Showing papers in "Journal of The Electrochemical Society in 1968"
TL;DR: In this article, the anodic oxidation pathways of carbazole and several N−substituted derivatives were investigated and a qualitative picture of active sites with regard to follow-up coupling reactions was given.
Abstract: Electrochemical and spectroscopic techniques have been employed in elucidating the anodic oxidation pathways of carbazole and several N‐substituted derivatives. For carbazole and the N‐alkyl or N‐aryl derivatives, ring‐ring coupling is the predominant decay pathway of the carbazole cations; the coupling rates are extremely rapid. N‐N coupling is observed initially for carbazole, but in long‐time electrolysis it is of little consequence. The oxidation products have been synthesized by chemical means and compared with the species formed electrochemically by matching of cyclic polarograms and visible absorption spectra. Molecular orbital calculations give a qualitative picture of active sites with regard to follow‐up coupling reactions in the carbazole series. N‐vinyl, N‐acetyl, N‐benzoyl, and N‐nitroso carbazole were investigated briefly but found to be extremely complicated.
366 citations
TL;DR: In this article, the luminescent properties of alkaline earth aluminates activated by divalent europium have been investigated and the performance details of these phosphors in fluorescent lamps are described.
Abstract: The luminescent characteristics of alkaline earth aluminates activated by divalent europium have been investigated. Ultraviolet excitation of these compounds can occur through the host lattice and from the 4f7 ground state to excited states of the 4f7 and 4f65d1 electronic configurations of divalent europium. The emissions involve 4f‐5d transitions as evidenced by the broadness of the spectra, sensitivity to structure, and sensitivity to temperature. Evidence is also presented that the Eu2+ occupies cationic‐lattice sites. The performance details of these phosphors in fluorescent lamps are described.
312 citations
236 citations
TL;DR: The dependence of the emission spectra on compositional variations has been studied in binary alkaline earth orthosilicate systems activated by divalent europium as mentioned in this paper, and a complete series of crystalline solutions exist between the end-members at 1200°C.
Abstract: The dependence of the emission spectra on compositional variations has been studied in binary alkaline earth orthosilicate systems activated by divalent europium. Isotherms at 1200°C were run in the systems (i) , (ii) , and (iii) . Phosphors produced in the system were considerably more efficient than those in either of the other two systems and consequently were studied in much greater detail. A complete series of crystalline solutions exist between the end‐members at 1200°C. The corresponding emission spectra vary in a fairly continuous manner from 505 nm for the pure barium end‐member to 575 nm for the pure strontium end‐member. X‐ray diffraction data revealed complete crystalline solution between and at 1200°C. However, the low level of brightness and the pronounced asymmetry of the emission peaks rendered this system less amenable to a detailed investigation. Emission spectra indicated the formation of an intermediate compound in the system. The existence of this compound, , was verified by x‐ray diffraction. The emission spectrum of this compound peaks at a considerably lower wavelength (~490 nm) than those of its bounding compositions. The two later systems were further complicated due to the polymorphism of . Frequently the phase was partially converted from to .
236 citations
TL;DR: In this article, it was shown that boron-nitride films of up to 6000Aa thick have been deposited on a variety of substrates at 600 °-1000 °C by a reaction between diborane and ammonia in hydrogen or inert carrier gas.
Abstract: Clear, vitreous films of boron nitride up to 6000Aa thick have been deposited on a variety of substrates at 600 °–1000 °C by a reaction between diborane and ammonia in hydrogen or inert carrier gas. Deposition rate may be readily adjusted to 50–1000 Aa/min. Most samples were made at either 600° or 800°, with some attendant variation in film properties. The 600° material contains some residual B‐H bonding. The film is essentially amorphous to electron diffraction. The refractive index is 1.7–1.8, the 1 MHz dielectric constant ~ 3 1/2, the dielectric strength , and the The band gap is 3.8 ev and the phonon temperature in the neighborhood of 2000°K. For semiconductor junction protection boron nitride has no advantage over silicon nitride. 600° deposition directly on Si has produced surface charges as low as , but there are room‐temperature drifts, and high‐field conduction also. BN deposited at 800° on Si is electrically similar to silicon nitride. Etching of BN film also presents the same problems as does silicon nitride. BN is not as good a barrier against sodium ion permeation. Attack by atmospheric moisture over a long period has varied from insignificant to extensive conversion to orthoboric acid.BN film on Si dopes the substrate with boron at temperatures above 900 °C in inert ambient. Uniform junction depths are produced. D‐C conductivity in 500–4000Aa films has been studied from room temperature to 270 °C. With fields ≥ 106 v/cm BN film shows stable, nonohmic conductivity which is independent of polarity. The 25 °C d‐c conduction is describable over at least seven decades of current by , , where , . The 600°‐deposited BN is the more conductive and can carry indefinitely. is linear, and the slope of the curve is in good agreement with the theoretical value for a Frenkel‐Poole conduction mechanism. Possible use of BN as a thin film varistor is discussed.
225 citations
TL;DR: In this paper, a closed system solid electrolyte electrochemical cell has been designed to investigate the thermodynamic properties of metal oxides, which are free of mixed potentials arising from nonequilibrium oxygen pressure conditions in the electrode compartments.
Abstract: A "closed system" solid electrolyte electrochemical cell has been designed to investigate the thermodynamic properties of metal oxides. The measurements with this cell are free of mixed potentials arising from nonequilibrium oxygen pressure conditions in the electrode compartments. The oxide systems investigated include , , , , , , , , and .
217 citations
TL;DR: In this article, the sign and magnitude of the intrinsic stresses observed in metal films cannot be predicted from a priori knowledge, and it is suggested that such high values of stresses are generated by the annealing and constrained shrinkage of disordered material buried behind the advancing surface of the growing films.
Abstract: The sign and magnitude of the intrinsic stresses observed in evaporated metal films cannot be predicted from a priori knowledge. In an effort to correlate the observed intrinsic stress, S, with other physical parameters, S has been measured in films of fifteen different metals. The stress was measured in situ by the cantilevered substrate technique. The films were evaporated from an electron bombarded source in vacuums of 10−6 to 10−7 Torr onto glass substrates at room temperature. Under these conditions the intrinsic stress was generally found to be tensile, though exceptions were observed. The data obtained indicate that films of metals with higher melting temperatures and larger shear moduli have intrinsic stresses which approach a magnitude roughly equal to 0.01 of the shear modulus. It is suggested that such high values of stresses are generated by the annealing and constrained shrinkage of disordered material buried behind the advancing surface of the growing films. Reduction of the stress is predicted when surface rearrangements preempt the need for extensive subsequent internal annealing. This proposal is considered in the relation to the experimental observation that the intrinsic stress is small when the ratio of the (absolute) substrate and melting temperatures exceeds 1/4.
193 citations
TL;DR: In this article, the formation of hollow whiskers by the action of slightly acidified potassium ferricyanide and ferrocyanide solutions on metals and alloys appeared to indicate that corroding metals produce bursts of metal ions from various point anodes.
Abstract: : The formation of 'hollow whiskers' by the action of slightly acidified potassium ferricyanide and ferrocyanide solutions on metals and alloys appeared to indicate that corroding metals produce bursts of metal ions from various point anodes. Since these bursts of ions appeared to be of a sporadic nature, it seemed possible that there might be transient fluctuations of the electrical charge on the metal. The communication reports on the detection of such fluctuations in electrical charge.
165 citations
TL;DR: In this article, critical pitting potentials for the binary Cr•Fe and Cr•Ni alloys in become more noble (correspondingly more resistant to pitting) with increasing content, particularly in the region 25−40% and 10−20% Cr, respectively.
Abstract: Critical pitting potentials for the binary Cr‐Fe and Cr‐Ni alloys in become more noble (correspondingly more resistant to pitting) with increasing content, particularly in the region 25–40% and 10–20% Cr, respectively. The potentials for 57.8% Cr‐Fe and pure Cr fall within the transpassive region. Ni containing 3.2% Mo, to the contrary, shows a lower (more active) critical potential; higher per cent Mo‐Ni alloys appear to fall within the transpassive region corroding anodically as plus Ni++ without pitting. Ni alloyed with 15% Cr‐Fe shifts the potential in the noble direction; Mo alloyed with 15% Cr, 13% Ni stainless steel has a similar but even greater effect. At 0°C, 15% Cr, 13% Ni stainless steel exhibits a potential 0.5v more noble than at 25°C, corresponding to greatly increased resistance to pitting. This shift is less pronounced for the stainless steels containing Mo; in fact, at or above 1.5% Mo, the critical potentials at 0°C are below those at 25° C. In , alloyed Mo shifts the potentials slightly in the active direction, contrary to a marked noble shift in . At 0°C the potentials are still more active. These trends correlate with observed pitting for 15% Cr, 13% Ni stainless steel and the similar alloy containing 2.4% Mo in 10% both at 0° and 25°C. Absence of pitting is observed in 10% at 0°C for 15% Cr, 13% Ni stainless steel, but not for the similar alloy containing 2.4% Mo, which pits. The over‐all results are explained on the basis of competitive adsorption at the metal surface and an effect of temperature on the structure of the double layer.
151 citations
TL;DR: The properties of silicon nitride, oxynitride, and oxide films formed by the pyrolysis of various mixtures of,, and are presented The variation in physical, optical, and electrical properties of this oxynitized series is examined The electrical and passivation properties of these films on Si are examined and compared with oxides as discussed by the authors.
Abstract: The properties of silicon nitride, oxynitride, and oxide films formed by the pyrolysis of various mixtures of , , and are presented The variation in physical, optical, and electrical properties of this oxynitride series is examined The electrical and passivation properties of these films on Si are examined and compared with oxides These electrical data describe the general characteristics of nitride and oxynitride on top of Si and over thin (~300Aa) and thick (~1000Aa) thermal oxide films
146 citations
TL;DR: The electrochemical oxidation of adenine (6-aminopurine), which gives a single well defined voltammetric wave at the pyrolytic graphite electrode (PGE), was investigated by macroscale controlled electrode potential at the PGE in aqueous 1M acetic acid solution (pH 2.3) with exhaustive isolation, identification, and determination of reaction products and intermediates as discussed by the authors.
Abstract: The electrochemical oxidation of adenine (6‐aminopurine), which gives a single well‐defined voltammetric wave at the pyrolytic graphite electrode (PGE), was investigated by macroscale controlled electrode potential at the PGE in aqueous 1M acetic acid solution (pH 2.3) with exhaustive isolation, identification, and determination of reaction products and intermediates. The electrochemical oxidation of adenine appears to follow initially the same path as the enzymatic oxidation, but further oxidation and fragmentation of the purine ring system occur. Thus, adenine is oxidized in a process involving a total of 6 electrons per adenine molecule to give as the primary product a dicarbonium ion intermediate, which, being unstable, undergoes a further series of reactions: (a) electrochemical oxidation to parabanic acid (some of which is further hydrolyzed to oxaluric acid), urea, carbon dioxide, and ammonia; (b) electrochemical reduction to give ultimately 4‐aminopurpuric acid, carbon dioxide, and ammonia; and (c) hydrolysis to allantoin, carbon dioxide, and ammonia.
TL;DR: In this article, the low-temperature (77°K) MOSC curves used to measure the number of fast interface states are analyzed and the results suggest that these bands of donor and acceptor levels arise from a single type of defect which is electrically amphoteric.
Abstract: The low‐temperature (77°K) MOS‐C (V) curves previously utilized to measure the number of fast interface states are analyzed. Quantitative variations in the number of fast states with variations in crystal orientation, oxidation atmosphere, vacuum and hydrogen annealing, together with some results of MOS‐FET vacuum annealing are presented. For instance, high‐temperature vacuum annealing of oxidized silicon wafers is shown to be capable of producing a very high density of donor and acceptor type fast interface state levels of the type previously identified by measuring MOS‐C (V) flatband voltage at low temperatures. These results suggest that these bands of donor and acceptor levels arise from a single type of defect which is electrically amphoteric.
TL;DR: In this paper, the effects of substrate temperature on the GaAs deposition rates were studied for {111}A, {112}A and {113}A], {115, {100, {113,B, { 112}B, and { 111}B substrate orientations.
Abstract: The effects of substrate temperature on the GaAs deposition rates were studied for {111}A, {112}A, {113}A, {115}, {100}, {113}B, {112}B, and {111}B substrate orientations An open tube chloride transport system with elemental gallium and arsenic sources was employed This apparatus allowed independent control over the gallium monochloride, arsenic, and hydrogen chloride partial pressures The sensitivity of the deposition rate to substrate orientation is observed to be strongly temperature dependent Experimental evidence is provided which indicates that the deposition rate is kinetically limited in the temperature range from 725° to 800 °C
TL;DR: In this article, a bias is applied across the vibrating and fixed electrodes sufficient to produce zero output signal, and the value of this bias and a simple calculation yields the surface charge and its polarity.
Abstract: A new method of measuring the charge density on a dielectric surface has been developed. An electrode is vibrated in the surface field to produce a signal that is displayed on an oscilloscope, or measured with a VTVM. A bias is then applied across the vibrating and fixed electrodes sufficient to produce zero output signal. The value of this bias and a simple calculation yields the surface charge and its polarity. The method is simple, nondestructive, gives reliable results when compared with other techniques, and has few disadvantages. Measurements may be made at atmospheric pressure without fear of discharges at a wide range of surface‐to‐electrode gaps. The measurement of the surface charge is independent of circuit parameters.
TL;DR: In this paper, a survey and discussion are given of the correlation between fluorescent properties and chemical properties, like composition and structure, in order to predict the efficiency of phosphors with electronic transitions in localized centers.
Abstract: No general theory exists that can predict the efficiency of phosphors with electronic transitions in localized centers. In this paper a survey and discussion are given of the correlation between fluorescent properties and chemical properties, like composition and structure. Points of discussion are (a) choice of the activator together with concentration quenching and critical concentration for this phenomenon, (b) influence of the host lattice on the photoluminescence efficiency for direct excitation of the activator, and (c) energy transfer between fluorescent centers. These considerations are illustrated by a large number of experimental examples.
TL;DR: Using a simple new physical technique, dielectrophoresis, living cells can rapidly be distinguished from dead ones, and collected separately, enabling remarkably selective collection of living cells from a mixture of living and dead cells.
Abstract: Using a simple new physical technique, dielectrophoresis, living cells can rapidly be distinguished from dead ones, and collected separately. A detailed study using yeast cells is reported here. A comparative study of the dielectrophoresis of aqueous suspensions of living and dead yeast (Saccharomyces cerevisiae) was made over a range of frequencies, aqueous conductance, field strength, and time. The amount collected in a given period was observed to increase with field strength and aqueous resistivity except in the highest ranges where a reverse trend occurs. At high field strengths reversal of collection occurs (i.e., dispersion). The frequency responses of living and dead cells are different, enabling remarkably selective collection of living cells from a mixture of living and dead cells. Cells collected in this manner survive.
TL;DR: The nucleation, early growth, and structure of NiP on activated dielectric substrates were studied in this article, where the treatment was found to provide small catalytic sites on the substrate, serving as the nuclei for NiP growth.
Abstract: The nucleation, early growth, and structure of Ni‐P on activated dielectric substrates were studied. The treatment was found to provide small catalytic sites on the substrate, serving as the nuclei for Ni‐P growth. The average diameter of catalytic sites was estimated to be less than 10Aa. The microscopic time rate of Ni‐P growth on the nuclei was found to be constant and the growth to be isotropic. The resulting Ni‐P deposit in the early stages of growth consists of circular islands. The surface density σ of islands were affected by activation. In later stages of growth, the circular Ni‐P islands merged to form a continuous film. The critical film thickness at which continuity is attained is shown to be a function of σ. The structure of as‐deposited islands, as well as that of fresh continuous film, was determined by electron diffraction to be liquidlike.
TL;DR: The electrical properties of vapordeposited silicon nitride and silicon oxide films on silicon have been investigated in this article, showing that the silicon oxide properties are more similar to those of thermal oxides.
Abstract: The electrical properties of vapor‐deposited silicon nitride and silicon oxide films on silicon have been investigated. The silicon nitride films were produced by the reaction at 950°C, while the oxides were prepared at 400°C using the reaction. The properties were compared with those of thermal oxides prepared in dry O2 at 1200°C. As contrasted to the thermal oxides, the silicon nitride films are characterized by polarization and room temperature trapping instabilities, relatively high conductance, and high surface state charge densities. The vapor‐deposited oxides tend to resemble the nitrides in those properties which are associated with the silicon‐ dielectric interface, but the bulk properties are more like those of thermal oxides.
TL;DR: In this paper, the cathodic reduction process of, which is produced from or by electrochemical reduction, was studied in with various particle sizes of the original and various depths of discharge.
Abstract: The cathodic reduction process of , which is produced from or by electrochemical reduction, was studied in with various particle sizes of the original and various depths of discharge. The polarization of produced from electrolytic is small, less than 60 mv, until a certain current density is reached. Above the current density, a limiting current is reached and polarization increases sharply. There are two possible reduction mechanisms for the process from to , i.e.: (i) reduction through Mn(III) ion dissolved in the electrolyte, and (ii) reduction of directly to in solid state. It was concluded that most of the discharge current is attributed to the dissolved ion mechanism.
TL;DR: The morphology of the solid-liquid interface and the contact angle configuration of the liquid alloy droplet determine the direction of growth of crystals prepared by the vapor-liquid-solid (VLS) technique.
Abstract: The morphology of the solid‐liquid interface and the contact angle configuration of the liquid alloy droplet determine the direction of growth of crystals prepared by the vapor‐liquid‐solid (VLS) technique. There are four different processes by which both growth kinks and branches can be formed. A change in solid‐liquid interface shape during VLS caused by a lateral temperature gradient results in the formation of growth kinks. Branches are formed if the alloy droplet ruptures during the kinking sequence. A sudden increase in temperature can cause an unstable contact angle configuration. The alloy droplet may run down the side faces of the growing crystal, leading to the formation of growth kinks or branches. A sudden decrease in temperature may cause "pinching off" of small droplets from the main droplet, giving rise to branches. Finally, the codeposition of liquid‐forming impurities may also lead to branch and kink formation. The proposed models have been verified experimentally for VLS growth of silicon and germanium. Crystalline defects, such as dislocations, are not essential for the branching and kinking process. It is shown that "growth shaping" during the VLS process is possible.
TL;DR: In this article, the authors used vibratory polishing to remove thin sections of anodic oxides and implant anion, cation, and inert gas radiotracers to measure the mode of oxide formation on Zr and Ta.
Abstract: The technique of removing thin sections of anodic oxides by vibratory polishing has been used in conjunction with implantation of anion, cation, and inert gas radiotracers to measure the mode of anodic oxide formation on Zr and Ta. The measured transport number for metal during the growth of (0.28) is in good agreement with previous work. is shown to grow by oxygen migration and preliminary experiments suggest that the process occurs by rapid movement of the oxygen along defects. Comparison of the movement of anion and cation radiotracers with that of an inert gas provides additional evidence that xenon and krypton may be regarded as immobile markers for use in oxidation studies.
TL;DR: Spectral properties of rare earth phosphate phosphors are presented and compared to rare earth oxide phosphors studied previously as discussed by the authors, and it is shown that hanging to a phosphate host does not affect the wavelengths produced, but has a major effect on the total energy efficiency as well as the intensity of the emission lines produced relative to one another.
Abstract: Spectral properties of rare earth phosphate phosphors are presented and compared to rare earth oxide phosphors studied previously. It is shown that hanging to a phosphate host does not affect the wavelengths produced, but has a major effect on the total energy efficiency as well as the intensity of the emission lines produced relative to one another. The latter observation is attributed to site symmetry effects on transition probabilities from an emitting energy level.
TL;DR: In this paper, the temperature stability range in air for each compound was investigated by DTA and TGA methods, and X-ray diffraction powder data were presented for the fourteen compounds isolated.
Abstract: The hydrated sulfate, sulfate, oxysulfate, and oxysulfide compounds of yttrium, lanthanum, gadolinium, and lutetium were prepared using precipitation techniques and controlled atmosphere high temperature heat treatments. The temperature stability range in air for each compound was investigated by DTA and TGA methods. X‐ray diffraction powder data are presented for the fourteen compounds isolated. The only compounds that showed significant Eu3+‐activated luminescence were the oxy sulfates and oxysulfides. , the most efficient phosphor examined, is as bright as and distinctly more "red." Luminescence data are presented and discussed.