Table of contents

In order to carry out in situ mass measurements in well‐defined flowing electrolyte conditions, an electrochemical quartz microbalance was adapted to a submerged impinging jet cell. The performance of this new device is illustrated by an in situ cathodic efficiency evaluation of the nickel electrodeposition.

Composite cathodes for lithium‐ion rocking‐chair cells have been fabricated based on which was synthesized by a new solution route that may be carried out in air. These cathodes have been cycled in three‐electrode cells at discharge and charging current densities of 1 and 0.5 mA cm⁻², respectively (corresponding to a discharge rate of C/2), between limits of 4.4 and 3.3 V. The specific discharge capacity obtained initially is 110 mAhg⁻¹ of active material decreasing by only 25 mAhg⁻¹ to yield a capacity of 85 mAhg⁻¹ at 300 cycles. This performance is very promising in the context of developing rechargeable lithium‐ion batteries using lithium manganese oxide‐based positive electrodes.

The electrochemical deposition of lithium on an Ni substrate was conducted in propylene carbonate (PC) containing 1.0 mol dm⁻³. The morphology of the lithium deposited on the Ni substrate had the typical dendrite form. The electrodeposition of lithium was then performed in containing . The lithium deposited on the Ni substrate in this electrolyte had a hemispherical form, and irregular shapes were not observed. The color of the Ni electrode surface turned to brilliant blue during the electrodeposition of lithium. This indicates that the lithium surface is very smooth and uniform. After five discharge and charge cycles, there were no lithium dendrites on the electrode surface. From these results, it can be concluded that the addition of a small amount of to the electrolyte is significantly effective for the suppression to the lithium dendrite formation.

A new ion‐selective membrane composition for ion sensors based on aliphatic urethane diacrylate oligomer is presented. The membrane can be deposited and photolithographically structured on a wafer containing ion‐sensitive field effect transistors (ISFETs). Compatibility of the polymer matrix with various plasticizers commonly used in polyvinyl chloride‐based ion‐selective membrane formulations has been established, and it is shown that the membrane may hold more than 50% of different plasticizers. The photopolymerization rate was found to be higher than for the other compositions used for this purpose. Characteristics of an ammonium ISFET with the developed membrane are presented, the sensitivity was found to be 55 to 59 mV per concentration decade and the range of linear response was from.

The use of a working electrode coated with a thin layer of frost‐like ice has been investigated. It was found that copper can be continuously electrodeposited at such an electrode, and the resultant particulate deposit can be trapped in a growing ice layer.

A series of alloys have been electrodeposited from a melt containing ∼0.1 mol/liter Cr²⁺at 175°C. The alloy composition and structure were functions of the deposition potential. Depending upon the specific deposition parameters, the deposit microstructure consisted of the compound, metallic glass, and/or an fcc phase. The Cr²⁺ concentration was monitored by voltammetric analyses of the quasi‐reversible Cr²⁺/Cr³⁺ couple, carried out at high sweep rates due to the limited solubility of Cr³⁺. Specular alloys were also deposited from a room temperature melt.

Ultrafine particles of binary oxides with various compositions of Ru and Ir have been prepared by a sol‐gel process consisting of hydrolysis and condensation of metal ethoxide ethanol solutions. The rutile‐type solid solution of binary oxides was formed. High‐resolution scanning electron microscopy micrographs of the Ru‐Ir binary oxides showed the spherical‐like crystallites for Ru‐rich oxides and needle‐like ones for Ir‐rich oxides. The particle size was the smallest for the binary oxide with comparable Ru‐Ir composition.

A phase differential scanning optical microscope is used to observe oxygen precipitates in Czochralski‐grown silicon wafers. The microscope focuses infrared light into a small spot onto the wafer and detects the transmitted light using a split detector. A differential signal from the detector is used to build up images on a display as the wafers are scanned. The vertical density distributions of oxygen precipitates are measured from the images.

A contact method for providing a constant, low‐resistance connection to rotating electrodes is discussed. It is based upon the use of a consistent, solid/liquid contact between a stationary copper wire and a small mercury pool which rotates with the electrode. The design is shown to reduce the noise of electrochemical data. This is particularly important for experiments on oscillations and chaos in which analysis methods from nonlinear dynamics are employed. A second advantage of this design compared to a silver‐carbon brush is that there is less change or drift in the measured signal during a long‐term experiment.

An amperometric sensor for the measurement of concentration in a mixture of and has been studied using as a high temperature protonic conductor. When the sensor heated at 1173 K was exposed to air passed through the mixture at 293 K, it could respond to in the concentration range of 5 to 100% with a 90% response time of about 15 min.

Thin and Sb‐doped films have been prepared from aqueous colloidal solutions containing and precursors by the dip‐coating technique. The films are characterized as small grains (40 to 70 Å) and exhibit the ability to uptake reversibly Li⁺ and H⁺ ions from solutions of (0.1 M) in acetonitrile (AN) or water, (0.1 M) and (0.001 to 0.01 M). It was found that Sb‐doped (7 a/o Sb) films thicker than 100 nm exhibit about three times greater (de)inserted charges as compared to the undoped films. With regard to the amount of (de)inserted charge (up to 8 mC/cm²), Sb‐doped films are suitable for mixed electronically conductive, ion‐storage electrodes in electrochromic devices.

A novel electrochemical reduction system has been developed in which liquid was reduced electrochemically at a Cu electrode producing , , , and . We have succeeded in reducing with a current density of 420 mA/cm² and a current efficiency of 85%; the former is higher than that used in industrial electrolyses such as in the chloralkali industry. The Tafel plots indicate that the supply of is no longer limited by its mass transfer.

The life tests, at 100 and 200 mA/cm² in a solid‐polymer fuel cell, indicate that the Pt‐Cr‐Cu/C catalyst is relatively more active than the Pt/C catalyst even after operating the cell for 300 h. The elemental analyses of the anode and cathode catalysts, before and after the stability test, indicate an excessive loss of copper from the cathode. The enhanced activity of this catalyst is explained in terms of its improved wetting of the catalyst particles and of the Raney‐type Pt‐Cr‐Cu alloy formation..

Sulfonated fluorochlorocarbon ionomer films were prepared by radio frequency plasma polymerization of trifluorochloroethylene (TFCE) and trifluoromethane sulfonic acid (TFMSA). The TFMSA was introduced into the plasma chamber by bubbling a carrier gas through a vessel containing the neat acid. We show that the sulfonate content of the film prepared can be controlled by varying the temperature of the TFMSA‐containing vessel. We also show that films with high sulfonate contents can be prepared by using TFCE as the carrier gas for the TFMSA and then allowing this gas mixture to sustain the plasma. This may be contrasted to previous experiments of this type, where Ar was used to sustain the plasma and as the carrier gas. To our knowledge, this approach (i.e., of using the reactant gases to support the plasma) has never been used in the synthesis of plasma‐polymerized films. Finally, we have measured the ionic conductivities of the plasma‐polymerized films. The films prepared from the TFCE plasma are an order of magnitude more conductive than the films prepared from the Ar plasma.

We show that the lithium atoms in the inverse spinel, , can be electrochemically removed and reinserted in nonaqueous electrochemical cells at about 4.8 V vs. metallic Li. Using in situ x‐ray diffraction methods, we prove that this is an intercalation reaction. To our knowledge, this is the Li intercalation reaction with the highest voltage known. The isostructural compound , also shows reversible lithium intercalation, but only near 4.2 V vs. Li.

Stationary carbon electrode voltammetry has been used for studying the electrochemical oxidation processes of 4,5‐Dihydro‐1,2,4‐triazin‐6‐one in acetonitrile. The electron process of dihydrotriazin electrochemical oxidation is shown to correspond to the multistage oxidation of both nonprotonated and protonated forms. Surface protonation is due to the rapid addition of protons formed during the electro‐oxidation process of initial dihydrotriazin molecules. It leads to the formation of extra molecules in the protonated form which oxidize to the end product. The protonation of the final products is also shown. The electrochemical oxidation mechanism of dihydrotriazin has been verified by infrared and nuclear magnetic resonance analysis of products obtained during macroscale electrolysis at controlled potential.

The chemical and electrochemical properties of solutions of molybdenum chlorides in the fused eutectic were studied at 500°C. The chemical stability of solutions is an important parameter which must be controlled to ensure reproducible electrochemical measurements. Polarization curves at vitreous carbon electrodes revealed the existence of an electronic exchange between the stable species Mo(III) and Mo(IV) with a standard potential equal to 880 mV vs. the reference electrode. The reduction process appeared as a simple irreversible three‐electron exchange coupled with significant crystallization problems.

Roughness relaxation of thin columnar Au electrodeposits in and aqueous solutions at 298 K has been followed through the change of both the roughness factor , measured from the O adatom voltammetric electrodesorption charge, and the electrode capacitance at constant potential (E) determined at different frequencies. After a certain relaxation time , and fit the and proportionality, respectively, where and . Otherwise, the proportionality has been found, where denotes the electrodeposit real surface area. When was measured in concentrated solutions in the 165 to 1070 Hz range or in dilute solutions at low frequencies, and . As increased, the specific capacitance, vs. E plots shifted upward approaching the behavior of a smooth Au electrode, without any appreciable change in the value of E associated with the minimum value of . These results were interpreted through a porous model with a time‐dependent average pore radius.

The process of intercalation is thermodynamically analyzed. It is shown that an ionic and an electronic component of the intercalation free energy can be distinguished. A prediction of the electronic contribution is possible if the electronic band structure of the host material in the energy range above the Fermi energy is known. An experimental way for measuring the electronic contribution is suggested.

Lithium cycling efficiency was evaluated for mixed‐solvent electrolyte with several additives: tetraalkylammonium chlorides with a long n‐alkyl chain and three methyl groups. The ammonium chlorides with n‐alkyl group longer than increased lithium cycling efficiency. Cetyltrimethylammonium chloride (CTAC) produced the best improvement in lithium cycling efficiency. A figure of merit (FOM) of lithium for 0.01M CTAC was 46, which was 1.5 times the FOM for the corresponding additive‐free electrolyte. The with CTAC showed an increase in FOM with stack pressure, but the effect was less than that for the additive‐free . Scanning electron microscope observation showed that the addition of CTAC decreased the needle‐like lithium deposition and increased particulate lithium deposition. This deposition morphology may be the main cause of the increase in FOM. The additive had no effect on rate capability for cell cycling at 3 mA/cm²discharge and 1 mA/cm² charge.

Negative electrodes for use in nickel‐hydride batteries were prepared from alloy being mixed with or powder. Then the hydrogen evolution reactions at the electrodes were investigated by measuring the potential decay immediately after the interruption of an applied cathodic current. The reactions were found to proceed by the Volmer‐Tafel mechanism. The total overvoltage (η) was divided into two components ( and ) corresponding to the Tafel and Volmer reactions. The exchange current densities of the elementary reactions, and , were then evaluated by extrapolating the Tafel lines for and . The Volmer reaction is much more accelerated by surface modification with or powder than the Tafel reaction, which results in the enrichment of adsorbed hydrogen, leading to higher charging efficiency.

Lithium can be intercalated into a wide variety of materials using nonaqueous electrochemical cells. The use of aqueous methods is less common because of the reactivity of many lithium intercalation compounds with water. Here we show that lithium can be intercalated into host compounds from aqueous solution, provided the chemical potential of the intercalated lithium is sufficiently lower than the chemical potential of lithium in lithium metal. Using as the host, we formed by intercalating Li from solution in an aqueous cell. This method may prove to be an economical way of preparing lithium transition metal oxides with high lithium contents for lithium‐ion cell cathodes.

The Pb‐Sb alloy consists of α‐Pb crystals and eutectic phase. On anodic polarization of Pb‐Sb electrodes in these phases are oxidized forming and lead oxides: , , as well as , , . The potential regions of formation of the above phases have been determined through x‐ray diffraction analysis as well as their stability and the effect of antimony on the boundaries of these potential regions. It has been established that antimony facilitates the appearance of a potential region between 0.8 and 1.2 (1.3) V in which nonstoichiometric is formed. This leads to a shift in the potential of oxidation of to from 1.0 V for Pb electrodes to 1.2 (1.3) V for Pb‐Sb ones. The reason for the formation of (which has the same crystal structure as that of or is amorphous) has been investigated. It has been established that antimony has a catalytic effect on the reaction and slows down the rate of reaction . It has been proven experimentally that antimony increases the degree of hydration of lead dioxide from 10% (for Pb electrodes) to 30% (for Pb‐20% Sb electrodes). This leads to the formation of elastic elements in the structure of the corrosion layer which, in their turn, reduce cracking of the corrosion layer.

The performance of a composite film of polypyrrole (PPy) and poly(4‐styrenesulfonate) (PSS) was studied in combination with an organic electrolyte as a possible lithium battery cathode. The composite film had a fairly flat morphology and exhibited electroactivity in organic electrolyte solutions using dimethylsulfoxide and propylene carbonate (PC) solvents. We confirmed that during the redox process the film charge was compensated with cations. A lithium cell consisting of the composite film as a cathode and an electrolyte worked as a rechargeable battery. The energy density of the PPy/PSS cathode was calculated to be 220 Wh liter⁻¹ and the average output voltage of the rechargeable cell was 2.9 V.

The performance of two coating systems on cold‐rolled steel has been evaluated with electrochemical impedance spectroscopy and electrochemical noise analysis during exposure to 0.5N for five months. The decrease of the pore resistance and the polarization resistance and the increase of the double layer capacitance show qualitatively that the disbonded area increased with time for the alkyd system (CR‐2). No deviation from capacitive behavior was observed for the epoxy polyamide coating (CR‐9) which showed excellent performance. Potential and current noise data have been collected simultaneously. This approach allows evaluation of the frequency dependence of the spectral noise response and determination of the spectral noise resistance . From the statistical analysis of the noise data the noise resistance has been obtained. Good agreement between these two parameters has been observed. and show the same time dependence as and . However, their numerical values are much lower. For CR‐2 a parallel shift of the potential power spectral density (PSD) curves to lower values and of the current PSD curves to higher values with a constant slope of −20 dB has been observed for CR‐2. No obvious time dependence was indicated for CR‐9.

Steady‐state and transient measurements have been made at a rotating gold disk electrode in lithium carbonate at 800°C for simultaneously determining the diffusion coefficient and bulk concentration of peroxide ions. At high ratios where these measurements were made, the diffusion coefficient is found to be essentially independent of concentration with a mean value of . The bulk concentration of peroxide is two orders of magnitude higher than estimates based on thermodynamic calculations, but in agreement with values derived from oxygen solubility measurements in the literature.

Electrochemical polarization experiments in conjunction with surface analyses using ultrahigh vacuum transfer showed that the presence of S, above a certain threshold amount, accelerated the corrosion of Fe when polarized at a normally passive potential in 55 weight percent solution at 60°C. Above the threshold amount, the corrosion rate did not depend on the S content. During corrosion, much of the S remained in the corrosion product film, and a large portion of the charge passed contributed to film growth. Similarities between the effects of S and those of P reported previously may help explain the similar influences of S and P as grain boundary impurities on the intergranular stress corrosion cracking of Fe.

Perfluorinated, ultrathin polymer films containing sulfonic acid groups were prepared by plasma polymerization of trifluoromethanesulfonic acid and hexafluoropropylene. Electron spectroscopy for chemical analysis and Fourier transform infrared spectroscopy measurements indicated that the sulfonic acid groups were fixed to the backbone chain of the perfluorinated polymer. The structure of the plasma polymer was strongly dependent on the applied RF power. At high levels of applied RF power, the sulfonic acid groups of the starting material were easily decomposed during plasma polymerization. The perfluorinated cation‐exchanger films prepared at low applied RF power were about 1 μm thick and free from pinholes. The films showed high cation permselectivity, as confirmed by a K⁺ ion transference number of 0.99 in aqueous solution.

The electroless deposition mechanism of nickel, in a chloride‐based solution, using hypophosphite ion as reducing agent was examined using potentiodynamic method and open‐circuit potential measurements. The results indicate that the mixed potential theory is unable to describe this system. This is due to the nature of the involved mechanism. It is assumed that the process is initialized by adsorption of hypophosphite ions, followed by the homolysis of primary reductant species, resulting in the formation of atomic and ionic radicals which promote nickel and hypophosphorous acid reduction to originate the Ni‐P deposit. The initial deposition stages of Ni‐P were observed, revealing that the substrate induction, which leads to an increase in the catalytic activity, is not related to a galvanic displacement process, but rather to the establishment of the electrochemical conditions which allow the adsorption/breakdown of the hypophosphite ions. The experimental results are in good agreement with the proposed mechanism.

Multilayer hydrous oxide formation and reduction on platinum in aqueous phosphoric acid solution was investigated using potentiodynamic techniques. The behavior of this system was rather similar to that reported earlier for platinum in aqueous sulfuric acid. However, it was noted that such deposits could be produced under quite severe conditions, e.g., 95% at 160°C; thus they may be of relevance to the operation of the oxygen cathode of phosphoric acid fuel cells. Evidence of unusual, independently reported, premonolayer oxidation responses (within the double layer region) for the platinum/ interface was confirmed. Since the role of impurities in this area has been discounted previously, and the effects may also be observed with as electrolyte, these premonolayer peaks are attributed to formation of active oxide species. There is convincing evidence for the latter phenomenon in the case of gold in aqueous media. Premonolayer oxidation may inhibit the performance of the oxygen cathode in a fuel cell and a means of minimizing this effect may yield a significant increase in energy conversion efficiency.

Using a large polycrystalline Pt film electrode with one layer of electrochemically adsorbed Cu, we have measured the EXAFS of Cu at the K edge through a grazing‐incidence fluorescence‐detection experiment while the sample was under electrochemical control. The quality of the data permit reliable analysis of the spectrum up to 800 eV above the K edge. Measurements with x‐ray electric field vector parallel and perpendicular to the surface were made on the same monolayer. The results indicate that the neighbors of Cu are: O at 2.06 Å, Pt at 2.58 Å, and Cu at 2.62 Å. These are similar to what is expected from considerations of metallic or covalent radii.

The polyimide/metal interface was studied by cyclic voltammetry, double‐step chronoamperometry, and electron paramagnetic resonance (EPR) spectroscopy. Experimental results indicated that a zone or a layer of metal carboxylate was formed between active metal (such as Al, Ti, or Cr) and PI, but for less active metal such as copper, bonding of copper (I) ion, and PI radical anion occurred. This PI radical was observed by EPR spectroscopy. Mixed potential theory has been used here to explain the equilibrium potential of Pi‐coated metal interfaces.

The lithium surface immersed in various electrolytes for 10 min or 3 days was analyzed by x‐ray photoelectron spectroscopy. The lithium surface was covered with the native film which consists of , , and . During the immersion of lithium in propylene carbonate or γ‐butyrolactone containing 1.0 mol dm⁻³ or , the native film reacted with the impurities in the electrolyte to form . However the native film remains after the immersion of lithium in electrolyte for 10 min. The surface film of lithium immersed in propylene carbonate or γ‐butyrolactone containing 1.0 mol dm⁻³ for 3 days was different from those immersed in propylene carbonate or γ‐butyrolactone containing 1.0 mol dm ⁻³. The surface film immersed in electrolyte containing for 3 days has a bilayer structure which consists of and . This surface film seemed to be dense and thin. In the electrolyte containing , the lithium surface was covered with a porous layer of . The morphology of lithium deposited on a lithium surface immersed in electrolyte containing 1.0 mol dm⁻³ for 3 days was semi‐spherical. Typical dendrites were observed on lithium surfaces immersed in electrolyte containing for 3 days. Moreover the lithium dendrite was formed on lithium surface immersed in electrolyte for 10 min. From these results, it can be said that the surface state of lithium is strongly related to the morphology of lithium.

The magnetic properties of chemically deposited films which had been deposited from an ammoniacal‐tartrate‐hypophosphite bath were changed by electrolysis, applied simultaneously with the autocatalytic plating. Coercivity decreased remarkably; saturation magnetization also decreased for the films plated from the bath with. The coercivity first increased and then drastically decreased for films plated from the bath with. The changes in coercivity were found to be due to the changes in crystallinity of the film, while the changes in saturation magnetization were found to be due to the changes in the film composition. The magnetic properties were changed by changing these parameters; Therefore, electrolysis performed simultaneously with autocatalytic plating is an effective method for controlling the magnetic properties of chemically deposited films.

The electrochemical nucleation and growth of crystalline onto glassy carbon was studied by analyzing current‐time transients resulting from potential steps. Stripping voltammetry, x‐ray diffraction, and ex situ atomic force microscopy (AFM) were further used to characterize the deposit. The initial layers of deposited as amorphous material up to a driving‐force‐dependent critical thickness. The critical thickness was 77 nm at zero driving force, and decreased exponentially as the overpotential was increased. When the critical thickness was exceeded at times greater than the induction time, faceted islands of crystalline material were observed. At the induction time, crystalline islands with an average diameter of 1200 nm were observed by AFM. The increase in current after the induction time is attributed to an increase in the rate of deposition, rather than a simple increase in geometric area. The exchange current densities for amorphous and crystalline were measured to be , respectively. Crystalline development may proceed by a cooperative process between material depositing from solution and reorganization of amorphous material previously deposited on the surface. Open‐circuit measurements showed a 72 mV driving force for this reorganization process.

Hot electron reduction of iron ferricyanide was observed at room temperature using thin Pt films on n‐Si (111) and n‐Si (100) substrates. The average Schottky barrier heights on both (111) and (100), as measured by open‐circuit space‐charge capacitance measurements, were , for Pt film thickness from 100 to 700 Å. Below 100 Å the barrier height increased slightly with thickness. All Tafel slopes were 60 mV/decade. At HF etched n‐Si (111) surfaces, the exchange current for electron transfer was determined as a function of Pt film thickness using 0.3M each potassium, pH 6.0. The exchange current declined from Pt. For Si (111), the energy parameter, δ, varied from at zero thickness to and remained constant to 700 Å signifying fully cooled electrons for such thicker films. For Si (100), δ varied from at zero thickness to and remained constant. For both (111) and (110), the large magnitude of δ for the thinnest films indicates the major cooling occurs at the Pt/n‐Si interface rather than within the Pt film.

In this work, the hole‐injection effect on from Ce⁴⁺ ions reduction and the ulterior oxidation of the material are presented. The oxidizing‐species concentration varies from . Within this concentration range, the Levich law is observed for the cathodic current. This indicates that the injection current is limited only by Ce⁴⁺ diffusion from the solution. The presence or absence of a Te^o layer on the electrode surface does not modify the process, whether it comes from the etching or from the oxidation process. The etching of the material is linear with respect to the immersion time, and the oxidation process occurs in two steps: the formation of a Te^o film followed by its oxidation.

The current distribution in the positive current collector of a Na/Se(IV) battery has been studied by measuring the potentials of selenium reactions with inert tungsten microelectrodes. The radial potential distribution on discharge depended on the arrangement of the positive current collector and the conductivity of the graphite felt. A high reaction rate near the β''‐alumina tube observed in a cell with a homogeneous current collector could be inhibited by a dual‐mat design composed of a thin inner felt with high resistivity and bulk felt with high conductivity. Precipitation of sodium chloride on discharge influenced the current distribution and the polarization as well as the capacity.

The Planté method for forming the lead dioxide electrode represents one of the oldest known electrochemical processes, yet there remain gaps in our understanding of the mechanisms involved. Several mechanistic explanations have been presented which provide a framework for understanding these processes. Notable among these are the efforts of Reutschi, Pavlov, Lazarides, and Hampson, and Valeriote and their co‐workers. One key element of their models is the existence of regions of high pH within the anodized layer on the lead surface. These varying pH conditions are explained by inhibited mass transfer of liquid‐phase species. In this paper, the various models are assimilated, and a mathematical model of liquid‐phase mass transfer in the anodized layer is presented. This model is solved for conditions both with and without the lead‐solubilizing species (perchlorate) present. Solutions to the model without perchlorate present show that, within an idealized pore in the anodized region, sharp increases in pH occur at the solid/liquid interface, and that at that point sulfate ions are depleted and alkaline conditions can exist. At this interface, the ionic strength of the solution drops to a minimum. With perchlorate present, the minimum in ionic strength occurs away from the interface and moves farther out with time. These model predictions lend support for the theories that inhibited mass transfer leads to regions of high pH as well as conditions of low ionic strength, where electrolysis of water and hence OH⁻ production can occur.

The electrochemical oxidation of M(II) has been investigated using voltammetric and in situ spectroelectrochemical techniques at platinum, gold, lead dioxide, and bismuth‐doped lead dioxide electrodes. Various experimental parameters exerted significant effects on the oxidation process and its products. The Mn(III) or species is produced depending on the electrode potentials, concentrations of Mn(II), voltage scan rates, and initial potentials during potential scans. These effects are discussed in terms of the equilibrium reactions between Mn(III) and films at the electrode surface and relative stabilities of the products. While a catalytic mechanism is shown to be operative in the case of the oxidation of Mn(II) into at and Bi‐doped electrodes, it does not appear to play an important role during the oxidation to Mn(III). The Mn(III) is shown to be produced from a very early stage of the anodic potential scan and to undergo disproportionation‐conproportionation reactions depending on the relative concentration of each species near the electrode surface.

The electrochemical adsorption‐desorption of hydrogen on amorphous is strongly alkaline media was investigated by cyclic voltammetry and chronopotentiometry. After cathodic polarization, the voltammogram in the −1.0 to −0.6 V range (vs.) shows a new cathodic wave (C) and two anodic waves (A' and B'), due, respectively, to adsorption and desorption of H atoms at the surface of the alloy. The dependence of these waves on the sweep range and sweep potential is presented and discussed. The overpotential dependence on time at constant anodic current presents two plateaus, corresponding to the discharge of the two types of species on the surface of the alloy.

Electrochromic tungsten trioxide thin films were prepared by a photochemical vapor deposition. The source material was tungsten carbonyl. A 6 W low pressure mercury lamp was used as a light source. Amorphous tungsten trioxide thin films were obtained at a substrate temperature of 200°C. The UV radiation enhances the oxidation of tungsten, in addition to the acceleration of the deposition of the films. Reduction and oxidation of the films in a 0.3M propylene carbonate solution resulted in desirable changes in optical absorption. The bleaching time was short compared to the amorphous CVD film. Coulometry indicated that the coloration efficiency was 222 cm² · C⁻¹.

Thin layers of niobium oxide were accumulated by the sol‐gel process, with the sol of in ethanol prepared by partial hydrolysis of commercial niobium(V) ethoxide, on glass plates coated with transparent conducting tin oxide. Characterization by x‐ray diffraction, differential thermal analysis, and thermogravimetry revealed that the as‐prepared film, consisting of fully hydrated amorphous niobium(V) oxide, undergoes dehydration into the partially hydrated form and, finally, crystalline niobium(V) oxide by calcination at the temperature up to 873 K. The films exhibited electrochromic (EC) properties; the reversible color change was observed between colorless and brown‐black by alternating anodic and cathodic polarizations, respectively. Among the films used in this study the crystalline film showed the best EC properties and its spectral change, durability for repeated coloration‐decoloration cycles, and retentivity of colored states, i.e., memory characteristics under open‐circuit conditions were investigated in detail.

Numerous investigations have used the ion implantation of reactive elements (RE) such as Y or Ce, to study their effect on the growth of external oxide scales on alloys. Ion implantation has, nevertheless, some specific limitations, especially in alloys. The most notable limitation occurs at temperatures >1000°C where, owing to the shallowness of implantation, any effects of the ion‐implanted RE are short‐lived and differ significantly from those observed for an RE alloy addition or an RE oxide dispersion. Additionally, in alumina‐forming alloy systems, particularly , implanted Y stabilizes the first‐forming, metastable . The retention of the scale on Y‐implanted substrates is a chemical effect of the high concentration of Y near the substrate surface and is not a result of the implantation process itself. The loss of the RE effect at high temperatures and long times for implanted alloys is related to the outward diffusion of the RE and the formation of RE‐rich oxides near the gas interface of the scale.

Structure size dependent etch rates that lead to reactive ion etching lags and microloading are one of the big problems in microelectronics for structure transfer with plasma etch processes at high aspect ratios. This paper deals with the general role of neutral particles and ions in plasma etching processes. Starting from the fundamental laws of gas dynamics and vacuum technology, formulas are derived for the maximum etch rate of an unstructured surface as well as for the aspect ratio dependence of the etch rates of cylindrical trench holes. The theoretical results are compared with experimental results obtained from single‐crystal silicon etching for generating trench capacitors for memory cells in multi‐Mbit dynamic random access memory.

Small defects in Czochralski silicon substrates are responsible for defect generation in oxide layers grown thermally on the substrates. The relationship between the defect density and the thickness of as‐grown oxides is shown to be , where and are constants. Good agreement is obtained between these equations and experimental data. We show that the implantation of ions straight through the oxide layers eliminates oxide defects at implantation doses above 10¹⁴ cm⁻². This suggests that oxide defects are associated with structures that are destroyed by the ion implantation, during which their constituent atoms are randomly displaced. In addition, we show that pouring deionized water on a rotating wafer with an oxide layer eliminates oxide defects. Electrostatic measurement reveals that negative charges are produced during the rotation. We propose a model in which electrons produced through friction between the water and the surface induce a high electric field, and an oxide defect is selectively subjected to excessive electron conduction followed by local joule‐heating, which changes the chemical state of the defect.

The electrokinetic characteristics of low pressure and plasma‐enhanced chemical vapor deposited silicon nitride wafers subjected to different cleaning procedures were measured using a streaming potential technique. A streaming potential cell for handling 5 in. wafers was designed and fabricated to make these measurements. The isoelectric point (IEP) of silicon nitride was dependent on the cleaning method as well as the deposition technique. X‐ray photoelectron spectroscopic measurement of Si/O and Si/N ratio of films was made to explain the difference in the measured IEP values. Polystyrene latex particle deposition from aqueous solutions onto silicon nitride wafers was investigated and correlated with the electrokinetic potential data.

Criteria have been developed for assuring epitaxial film growth in the presence of trace amounts of water and oxygen for both low and high temperature regimes. These concise and quantitative relationships can be used as a tool for guiding experiments and explaining conflicting experimental results. The criterion for the low temperature regime is based on the fundamental adsorption/desorption behavior of hydrogen known to date. The criterion for the high temperature regime is synthesized in a similar manner. Flow effect is given along with the effect of deposition rate. A new concept for effective oxygen partial pressure is introduced.

A special metal oxide semiconductor (MOS) diode is built with amorphous silicon (a‐Si:H) as the semiconductor. The process is carried out so that the a‐Si is not subject to high temperatures. This allows the characterization of solar grade a‐Si:H by MOS diagnostic methods. Two types of structures (blanket a‐Si layers as well as reactive ion etched a‐Si mesas) are produced. Based on C‐V and C(ω) measurements an equivalent network is established which includes the effects of the majority carrier dissipation time constant, of the space‐charge punch‐through in depletion and inversion, and of lateral current flows. The network is checked at selected bias and frequency conditions using given geometrical and material data. When applied to accumulation, it delivers the layer resistivity and net carrier density.

Atmospheric pressure ionization mass spectrometry (APIMS) was used to detect hydrocarbons; e.g., methane, ethane, and propane, and organic cleaning solvents; e.g., isopropyl alcohol (IPA) and acetone in nitrogen. The technique of collision‐induced dissociation (CID) was used to fragment parent molecular ions by accelerating them through the declustering region of the APIMS source in an effort to detect the hydrocarbon impurities at a single m/e. Using high declustering voltages it is possible to detect all the compounds studied, except IPA, at m/e 12 (C⁺). At moderate declustering voltage fragments characteristic of the compounds of interest can be used for monitoring and identification purposes.

It has been reported earlier that the attenuation lengths of photoelectrons from very thin amorphous silicon nitride films (3 to 11 nm) increase with film thickness. These changes were attributed to systematic variations in the film density. Spectroscopic ellipsometry has been used here as an independent technique to evaluate the refractive indexes of several of the same films. The ellipsometric results are consistent with the earlier finding that the relative densities of these films vary with thickness. The density variations may be attributed to either structural changes in the films or differences in the oxygen content of the films with film thickness.

The generation mechanism of photoresist residue after the ashing process of aluminum interconnect etching was investigated by changing the cross‐sectional profile of resist pattern, resist thickness, and resist pattern width. The generation mechanism of resist residue after ashing is clarified by analyzing the resist residue with Auger electron spectroscopy. It has been revealed that aluminum is attached to the sidewall of resist pattern during aluminum etching and if the cross section of the resist pattern has a negative slope, the attached aluminum on the sidewall of the resist pattern is scarcely removed by etching ions and the thickness of aluminum does not decrease. This attached aluminum is oxidized in an ashing gas and removal becomes harder. When the ashing process proceeds, the sidewall falls down on the center of the resist pattern and covers the pattern. Therefore, the resist ashing is terminated and resist residue is generated.

The etch rates and plane selectivity for single‐crystal silicon anisotropic etching in aqueous rubidium hydroxide are reported. Silicon wafers of (100) and (110) orientation were etched in 25, 30, 40, and 50 weight percent (w/o) aqueous at 50, 60, 70, and 80°C. The activation energy, based on an Arrhenius equation, was 0.48 eV for the (100) and (110) planes. The etch rate ratio for the (110)/(100) planes was equal to 1.5 at 50 w/o, and 0.6 at 25 w/o. The plane selectivity is not a function of temperature. Silicon spheres, approximately 0.25 in. diam were etched to reveal fast etching high index {522}/{311} planes in the vicinity of the '100' direction.

A rapid thermal anneal (RTA) at low pressure is proposed as an efficient method for the elimination of the surface inversion layer formed by the charges within the field oxide or by the leakage current along the field oxide surface which is easily contaminated by photoresist, water molecules, and mobile ions. From the high‐low frequency C‐V measurements, it was found that a 900°C RTA at a pressure of 300 Torr can remove the field oxide surface contaminants sufficiently and make the distorted portion in the strong inversion region of the high frequency C‐V curve return to normal. The practice of rapid thermal annealing after chemical etching and cleaning can prevent the field oxide surface from contamination caused by the subsequent high temperature process. It was also found that after a low pressure RTA the gate oxide endurance can be dramatically enhanced and is comparable to that of the conventional furnace‐annealed gate oxide.

We describe an electrochemical planarization technology involving electroplating followed by electropolishing, resulting in a very flat surface containing embedded conductors. Electrochemical planarization technology has been used to produce silicon substrate multichip modules.¹ Both the electroplating and electropolishing processes have a thickness uniformity of better than ±2% (±3σ) across a 100 mm wafer.

The morphology of palladium particles supported on both highly oriented pyrolytic graphite (HOPG) and glassy carbon was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The particles on the HOPG were linked with neighboring particles to agglomerate, while the particles on the glassy carbon were circular. AFM data with tapping mode for the palladium particles on HOPG were consistent with the high‐resolution SEM image. Although the lateral resolution of the AFM image was lower than that for the high‐resolution SEM data, the AFM image clearly indicated the height distribution of the agglomerates.

The performance of a powder direct current electroluminescent (DCEL) device depends on the conductivity of its copper‐coated phosphor, but little effort has been spent on the study of this problem. We report a series of experiments the results of which are used to analyze the forming and aging behavior in a DCEL device. Factors affecting the conductivity of a copper‐coated DCEL phosphor are found to be its temperature, coating solution temperature, and gaseous atmosphere. Based on these results, new theories about forming and the effect of a gaseous atmosphere on a DCEL device, as well as how to produce a long lifetime DCEL phosphor are discussed.

The structure and electronic state of fine Pt particles on the carbon electrode were investigated by XANES and extended x‐ray absorption fine structure (EXAFS) spectroscopies. The white line intensities were processed into the parameter representing the density of unoccupied 5d state. They were described as kinds of voltammograms. It was different between the cathodic sweep and the anodic sweep even in the same potential. The small particle electrode showed large hysteresis of the d‐density change. These changes by potential sweep are discussed in relation to the structure of the particle on the basis of the parameters of EXAFS. The large change in the small particle was explained by the ratio of the surface atoms in the whole particle. The thickness of the oxide layer and lattice disorder in subsurface was estimated from these structural parameters.

The potential and restrictions of cryogenic SOI technologies are reviewed. First the low temperature device operation, illustrated by extensive experimental data covering a broad temperature range down to liquid helium, is discussed in order to validate the theoretical models. Attention is given to the kink phenomenon, transient and hysteresis effects, the device breakdown and latch‐up behavior, and the noise performance. Several design methodologies and technological modifications for eliminating the cryogenic artifacts are critically discussed. Alternative device concepts such as the twin‐transistor structure and the gate‐all‐around concept are also addressed. Finally some considerations for digital and analog circuit applications are given in view of the future perspectives of cryogenic SOI CMOS technologies.

A zero‐bias photocurrent (ZBPC) is observed in Cr‐doped semi‐insulating (Si) bulk crystals under illumination in the subbandgap energy range at low temperatures. It is ascribed to photocarriers driven by local electric fields associated with internal potential barriers due to random defect density fluctuations in the sample. An interpretation of the ZBPC spectral behavior is proposed based on comparison with the conventional photocurrent spectrum. To our knowledge this is the first attempt to investigate the spectral behavior of the ZBPC in compensated semiconductors. The effect of the optical stimulated polarity changes of the ZBPC could be considered as an alternative approach to the analysis of phototransport properties of Si semiconductor materials.

We report on the interfacial diffusion of metal ions occurring during air annealing of multilayer films (0.15–0.6 μm) deposited on thin coating of or (≈0.06 μm) on glass substrates. All the films are deposited from chemical baths at room temperature. The interfacial diffusion on the metal atoms during the air annealing is illustrated by x‐ray photoelectron spectroscopy studies. A multilayer of 0.3 μm thick film deposited over a thin film of upon annealing at 150°C shows atomic ratios of Zn to Cu of ∼0.15 and ∼0.48 at the surface layers of the samples annealed for 12 and 24 h, respectively. In the case of on film, the corresponding Pb to Cu atomic ratios at the surface layers are 0.43 and 0.83. The optical transmittance spectra and sheet resistance of these multilayer films indicate thermal stabilities superior to that of the coatings. Application of the interfacial diffusion process in the production of thermally stable solar control coatings, solar absorber coating, or p‐type films for solar cell structures is discussed.

A new electron‐beam‐enhanced plasma process apparatus was proposed, which was separated from an electron‐beam source and a reactor by a polyester film of 1.5 μm. Electrons were thermally emitted from a W filament, accelerated by the voltage applied on an anode, and injected into the reactor through the interface. The ablation of the interface material was observed at a high electron‐beam current density, but it was suppressed at a lower current density. Under suppressed ablation conditions, etching of the Si wafer was achieved in plasma which was induced by the electron beam under an applied dc voltage. The plasma current could be increased and the etching was enhanced by the injected electrons. A fine pattern 0.5 μm wide was etched at the rate of 8.3 nm/min through the silylated resist window.

A simulation model is presented for nonplanar CVD over device feature scale structures. The direct simulation Monte Carlo method is used to describe the rarefied gas transport in a localized region above the feature. A new approach is outlined to simulate the evolution of the film profile which provides dynamic step‐coverage performance and microstructural detail of the growing film. The method allows simulations of nonequilibrium effects resulting from rarefaction of the gas above surface features. Results of a parametric study are presented for deposition within a long narrow trench and a cylindrical contact hole. The parameters investigated include the reactive sticking coefficient, the surface mobility of the adsorbed reactants, the Knudsen number (the ratio of the mean‐free path to the feature scale), the feature aspect ratio and feature geometry. A sample calculation is presented for deposition over a square hole structure to demonstrate the extension to realistic three‐dimensional structures.

The dielectric strength of the gate oxide under a molybdenum polycide electrode ( on polycrystalline silicon films) has been studied as a function of the fabrication processing steps of complementary metal oxide semiconductor very large scale integration. It was found that the thermal oxidation process step, after the source/drain formation using high dose ion implantation, thins the underlying polycrystalline silicon (poly‐Si) of Mo polycide films and increases the degradation of thin gate films in metal‐on‐oxide semiconductor capacitors. The effect of ion implantation on the oxidation behavior of Mo polycide films was compared with that of poly‐Si films doped with phosphorus using a source. An anomalous oxidation enhancement of Mo polycide films was observed when ions or and As ions are implanted into the Mo polycide films. This anomalous oxidation can cause gate oxide degradation.

Planarity and control of the configuration of the cross‐sectional area are important parameters to be considered for high density VLSI devices. The anodization process seems best to fulfill such conditions, but anisotropy (i.e., difference in vertical and lateral anodization rates), must be increased to obtain a competitive technique. In this work factors affecting the anisotropy of the aluminum anodization process were investigated. By varying the electrochemical process parameters, a degree of anisotropy of about 0.6 was obtained. The dimensions of the aluminum porous oxide were determined by scanning electron microscopy. At high forming voltages, the electric field across the barrier layer of the porous oxide cells were calculated and plotted.

In this study, the effects of different reactants, namely, , and , on the nucleation and deposition of polycrystalline silicon‐germanium films on oxide surface in an ultrahigh vacuum chemical vapor deposition reactor were explored. The results show that the addition of tends to retard the nucleation process of poly films while is preferential for adsorbing on the oxide surface. These effects lead to different incubation duration depending on the kind of reactants used. On the deposition of films, it is observed that the Ge incorporation is only slightly related to the substrate type, but the deposition mode of films is much different from that of epitaxial growth on Si(100). The incorporation of Ge atoms also overcomes the anomalous doping effect encountered in heavily boron‐doped poly‐Si films and allows extremely low resistivity (below 2 mΩ‐cm) poly films to be obtained at low temperatures (≤550°C).

An electrochemical oxygen sensor based on stabilized zirconia was developed for measurements of the oxygen concentration in molten silicon. The mixture of Mn and was found to be an appropriate system for the generation of the reference oxygen partial pressure which should be close to that of oxygen in the silicon melt. The free‐energy of solution of oxygen in molten silicon was evaluated by calibration experiments. A prototype sensor was tested to measure the oxygen content in the silicon melt in a commercial Czochralski puller. The difference in the radial oxygen concentration between center and periphery increased with increasing crucible rotation. This result is consistent with the experience in silicon crystal growth as well as with recent numerical and experimental results on the impact of crucible rotation on the flow patterns in silicon melts in an industrial‐size Czochralski crucible.

The generation kinetics and origins of pyramidal hillocks grown on Si(111) surfaces with an off angle of 0.55° from [111] were investigated for the chemical vapor deposition of Si with . According to the top shape of the hillock, most hillocks can be classified to three kinds: bright‐, sharp‐, and flat‐top hillocks. It was shown that the flat‐top hillock is grown with the stacking fault and the sharp‐top and bright‐top hillock result from the hydrocarbon and oxide (Si particle) contaminants on the substrate, respectively. The sharp‐top hillock was observed to develop along the dislocation. The generation kinetics of the stacking fault was suggested to be involved with chlorine adsorbate on the surface. Because of the large hillock size, the existence of growth defects due to the stacking fault and dislocation can be detected easily for very thin films with no etching. Furthermore, we found that the three kinds of hillocks can be drastically reduced in density by using carrier hydrogen gas excited with ultraviolet light from low‐pressure Hg lamps during growth as well as substrate cleaning at atmospheric pressure. This indicates that the photoexcited hydrogen has a cleaning effect for the hydrocarbon, oxide, and chlorine on the surface during Si growth.

Propagation properties of reactive hydrogen atoms generated by catalysts at low pressure were investigated by thermal etching experiments. It was found that the propagation distance of reactive hydrogen atoms is prolonged when the reactor pressure is decreased. The catalysts are used in low pressure organometallic vapor‐phase epitaxy growth of using triethylarsine. It is shown that carbon contamination in a substrate can be considerably reduced by the catalysts in a wider region compared with the case of atmospheric pressure growth.

Abstract not Available.