing and irreversible breakdown, which play vital roles in deciding electron transport and interconnect reliability, respectively. These phenomena occur at the time scale of 1–100 ns and hence cannot be precisely captured by conventional steady-state or DC measurement techniques. In this work, we explore these two phenomena by investigating electro-thermal transport through the inner and outer shells of MWCNTs, both suspended and substrate-supported, at the time scale of nano-seconds.

Analysis of Transport Properties of MOD YBCO Films With BaZrO3as Artificial Vortex Pinning Centers

The transport properties of nanocomposite YBa 2 Cu 3 O 7-x (YBCO) films grown by metal-organic decomposition (MOD) and prepared with a low-fluorine-coating solution on SrTiO 3 single-crystal substrates were studied with dc and microwave measurement techniques. As demonstrated in previous studies, the combination of these two techniques is a powerful tool for vortex pinning investigation. The BaZrO 3 inclusions (BZO) as artificial pinning centers were introduced into the YBCO matrix by the excess of corresponding Ba and Zr precursor salts to the initial YBCO precursor solution up to 5 mol%. The effect of BZO was clearly observed in magnetic field dependence relations of critical current density (J c ) and the complex surface impedance, i.e., ΔZ, at fixed temperature and magnetic field parallel to the c-axis. The result shows that BZO particles mainly act as isotropic pinning centers. The short-range vortex dynamics was probed by the ~47.7-GHz microwave surface impedance technique. The derived vortex parameters r and k p were sensitive to the presence of nanoparticles, indicating the effect of BZO on pinning. The joint field dependence relations of J c and k p help in elucidating the pinning regime in our nanocomposite MOD YBCO/BZO films.

Determination of Curves of HTS Tapes From the Frequency-Dependent AC Transport Loss

The current-voltage characteristics of superconductors are commonly determined by means of a standard 4-probe DC measurement technique. In coated conductors, however, one often encounters problems due to weak or no stabilization and in such case, when the risk of burning the tape is high, the 4-probe approach can fail. In other cases such as in HTS cable structures, besides vulnerability and high risk of damage, it may also be difficult to achieve a high critical current level with a power supply that is normally used to characterize single strands. We therefore investigated an alternative method to determine the DC I-V curve, based on measuring the AC transport loss as a function of frequency in overcritical current range. In the AC regime, both the hysteretic loss component and the joule dissipation are present for applied transport currents exceeding the critical current Ic. In this work, AC loss measurements at different frequencies are related to different electric fields in DC and a curve similar to the DC I-V is obtained. From this curve, the power index N and Ic values are estimated. AC regime operation can be more beneficial for two reasons: firstly, because very high currents can be achieved easily by using a transformer; secondly, because the effective joule heat dissipation with overcritical AC currents is much lower than that with DC of the same amplitudes. In the experiment, we used a 4 mm wide YBCO reference tape with 20 {\mu}m of Cu-stabilization. For the comparison with AC transport loss, the sample was measured with the standard 4-probe technique and remained stable even in overload condition. To support our study, numerical simulations, reproducing both transient and stationary operation conditions, were performed. A similar relation between the AC current transport loss and the I-V curves was also observed in the simulations.

Active Material Arrangement and Its Effect on Electronic Conductivity in a Suspension Electrode

Flowable or suspension electrodes are multiphase electrode systems, where an active solid material is suspended in electrolytic medium. Suspension electrodes have been demonstrated for large-scale energy storage [1], water deionization [2-4], and energy generation applications [5]. Several material chemistries have been examined in a suspension form, and all systems rely on the use of carbon-based materials to form percolation networks for efficient electron transport. Suspension electrodes based on metal oxides typically demonstrate low electrical conductivities (~10-6 mS/cm) and require the addition of conductive additives to enable efficient charge storage and rate handling. Capacitive suspension electrodes, composed of activated carbon, are significantly more conducting than those based on metal oxides (~10-1-100 mS/cm). Nevertheless, both types of suspension electrodes display electrical conductivities significantly lower than their film counterparts, because of the presence of a highly resistive solution region. One solution to this challenge is the addition of more conducting materials (carbon black or activated carbon) or controlled arrangement of the active material. The former results in high viscosity material systems which are challenging to flow. The arrangement of the active and inactive material in a suspension electrode is expected to affect charge and ion percolation and material utilization in a suspension electrode. In this work we compare DC and AC electronic conductivity measurement techniques, and present work on visualization of the active material arrangement in a suspension electrode.

Scaling of Electrode-Electrolyte Interface Model Parameters In Phosphate Buffered Saline.

We report how the impedance presented by a platinum electrode scales with the concentration of phosphate buffered saline (PBS). We measure the response in various dilutions of PBS with an electrode array as is commonly used in spinal cord stimulator (SCS) implants. We match the parameters of a non-linear electrode-electrolyte interface model to these measurements. We find that the constant phase element of the model scales with approximately the log of concentration, whereas the resistivity is inversely proportional. Using a novel DC measurement technique we show that the onset of Faradaic conduction for a platinum electrode, and thus the safe exposure limit, does not scale with concentration. We compare objective measurements made in saline to those made in the spinal cavity of live sheep. We comment upon the appropriateness of using PBS as a substitute for in-vivo measurements.

EVALUATION OF TECHNOLOGY OPTIONS FOR SUBSTRATE NOISE REDUCTION

Substrate coupling is a phenomenon that affects the behavior and performance of RF and mixed signal ICs. Prediction of such crosstalk during the design process can help designers. In this paper, a new methodology is presented for performing a fast and reliable characterization of the noise transmission path, modeling the substrate as a resistive network. Adopting only DC measurement techniques, the dependence of disturbances attenuation on the geometric parameters is found. Moreover, the relation between attenuation and disturbance types is indicated. Finally, a qualitative comparison is made between the efficiency of the most commonly used technology measures against substrate crosstalk.

High temperature electrical properties of highly epitaxial CaCu3Ti4O12 thin films on (001) LaAlO3

The high temperature electrical behavior of highly epitaxial CaCu3Ti4O12 thin films on (001) LaAlO3 have been systematically investigated with traditional four-probe dc and ac resistance measurement techniques and two-probe ac impedance spectroscopy. Both ac and dc resistance measurements reveal that the Arrhenius plot, ln(σ) vs (1/T), forms two linear sections with a transition temperature between them at 773 K, one with the activation energy Ea of ∼1.3 eV at low temperature, and the other with the activation energy Eb of ∼0.5 eV at high temperatures. The high temperature impedance spectra also confirm these phenomena and suggest that unlike in polycrystalline bulk material, the high frequency response is predominantly from grains rather than grain boundaries.

OS09W0167 Damage detection of hybrid CFRP reinforcements by DC measurement technique

OS09W0167 Damage detection of hybrid CFRP reinforcements by DC measurement technique

Diagnosis of Reference Electrodes in Cathodic Protection Systems by Electrochemical Impedance Spectroscopy

Laboratory and field investigation results have been presented of cathodic protection installation elements of an underground steel pipeline by the electrochemical impedance spectroscopy (EIS) technique. Impedance spectrahave been presented of the following systems: reference electrode/auxiliary electrodes, pipeline/buried and portable reference electrodes. It has been shown that the discussed technique makes it possible to investigate the technical state of reference electrodes, allowing evaluation of the reliability of potential measurement results of the protected structure. EIS gives information unavailable through traditional DC measurement techniques used in cathodic protection installations. It allows, for example, determination of the resistance of the system: structure/reference electrode. This can be used for estimation of the potential IR component.

Dc measurement technique used for national electric standards

Dc measurement technique used for national electric standards

Measurement of the response of resistive sensors using logic oscillators and integrated frequency measurement

A simple method for the interrogation of resistive sensors is presented together with its application to the measurement of conducting polymer sensors. The noise present in the system was analysed using a precision fixed resistor and a conducting polymer sensor exposed to varying levels of humidified air. The sensitivity of the technique was found to be equivalent to other direct current (dc) measurement techniques. A technique to measure frequency changes is also presented where the main component is a field programmable gate array (FPGA). The noise in this system was compared to that of a commercial counter and found to be only six times greater at ±0.001% (1 standard deviation).

Current–voltage characteristics and aging of sepiolite oriented by magnetic field

Current–voltage characteristics and aging properties of modified sepiolite taken from Anatolia have been studied. Sepiolite mineral dispersed by ultrasonic methods and saturated with Fe 2+ by ion-exchange has been oriented in an 11 kG magnetic field. DC measurement techniques have been applied to ribbon type samples oriented in a magnetic field. Whereas, application of these techniques to samples that have not been oriented in a magnetic field was possible because of very small and unstable current, samples oriented in a magnetic field have shown a linear change. The current–voltage studies done at different time periods have shown that sample resistance has risen in time approximately 100 times, and aging has begun. This has been evaluated as being the result of sepiolite interaction with water vapor in the medium, rather than the oxidization of the contacts.

Electrical conductivity of modified bentonites and FT-IR spectroscopic investigations of some aromatic molecules adsorbed by bentonites

Abstract Electrical conductivity of natural and ion-exchanged Anatolian bentonites (Ag–, Cu–) and of different organic molecules (benzidine–, pyrazine– and 1,4-diamino benzene–) adsorbed by bentonites were investigated. Dc and ac measurement techniques were applied to ribbon and sandwich type samples. Measurements were made under standard pressure, humidity and room temperature. It was observed that conductivity of ion exchanged Ag–, Cu–bentonite and benzidine–bentonite complexes has increased. In addition, FT-IR spectrometry was used to assign complex pattern and composition in clay–organic molecule complexes. Spectroscopic investigations suggest that organic molecules intercalate the interlayers of bentonite with a monolayer arrangement.

A new approach for direct observation of base width modulation in vertical bipolar transistors

A new DC measurement technique that allows direct observation of the forward and reverse Early effects is described. The technique employs a special test structure and is used to accurately determine the Early voltage parameters in the Gummel-Poon model. The improvements provided by this method over existing parameter extraction techniques are realized by using a direct measurement of the normalized base charge as a function of the emitter and collector junction biases. The new technique described here allows the Early voltage parameters to be extracted as a function of applied bias in a straightforward manner and is suitable for high volume measurements for statistical characterization and for process monitoring in an industrial setting.

DC and AC Techniques for Resistance and Impedance Measurements

Techniques related to the establishment and the comparison of primary standards of resistance and capacitance are described and discussed. In the field of resistance, the characteristics of primary standard resistors of 1 Ω and 10 000 Ω are presented and dc resistance-ratio measurement techniques reviewed, including the series-parallel method, the Warshawsky bridge and the cryogenic current comparator bridge. A review of techniques and results regarding very low-frequency ac measurements of dc standard resistors is also given. In the field of capacitance, the realization of the farad using calculable standards is discussed as well as the techniques for accurate measurements of four terminal-pair impedances used in particular for linking the farad and the ohm.

Magnetic characterisation of recording media

The basic characterizing parameters of magnetic recording media are critically examined. The applicability and usefulness of the measurement of remanence curves are discussed together with their relationship to time-dependent phenomena. Techniques for the determination of anisotropy fields are also presented. The application of DC and AC magnetic measurement techniques to the characterization of pigment dispersions is briefly discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Narrow pulse measurement of drain characteristics of GaAs MESFETs

A measurement technique is presented which uses narrow, fast-rise-time pulses applied to both the gate and the drain of a GaAs MESFET to obtain the drain characteristics of the device. This allows the characteristics of the device to be obtained which correspond to frequencies above those at which surface and substrate traps can respond. The resulting characteristics show significant departures from those obtained using conventional long pulse and DC measurement techniques.