Table of contents

Copper indium disulfide thin films for photovoltaic applications were grown by close‐spaced vapor transport in a vertical reactor closed under vacuum. Solid iodine was used to provide the reagent. Optimal deposition conditions were determined by studying samples deposited on soda‐lime glass with X‐rays, scanning electron microscopy, energy‐dispersive spectroscopy, optical absorption, and Hall effect. The stoichiometry temperature range is relatively large compared to other I‐III‐VI compounds: the lower limit (∼370°) corresponds to the formation of CuI in the layers and the upper limit (∼680°C) is imposed by the glass substrate. No phase change was observed in this temperature range. All the layers are p‐type conducting, with carrier densities of the order of and high mobility values in certain cases. © 2000 The Electrochemical Society. All rights reserved.

To evaluate the effects of on the performance of molten carbonate fuel cells, bench‐scale cell tests were performed and the meniscus heights of the electrolyte on Ni were measured with fuel gases containing various amounts of . In bench‐scale cell tests, in the fuel gas had a large effect on cell voltage in the early operating stages, but this effect showed a tendency to decrease with operating time. Basic wetting property measurements revealed that Ni becomes better wetted at higher concentrations. In calculations of the electrolyte distributions, the electrolyte fill of the anode with was found to be higher than that without . This study simulates the electrolyte distributions taking into account the effects of levels, the electrolyte loss and the change in pore size distributions of the electrodes, and discusses the relation between electrolyte distribution and cell performance. © 2000 The Electrochemical Society. All rights reserved.

Carbon‐coated natural graphite has been prepared by thermal vapor decomposition treatment of natural graphite at 1000°C. Natural graphite coated with carbon showed much better electrochemical performance as an anode material in both propylene carbonate‐based and ethylene carbonate‐based electrolytes than "bare" natural graphite. The effect of carbon coating on the electrochemical performance was investigated by solid‐state in conjunction with standard electrochemical techniques. © 2000 The Electrochemical Society. All rights reserved.

Inorganic‐organic composite solid polymer electrolytes (CSPEs) have been prepared from the poly(ethylene oxide) (PEO)‐like electrolytes of the general formula polyvinylidene fluoride‐hexafluoropropylene and ceramic powders. In the PEO‐like electrolytes, PVdF‐HFP is the copolymer of PVdF and HFP, is a nonvolatile oligomeric polyethylene oxide of ∼400 g/mol molecular weight, and LiX is lithium bis(trifluoroethylsulfonyl) imide. Two types of inorganic oxide ceramic powders were used: a highly material of the composition 14 mol % , and the poorly Li‐silicates where M is Ca or Mg and x is 0 or 0.05. The composite electrolytes can be prepared as thin membranes in which the conductivity and good mechanical strength of the inorganic ceramics are complemented by the structural flexibility and high conductivity of organic polymer electrolytes. Excellent electrochemical and thermal stabilities have been demonstrated for the electrolyte films. Li//composite electrolyte// rechargeable cells have been fabricated and cycled at room temperature and 50°C. © 2000 The Electrochemical Society. All rights reserved.

The microstructure and electrochemical properties of pristine and boron‐doped mesocarbon microbeads (MCMBs) were comparatively studied by X‐ray diffraction, field‐emission scanning electron microscopy, Raman spectroscopy, and electrochemical measurements. We examined the correlation between the boron‐doping effect and the electrochemical properties of boron‐doped MCMBs prepared at different heat‐treatment temperatures. It was found that boron doping in MCMBs starts above 1800°C, and then the substitution reaction proceeds with increasing heat‐treatment temperature. The effect of boron doping is to accelerate graphitization of MCMBs for heat‐treatment temperatures in the range from 1800 to 2500°C. Electrochemical lithium intercalation takes place at a higher potential in boron‐doped MCMBs than in undoped MCMBs, presumably because the substitutional boron acts as an electron acceptor in the MCMBs. © 2000 The Electrochemical Society. All rights reserved.

The structure and anode performance of Li‐ion batteries for three different forms of carbon materials (powder, spheres, fibers) and three boron‐doped samples have been studied comparatively. The characterization and properties were obtained by X‐ray diffraction, X‐ray photoelectron spectroscopy, Raman spectroscopy, and electrochemical measurements. The B 1s peak of boron‐doped graphite I was split into three peaks at 185.6, 187.7, and 189.8 eV, which were assigned to boron in boron carbide, in a boron cluster, or boron bound to incorporated nitrogen atoms, respectively. The electrochemical introduction of Li ions takes place at ∼40 mV higher potential in boron‐doped samples than in undoped samples, presumably because the substitutional boron acts as an electron acceptor in the graphite lattice. Also, it is suggested that the electrochemical properties of boron‐doped graphitized materials depend on the structural geometry and chemical composition of the pristine host materials. © 2000 The Electrochemical Society. All rights reserved.

Electrochemical techniques have been used to study the reversible insertion of sodium into hard‐carbon host structures at room temperature. In this paper we compare these results with those for lithium insertion in the same materials and demonstrate the presence of similar alkali metal insertion mechanisms in both cases. Despite the gravimetric capacities being lower for sodium than lithium insertion, we have achieved a reversible sodium capacity of 300 mAh/g, close to that for lithium insertion in graphitic carbon anode materials. Such materials may therefore be useful as anodes in rechargeable sodium‐ion batteries. © 2000 The Electrochemical Society. All rights reserved.

Failure mechanisms due to high charging rates of rechargeable lithium batteries comprised of Li metal anodes, cathodes (tunneled structure), and electrolyte solutions based on the combination of 1,3‐dioxolane (DN), , and tributylamine (antipolymerization stabilizer) were explored with the aid of postmortem analysis. It was found that at high charging rates, lithium deposition produces small grains, which are too reactive toward the electrolyte solution, in spite of the excellent passivation of lithium in this solution. In practical batteries such as AA cells with spirally wound configurations, the amount of solution is relatively small, and the solution is spread throughout the battery in a thin layer. Therefore, upon cycling, the Li‐solution reactions deplete the amount of the solution below a critical value, so that only part of the active materials continues to function. This leads to a pronounced increase in the internal resistance of these batteries, which fail as a result of their high impedance and the decrease in the effective working electrodes area. Another failure mechanism relates to the extremely high charge‐discharge current densities developed as the active electrode area decreases. These high currents, developed after prolonged cycling, lead to the formation of dendrites that short‐circuit the battery, thus terminating its life. © 2000 The Electrochemical Society. All rights reserved.

A novel approach for suppressing the solvated lithium intercalation in graphite was developed by microencapsulating graphite with nanosized Ni‐composite particles. The Ni‐composite graphite showed great improvement in charge‐discharge performance, coulomb efficiency, and cycling behavior when used as the negative electrode in a Li‐ion cell with propylene carbonate (PC)‐based electrolyte. For example, a 10 wt % Ni‐composite coating increased the initial charge‐discharge coulomb efficiency of SFG75 graphite (75 μm, Timcal America) from 59 to 84% and the reversible capacity by 30–40 mAh/g. The Ni‐composite coating consisted of nanosized particles distributed over the surface of the graphite particle, which effectively blocked some of the edge surfaces exposed to the electrolyte. This minimized solvated lithium intercalation at these edge sites, which subsequently minimized the PC reduction within the graphite and the exfoliation of the graphene layers, and also gas evolution. Corresponding improvements in both the charge‐discharge performance and safety of the negative electrode in a rechargeable Li‐ion cell resulted. © 2000 The Electrochemical Society. All rights reserved.

Proton conductivities as well as methanol permeabilities were investigated for two commercial partially fluorinated ionomeric membranes: IonClad® R-1010 and R-4010, both manufactured by Pall Company. The investigation was carried out in the temperature range 20 to 60°C. The results were compared with data for Nafion® 117 (DuPont) obtained in the same temperature range. We found that IonClad membranes, while exhibiting proton conductivity approximately equal to that of Nafion 117, are considerably less permeable to methanol. The permeability measured for R-4010 membranes was almost four times smaller than for the Nafion membrane. These characteristics together with the low cost make the IonClad membranes interesting potential candidates for application in the direct methanol fuel cell. © 2000 The Electrochemical Society. All rights reserved.

Surface modification of the electrode dramatically improved the performance of a electrode charged to 4.6 V. A diamond‐like carbon thin film was deposited uniformly on the electrode surface using dc plasma chemical vapor deposition. This surface treatment suppressed electrolyte decomposition during the charge process. When a coin‐type cell using this electrode was charged to 4.6 V, the discharge capacity in the first cycle was 212 mAh/g and the charge‐discharge efficiency was over 90% through five cycles. This treatment suggests a new approach to the development of cathodes for lithium‐ion secondary batteries. © 2000 The Electrochemical Society. All rights reserved.

The thermal expansion behavior and mechanism of A‐site‐deficient lanthanum manganite perovskites, , and alkaline earth metal (AE)‐doped lanthanum manganite perovskites, , under oxidizing atmospheres have been investigated. The average linear thermal expansion coefficients of the AE‐doped lanthanum manganites decreased with increasing Ca content up to 20 mol % and with increasing Sr content up to 10 mol %, and then increased. During the thermal cycle measurement, the perovskite samples and the perovskites (0 ≤ x ≤ 0.3) shrank, while no anomalous shrinkage behavior was observed for the samples. From the results of high‐temperature X‐ray diffraction analysis, no dependency of cell volume of the perovskites on aging time at selected temperatures and on thermal cycles was observed. © 2000 The Electrochemical Society. All rights reserved.

The performance of a polymer electrolyte fuel cell is critically dependent on the water uptake in the polymer electrolyte, usually Nafion. Nafion in solution is often painted onto the electrodes of the fuel cell. It is important that this cast Nafion film stay amorphous and not crystallize. Cast Nafion films, ca. 1 μm thick, crystallized on silicon plates when kept in air at room temperature for a long time. The films contain large crystalline regions ranging from 0.5 mm to several millimeters in size. X‐ray diffraction (XRD) and Fourier transform infrared (FTIR) microspectroscopy have been used to investigate the crystalline and amorphous regions. The XRD shows two sharp peaks. One of the peaks is developed before the second one appears in the diffractogram, indicating that there might be two types of crystallizing processes. FTIR spectra of the amorphous and crystalline regions in the films show important differences. In the crystalline regions, the film contains the sulfonic acid at the end of the side chains; hence, the crystalline regions contain no water molecules. In the amorphous regions there is a complete proton transfer from the acid to the water molecules, and sulfonate groups are obtained. © 2000 The Electrochemical Society. All rights reserved.

As an attempt to understand better how cobalt hydroxide additives improve the nickel electrode performance, the redox system has been investigated through electrochemical cycling starting from a commercial sample. A study of the influence of texture and morphology as well as cycling parameters was performed. For charge rates greater than C/5, relative to the amount of , the electrochemical oxidation was found to be a solid‐state process. This process led to a nonstoichiometric phase having a mosaic texture with enhanced electronic conductivity due to the presence of ions. For lower charge rates (C/100), the reaction rate is slower, and can dissolve in the electrolyte, leading to a less conductive phase having a stoichiometric composition (CoOOH) and a monolithic texture. When present, the ions are reduced to , at 1.05 V while other reductions and take place at a lower potential, 0.67 and 0.0 V, respectively. These two reactions are both associated with a dissolution of Co(II) species, followed by a migration of cobalt toward the current collector, with the overall result being an electrode degradation. © 2000 The Electrochemical Society. All rights reserved.

A study of the system at high potential has shown the successive formation of two phases with O3 (AB CA BC) and O1 (AB) oxygen packings, respectively, near the composition. For the phases with z ≥ 0.07, only the O3 packing is observed at the end of lithium deintercalation: the extra nickel ions present in the interslab spaces destabilize the O1 type packing. The nonhomogeneous distribution of extra nickel ions from one interslab space to another leads to the presence of stacking faults in both phases. Lithium can be reversibly reintercalated into the phase. Good stability is observed at low charge‐discharge rates during long‐term cycling of the system over a large potential range. This study also provided evidence for inhomogeneity in the starting material at the crystallite scale. The material corresponds to a mixture of various phases with very similar stoichiometries. The crystallites which are closest to the ideal stoichiometry form an O1 type phase which is stable at high potential, whereas those which are farthest from stoichiometry lead to an O1 type phase which is slowly transformed into a new phase, characterized by an O3 type packing, through a migration from the slab to the interslab space. © 2000 The Electrochemical Society. All rights reserved.

We report herein on the comparative study of and electrodes in three salt solutions, namely, , , and in a mixture of the commonly used ethylene and dimethyl carbonates. The surface chemistry of the electrodes in these solutions was studied by surface‐sensitive Fourier transform infrared spectroscopy. X‐ray photoelectron spectroscopy, and energy‐dispersive X‐ray analysis, and their electrochemical behavior was studied by variable‐scan‐rate voltammetry and impedance spectroscopy. It was found that the electrochemical behavior of these electrodes is strongly dependent on their surface chemistry. Complicated reactions between the active mass and solution components, which include the solvents, the salt anions, and unavoidable contaminants such as HF and perhaps, , lead to the precipitation of surface films through which the Li ion has to migrate in order to reach the active mass. The impedance spectroscopy of these electrodes clearly reflects their surface chemistry. It demonstrates the serial nature of the Li insertion‐deinsertion processes, which includes, in addition to solid‐state diffusion and accumulation, Li‐ion migration through surface films and their charge transfer across the surface film/active mass interface, which strongly depends on the chemical composition of the surface films and hence, the solution chosen. is considerably more reactive with these solutions than , probably due to its stronger nucleophilic nature. In addition, in solutions, the electrodes' impedance is higher due to precipitation of films comprising LiF, which is highly resistive to Li ion transport (probably produced by reactions of the active mass with trace HF). © 2000 The Electrochemical Society. All rights reserved.

Effects of small amounts of Fe doping for Ga site in oxide on oxide ion conductivity is investigated in this study. It is found that doping a small amount of Fe is effective for improving the oxide ion conductivity in (LSGM). The highest oxide ion conductivity was exhibited at x = 0.03 in among the Fe‐doped samples. Electron spin resonance (ESR) measurements suggest that Fe is trivalent in lattice. The application of the Fe‐doped oxide for the electrolyte of solid oxide fuel cell was further investigated. Power density of the solid oxide fuel cell was increased by using Fe‐doped LSGM for electrolyte. This can be explained by the decrease in electrical resistance loss by improving the oxide ion conductivity. A maximum power density close to was obtained at 1073 K on the cell using 0.5 mm thick (LSGMF) and as the electrolyte and the oxidant, respectively. Therefore, close to the theoretical open‐circuit potential was exhibited by the LSGMF cell. On the other hand, the power density was slightly smaller than that of the cell using Co‐doped LSGM as electrolyte, especially, at temperatures lower than 973 K. This may result from the large activation energy for ion conductivity. However, the power density of the LSGMF cell was higher than that of the LSGM cell. Therefore, LSGM doped with a small amount of Fe is a promising electrolyte similar to Co‐doped LSGM for the intermediate solid oxide fuel cell. © 2000 The Electrochemical Society. All rights reserved.

The performance of a single‐chamber solid‐oxide fuel cell (SOFC) made from an yttria‐stabilized zirconia solid electrolyte with a (GDC)‐containing Ni anode and a cathode was found to be significantly enhanced by the deposition of Mn, Ga, Cr, Ce, and Lu oxide layers on the YSZ surface. In particular, the deposition of the Mn oxide layer increased the maximum power density from 161 to in a mixture of methane and air having a volume ratio of methane to oxygen of 1/1 at a flow rate of (methane , oxygen , nitrogen ), and at an operating temperature of 950°C. This effect was the result of the promoted anodic and cathodic reactions. Two types of cell designs were examined for the single‐chamber SOFC; the two electrodes were deposited on opposite surfaces (A‐type cell) and on the same face (B‐type cell) of the solid electrolyte. The A‐type cell showed an increasing power density with decreasing thickness of the solid electrolyte. The maximum power density was at a solid electrolyte thickness of 0.3 mm. The B‐type cell showed an increased power density for a decreased gap between the two electrodes. The maximum power density was for a gap of 0.5 mm between the two electrodes. In addition, the long‐term stability of the single‐chamber SOFC was also studied and found to have a direct relationship with the carbon deposition on the GDC‐containing Ni electrode. © 2000 The Electrochemical Society. All rights reserved.

Ellipsometric measurements on anodic oxide films grown on niobium in phosphoric acid were found to show behavior characteristic of films consisting of two layers, but films grown in chloride solution showed the behavior typical of uniform films. It was concluded that as with tantalum, phosphate but not chloride ions are taken up in the outer part of the film, which grows by metal ion motion. The logarithm of the steady‐state current density was linear in the field in the oxide for films grown in chloride solution and nonlinear for films formed in phosphate solution. It is concluded that, as with tantalum, the nonlinearity for some electrolyte solutions is caused by incorporation of electrolyte species in the outer part of the films rather than being a fundamental feature of the ionic transport process. The small signal ac response of the ionic current density was studied for both electrolyte solutions. These measurements gave information on steady‐state and stepped field kinetics and on the distribution of relaxation times involved in the transients observed when the current or field is suddenly changed. The steady‐state and stepped field admittivities from the ac + dc measurements were normalized by the dielectric permittivities of the films grown in the different solutions. © 2000 The Electrochemical Society. All rights reserved.

The anodic dissolution of pure aluminum in pH 11 chloride media was investigated. Individual hemispherical corrosion pits were produced by a laser initiation technique, and electrochemical measurements were analyzed to determine the effect of diffusion and migration on single pit growth. Several mathematical models, which included both migration and diffusion as transport modes, were developed to interpret experimental results and to predict concentration profiles that resulted from dissolution based on the assumption of a hemispherical corrosion pit geometry. Model equations were solved by a quasi‐potential transformation technique. The results for a model that considered a simple case of three ionic species demonstrated that it was essential to include both migration and diffusion phenomena in the model, contrary to previous experimental studies that concluded that pit dissolution was controlled by diffusion only. The results of a more advanced model that included two hydrolysis reactions for aluminum predicted a pH (<3.5 in 90% of the computational domain) that was in good agreement with experimental data (pH 3–4). The addition of the hydrolysis reactions had no effect on the concentration profiles of the three species considered in the simple chemistry model. Models that included homogeneous reactions to test the hypothesis of formation of an aluminum oxychloride salt predicted a pH ≥ 5, and also that the concentration of the salt was significantly smaller than the estimated saturation concentration of 3 mol/L. © 2000 The Electrochemical Society. All rights reserved.

The critical solution composition required for sustained growth of hemispherical single corrosion pits on pure aluminum in basic sodium chloride solution was studied. Single corrosion pits were initiated by using a laser initiation technique. Electrochemical current interruption experiments were used to probe the effects of bulk solution concentration and potential on pit stability. A mathematical model was used to analyze the results from one type of current interruption experiment that investigated the effect of pit size on pit stability. The mathematical model extended the results of previous work (Part I, the previous article), which considered the profiles that develop during pit growth, to include transient behavior during the relaxation of the concentration profiles. The solution of the transient model was performed by first transforming the equations using the conformal mapping technique of Verbrugge et al. [Electrochim. Acta.38, 1649 (1993)]. Numerical results were compared with experimental data and were interpreted on the basis of the hypothesis that a critical concentration of an ionic species is required in the pit for stability. © 2000 The Electrochemical Society. All rights reserved.

Photoelectrochemical experiments have been carried out for characterizing passive films on Mo‐Ta sputtered alloys having different compositions, as well as on pure Mo and Ta metals. Both corrosion layers, formed by simple immersion in solution, and films grown anodically were investigated. The presence of Mo species in the passive layer anodically shifts the flatband potential with respect to pure films. For high Mo contents the films change their behavior from an insulating to n‐type semiconducting one. A variation in the optical bandgap occurs due to the change of the ratio into the passive films. Cross experiments, performed in different solutions on the same film, suggest that a loss of ions occurs at the oxide/electrolyte interface under anodic polarization. The influence of Mo content on the electronic properties of the passive films is invoked in order to explain its effect on the corrosion resistance of the different alloys. © 2000 The Electrochemical Society. All rights reserved.

The potential‐dependent breakdown of the native oxide film (∼20 Å thick) on titanium has been investigated in aqueous solutions and in solutions that contain a mixture of and anions that inhibit oxide breakdown (i.e., , , , , and . The oxide film is unstable in neutral pH solutions containing only , resulting in the formation of stable corrosion pits at relatively low potentials (∼1.4 V vs. Ag/AgCl). The pitting potential, , is strongly dependent upon the concentration of , and can be modeled using a Langmuir isotherm to describe the adsorption of at the oxide film/electrolyte interface. Addition of a second anion inhibits oxide film breakdown, as indicated by a large positive shift in and a decrease in the number of stable corrosion pits. The dependence of on the relative concentrations of and the inhibitor anion is consistent with competitive adsorption of the anions. Equilibrium adsorption coefficients for , , and are estimated from the dependence of on anion concentration. The results are used to establish a physical basis for the anomalously low pitting potential for titanium in aqueous solutions. © 2000 The Electrochemical Society. All rights reserved.

Anodic alumina films with cellular porous structure grow in neutral organic electrolytes with low water content and containing ethylene glycol and a large dicarboxylic acid. An Al carboxylate precipitates in the pore and is extruded from the coating. The porous structure develops even though the current efficiency for film formation is near 95%. The coating matrix contains substantial organic material, 15 wt % by thermal analysis. It is an oxide/organic composite with higher field strength and lower dielectric constant than pure anodic alumina. © 2000 The Electrochemical Society. All rights reserved.

Anodic coatings grown on aluminum in certain organic electrolytes have been studied by transmission electron microscopy examination of thin cross sections. The electrolytes have low water content and contain ethylene glycol as a solvent component and a dicarboxylate as solute. A cellular porous coating grows although aluminum is insoluble and oxide deposits with about 95% faradaic efficiency. Inner and outer layers in the oxide are easily distinguished, and it is found that the field strength of the outer layer is up to 50% higher than for conventional amorphous alumina due to a high concentration of incorporated organic species. The transition from barrier to porous growth occurs when cusps initiate at concavities that evolve from the initial metal surface texture. A cusp develops into a stable pore because the high field at this site causes Al ion ejection and the unusually small cation transport number in this oxide/organic composite is insufficient for oxide growth at the coating/electrolyte interface. © 2000 The Electrochemical Society. All rights reserved.

The structure of Ni(111) single‐crystal surfaces in (pH 3) has been investigated in situ by scanning tunneling microscopy after cathodic reduction and after passivation at potentials ranging from 0.45 to 1.15 V/SHE. The metallic surface has monoatomic and diatomic step edges and an unreconstructed Ni(111)‐(1 × 1) atomic lattice. The passivated surface has two different structures corresponding to the two chemical layers of the passive film. The hydroxide outer layer has a granular and amorphous structure. The lack of crystalline order is assigned to the incorporation of water molecules. Aging under polarization favors the hydration of this layer and the increase of the passivation potential favors its thickening. The oxide inner layer of the passive film has a crystalline structure with a stepped surface independent of the passivation potential. The average tilt angle between the terraces of the oxide layer and the substrate terraces is 3 ± 1°. The lattice parameters correspond to NiO(111) in parallel or antiparallel epitaxy with the substrate. The (111)‐(1 × 1) unreconstructed orientation of the oxide layer is stabilized by surface hydroxylation. The local orientation of the step edges of the oxide is assigned to its dissolution in the passive state. © 2000 The Electrochemical Society. All rights reserved.

The passive behavior of zinc in alkaline pH 13.0, 10.3, and 9.2 solutions, under dark and illumination conditions, has been studied using dc polarization and ac impedance techniques. It was found that illumination with polychromatic light caused dissolution of anodically formed passive layers on zinc, with this photoinduced dissolution effect being more pronounced in the more alkaline pH 13.0 solution. Photoinduced dissolution in the pH 10.3 and 9.2 solutions is explained in terms of the photodecomposition of ZnO through reaction with photogenerated holes. The more intense dissolution in the pH 13.0 solution is explained in terms of the photodecomposition of ZnO and the additional electrochemical dissolution in this alkaline solution which occurs as a result of the photodecomposition of the passive layer. Although the electrodes repassivated once the light source was removed, it was found that prior illumination led to a decrease in the donor densities and thus a modification of the defect structure of the passive layers. © 2000 The Electrochemical Society. All rights reserved.

The ratio of the photoionization cross section of the transition to that of the O 1s electrons is determined as 2.16 ± 0.02 for the Al Kα X‐ray excitation. Application of this value is limited to oxidic Mg. Based on the above ratio, the photoionization cross section ratio of the Mg 2p electrons to the O 1s electrons, σ(Mg 2p)/σ(O1s) was determined to be 0.147 ± 0.005, which can be used for quantitative X‐ray photoelectron spectroscopy analysis of both oxidic and metallic states of Mg. Using the σ(Mg 2p)/σ(O 1s) thus determined, the surface compositions and film thicknesses were quantitatively determined of (i) a pure magnesium specimen immediately after scratching in laboratory air at room temperature, (ii) a specimen scratched and then aged in air for a month, and (iii) a specimen immediately after scratching in cyclohexane. A clear correlation between the composition and the thickness of surface film is observed, i.e., thickness where [E] denotes molar composition of E. © 2000 The Electrochemical Society. All rights reserved.

An analytical solution for the metal resistance‐controlled plating current distribution on circular wafers is obtained for determining the conditions under which a uniform metal film can be electrodeposited on a resistive film. Results indicate that, when using conventional copper plating solutions, uniform films cannot be deposited on 500 Å thick barrier layers consisting of Ta (or more resistive metals) on 200 mm wafers, regardless of plating current density or the use of pulse reverse plating. Uniformity can be characterized by a dimensionless polarization parameter that reflects the influences of current density and physical and chemical properties. Of these properties, the only one that can be varied enough to allow Cu plating on a barrier film is the plating exchange current density, . By lowering the copper concentration and thus in the plating bath by one or two orders of magnitude below levels that are commonly employed, the terminal effect can be reduced to the point where a uniform conformal conduction layer can be electrodeposited. Subsequently, the bulk copper film can be plated at high rates. © 2000 The Electrochemical Society. All rights reserved.

A technique for laser direct writing of micron‐scale copper conductor lines from and on Si substrates using the laser enhanced electroless plating (LEEP) technique was developed. In this process a focused Ar ion laser beam was used to induce a temperature rise on Si substrate surfaces immersed in reactant solutions. Increasing the Si surface temperature enhances the reducing reaction and results in Cu deposition. Glucose and glycerol were used as reducing agents for copper sulfate and copper formate, respectively. Line geometries of 2–12 μm width by 0.25–1.2 μm thickness were achieved for scan rates of 0.1–0.8mm/s for , for example. The maximum deposition rate for the LEEP of Cu from on Si is 80 μm/s which is approximately five orders of magnitude faster than deposition rates produced by conventional electroless plating of Cu. The deposited copper films from have a minimum resistivity of 3.6 μΩ‐cm, approximately twice the resistivity of pure copper (1.68 μΩ‐cm). The resistivity of the Cu deposits shows strong pH dependence. The optimum resistivity for deposition from copper sulfate is produced at a pH level of approximately 13. Our experiments show that there is no significant etching of Si at pH values less than or equal to 13. To keep the copper ion in solution at high pH levels, ethylenediaminetetraacetic acid was added to the solution as a complexing agent. © 2000 The Electrochemical Society. All rights reserved.

Local deposition of copper on aluminum was attempted by the successive processes of anodizing, laser irradiation, and electroless plating. Aluminum specimens covered with anodic oxide films were immersed in , , and diluted NaOH solutions, and irradiated with a pulsed yttrium aluminum garnet (YAG) laser. The time variation in the rest potential of the specimens was followed during laser irradiation by a potentiometer, and the change of the surface composition by laser irradiation was examined by X‐ray photoelectron spectroscopy (XPS). After the laser irradiation, copper electroless plating was carried out in solutions with or without or thiourea. The rest potential measurements and XPS analysis suggested that Cu particles nucleate at the film‐removed area by laser irradiation in and solutions. A copper layer was obtained at the irradiated area by the subsequent electroless plating, and the copper nuclei acted as catalytic centers at the very initial stage in copper electroless plating. The effects of and thiourea concentration and the deposition temperature on the kinetics of copper deposition is also discussed. © 2000 The Electrochemical Society. All rights reserved.

The crystal size of nanocrystalline CdS and CdSe films, electrodeposited from dimethyl sulfoxide solutions containing a Cd salt and elemental S or Se, is shown to depend on the nature of the anion of the Cd salt. Relatively strongly adsorbing anions, such as chloride, result in a smaller nanocrystal size than relatively nonadsorbing anions such as perchlorate. This difference in nanocrystal size is explained by blocking (or capping) of the growing crystals by the adsorbed ions. Very strongly adsorbing species, such as alkyl phosphines, result in even smaller crystal size (3.5 nm average diameter). © 2000 The Electrochemical Society. All rights reserved.

A model is presented for predicting the preferential crystallographic orientation of chemical‐vapor‐deposited (CVD) films. This model incorporates the evolutionary selection model that the orientation occurs along the fastest growing plane. The model assumes that surface growth is a consecutive process of collision, adsorption, and reaction of a film growth species and considers that the atomic unit of a crystal is constructed from a single growth species. The model predicts that with increasing temperature many films change from amorphous, to an orientation along the plane packed most densely with the atomic unit, to an orientation along the plane of the fastest adsorption, and finally to a random orientation. The applicability of the model was successfully tested for CVD systems to form Cu, Al, Si, , and . © 2000 The Electrochemical Society. All rights reserved.

Density functional theory of bond dissociation energies of the metal‐ligand bonds, thermodynamic investigation of the stability of intermediate species, and experimental investigation of the composition of the gas phase by on‐line mass spectrometry have been performed in order to study the growth mechanisms and the carbon incorporation in nickel films during metallorganic chemical vapor deposition (MOCVD) of nickel from nickelocene. A model is proposed, according to which nickelocene molecules are adsorbed on the surface. Cyclopentadiene is formed from the reaction between two cyclopentadienyl ligands of neighboring molecules, while hydrogen‐deficient rings serve as starting species for carbon incorporation in the films via subsequent dehydrogenation. The hydrogen atoms available react with nickel cyclopentadienyl radicals to form hydrogenated intermediate species which are desorbed from the surface. This model is compatible with the data from the literature on the different steps of the decomposition process. © 2000 The Electrochemical Society. All rights reserved.

A sheet of carbon felt employed as an electrode exhibits characteristic voltammeteric waves for the electrolysis of solutions reflecting a three‐dimensional fiber structure of the electrode, in which the solutions both inside and outside the felt electrode undergo electrolysis. The electrolysis behavior can be characterized by three parameters: for the electrolysis of the outside solution, and l and for that of inside solution. expresses the effective outer surface area, and l and the average distance between the carbon fibers and the effective total surface area of the fibers constituting the felt electrode, respectively. It is shown that chronoamperometry provides a useful means of determining these parameter values. The value of , , (m is the mass of the felt electrode) is in the range of the reported values for the surface area per unit weight of carbon felts, and l is in fair agreement with the average distance between the fibers measured with an optical microscope. It is shown that and l are important parameters determining the rate of bulk electrolysis of a given volume of stirred solution, and that is a key parameter determining the magnitude of the current for biocatalyst‐assisted electrolysis. © 2000 The Electrochemical Society. All rights reserved.

Diffusion coefficients (D) of ferrocene in materials composed of the ambient temperature ionic liquids 1,2‐dimethyl, 3‐(1‐propyl) imidazolium tetrafluoroborate or 1‐ethyl‐3‐methylimidazolium tetrafluoroborate and hexafluoropropylene‐vinylidene fluoride copolymer were estimated using chronoamperometry. The values of D obtained with the composite materials based on ranged from to and depended on the composition and pretreatment of the composite material. The latter value is equal to the diffusion coefficient of ferrocene in liquid . The values obtained with the composite materials based on ranged from to and they are lower by a factor of more than four than that of ferrocene in liquid . © 2000 The Electrochemical Society. All rights reserved.

Differential surface stress measurements performed using the estance technique and simultaneous measurements of the differential capacitance provide experimental evidence for deviation of n‐tin oxide electrode's properties from the electrocapillary relationship that has the form of the classical Lippmann equation. The differential stress curves consist of two distinct regions. At positive potentials, where the electrical properties of n‐tin oxide electrode are consistent with the Mott‐Schottky model, the differential stress does not depend upon polarization and is insensitive to solution pH. In this region, the main contribution to the surface stress originates from the ordered dipole layer, which could include water molecules. In the negative potential range, where deviations from the Mott‐Schottky model occur, the differential stress curves exhibit nonmonotonic behavior and become pH sensitive. The similar behavior of differential surface stress and semiconductor electrode charge was observed in this potential range. © 2000 The Electrochemical Society. All rights reserved.

Electrochemical measurements in aqueous and aprotic media have been carried out on anatase single crystals with exposed (101) and (001) surfaces, respectively. Water reduction and photo‐oxidation take place at more negative potentials for the (001) surface than for the (101) surface. This can be rationalized in terms of a more negative flatband potential (by ca. 0.06 V) for the (001) face, which is due to dissociative chemisorption of water molecules on this surface. Lithium insertion is favored on the (001) surface, as evidenced by a higher standard rate constant for charge transfer and a higher chemical diffusion coefficient for insertion for the propagation along the c axis. This can be explained by a more open structure of the anatase lattice in this direction. © 2000 The Electrochemical Society. All rights reserved.

Silicon oxide films have been deposited with chemical vapor deposition from at low temperature below 400°C for the gate insulator of thin‐film transistors. The electrical properties of the bulk silicon oxide film and the interface were investigated as a function of process parameters such as deposition temperature and ratio using capacitance‐voltage and current‐voltage measurements. The breakdown strength increased and the leakage current decreased as the deposition temperature increased, but both were not significantly dependent on the ratio. The breakdown strength of the film deposited at 380°C was about 5 MV/cm. As the deposition temperature increased, the interface trap density at Si midgap was almost constant, but near and , which is the center, decreased. The interface trap density was lowest when the ratio was 0.35. It was confirmed that the deposition temperature influenced the electrical properties of the bulk oxide and the interface, but the ratio affected only the interface properties. © 2000 The Electrochemical Society. All rights reserved.

A new spin‐on‐glass (SOG) solution has been obtained by the hydrolysis of methyltriethoxysilane and dimethoxymethyl‐3,3,3‐trifluoropropylsilane. When the SOG film is cured at 360°C, it contains both trifluoropropyl and methyl groups and exhibits the dielectric constant of 3.0. Curing the SOG film at 450°C in nitrogen decomposes only the trifluoropropyl group. The resultant film shows the Brunauer‐Emmett‐Teller surface area of indicative of a porous structure. The thermal decomposition of the trifluoropropyl groups gives few silanol groups, showing hydrophobic property in spite of the porous structure. The dielectric constant of the film is reduced to 2.3 owing to the pores introduced into the methylsiloxane network. © 2000 The Electrochemical Society. All rights reserved.

High‐density plasma technology is becoming increasingly attractive for the deposition of dielectric films such as silicon nitride and silicon dioxide. In particular, inductively coupled plasma chemical vapor deposition (ICPCVD) offers a great advantage for low‐temperature processing over plasma‐enhanced chemical vapor deposition (PECVD) for a range of devices including compound semiconductors and magnetic heads. In this paper, the development of low temperature (<200°C) silicon nitride and silicon dioxide films utilizing ICP technology is discussed. The material properties of these films have been investigated as a function of ICP source power, radio‐frequency chuck power, chamber pressure, gas chemistry, and temperature. The ICPCVD films are compared to PECVD films in terms of wet etch rate, stress, and other film characteristics. Two different gas chemistries, and , were explored for the deposition of ICPCVD silicon nitride. The ICPCVD silicon dioxide films were prepared from . The wet etch rates of both silicon nitride and silicon dioxide films are significantly lower than films prepared by conventional PECVD. This implies that ICPCVD films prepared at these low temperatures are of higher quality. The advanced ICPCVD technology can also be used for efficient void‐free filling of high aspect ratio (3:1) sub‐micrometer trenches. © 2000 The Electrochemical Society. All rights reserved.

Tantalum‐chromium (Ta‐Cr) alloy films have been examined as contact materials for ferroelectric memories. Ta‐Cr films were prepared by dual‐source radio frequency (rf)‐magnetron sputtering and with a film composition that was varied by control of rf power applied to the targets. Three types of films were obtained by the controlling film composition. Films with no or low levels of added Cr had high resistivity and a β‐Ta structure. Films with intermediate levels of added Cr had high resistivity and an amorphous structure. Films with high levels of pure Cr had low resistivity and a bcc‐Cr structure. Amorphous Ta‐69%Cr and crystalline Ta‐74%Cr alloy films were highly stable despite changes in thermal and oxidation conditions, maintaining a constant resistivity even after annealing at 700°C in an oxygen atmosphere. The high oxidation resistance of these films has been attributed to the chromic scale surface barrier layer. © 2000 The Electrochemical Society. All rights reserved.

The initial stage of oxidation of amorphous hydrogenated silicon nitride (a‐SiN:H) films biased in ionic water at room temperature was studied. A stoichiometric and insulating a‐SiN:H film is oxidized chemically to form hydrogenated silicon oxynitride and has relatively low reactivity. A Si‐rich and semi‐insulating a‐SiN:H film reacts electrochemically; the anodic oxidation proceeds easily to form silicon oxide on the anode, and the precipitation reaction proceeds easily to form silicate or polymerized oxide on the cathode. The anodic oxidation and the cathodic precipitation reaction mechanisms of semi‐insulating a‐SiN:H are discussed briefly. © 2000 The Electrochemical Society. All rights reserved.

A new approach is presented to analyze trace metals in silicon nitride films, using analytical techniques currently used in the semiconductor industry. Sample preparation involves decomposition of the nitride matrix by exposure to moist hydrofluoric acid followed by a short heat‐treatment at 300°C and collection of metallic impurities by the droplet scanning method. Analysis for metals was performed by total reflection X‐ray fluorescence. Lower detection limits compare favorably with published values obtained with other approaches and techniques that necessitate much higher quantities of sample. In view of possible applications of silicon nitride as a high‐dielectric‐constant material, the analysis of silicon nitride films (1–200 nm) deposited by low‐pressure chemical vapor deposition reveals that the deposition process is the major source of metallic impurities in the films, in contrast with currently used silicon dioxide films where wafers are the major source of metallic impurities. © 2000 The Electrochemical Society. All rights reserved.

A transport‐based, three‐dimensional numerical modeling approach has been developed to simulate chemical mechanical polishing processes occurring in microelectronic materials processing. A unique aspect of this model is that the detailed morphology of the slurry flow domain between the wafer and polishing pad is approximated with a regularly updated sequence of geometries evenly positioned along the polishing orbit. Additionally, the modeling approach allows the use of any constitutive relationship for the rheological behavior of the polishing slurry. The local polishing rate is taken to be proportional to the local hydrodyanmic shear stress generated on the to‐be‐polished wafer surface. To illustrate the modeling approach, the development of planarity during polishing of a prototypical 3 × 3 array of square roughness elements was simulated. The rheology of the polishing medium was described as a power‐law fluid with a Newtonian plateau, which is appropriate for an aqueous slurry of colloidal silica. Two modes of pad‐to‐wafer tracking during polishing are discussed. Modeling results show good agreement with typical experimental data. © 2000 The Electrochemical Society. All rights reserved.

Although germanosilicates with and without boron and phosphorus dopants have been shown to planarize over steps at temperatures below 800°C, other properties of the films, such as water solubility, electrical conductivity, and mechanical stress, are also concerns with these materials. This study examines these film properties for undoped and boron‐ and/or phosphorus‐doped germanosilicate glasses deposited by plasma‐enhanced chemical vapor deposition. Water solubility resistance was improved for most film compositions after anneals in argon, steam, forming gas, or two‐step anneals in argon and steam or argon and forming gas. Electrical leakage and breakdown behavior was also found to improve in steam anneals and even further in two‐step argon‐steam anneals but leakage increased following forming gas anneals. Mechanical stress was found to generally increase in magnitude following argon anneals, but stress levels were reduced again to near as‐deposited values following a subsequent steam anneal. For the greatest improvement in properties, a two‐step anneal, first in argon and subsequently in steam, is recommended. © 2000 The Electrochemical Society. All rights reserved.

Transmission electron microscopy (TEM) combined with selective chemical etching was used to assess two‐dimensional dopant profiles in the metal‐oxide‐semiconductor field effect transistor (MOSFET) test structures with a gate length of ∼ 1 μm and real MOS devices with gate lengths of 500 and 80 nm. It is shown that the chemically delineated junction depth increases gradually with increasing implantation energy and dose. The TEM results show that crystallographic defects hamper the doping‐dependent etching process in the n‐type semiconductor. The lateral dopant profiles simulated by SUPREM IV are compared with TEM results calibrated by secondary ion mass spectroscopy. The delineation technique is effectively applied to characterize MOS devices. © 2000 The Electrochemical Society. All rights reserved.

Chemically treated Si(100) surfaces in an aqueous NaOH solution at 20°C have been studied using spectroscopic ellipsometry (SE) and ex situ atomic force microscopy (AFM). The SE data indicate that a surface native oxide can be etched very slowly by NaOH etching. When the native silicon oxide is partly etch‐removed, the resulting surface is very rough. This occurs because the solution does not etch surface native oxide rapidly, but attacks bulk silicon vigorously. The AFM image confirms a roughened surface of ∼5.5 nm rms. Just after the native oxide is etched away completely, the SE data yield the spectrum of a nearly flat surface, as also confirmed by the AFM observation. © 2000 The Electrochemical Society. All rights reserved.

The surface of sulfur (S)‐implanted gallium arsenide (GaAs) was covered with hydrogenated amorphous silicon (a‐Si:H) film and subsequently heated to 1000°C. Silicon amounts larger than the implanted dose of ions diffuse from the a‐Si:H film into GaAs during annealing. The GaAs had sheet carrier concentrations smaller than that of doped Si atoms. The carrier concentrations decreased with increasing time on cooling from the annealing temperature of 1000 to 50°C, whereas the S and Si atom concentrations were independent of the cooling time. © 2000 The Electrochemical Society. All rights reserved.

The main goal of this study is to examine the possibility of using detailed three‐dimensional simulations of transport of momentum, energy, and mass in horizontal single‐wafer epitaxial silicon reactors in conjunction with relatively simple kinetic models to describe the reactor's performance over the entire range of operating conditions. As the system is a widely used precursor for epitaxial silicon deposition in industrial applications, we have chosen to focus our model development on this system. In the development of the model we have considered the dependence of the gas properties on the gas composition as well as on the temperature. In addition, mass transport due to thermal diffusion has been considered. The accuracy of the simulation model has been examined by comparing the predicted silicon deposition rates and profiles in two commercial chemical vapor deposition (CVD) reactors with the experimentally measured values. A comparison of simulation and experimental results has indicated that a detailed transport model in conjunction with a Langmuir‐Hinshelwood type kinetic model for silicon deposition accurately describes the epitaxial silicon deposition rate and deposition profile. In turn, this lumped reaction kinetic model has been used for optimization of commercially available horizontal CVD reactors for epitaxial deposition of silicon. © 2000 The Electrochemical Society. All rights reserved.

We have investigated formation of on various grain sizes of polycrystalline Si (poly‐Si) with emphasis on its thermal stability. As the grain size of poly‐Si decreases, phase is formed at lower temperature because of the diffusion of Co atoms along grain boundaries of poly‐Si during the rapid thermal annealing process. The enhanced reaction of cobalt with silicon on small‐grain‐sized poly‐Si creates a rough interface, which becomes thermally unstable. formed on amorphous Si showed less thermal stability than that found on medium and large grain sized poly‐Si. © 2000 The Electrochemical Society. All rights reserved.

We use infrared absorption spectroscopy in the multiple internal reflection geometry to investigate in situ and in real‐time the chemical process at Si(100) surfaces that are immersed in a dilute solution of ammonium fluoride, . We have followed spectral changes in the Si‐H stretch vibration region of the surface during immersion in the solution. Infrared spectroscopic data show that the native oxide on the surface is initially removed by solution and subsequently, H‐terminated Si(111) microfacets are increasingly populated. Long‐term immersion in dilute leads to oxide formation on the surface. The rate of oxide formation strongly depends on the concentration of ; oxide formation is enhanced at concentrations below 10% and it does not occur at concentrations above 20%. We suggest that oxide formation and subsequent oxide removal proceed on Si surfaces in dilute solution and that at low concentration, the rate of oxide formation is higher than that of oxide removal. © 2000 The Electrochemical Society. All rights reserved.

Glass films of undoped and boron and phosphorus doped glass films were prepared by plasma enhanced chemical vapor deposition using germane, silane, phosphine, diborane, and oxygen as precursor gas sources with argon as a carrier gas. Film synthesis was carried out at 200°C using a dual‐coil, inductively coupled plasma system. The presence of silane was not necessary to catalyze the decomposition of germane in the plasma environment as required in a strictly thermal environment. The index of refraction of undoped films changes linearly with composition, and deposition rate was nearly constant across all film compositions. Oxide film composition was determined using energy dispersive X‐ray spectroscopy and Auger energy spectroscopy. For undoped films, solid‐phase composition varied linearly with silane gas‐phase composition. For doped compositions, phosphorus mole fraction in the solid phase was up to a factor of two greater than that present in the gas phase. In contrast to this, the quantity of boron incorporated into the solid phase was a factor of five to six less than present in the gas phase. When both dopants were present in the gas phase, the amount of each incorporated into the solid phase was similar to that in the gas phase. © 2000 The Electrochemical Society. All rights reserved.

The epitaxial wafer is expected to become the industry standard for super large‐diameter wafers over 300 mm. The demand for reductions in production cost along with stringent quality improvements are driving diameters upward. The super silicon project has developed an epitaxial process, for 400 mm epitaxial wafers, using gas at a low temperature just under 1000°C. This process promises to decrease contamination, to prevent slip generation, and to improve productivity. Since the epitaxial layer quality is tightly correlated with the growth process, we also characterized the microdefects and microroughness on the surface of epitaxial wafers that were grown with the process. Comparing the results of this experiment with those of a conventional process, we conclude that the process presents no problems when applied to super large‐diameter epitaxial wafer production. © 2000 The Electrochemical Society. All rights reserved.

Low‐resistance ohmic contacts to the Si‐doped were obtained using the W metallization schemes. It is shown that the specific contact resistances improve with increasing annealing temperature. The annealing of the contact at 950°C for 90 s results in a specific contact resistance of . X‐ray diffraction results show that a phase is formed at the interface between the W and InGaN when annealed at temperatures ≥500°C. Conduction mechanisms in the contacts are found to depend on annealing temperature. Possible explanations are given to describe the annealing temperature dependence of the specific contact resistance. © 2000 The Electrochemical Society. All rights reserved.

A new method for evaluating both surface recombination velocity and bulk minority carrier lifetime by photocurrent measurements was proposed and validated by comparison with capacitance‐voltage measurements of interface state density. This method is an evolution of the measurement of surface recombination velocity by the Elymat technique. It does not require the oxide to be etched off and consists of measurements of surface recombination velocity under an applied surface bias. The application of a surface bias allows the control of the interface potential and the identification of the suitable interface condition such that surface recombination velocity can be considered as a measurement of interface state density. In addition, it is shown that surface recombination velocity is suppressed when the surface is under accumulation conditions, so the application of a surface bias provides the possibility of a surface passivation by driving the surface into accumulation. This passivation by surface polarization is about as effective as the chemical passivation by HF. Finally, the dependence of surface recombination velocity on the injection level is shown to be reversed when the interface changes from depletion to accumulation or inversion conditions. © 2000 The Electrochemical Society. All rights reserved.

A mixed‐potential sensor was constructed and its response to reducing gases in an oxygen containing stream was measured at T = 550 and 600°C. The sensor response was maximum for and negligible for methane; other gases followed the trend methane < propane < CO, propylene < hydrogen. The mixed potentials developed at the Au and Pt electrodes were also independently monitored with respect to Pt air‐reference electrodes. The mixed potential at the Au electrode was always higher (more negative) than that at the Pt electrode irrespective of the type of reducing gas used. The polarization curves of the two electrodes during oxygen reduction were also measured. These measurements revealed that the mixed potential at the electrodes was dependent on both the amount of electrochemical oxidation of reducing gas and the overpotential for oxygen reduction. While the response of the Pt electrode was found to be stable at both 600 and 550°C, the Au electrode had stability problems at 600°C due to the changing morphology of the gold film. © 2000 The Electrochemical Society. All rights reserved.

A novel surface treatment of an sensor element using a thiourea solution has been developed. The surface treatment is accomplished by dipping the sensor element in the dilute thiourea solution for only a few seconds followed by calcination. The sensor element modified by this simple procedure shows remarkable improvements in the sensitivity and selectivity for CO detection over a certain thiourea concentration range. The long‐term transients of these gas‐sensing properties were also demonstrated for over 450 days. The results prove that the performance of the CO gas sensor is drastically stabilized by this surface modification, thus promising significant enhancement in the stability and reliability for CO gas alarm applications. © 2000 The Electrochemical Society. All rights reserved.

Response of steady‐state photoconductivity to changes in oxygen partial pressure ( to 1 atm) has been quantitatively studied in thin‐film polycrystalline and ZnO at 80–120°C. The magnitude of photoconductivity varied as a square root of illumination intensity regardless of oxygen pressure. Both materials showed fast response to oxygen, although in different pressure ranges. Zinc oxide was more sensitive to lower oxygen pressures while titanium dioxide worked better at pressures close to 1 atm. © 2000 The Electrochemical Society. All rights reserved.

In a study of the electrochromic properties of the system, the cyclic voltammograms accompanying the aqueous electrodeposition of the reduced bipyridilium "cyanophenylparaquat" gave traces specific to the particular anion involved in the deposition. This useful fingerprint is then used to identify which one of a pair of anions in a mixed‐electrolyte medium causes the electrodeposition from the mixture. These assignments allow the ranking of anion efficiencies, in a "dominance" sequence. Here it is shown that the mobility of an anion is the key to its success in deposition, and a diffusion‐based rate constant for initial nucleation is proposed, involving the ionic conductivities of the anions. This conclusion is applicable to singly charged species, the necessarily slower multistep mechanisms required for 2‐ and 4‐ charge anions being deemed responsible for the lower effectiveness of these reactants. © 2000 The Electrochemical Society. All rights reserved.

In this paper, we present the first report characterizing the cathodoluminescent properties of . Firing the precursor powder at 1300°C for 8 h gives a luminescence efficiency of 2.8 lm/W at 2 kV and 4.8 lm/W at 5 kV. The emission peak of this phosphor is located at ∼630 nm and the Commission International del'Eclairage coordinates are x = 0.63, y = 0.35. The optical properties of phosphor under UV or electron‐beam excitation is investigated and the suitability for the application of field emission displays is discussed. © 2000 The Electrochemical Society. All rights reserved.

phosphor particles of spherical and filled morphology were prepared by spray pyrolysis. Morphology control phosphor particles in spray pyrolysis was attempted by using colloidal and aqueous solutions. The particles prepared from colloidal solutions containing small amounts of gadolinium hydroxy carbonate sol as seed material had a filled morphology before and after the post treatment; whereas the particles prepared from aqueous solutions were hollow and the structure was broken after post treatment at 1200°C. The particles prepared from colloidal seed solution with 250 nm sol had a spherical and filled morphology with a clean surface; the particles prepared from colloidal seed solution with 70 nm sol had a collapsed spherical shape. The particles prepared from colloidal and aqueous solutions had similar photoluminescent intensities. © 2000 The Electrochemical Society. All rights reserved.

The influence of process induced defects on the surface quality of wet anisotropically etched cavities in silicon wafers is investigated. Localized thinning of silicon substrates using cavities of this kind is a common method for fabricating, e.g., diaphragms for silicon pressure sensors. Wafers with four different concentrations of interstitial oxygen varying from to were exposed to a thermally simulated complementary metal oxide semiconductor process and subsequently anisotropically etched with potassium hydroxide or tetramethylammonium hydroxide solution. Crystal defects caused by oxygen precipitation, such as stacking faults, punching systems, and dislocations, were found to be the origin of large craterlike defects in the sidewalls of the cavities. Wafer material with an initial concentration of interstitial oxygen between and exhibits a very low density of small precipitate‐dislocation complexes and, thus, etched cavities of good surface quality are obtained. In wafers with interstitial oxygen concentrations higher than bulk stacking faults were observed and the surface quality of the cavity sidewalls diminishes. The microscopic morphology of the craterlike defects in the {111} sidewalls of the etched cavities is explained using a computer simulation of the etching process. An influence of process induced defects on the surface quality of wet anisotropically etched {100} surfaces was not found. © 2000 The Electrochemical Society. All rights reserved.

Fine‐particle red phosphor (∼1 μm) with spherical shapes was synthesized from a submicron‐size yttrium (europium) oxide, obtained by controlled hydrolysis of yttrium alkoxide‐europium chloride, employing sodium thiosulfate as a sulfurizing agent. Various preparative parameters, such as activator concentration, firing temperature, and duration, were optimized for the maximum luminance at low‐voltage excitation (<1000 V), and the best phosphor was compared with a commercial phosphor. The best phosphor with an improved luminance can be obtained for the phosphor prepared at 1000°C for 6 h and doped with 4 mol % europium. The fine‐grained phosphor showed increased luminance at low current densities and decreased luminance at high current densities. The improvement in luminance is attributed to the small particle size of the phosphors and uniform distribution of the activator. Synthesized phosphors were analyzed using X‐ray diffraction and scanning electron microscopy to interpret the observed luminescent properties. © 2000 The Electrochemical Society. All rights reserved.

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