Sputtered Platinum Electrodes Research Articles

Characterization of High-Flux CdZnTe with optimized electrodes for 4th generation synchrotrons

In this collaboration work between IMEM-CNR and the ESRF, we explore the potential of the Redlen Technologies High-Flux Cadmium Zinc Telluride (HF-CZT) material for direct X-ray detection at fluxes ranging from 10+7 to 10+12 photons mm−2 s−1. HF-CZT single crystals with optimized electroless gold and sputtered platinum electrodes are characterized both under dark conditions and under X-ray irradiation. We report low leakage current under dark conditions (<100 pA/mm2 at 5 kV/cm). We also report good linearity (R 2 > 0.999) under moderate to high incident X-ray flux (10+7 to 10+10 photons mm−2 s−1) as well as good stability and reproducibility for incident X-ray fluxes up to 10+12 photons mm−2 s−1. Finally, we study transient phenomena in the seconds time range and report fast stabilization time (<200 ms) and negligible afterglow in this time range.

Electrochemical attack and corrosion of platinum electrodes in dielectrophoretic diagnostic devices.

Though the advances in microelectronic device fabrication have realized new capabilities in integrated analytical and diagnostic platforms, there are still notable limitations in point-of-care sample preparation. AC electrokinetic devices, especially those leveraging dielectrophoresis (DEP), have shown potential to solve these limitations and allow for sample-to-answer in a single point-of-care device. However, when working directly with whole blood or other high conductance (~ 1S/m) biological fluids, the aggressive electrochemical conditions created by the electrode can fundamentally limit the device operation. In this study, platinum wire-based electrode devices spanning circular polytetrafluorethylene (PTFE) wells and a planar microarray device with sputtered platinum electrodes were tested in plasma and PBS buffers of differing concentration across a wide range of frequencies and electric field intensities (AC voltages) to determine their respective safe regions of operation and to gain an understanding about the failure mechanisms of this class of device. At frequencies of 10kHz and below, the upper bound of operation is the degradation of electrodes due to electrochemical attack by chlorine overcoming the native platinum oxide passivation. At higher frequencies, 100kHz and above, the dielectric loss and subsequent heating of the buffer will boil before the electrodes suffer observable damage, due to the slow irreversible reaction kinetics. Effective dielectrophoretic capture of small biological particles at these frequencies is limited, and heat/oxidative denaturation of target material are a major concern. A new class of smaller devices, ones capable of high throughput at voltages low enough to maintain the integrity of the platinum passivation layer, is needed to mitigate these fundamental limitations.

Development of Thin Glass-Ceramic Electrolytes Via a Sol-Gel Route

Due to their high energy densitites lithium-air and lithium-sulfur are the most promising battery technologies. Both systems inhibit substantial drawbacks, though. The dendrite formation on the lithium anode and subsequent shorting of the cell is still unsolved since the first market introduction of rechargeable lithium-batteries in the early 1990s. With common liquid electrolytes dendrite formation cannot reliably be prevented. However, solid electrolytes with a high shear modulus effectively inhibit this effect.[1] Solid NASICON-type electrolytes (e. g. Li1+xAlxTi2-x (PO4)3, LATP) offer a high ionic conductivity at room temperature and a high anodic stability. The low stability against metallic lithium, due to the reduction of the transition metal (e. g. Ti4+), requires an intermediary layer.[2] Additionally, a reliable concept for the integration of a free standing and thick (> 50 µm) “electrolyte-sheet” has yet to be proven.In our work, dense electrolyte layers with a thickness below 1 µm were prepared by sol-gel methods (Figure 1). It was intended that a wet chemical deposition of cathode material onto the sintered electrolyte should reduce the interface resistance and that the resistance could be further optimized by varying the deposition and sintering conditions. The electrolyte/electrode interface was analyzed by means of SEM and depth-profiling XPS. Temperature dependent XRD allows for the analysis of the sintering process in situ. The interface resistance was tested galvanostatically and by electrochemical impedance spectroscopy. Electrochemical tests on the electrolyte were performed with sputtered platinum electrodes. The (spectro) electrochemical characterization (Figure 2) of thin-film electrodes on TCO coated glass substrates was realized in specially designed test cells.This poster presents the first results on the sol-gel deposited glass ceramics as electrolyte, thin film cathodes and the interface between both components. Future work will focus on the anode/electrolyte interface (Lithium/polymer/glass-ceramic) and finally a working solid-state cell. [1] W. Xu, J. Wang, F. Ding, X. Chen, E. Nasybulin, Y. Zhang, J.-G. Zhang, Energy Environ. Sci. 2014.[2] P. Knauth, Solid State Ionics 2009, 180, 911–916.

Micro‐Solid Oxide Fuel Cell Membranes Prepared by Aerosol‐Assisted Chemical Vapor Deposition

Free‐standing electrolyte membranes for low‐temperature micro‐solid oxide fuel cells (micro‐SOFCs) are prepared by aerosol‐assisted chemical vapor deposition (AA‐CVD), a cost‐effective, non‐vacuum thin‐film deposition technique. Thin, yttria‐stabilized zirconia (YSZ) membranes (50–400 nm) as well as bilayer membranes of YSZ and gadolinia‐doped ceria are prepared at temperatures of 600 °C and below. AA‐CVD, which is a gas‐phase deposition method, allows for the synthesis of precursor‐free crystalline layers, thereby limiting the development of tensile stress. High membrane survival rates of around 90% are thus obtained. The columnar structure of the electrolyte ensures high oxygen‐ion conductivity and results in negligible ohmic losses. Using sputtered platinum electrodes, the demonstration of a micro‐SOFC based on AA‐CVD electrolyte is achieved and first power density data of 166 mW cm‐2 at 410 °C is obtained.

Multilayer thin and ultrathin film capacitors fabricated by chemical solution deposition

Chemical solution deposition has been used to fabricate continuous ultrathin lead lanthanum zirconate titanate (PLZT) films as thin as 20 nm. Further, multilayer capacitor structures with as many as 10 dielectric layers have been fabricated from these ultrathin PLZT films by alternating spin-coated dielectric layers with sputtered platinum electrodes. Integrating a photolithographically defined wet etch step to the fabrication process enabled the production of functional multilayer stacks with capacitance values exceeding 600 nF. Such ultrathin multilayer capacitors offer tremendous advantages for further miniaturization of integrated passive components.

Influence of the Nature of the Contact Electrode on the Conductivity Measurements of Doped Ceria

Gadolinia doped ceria powders were prepared by the oxalate coprecipitation technique and pellets of these powders were sintered for 10 h at 1400°C. The impedance spectra were taken at temperatures ranging from 150°C to 800°C with different contact electrodes. Gold, platinum and silver from commercial paints and inks as well as sputtered platinum and La 0.8 Sr 0.2 Co 0.8 Fe 0.2 O 3 were used as contact electrodes. The total conductivities at temperatures higher than 500°C were roughly the same except when sputtered platinum electrodes were used. At lower temperatures, however, there is significant difference in the conductivity. While the grain interior resistivities are approximately the same regardless of the electrode nature, the grain boundary resistances are strongly influenced by the electrode nature.

New insights into the influence of upd Sn on the oxidation of formic acid on platinum in acidic solution

The influence of a stabilized submonolayer of upd tin adatoms on the oxidation of adsorbed and bulk formic acid on sputtered platinum electrodes in 0.1 M HClO 4 has been investigated by measuring simultaneously the rate of CO 2 production from both adsorbed and bulk formic acid. The use of on-line MS technique (DEMS) enables us to distinguish the volatile products (CO 2) formed in the oxidation of adsorbed and bulk species, respectively, with the help of isotope-labeled 13C-formic acid as a probe. A considerable promoting effect of upd tin adatoms on the oxidation of the bulk formic acid was observed. This catalytic activity depends strongly on the coverage of the tin. On the other hand, the oxidation of the formic acid adsorbate is accelerated significantly in presence of Sn adatoms on the surface or tin ions in solution. Based on our results, a discrimination between the electrocatalytic models of tin adatoms postulated in literature was given. We suggested that a combination of a bifunctional mechanism and an electronic interaction between the upd Sn adatoms and Pt substrate could account for the pronounced catalytic influence on the oxidation of formic acid.

Electrodeposited iridium oxide pH electrode for measurement of extracellular myocardial acidosis during acute ischemia.

In the present paper, fabrication, characterization, and physiological applications of a solid-state pH electrode are described. The pH sensing layer was based on an anodic electrodeposited iridium oxide film (AEIROF). Sputtered platinum electrodes (1 mm diameter) fabricated on flexible Kapton films or platinum wires were used as planar or cylindrical supports. Each electrode site was coated with Nafion to attenuate the interference of anionic redox species and to protect the electrode surface during in vivo measurements. Performance of the AEIROF was evaluated, for the first time, as a pH electrode and proved to have a slightly super-Nernstian response with slope of -63.5 +/- 2.2 mV/pH unit for both wire and planar sputtered platinum electrodes. Linear pH responses were obtained in the pH range 2-10. The electrodes have a working lifetime of at least 1 month with accuracy of about 0.02 pH unit and fast response time. The electrodes showed very low sensitivities for different species, such as Na+, K+, Li+, NH4+, Ca2+, Mg2+, dissolved oxygen, lactate, ascorbate, and urate, which are important for physiological applications. The electrodes were applied in extracellular pH measurements during brief regional ischemia in a swine heart and no-flow ischemia in an isolated rabbit papillary muscle. A first report on extracellular pH, K+, and lactate simultaneous measurements during no-flow ischemia using the AEIROF pH electrode and the previously described K+ and lactate electrodes is presented as well.

Glucose detection at bare and sputtered platinum electrodes coated with polypyrrole and glucose oxidase

Recently, a glucose sensor has been developed, which is easily prepared, has a good stability and high glucose response, and is interference free for ascorbic acid. The sensor was made by galvanostatic polymerization of 0.3 M pyrrole in a HEPES buffer pH 7.0 with 200 U ml −1 glucose oxidase (GOx) using a current of 1 μA. In this study, bare and sputtered platinum electrodes, coated with polypyrrole in the presence of GOx and/or flavine adenine dinucleotide (FAD), are compared. FAD in excess in the polymerization or sample solution did not increase the glucose response. The selectivity with respect to other mono and oligosaccharides was good. The mechanism of electron transfer was studied. From measurements at low potentials and at anaerobic conditions there is a strong indication that the glucose sensor is a combination of indirect and direct electrontransfer (first and third generation, respectively).

Electrode polarization in a yttria-stabilized zirconia solid electrolyte cell

Anode and cathode polarization were measured in a yttria-stabilized zirconia solid electrolyte cell with sputtered platinum electrodes operated at 980°C in air. Competing electrode reactions associated with the presence of the “three-phase boundary” (air/electrode/electrolyte) found in typical cells were eliminated by the use of non-porous electrodes and a glass coating applied to the sides of the sample. Use of a cylindrical sample, with reference electrodes along its length, allowed the contribution of ionic resistance to be subtracted from total cell voltage. A time decay method was used to measure concentration gradient-induced potential. Data indicate that oxygen transport through the thin (<1 μm) non-porous sputtered platinum electrodes is rapid enough to support a current density of at least 500 mA/cm 2. At current densities up to 500mA/cm 2, no activation polarization was noted at either electrode's interface, provided the end surfaces of the zirconia had been properly prepared before sputtering. Measurements of ionic resistivity obtained ranged from 6.9 to 8.1 ω cm at 980°C.

Three-electrode current-voltage measurements on erbia-stabilized bismuth oxide with sputtered noble metal electrodes

The anodic and cathodic polarization behaviour of sputtered porous gold electrodes on (Bi 2O 3) 0.75(Er 2O 3) 0.25 (abbreviated BE25) was studied as function of temperature and oxygen partial pressure using a three-electrode cell. The anodic polarization is smaller than the cathodic polarization, allowing current densities of 2 × 10 3 A m −2 at 0.1 V and 1041 K in oxygen for oxygen evolution. Comparison with the polarization behaviour of similar sputtered platinum electrodes on BE25 shows little effect of the electrode material on the exchange current densities. This indicates that the electrolyte surface is active in the oxygen transfer process, while the noble metal electrode serves merely as current collector. Analysis of the electrode impedance shows strong influence of surface diffusion on the electrode reaction(s). For the exchange current density an unusual P o2 dependence is observed.

Electrode reaction at fixed platinum film. Fixation of platinum film on stabilized-zirconia electrolyte and its effect on the electrode performance of the solid-electrolyte fuel cell.

Reliable polarization characteristics of noble metal or oxide electrodes in contact with solid oxide electrolyte are quite important. To obtain such characteristics, we fixed sputtered platinum electrodes on yttria stabilized-zirconia (YSZ) electrolyte by covering the electrode with a porous ceramic layer. As a result of the fixation, the Pt film was kept stable and the resistance of the electrodes was very small.Electrode impedance and potential-current curves were measured on the fixed electrodes. The effect of the oxygen partial pressure, PO2, on the electrode resistance, Ri, which was obtained from the impedance plots, was represented as Ri ∝ PO2–1 at high temperature and low oxygen partial pressure, and as Ri ∝ PO21/4 at low temperature and high oxygen partial pressure. Furthermore, effects of the thickness of the Pt film and the ceramic layer on the polarization characteristics were examined. The cathodic current increased as the Pt thickness decreased. The anodic current increased as the ceramic layer thickness decreased.

In-situ IR study by MIRFTIRS of adsorption and oxidation of methanol on sputtered platinum electrodes in sulphuric acid solution

Les produits intermediaires et finaux de la reaction d'oxydation du methanol sur une electrode de platine en solution d'acide sulfurique sont examines par spectrometrie MIRFTIRS

Importance of electrode/zirconia interface morphology in high-temperature solid electrolyte cells

The role of electrode/electrolyte interface morphology in the overall polarization behaviour of high-temperature solid electrolyte cells has been studied. Carefully prepared and polished scandia-stabilized zirconia discs with sputtered platinum electrodes were examined using electron microscopy and electrical polarization techniques. Initially non-porous sputtered platinum electrodes were ‘conditioned’ by a progressive treatment to generate artificial porosity. This eliminated subsequent time-dependent changes in the interface-related impedance of such cells. After prolonged use, the anode and cathode morphologies were found to be distinctly different from each other.

The electrode resistance of ZrO 2Y 2O 3(-Bi 2O 3) solid electrolytes with Pt electrodes

The electrode resistance ( R e1) at low over-voltages has been determined for Bi 2O 3 free and Bi 2O 3 doped yttria-stabilized zirconia with sputtered platinum electrodes. The anode and cathode resistances are measured separately and are equal. Bi 2O 3 causes a decrease of the electrode resistance at small overvoltage and with 5 × 10 −4 < P O 2 ⩽ 1 atm. The rate determining step for the electrode reaction under the measuring conditions probably is a charge-transfer process in which oxygen adsorbs dissociatively on the bismuth free and associatively on the bismuth doped samples. The complex impedance behaviour of the electrode reaction can be interpreted in terms of R-C circuits in the P O 2 range of 10 −2−1 atm.

A capacitance enhancement resulting from the interaction of platinum with the alkali halides

Sputtered platinum electrodes are frequently used on alkali halide crystals for the measurement of dielectric constant and conductivity. In the course of such work large capacity enhancements were observed in several alkali halide crystals at temperatures of a few hundred degrees centigrade. Evidence is presented that the effect is due to an interaction between the electrodes and the crystal, so that results on such systems at high temperatures must be interpreted with care. A model in which the conductivity is a linear function of depth through part of the crystal gives satisfactory agreement with the experimental results.