Showing papers in "Journal of The Electrochemical Society in 1986"
TL;DR: In this article, a low temperature thermal cleaning method for Si molecular beam epitaxy (MBE) is proposed, which consists of wet chemical treatment to eliminate carbon contaminants on Si substrates, thin oxide film formation to protect the clean Si surface from contamination during processing before MBE growth, and desorption of the thin oxide films under UHV.
Abstract: A low temperature thermal cleaning method for Si molecular beam epitaxy (MBE) is proposed. This method consists of wet chemical treatment to eliminate carbon contaminants on Si substrates, thin oxide film formation to protect the clean Si surface from contamination during processing before MBE growth, and desorption of the thin oxide film under UHV. The passivative oxide can be removed at temperatures below 800°C. It is confirmed that Si epitaxial growth can take place on substrates cleaned by this method and that high quality Si layers with dislocations of fewer than 100/cm2 and high mobility comparable to good bulk materials are formed. Surface cleanliness, the nature of thin passivative oxide films, and cleaning processes are also studied by using such surface analytic methods as Auger electron spectroscopy, reflection high energy electron diffraction, and x‐ray photoelectron spectroscopy.
1,346 citations
TL;DR: In this article, a laboratory-scale cell was constructed to test the performance of V(II)/V(III) and V(IV/V(V) half-cells in an all-vanadium redox battery.
Abstract: A laboratory-scale cell was constructed to test the performance of V(II)/V(III) and V(IV)/V(V) half-cells in an all-vanadium redox battery. Graphite plates were used as electrodes, and the membrane was manufactured from a sulfonated polyehylene anion-selective material. The average charging efficiency of the cell was over 90 percent. Stability tests on the reduced and oxidized electrolytes, measured over the temperature range of -5 C to 60 C, showed no accelerated decomposition at high temperatures and no crystallization at the lower temperatures. After prolonged usage, however, a slow deterioration of the positive electrode and the membrane was observed. 9 references.
718 citations
TL;DR: In this paper, the activation energy of ion transport is independent of the anion, and remains mainly constant at 0.7 eV over the concentration range studied for the ion pair formation.
Abstract: systems have been characterized by x‐ray diffraction and optical microscopy, and the resulting phase diagrams are taken into account for the interpretation of ac impedance measurements. Eutectic reactions and multiple‐intermediate‐compound formation are characteristic of most systems. Simple phenomenological models do not explain the overall conductivity behavior. The activation energy of ion transport is independent of the anion, and remains mainly constant at 0.7 eV over the concentration range studied for . Ion‐pair formation seems to occur at low salt concentration.
408 citations
TL;DR: In this article, it was found that anions are formed in the solid state along with, which together are responsible for producing, in, a bipolar film consisting of a cation selective outer layer containing and and an intrinsically anion selective inner layer.
Abstract: The passive films formed on the surface of and alloys in have been characterized by AES and variable angle XPS. It is found that additions of Mo to results in the formation of a passive film with a more highly developed interfacial barrier film composed mainly of , containing in solid solution which forms a glassy phase. In addition, the passive films were found to contain more Fe. Molybdenum appears to be present as Mo4+ and Mo6+ identified as hydrated and , apparently as . It is proposed that anions are formed in the solid state along with , which together are responsible for producing, in , a bipolar film consisting of a cation selective outer layer containing and and an intrinsically anion selective inner layer. The ion selective property of this duplex film is considered to be largely responsible for the development of the barrier layer and resisting Cl− and OH− ingress. Both of these properties provide greater resistance to break down of passivity in Cl− ion media.
365 citations
TL;DR: In this article, the electrochemical properties of binary and ternary lithium alloys in propylene carbonate have been studied and the potentials and partial molar entropies for the alloys have been determined.
Abstract: In an attempt to overcome problems associated with the reversible lithium electrode in organic solvent-based electrolytes, the electrochemical characteristics of a number of binary and ternary lithium alloys in propylene carbonate have been studied. Thermodynamic and kinetic results for the Li-Sn, Li-Sb, and Li-Bi systems are reported here. In each of these systems, one or more two-phase regions with apparently rapid transformation kinetics at ambient temperature have been identified. Lithium chemical potentials and partial molar entropies for the alloys have been determined. Constant current charge-discharge characteristics and diffusion coefficient data have also been obtained.
340 citations
TL;DR: In this paper, the formation and the dynamics of a thin oxidation layer that forms at the surface of the electrode in the presence of an acid electrolyte were studied using light reflection techniques and ESCA.
Abstract: Monocrystalline n-FeS2 (pyrite, Eg = 0.95 eV) photoelectrodes with high photocurrent quantum efficiency (> 90%) have been obtained by improvement of the solid-state and interfacial chemistry. During intensive illumination (4-5 W/cm2), photocurrent densities between 1 and 2 A/cm -~ have been observed for single crystals with high electron mobility (/x = 180 cm2-(V-s) -') in presence of the I-/I3- redox couple. Under illumination, a charge of 623.000 C/cm 2 was passed without evidence of photocorrosion. The influence of etching treatments, various redox systems, and organic electro- lytes on the photochemistry of FeS2 was investigated. The formation and the dynamics of a thin oxidation layer that forms at the surface of the electrode in the presence of an acid electrolyte were studied using light reflection techniques and ESCA. FeS2 has a valence energy band with strong d-characterlike Mo- and W-dichalcogenides, that is significant for its stabilization. An unresolved problem with this photoelectrode concerning applications in solar cells is the small photopotential which up to now does not exceed 200 mV (500 mV is theoretically possible). A strong pinning of the Fermi level by surface states is evident from photoelectrochemical measurements. In addition, it is expected that the distance between the conduction band and the Fermi level in our sample will be too large. A low effective carrier den- sity (n = 0.7 x 10 '5 cm -3) was measured, resulting in an extended space-charge layer, which has to be compared with the high absorption coefficient (~ > 6.0 x 10 ~ cm-' for h~ > 1.3 eV). Recently we have shown that FeS~ (pyrite) can be used as a photoactive material for photoelectrochemical and photovoltaic solar cells (1). Several reasons justify the de- velopment, of this material: the semiconductor material consists of cheap, abundant, nontoxic elements. The en- ergy gap of approximately 0.9 eV is sufficient for solar energy applications. The absorption constant was deter- mined to be ~ > 6.0 x 105 cm-' for hv > 1.3 eV, which makes the use of pyrite in thin layer cells attractive (2). Electron mobilities as high as 230 cm~-(V-s) -' have been measured (3). Very important for photoelectrochemical applications is the high contribution of d-states to the val- ence energy band. Therefore, pyrite promises to become similarly favorable as Mo- and W-dichalcogenides in terms of corrosion stability (4, 5). However, the disadvan- tage of a two-dimensional structure, which poses prob- lems in the preparation of photosensitive material (6), can be avoided. FeS2 has the same crystalline and an electronic struc- ture similar to RuS2, which is an efficient and stable photoelectrode for oxygen and chlorine evolution in aqueous electrolytes (7, 8). Pyrite does not evolve oxygen from water under illumination, due to the different coordination chemistry of Fe as compared to Ru. Iron cannot reach high oxidation states or form peroxo- com- plexes with oxygen, which consequently will be trans- fered to sulfur, which forms water-soluble sulfate ions (9). Several authors have studied solid-state properties of pyrite, using both natural and synthetic samples (10-15). A number of publications have also appeared on the electro- chemistry of pyrite (16-20). They all deal with the electro- chemical behavior of natural pyrite obtained in the dark. A larger review was published on the aqueous oxidation of pyrite by molecular oxygen (21). In only one publica- tion from our laboratory small photoeffects were reported Downloaded on 2013-11-04 to IP 134.30.100.205 address. Redistribution subject to ECS license or copyright; see in an electrochemical setup (9). We ecsdl.org/site/terms_usepresent here the first €
313 citations
TL;DR: In this paper, the authors measured the flux of cuprous and cupric species from the disk and determined the dependence of disk and ring currents on H+ and Cl− and on rotating rate.
Abstract: Ring‐disk electrode studies of anodic polarization of Cu in acidic chloride solutions indicate four distinct potential regions: the apparent Tafel region, the peak current and current minimum region, the limiting current region, and potentials above the limiting current region. Ring currents measured the flux of cuprous and cupric species from the disk. Dependence of disk and ring currents on H+ and Cl− and on rotating rate has been determined. Models are proposed to describe Cu electrodissolution in the apparent Tafel region and the potential region above the limiting currents. The results indicate mixed mass‐transfer and kinetic control with cuprous chloride complex as the limiting diffusion species in the apparent Tafel region. At potentials above the limiting current region, there is simultaneous mass‐transfer control of the cuprous chloride complex and kinetic control of Cu++ formation via the reaction, . Within the peak current and current minimum region and the limiting current region, Cu electrodissolution by mass transport is controlled in accord with previous work.
303 citations
TL;DR: The nature of passive films formed on 304 stainless steel at + 0.25V (vs. SCE) in deaerated solutions of and has been determined by RHEED and variable angle XPS.
Abstract: The nature of passive films formed on 304 stainless steel at +0.25V (vs. SCE) in deaerated solutions of and has been determined by RHEED and variable angle XPS. Evidence is given of and Cl− incorporation into the outer Fe‐rich regions of the passive film. In addition to Cr3+ species which make up the inner layer of the film, and have been observed by XPS. The mechanism of formation of the Cr6+ species in the solid state and the influence of the incorporated anions on the passivation process are discussed. Evidence of a bipolar mechanism operating in the passive films formed on stainless steel is discussed.
272 citations
TL;DR: In this paper, a mathematical model of coupled gas-phase chemical kinetics and fluid mechanics in a chemical vapor deposition (CVD) reactor is presented. But the model is limited to the case of silicon from silane.
Abstract: We describe a mathematical model of the coupled gas‐phase chemical kinetics and fluid mechanics in a chemical vapor deposition (CVD) reactor. This paper presents refinements to our earlier model of the CVD of silicon from silane. The model predicts gas‐phase temperature and velocity fields, concentration fields for seventeen chemical species, and deposition rates. The major new features are a multicomponent transport model including thermal diffusion and a new formulation of the boundary conditions that describe deposition. A significant result is that thermal diffusion is predicted to make an important contribution to species density profiles and generally to reduce deposition rates.
252 citations
TL;DR: A series of four catalysts with 5, 10, 20, and 30 weight percent of Pt on carbon has been prepared and incorporated into Teflon-bonded electrodes The mean Pt crystallite sizes, as determined by chemisorption, were less than 1, 11, 14 and 41 nm as mentioned in this paper.
Abstract: A series of four catalysts with 5, 10, 20, and 30 weight percent of Pt on carbon has been prepared and incorporated into Teflon‐bonded electrodes The mean Pt crystallite sizes, as determined by chemisorption, were less than 1, 11, 14, and 41 nm Also, a Teflon‐bonded Pt‐black electrocatalyst with a Pt crystallite size of 12 nm was prepared These electrodes were used for the cathodic reduction of dioxygen in at 298 K The turnover frequency decreased by a factor of 20 with decreasing particle size Since surface area per weight of metal increases as particle size decreases, the optimum Pt crystallite diameter is about 3 nm
242 citations
TL;DR: In this article, the capacite electrique semble etre independante des conditions de synthese du polymere, voltammetrie cyclique, impedance, and chronopotentiometriques cyclique.
Abstract: Etude par voltammetrie cyclique, impedance et chronopotentiometrie cyclique. La capacite electrique semble etre independante des conditions de synthese du polymere
TL;DR: In this article, the characteristics of electrochemically produced polyaniline as the active material of secondary batteries were studied in aqueous electrolytes, and a cell of the type,, has the maximum capacity of 108 Ah/kg and the energy density of 111 Wh/kg.
Abstract: The characteristics of electrochemically produced polyaniline as the active material of secondary batteries were studied in aqueous electrolytes. The cell of the type, , has the maximum capacity of 108 Ah/kg and the energy density of 111 Wh/kg. The coulombic efficiency was close to 100% over at least 2000 complete cycles when cycled between 1.35V and 0.75V at a constant current of 1 mA cm−2. The cell, where polyaniline was used as the anode, also showed excellent recyclability. The effect of oxygen and of the exposure to high anodic potential to the characteristics of polyaniline electrodes was also studied.
TL;DR: Le taux d'eau contenu dans la membrane Nafion diminue un peu la solubilite des gaz et augmente fortement leur diffusivite.
Abstract: Le taux d'eau contenu dans la membrane Nafion diminue un peu la solubilite des gaz et augmente fortement leur diffusivite. Le depot de palladium metallique dans la membrane diminue fortement la diffusivite, qui presente une valeur similaire a celle observee dans le cas du palladium
TL;DR: In situ Raman spectroscopy and cyclic voltammetry have been used simultaneously to study anodic film growth and dissolution on Cu and Ag in strongly alkaline solution as mentioned in this paper.
Abstract: In situ Raman spectroscopy and cyclic voltammetry have been used simultaneously to study anodic film growth and dissolution on Cu and Ag in strongly alkaline solution. On copper, Cu/sub 2/O and another species, believed to be a hydroxide, were detected spectroscopically during anodic film formation. Raman spectra of electrochemically formed hydroxides on copper have not previously been reported. On silver, AgO was detected. Neither CuO nor Ag/sub 2/O was observed by Raman spectroscopy, although for certain potentials. AgO was apparently produced by photochemical conversion of Ag/sub 2/O. Experiments were performed using both the 488 nm line from an argon laser and the 647.1 nm line from a krypton laser. It was concluded that the detection of these thin film oxides was by spontaneous or resonant Raman scattering and did not involve surface enhanced Raman scattering (SERS).
TL;DR: In this paper, the Kramers-Kronig transforms are applied to analyze electrochemical impedance data with respect to spurious errors that are present in either the real or imaginary component.
Abstract: Algorithms have been developed to apply the Kramers-Kronig transforms in the analysis of experimental electrochemical impedance data. The application of these algorithms is illustrated by transforming calculated impedance data for an electrical equivalent circuit, by transforming experimental data for TiO/sub 2-/coated carbon steel in HCl/KCl solution at 25/sup 0/C, and by analyzing data for an aluminum alloy in 4M KOH at 60/sup 0/C. These transforms, coupled with statistical techniques, provide a powerful means of evaluating the validity of impedance data with respect to spurious errors that are present in either the real or imaginary component, and with respect to system stability.
TL;DR: In this article, the authors used chronocoulometry to study the physical adsorption of neutral organic molecules on solid electrodes and determined the film pressure and the Gibbs surface excess for this system as functions of potential from charge densities obtained by the analysis of potentiostatic transients.
Abstract: Chronocoulometry recorded during the first 100 ms of double layer charging has been used to study the physical adsorption of neutral organic molecules on solid electrodes. The adsorption of cyclohexanol on gold is used to illustrate the method. The film pressure and the Gibbs surface excess for this system are determined as functions of potential from charge densities obtained by the analysis of the potentiostatic transients. Charge densities determined by chronocoulometry are compared with results obtained from the integration of differential capacities, which were independently measured at 25 Hz. Film pressures determined from these differential capacity measurements are shown to be unrealistically low and inconsistent with changes in bulk cyclohexanol concentration. In contrast, chronocoulometry gives consistent results and allows the determination of results that are comparable to those obtained on mercury.
TL;DR: In this article, a simplified physical model of inhomogeneous aluminum oxide layers, including the formation of passive and active pits, was developed in order to explain experimental impedance data of technical samples prepared under different formation and sealing conditions.
Abstract: A simplified physical model of inhomogeneous aluminum oxide layers, including the formation of passive and active pits is developed in order to explain experimental impedance data of technical samples prepared under different formation and sealing conditions. Moreover, aging and corrosion effects after long time exposure in different climate are studied and compared with model simulations and experiments under artificial corrosion conditions.
TL;DR: Methode pour forcer les polymeres conducteurs a adopter une morphologie fibrillaire, macroporeuse, is described in this paper.
Abstract: Methode pour forcer les polymeres conducteurs a adopter une morphologie fibrillaire, macroporeuse
TL;DR: In this paper, the design of radiation sensitive polymeric imaging systems is reviewed, and the design principles leading to amplification and examples of systems that demonstrate amplification are presented, as well as some examples of such systems.
Abstract: In this paper the design of radiation sensitive polymeric imaging systems is reviewed. Advances in design have led to systems that function on the basis of radiation‐induced changes in the polarity of polymer repeating units rather than cross‐linking. These new systems offer improved resolution, since they do not swell during development. Improvement in sensitivity has been achieved by designing systems that incorporate chemical amplification. The design principles leading to amplification and examples of systems that demonstrate amplification are presented.
TL;DR: In this article, the electrochemical oxidation of phenol was studied using a packed bed reactor of pellets with recirculating anolyte in order to follow phenol loss and benzoquinone, maleic acid, and carbon dioxide formation.
Abstract: The electrochemical oxidation of phenol was studied using a packed bed reactor of pellets with recirculating anolyte in order to follow phenol loss and benzoquinone, maleic acid, and carbon dioxide formation. A carbon mass balance revealed a significant fraction of additional by‐products for initial phenol concentrations of ≥ 0.014M. Benzoquinone and carbon dioxide formation were measured as a function of applied current, initial phenol concentration, electrolyte acid concentration, temperature, and dissolved oxygen. Benzoquinone formation was favored by high current and acid concentration and by low phenol concentration, temperature, and dissolved oxygen at relatively short electrolysis times. Carbon dioxide formation depended on the degree of the oxidation and was favored by high current, acid concentration, temperature, dissolved oxygen, and by low phenol concentration.
TL;DR: Methode electrochimique pour produire des films flexibles de copolymere a partir de Nafion ioniquement conducteur and de polypyrrole as mentioned in this paper.
Abstract: Methode electrochimique pour produire des films flexibles de copolymere a partir de Nafion ioniquement conducteur et de polypyrrole
TL;DR: In this paper, a reduction de l'oxygene sur le fer pur, fait intervenir 4e − avec formation de peroxyde d'hydrogene en tant que produit intermediaire, and d'un radical superoxyde determinant la vitesse.
Abstract: La reduction de l'oxygene sur le fer pur, fait intervenir 4e − avec formation de peroxyde d'hydrogene en tant que produit intermediaire, et d'un radical superoxyde dans l'etape determinant la vitesse. Dans le cas du fer passif, la reduction d'O 2 fait intervenir 2e − et la formation de H 2 O 2 en tant que produit final
TL;DR: In this paper, the zinc-nickel deposition process has been characterized through evaluation of partial currents due to alloy components and the current efficiency of alloy deposition, and the design of multiple layered zinc-nikkel alloy films for the protection of steel is discussed on the basis of the accelerated corrosion behavior of the γ-phase and the equilibrium potentials of the phases.
Abstract: Potentiodynamic and galvanostatic stripping techniques have been applied towards the characterization of zinc‐nickel alloy deposition process and product. The current‐potential relations required to recover the equilibrium and kinetic properties of alloys have been obtained for the eutectic, solid solution, and intermediate phase types of alloys. The galvanostatic stripping response shows a series of plateau regions, and the potentiodynamic response reveals a peak structure. These stripping responses have been employed to determine the chemical and phase compositions of electro‐deposited zinc‐nickel alloys, evaluate their corrosion resistance, and estimate the equilibrium potentials of various zinc‐nickel phases (α, γ, and η‐phases). The zinc‐nickel deposition process has been characterized through evaluation of partial currents due to alloy components and the current efficiency of alloy deposition. The design of multiple layered zinc‐nickel alloy films for the protection of steel is discussed on the basis of the accelerated corrosion behavior of the γ‐phase and the equilibrium potentials of the phases.
Abstract: Spectroelectrochemical studies have been perfomed on anodic oxidation of copper in using a near normal incidence reflectance spectroelectrochemical (NNMRS) technique, and the results are reported. The results indicate that the anodic oxidation product film formed on the electrode surface can be identified and that their chemical transformations can be followed by recording spectra in situ. It is shown by this technique that hydroxides of Cu(I) and Cu(II) are first formed by anodic oxidation at corresponding potentials, and they transform to oxides upon aging.
TL;DR: In this article, a self-aligned layer formed on polysilicon was found to be electrically stable up to 900°C and the junction leakage and contact resistance to increase.
Abstract: Since is perhaps the most attractive candidate for the self‐aligned silicide technology, it is important to understand the high temperature process limitations of this material. Thin films are formed on single‐crystal silicon, or polysilicon, and, when annealed in He or at temperatures of 900°C or higher, result in degradation of surface morphology and a drastic increase in sheet resistance. Eventually, isolated agglomerates are formed on the surface in case of He annealing. In the case of nitrogen annealing, they are covered with . Shallow junctions with a thin self‐aligned layer formed on top were electrically stable up to 900°C. Heat‐treatment beyond this temperature caused both the junction leakage and the contact resistance to increase. In addition to agglomeration, when thin films were formed on polysilicon, mixing of into polysilicon at temperatures beyond 850°C was observed. In the case of MOS devices, this degrades gate integrity.
TL;DR: In this paper, the anodic oxide film is primarily composed of an anatase type of, and the relation between the Raman band intensity, film thickness, and surface morphology indicates that the film changes from the amorphous state to the crystalline state beyond a certain critical potential.
Abstract: Laser Raman spectroscopy has been applied under in situ and ex situ conditions to the anodic oxide films formed on titanium at various potentials in neutral phosphate and acidic sulfate solutions. The Raman spectra reveal that the anodic oxide film is primarily composed of an anatase type of . From the relation between the Raman band intensity, film thickness, and surface morphology, it is likely that the film changes from the amorphous state to the crystalline state beyond a certain critical potential.
TL;DR: In this article, it is shown that the geometrical arrangement of chromium atoms in the lattice is important for passivation, independent of other factors, and that the degree of connectivity of Cr atoms through the three-dimensional (3D) lattice, described by percolation theory, characteristically shows a sharp threshold (p/sub c/) which represents the concentration of occupied sites (or bonds) at which a connected cluster of ''infinite'' extent suddenly appears.
Abstract: It is well-known that Fe-Cr, Ni-Cr, and Fe-ni-cr alloys require about 12 at.% chromium to become ''stainless.'' The transition around 12% Cr is quite abrupt, especially when expressed as the change in passivation potential (E/sub p/). The occurrence of this transitional behavior is insensitive to alloy composition (apart from Cr) and is probably almost independent of temperature. This suggests that the geometrical arrangement of Cr atoms in the lattice is important for passivation, independent of other factors. The most important geometrical consideration in this problem is the degree of connectivity of Cr atoms through the three-dimensional (3D) lattice, ;which is described by percolation theory. Percolation processes characteristically show a sharp threshold (p/sub c/) which represents the concentration of occupied sites (or bonds) at which a connected cluster of ''infinite'' extent suddenly appears.
TL;DR: In this article, la possibilite d'utiliser la methode d'impedance en courant alternatif sur l'exemple d'etude du systeme Ru(bpy) 3 2+/3+, en tant que couple redox, avec bpy=bipyridine−2,2', incorpore dans le film de Nafion sur l 'electrode de Pt
Abstract: Donnees sur la possibilite d'utiliser la methode d'impedance en courant alternatif sur l'exemple d'etude du systeme Ru(bpy) 3 2+/3+ , en tant que couple redox, avec bpy=bipyridine−2,2', incorpore dans le film de Nafion sur l'electrode de Pt
TL;DR: In this article, photoelectrochemical investigations were performed with passivated titanium electrodes and the results of photocurrent spectra and the potential dependence of the photocurrent suggest a distinction of four different types of film behavior depending on the thickness of the passive film.
Abstract: Photoelectrochemical investigations were performed with passivated titanium electrodes. Passive films were formed in at constant potential, , with being varied between 4 and 105V. The results of photocurrent spectra and the potential dependence of the photocurrent suggest a distinction of four different types of film behavior depending on the thickness of the passive film. The most important changes in photoelectrochemical data occur below . An amorphous‐crystalline transition of the passive film can be assumed. This is inferred from the change of the optical transitions with thickness and the potential dependence of the photocurrent which seems to obey the Poole‐Frenkel effect for thinner films. The changes observed with thicker films can be related to an increasing long range order in the passive film. The results demonstrate that photoelectrochemistry is a suitable in situ technique for determining important properties of passive films including structurally related ones.