Low Electrode Resistance Research Articles

Thermally Stable Ag Thin Films Modified with Very Thin Al Oxide layers

Ag has long been of interest for use as a low-resistivity electrode material, but the problem of agglomeration caused by annealing must be resolved. One of the solutions is alloying Ag, but this often causes an increase in electrical resistivity. In this study, thermal stability of Ag thin films modified with thin Al oxide layers was investigated from the viewpoints of surface morphology and resistivity. It was found that agglomeration was suppressed in the multilayer films even after annealing at 600 °C, similarly to Ag(Al) alloy films, which were investigated previously. As a result, it was suggested that the presence of the Al oxide layers at the film surface and interface played a major role in suppressing agglomeration in Ag(Al) films. Moreover, the resistivity of the multilayer film was 1.8 µΩ cm, which was much lower than that of alloy films. Consequently, to achieve both agglomeration suppression and low resistivity, the structural modification of the Ag films using Al oxide layers is more useful than alloying the films.

LSM Cathodes Infiltrated With Er2O3 Stabilized Bi2O3

The La0.8Sr0.2MnO3 perovskite oxide (LSM) electrode was infiltrated with Er2O3 stabilized Bi2O3 (ESB) to improve the cathode performance of intermediate temperature solid oxide fuel cells. ESB infiltration was carried out by dropping the nitrate solution of Bi(NO3)3 and Er(NO3)3 (80:20mol ratio) on the LSM electrode surface prepared on yttria stabilized zirconia by screen-printing technique. The electrode performance of the infiltrated LSM electrode was studied by electrochemical impedance spectroscopy (EIS) analysis in open air. The EIS results showed that the electrode resistance was drastically decreased by the infiltration of Bi(NO3)3–Er(NO3)3 solution into the LSM electrode; the electrode resistance was as low as 2.31Ωcm2 for the infiltration LSM cathode at 600°C, which was compared with ∼380Ωcm2 for the noninfiltrated LSM cathode. The low electrode resistance could be explained by the formation of high oxide ion conductivity Er2O3-doped Bi2O3 on the LSM particles.

A Finite Element Model to Identify Electrode Influence on Current Distribution in the Skin

Discomfort experienced during surface functional electrical stimulation (FES) is thought to be partly a result of localized high current density in the skin underneath the stimulating electrode. This article describes a finite element (FE) model to predict skin current density distribution in the region of the electrode during stimulation and its application to the identification of electrode properties that may act to reduce sensation. The FE model results show that the peak current density was located in an area immediately under the stratum corneum, adjacent to a sweat duct. A simulation of surface FES via a high-resistivity electrode showed a reduction in this peak current density, when compared to that with a low-resistivity electrode.

Performance and Reliability Improvement by Optimizing the Nitrogen Content of the TaSiNx Metal Gate in Metal/HfSiON n-Type Field-Effect Transistors

We have investigated the impacts of the nitrogen content in a TaSiNx metal gate on the performance of metal/HfSiON n-type field-effect transistors (FETs). To obtain a low threshold voltage and low electrode resistance, low nitrogen concentration in TaSiNx is preferable. However, the use of a TaSi gate ([N] = 0%) causes the degradation of HfSiON dielectric characteristics such as an increase in leakage current under gate negative bias, positive-bias temperature instability lifetime degradation, time-dependent dielectric breakdown lifetime degradation, and reduction of the electron mobility. Then, a low-nitrogen-concentration TaSiN ([N] = 20%) gate shows the highest electron mobility, excellent reliability characteristics, and low threshold voltage.

Performance of Low Resistivity Electrode Prepared by Electroless Plated for Amorphous Silicon Thin-Film Transistors

The TFTs array fabrication process for large-area TFT-LCD has been continuously developed for simplifying processing steps, improving performance and reducing cost in the process of mass production. In this study, the hydrogenated amorphous silicon (a-Si:H) TFTs with low resistivity electrodes , silver thin films, were prepared by using the selective deposition method that combined lift-off and electroless plated processes. This developed process can direct pattern the electrode of transistor devices without the etching process and provide ease processing steps. The as-deposited Ag films were annealed at 200 oC for 10 minutes under N2 atmosphere. The results shows that the adhesion properties can be enhanced and the resistivity has been improved from 6.0 μ,-cm, significantly decrease by 35%, of as-deposited Ag films by annealed. The thickness of Ag thin film is about 100 nm and the r. m. s roughness value is 1.54 nm. The a-Si:H TFT with Ag thin films as source and drain electrodes had a field effect mobility of 0.18 cm2/Vs, a threshold voltage of 2.65 V, and an on/off ratio of 3×104.

Characteristics of BST Capacitors with Aluminum Electrode and Iridium Oxide Barrier Layers

AbstractThe high frequency operation of BST capacitors necessitates the development of low series resistance electrodes. As an alternative to platinum, DC magnetron sputtered IrO2/Aluminum top electrode metallization for BST capacitors has been proposed. The capacitance voltage characteristics of BST capacitors did not change significantly due to the deposition of aluminum on iridium oxide. Post annealing in nitrogen environment shows that IrO2/Al metallization does not degrade annealing temperature up to 450 oC.

Laser Fabrication of Low Resistivity Electrode on Glass

A method for low resistivity resistor on transparent substrate with laser induced plasma assisted by ablation and laser annealing was described. The diffusion distribution for metallization was measured with XPS. The surface profile was analysed with SEM. The minimum resistivity we got was 0.1 /Sq. It demonstrates that the electronic thin film obtained has a very good conductivity. The most important factors for forming electrically conducting films on the transparent substrate are laser fluence, beam scanning and pulse repetition rate. This technology will be useful in the fabrication of LCD electrode, glass defused resistor and circuit on glass.

Effect of substrate temperature and annealing treatment on the electrical and optical properties of silver-based multilayer coating electrodes

Multilayer coatings consisting of thin silver layers sandwiched between layers of transparent conducting metal oxides are investigated from the view point of low-resistance electrodes for use in flat panel displays, solar cells, etc. ZnO/Ag/ZnO multilayer films were prepared on glass substrates by simultaneous RF magnetron sputtering of ZnO and dc magnetron sputtering of Ag. Optimization of the deposition conditions of both ZnO layers and metallic layers were performed for better electrical and optical properties. The structural, electrical and optical properties of the films (deposited at room temperature, different substrate temperature and annealed at different conditions) were characterized with various techniques. We could not produce high-quality transparent conductive electrodes simply by annealing at various temperatures. However, improved electrical properties and a considerable shift in the transmittance curves was observed after heat treatment. The experimental results show that the electrical resistivity of as-grown films can be decreased to 10 − 5 Ω cm level with post-annealing at 400 °C for 2 h in vacuum atmosphere. After heat treatment, the sheet resistance was reduced as much as 20% which was due to the increased grain size of Ag film. The samples heat treated at 200–400 °C under vacuum or nitrogen atmosphere showed the best electrical properties. The key to the superior electrical and optical properties of the multilayer is the optimization of growth conditions of the silver layer by careful control of the oxide properties and the use of appropriate annealing temperature and atmosphere.

Effects of sample thickness on the van der Pauw technique for resistivity measurements

The van der Pauw technique is commonly used for electrical transport measurements on solid materials and is suited to thin, arbitrarily shaped samples, with the contacts placed anywhere on the periphery. Previous investigations have determined the effects of sample shape, contact size, and contact placement on the accuracy of this technique. Sample inhomogeneity effects have also been investigated. The effects of the sample thickness appear not to have been previously studied and are investigated here in order to establish precisely what is meant by a thin sample. The deterioration in the accuracy of the technique is followed as the sample thickness is increased. The results indicate that the van der Pauw technique may be used for samples where the thickness is comparable to the surface dimensions. The investigation also shows that the technique is valid for arbitrarily thick samples provided that low resistance electrodes are placed across the entire edge, perpendicular to the surface, in order to maintain an effective two-dimensional current distribution. This finding is useful for transport measurements on materials that have been prepared, for example, by solid state reaction using sintering methods.

Low Loss Tungsten-Based Electrode Technology for Microwave Frequency BST Varactors

Composite metallization stacks consisting of 1.5 μm W layers and 0.1 μm Ir layers have been developed for low series resistance electrode applications. These hybrid metallization layers are compatible with barium strontium titanate deposition and standard patterning/etching procedures. The multilayer stacks were prepared for use as bottom electrodes in microwave varactors based upon the electrically tunable dielectric barium strontium titanate. These low resistivity layers are critical for realizing low insertion loss devices, and overcome difficulties associated with delamination or hillocking in traditional noble metal layers. Controlling the oxygen content during BST deposition was necessary to achieve high-quality BST and a stable electrode stack. Using these metallization stacks and optimized deposition conditions, BST films with tan δ values below 0.007 and tunabilities of 2:1 were realized. These properties are comparable to those measured on typical Pt/BST/Pt/SiO2/Si capacitors. Finally, a combination of reactive ion and wet chemical etching were used to demonstrate that the thick hybrid metallization layers are patternable using routine and manufacturable process methods.

GaN-based Light Emitting Diode with Transparent Nanoparticles-Embedded p-Ohmic Electrodes

AbstractOptoelectronics related to GaN-based semiconductors (i.e., InGaN, GaN, and AlGaN) are new technologies that have the potential to far exceed the energy efficiencies of incandescent and fluorescent lighting sources. Among the GaN-based optoelectronic devices like light emitting diode (LED) and laser diode (LD), the GaN-based LEDs are of interest for the next generation illumination because of the representative characteristics such as small, highly radiant, reliably long, and fast responding, compared with the existing general lighting systems.Achievement of high luminous intensity by flip-chip LED (FCLED) with Ag-metallic reflector or using top emitting LED (TELED) with highly transparent ITO contact is required to improve the external quantum efficiency (EQE) and light output of GaN-based LEDs. However, since the work function of Ag and ITO is lower than 5.0 eV, it is difficult to produce low-resistance p-ohmic electrode with Ag-metallic reflector or ITO only.In this study, in order to develop new ohmic contact materials having low contact resistance and high transmittance, transparent nanoparticles-embedded p-ohmic electrode, Mg-doped indium oxide (MIO) (3 nm)/indium tin oxide (ITO) (400 nm) ohmic contact for high brightness TELEDs for solid-state lighting, was suggested. The MIO/ITO contact become ohmic with specific contact resistances of 2.64 × 10-3 Ωcm2 and give transmittance higher than 94.6 % at a wavelength of 450 nm when annealed at 630 °C for 1 min in air. GaN-based LEDs fabricated with the annealed MIO/ITO p-contact layer give a forward-bias voltage of about 3.38 V at injection current of 20 mA. It is further shown that the output power of the LEDs with the MIO/ITO contact is enhanced by about 1.86 times at 20 mA as compared with that of LEDs with the conventional Ni/Au contact.

Development of low contact resistivity electrode for HTSC films

The electrodes on LPE films for the case of persistent current switches were developed. The electrode was fabricated by the sputtering method using targets of Ag-based metal alloys. In the targets, the different amounts of Cu were added in order to suppress the reaction between the RE123 and the electrode metal films. Consequently, the suitable composition of the Ag–Cu electrode to obtain a low contact resistance was found. When the copper composition in the Ag electrode was controlled to be 1.09 wt.%, the lowest contact resistance of 1.7 × 10 −12 Ω m 2 was obtained. And all of these results are reasonable values as the requirements for the LPE film. Moreover, we found that a thick film is necessary to fabricate electrodes with low contact resistivity since fine grains in a small bare surface area were expended due to vaporization, etc., by the heat treatment in the case of thin films.

Low-resistivity Mo thin films prepared by evaporation onto [formula omitted] cm glass substrates

In order to obtain a suitable back contacting material for CuInSe 2-based photovoltaic devices, molybdenum thin films have been deposited onto glass substrates up to 30 cm×30 cm area using an electron beam evaporator. In the CuInSe 2-based devices, molybdenum has to provide the electrical properties of a low-resistivity electrode and must also serve as a part of the substrate during the growth of successive photovoltaic components, maintaining chemical and mechanical stability during the whole device fabrication process. Film thickness, sheet resistance, optical reflectance and surface roughness measurements have been performed for the Mo layers prepared at various deposition power and time. The film microstructure, such as the preferred orientation and the residual intrinsic stress, has been determined by X-ray diffraction. The electrical requisites for photovoltaic applications have been achieved for Mo layers evaporated at different experimental conditions with similar homogeneity over the substrate area. On the other hand, the intrinsic stress in Mo films has been found depending on the evaporation parameters, mainly on the thin-film deposition rate.

RPC operation at high temperature

The resistive electrodes of RPCs utilised in several current experiments (ATLAS, CMS, ALICE, BABAR and ARGO) are made of phenolic/melaminic polymers, with room temperature resistivities ranging from 1010Ωcm, for high rate operation in avalanche mode, to 5×1011Ωcm, for streamer mode operation at low rate.The resistivity has however a strong temperature dependence, decreasing exponentially with increasing temperature. We have tested several RPCs with different electrode resistivities in avalanche as well as in streamer mode operation.The behaviours of the operating current and of the counting rate have been studied at different temperatures. Long-term operation has also been studied at T=45°C and 35°C, respectively, for high and low resistivity electrodes RPCs.

Reduction of effective dielectric constant of gate insulator by low-resistivity electrodes

On metal–oxide–semiconductor capacitors, the effective dielectric constant (keff) values extracted from high-frequency capacitance–voltage measurements were found to decrease when gate electrodes of very low resistivity were used. The equivalent-oxide thickness increase reaches about 1 nm with the low-resistivity electrodes. We examined gate insulators of SiO2, Al2O3, and HfO2 and gate electrodes of Al, TiN, Au, Cr, and TaN. The equivalent-oxide thickness increase can be prevented by inserting a high-resistivity metal film only 0.3 nm thick between the very low-resistivity metal and the insulator. The present results suggest that keff is reduced by the screening of ionic insulators with free electrons of the metal due to a quantum effect.

Increase of separation resolution through field enhancement in microchips.

An enhanced ability to separate charged species from neutral compounds in a microfluidic chip is demonstrated using a chip design with low-resistance electrode channels operating with a multiport pressure/voltage controller. A factor of 2.7 improvement in resolution was obtained from chips made using identical mask designs but different etch depth protocols. Greater separation power allows one to cover a wider dynamic range for compounds with different electrophoretic mobilities.

Development of Silver-Based Multilayer Coating Electrodes with Low Resistance for Use in Flat Panel Displays

Multilayer coatings consisting of thin silver layers sandwiched between layers of transparent conducting metal oxides were investigated from the view-point of low-resistance electrodes for use in flat panel displays. Optimization of the multilayer coatings resulted in a five-layer coating composed of indium and zinc oxide composite material (IZO) and silver containing 1 wt% of palladium (Ag–Pd). The coatings had satisfactory properties of low resistance, high transmittance, high moisture and alkali resistance, and good patterning.

Inhibition of the acetylcholine-activated potassium current by endothelin-1 in atrial cardiomyocytes

Endothelin-1 (ET-1), is a 21 amino-acid peptide with potent inotropic and chronotropic actions in the heart. Relatively little is known about the underlying electrophysiological effects of the peptide. In this study the effects of ET-1 on the acetylcholine-activated potassium current (IK(Ach)) were investigated in the absence and presence of the receptor-selective antagonists, PD155080 (ETA receptor-selective) and RES-701 (ETB receptor-selective) in atrial cardiomyocytes. Cells were obtained from New Zealand White rabbits (2·5–3 kg) by enzymatic dissociation using collagenase. Potassium currents were recorded, in the presence of nifedipine (5 μM), using the whole cell ruptured patch-clamp technique. Low resistance electrodes (1–3 MΩ) were filled with potassium gluconate solution (pH 7·2). Cells were superfused with a modified Tyrode's solution. Following stabilization, control recordings were made using standard pulse protocols, and drugs were applied using a gravity fed microperfusion system. Data were expressed as mean±standard error, and comparisons were made using Friedman's ANOVA and Wilcoxon's Signed Ranks tests; p<0·05 was considered significant ET-1 (10 nM) alone did not affect the potassium current. Acetylcholine (Ach, 1 μM) increased (p<0·05) the potassium current to −1321±290 pA, from a control value of −955±191 pA, at a step potential of −100 mV. This change in current is attributed to IK(Ach) as it was blocked by atropine (10 μM). ET-1 (10 nM) inhibited (p<0.05) the IK(Ach) obtained in the presence of Ach (−882±88 compared to a control value of −870±98 pA) Ach also increased the holding current from +80±9 to ±242±38 pA, and this effect was blocked (p<0·05) in the presence of ET-1 (44±13 pA). The ETA receptor-selective antagonist, PD155080 (1 μM), prevented (p<0·05) the ET-1 induced inhibition of IK(Ach) (control vs Ach±ET-1+PD155080: −804±224 vs −1030±210 pA; at −100 mV; n=6). The ETB receptor-selective antagonist, RES-701 (1 μM), also prevented (p<0·05) the inhibitory effect of ET-1 on IK(Ach) (control vs Ach+ET-1+RES-701: −733±116 vs −913±137 pA; at −100 mV; n=6). However, unlike PD155080, RES-701 failed to sustain this inhibitory effect after a further 90 s exposure to Ach and ET-1 (control vs Ach+ET-1+RES-701; −733±116 vs 768±96 pA; at −100mV; n=6). In summary, ET-1 clearly inhibits the effects of Ach on IK(Ach) in rabbit atrial cardiomyocytes. This effect is mediated by an ETA receptor-subtype, and an RES-701 -sensitive ETB receptor subtype.

The effect of thermal treatment on the resistance of LSCF electrodes on gadolinia doped ceria electrolytes

The effect of thermal treatment on the structure and electrical characteristics of La 1 − x Sr x Fe 1 − y Co y O 3 − δ (LSCF) electrodes on Ce 0.9Gd 0.1O 1.95 (CGO) electrolytes has been investigated. Low calcination temperatures and short sintering times leads to the formation of a cubic A-site deficient perovskite, with the composition La 0.6Sr 0.13Co 0.2Fe 0.8O 2.52, which exhibits a low electrode resistance. Higher calcination temperatures and longer sintering times leads to the incorporation of strontium, derived from the decomposition of SrCO 3, into the perovskite structure, producing a stoichiometric rhombohedral perovskite. Electrodes containing a larger proportion of the stoichiometric perovskite had a higher resistance than those consisting largely of the A-site deficient perovskite.

Computer simulations of voltage clamping retinal ganglion cells through whole-cell electrodes in the soma.

1. Computer simulations of voltage-clamp experiments in retinal ganglion cells were implemented to better understand the insights that can be obtained with this physiological approach. 2. Simulation studies of voltage clamping were based on the contemporary approach of using whole-cell recordings with low resistance electrodes attached to the soma. Realistic ganglion cell morphologies were provided by cell staining experiments in the mudpuppy retina; selected cells included small-, medium-, and large-field neurons whose morphologies were entered into a computer through a neuron tracing program. 3. Values for the specific membrane resistance (Rm) varied from 5,000 to 100,000 omega/cm2 to conform to the range of Rm values obtained with intracellular sharp electrodes and whole-cell recordings. 4. Synaptic input currents were simulated by injecting current with and without an underlying conductance change into different regions of the dendritic tree. The time-variant waveform of the current included a combined transient and sustained component similar to the waveform of ON-bipolar activation. 5. Simulations were base on 1) intact structures, which included the soma and the entire dendritic tree, and 2) a more limited cell geometry that included representation of the soma, but only part of the dendritic tree, to represent the restricted morphology that might be rendered after cutting the retina into 150-microns cross sections for retinal slice experiments. 6. The results of this study indicate that voltage clamping from the soma, with optimal, low resistance electrodes and series resistance compensation, provides an error-free voltage clamp for slow signals that are generated within a small electrotonic distance from the soma (approximately 0.1 lambda). 7. The ideal voltage-clamp conditions are optimized when synaptic conductances are small and nonlinear membrane elements are minimally activated: small-field neurons best approximate these conditions, but clamping errors are evident in these cells when more distal branches are activated. The degree of error in voltage clamping was much greater when medium-and large-field neurons were evaluated. 8. It was not possible to clamp action potentials (nonpropagating) even when they were generated near the soma in any of the three model cells examined. 9. Experimental paradigms were developed to demonstrate that inadequate voltage clamping can lead to errors in the interpretation of experimental data when relevant variables are not taken into consideration. Suggestions are made for determining and optimizing favorable clamp conditions.