Diffusion Of Silver Research Articles

Measurement of grain-boundary diffusion at low temperature by the surface-accumulation method. II. Results for gold-silver system

Grain-boundary diffusion rates in the gold-silver system were measured at relatively low temperatures by the surface-accumulation method which was analyzed in Paper I. The specimen was a polycrystalline gold film possessing columnar grains on which a silver layer was initially deposited epitaxially on one surface. During subsequent low-temperature annealing lattice diffusion was frozen out, and diffusion then occurred along the grain boundary and free-surface short circuits. The silver, therefore, diffused into the film from the silver layer along the boundaries, eventually reaching the opposite surface where it accumulated and was measured by Auger spectroscopy. The silver layer acted as an effective constant silver source, and grain-boundary diffusivities were calculated from the accumulation data. However, the exact location of the effective constant source in the silver layer could not be determined and this led to an uncertainty in the values of the grain-boundary diffusivities of a factor of 10. Lower- and upper-bound values were therefore described by Db(lower bound) =7.8×10−6 exp(−0.62eV/kT) and Db(upper bound) =7.8×10−5 exp(−0.62eV/kT) cm2/s in the temperature range 30–269 °C. An examination of available grain-boundary diffusion data (including the present) suggests a tendency for the observed activation energy to decrease with decreasing temperature, and this was ascribed to a spectrum of activated jumps in the grain boundary and/or a spectrum of grain-boundary types in the specimen employed. The constant source behavior was tentatively ascribed, at least in part, to a grain-boundary ’’Kirkendall effect’’ resulting from the faster diffusion of silver than gold. The work indicates a need for increased understanding of the details of grain-boundary diffusion in alloys.

Potentiostatic Transients at Rotating Solid‐Electrolyte Electrodes

Current transients at rotating electrodes of Ag, , , , and in aqueous silver salt solutions were studied under potentiostatic conditions in which the current is controlled by either diffusion of silver ions in the solution or by diffusion processes in the solid. The electrical charges involved were compared with those expected from the Levich theory of the diffusion layer. In the case of this charge exceeds the expected value by orders of magnitude and the steady state is established sluggishly. This is explained in terms of chemical diffusion in the solid of cations injected from the solution. As a result of decomposition the solid electrolyte does not show diffusion‐limited current under cathodic polarization.

Ionic Motion inα-AgI

A molecular-dynamcis study of silver diffusion in superionic conductor $\ensuremath{\alpha}$-AgI is performed. Interionic potentials are constructed using Pauling's ideas of ionic radii. The diffusion constant for silver and its temperature dependence are in good agreement with experiment. Good agreement is also obtained for the silver density map with the experiment of Cava, Reidinger, and Wuensch.

Kinetics of the Reaction at the Silver Sulfide–Liquid Sulfur Interface

Abstract The reaction rate, v, at the Ag2S/S(1) interface was determined as a function of the silver activity aAg in Ag2S utilizing a solid-state electrochemical cell, Ag/AgI/Ag2S/Pt. The rate equation was found to be expressed by v=k(aAg)2–k′ On the basis of the theory by Kobayashi and Wagner, the rate-controlling step of the Ag2S/S(1) interface reaction is concluded to be S−(ad)+e→S2−(ad). The overall reaction rate of silver sulfidization by liquid sulfur can be well explained by the mixed control of a three-step reaction; the Ag2S/S(l) interface reaction, the diffusion of silver ions in Ag2S, and the Ag/Ag2S interface reaction.

Silver and tin bulk diffusion in AgSn alloys

Silver and tin bulk diffusion in AgSn alloys

Interference of light in diffused and thin-film glass waveguides

An investigation was made of the interference of light in planar optical waveguides formed in barium crown and barium flint glasses by solid-state diffusion of metals and high-frequency sputtering of glasses. Interference between the waveguide and substrate modes was observed in thin-film glass waveguides of near-critical thickness and in some diffused waveguides prepared by the thermal diffusion of silver and copper. The reasons for this interference were analyzed.

Prevention of silver ion diffusion into Pyrex glass by surface treatment

Prevention of silver ion diffusion into Pyrex glass by surface treatment

Reliability Study of Wire Bonds to Silver Plated Surfaces

The influence of temperature and environment on bond integrity was investigated for both aluminum ultrasonic and gold thermocompression wire bonds made to silver plate. Storage of aluminum-silver bonds at 85°C-8S-percent relative humidity (85/85) (no bias) resulted in progressive bond strength degradation and a shift in the primary failure mode from wire breaks to bond lifts. Degradation was attributed to massive aluminum corrosion. Bond degradation was not observed for the gold-silver system during storage at 85/85 (no bias) for 1500 h. In addition to humidity testing, gold-silver bonds were isothermally aged at 150, 250, 350, 450, and 540°C for a minimum of 10 min at each temperature to a maximum of 2000 h at 150°C, 1500 h at 250 and 350°C, 1000 h at 450°C, and 500 h at 540°C. Although rapid silver diffusion was observed in samples aged above 150°C, the system was determined to be mechanically reliable. An effective silver diffusion coefficient for the wire bond system was calculated from destructive wire pull data and was found to obey the equation

Direct observation of grain-boundary diffusion by scanning Auger microscopy

Scanning Auger electron microscopy has revealed the diffusion of silver at relatively low temperature along grain boundaries in gold films, and its subsequent diffusion over the surface of the films. The results point the way to quantitative studies of grain boundary and surface diffusion coefficients on a microscopic scale.

Fabrication of optical waveguides by solid-state diffusion of Ag and Cu in barium crown and flint glasses

Waveguides were fabricated by thermal diffusion of Ag and Cu in crown, barium crown, and barium flint glasses. The main properties of these waveguides were studied. It was found that waveguides were formed as a result of thermal diffusion of silver only in the presence of oxygen or as a result of thermal diffusion of copper but only in vacuum. The rate of diffusion of silver was independent of the composition of the glasses and was governed only by their viscosity at the diffusion temperature. The mechanisms of the diffusion of Ag and Cu were analyzed.

Diffusion of silver in polycrystalline aluminum in a temperature gradient

Diffusion of silver into polyerystalline aluminum samples exposed to a temperature gradient demonstrates an activation energy comparable to isothermal results. This activation energy does not agree with previous single-crystal experiments using a temperature gradient.

Radiation-stimulated diffusion of silver in quartz

Sequential etching was used to measure the distribution; first, the silver film was removed from the quartz with concentrated ItNO3, which disrupted the structure and distribution of the silver near the surface. Therefore, we disregarded the top layer of thickness about 0.2 #m. Layers of thickness 0.2-0.5 #m were then etched from the surface in a mixture of concentrated NHO 3 and HF at about 95~ The thickness of the etched layer was monitored from the etching time and from the change in resonant frequency, which indicated the thickness change to better than ~0.05 ~m. The solution was run into a PTFE vessel and evaporated to dryhesS o The silver content was determined from the activity due to the long-lived ll~ half-life 253 days; calculations and experiments showed that virtually all the radiation was due to this isomer after a cooling period of 10 days.

Diffusion of silver in silver vanadium bronzes

Diffusion constants of silver in silver vanadium bronzes Ag xV 2O 5 are given as a function of x in the temperature range 200 – 450 °C. The measurements were done by means of a galvanostatic pulse technique. The results indicate a very slow diffusion of the silver (e.g. D Ag + = 10 −12 cm 2s −1 at 400 °C, x=0.30).

Lightguiding in ion-exchanged glasses

A comparison is made of different Gaussian refractive index distributions in waveguides formed by thermal diffusion of silver ions into glass. Guides prepared for various diffusion times are investigated. It is shown that only one set of mode indices is insufficient to determine whether some index profile asymmetry exists.

Discussion on the mechanism of photodoping

The photo-enhanced reaction between metallic silver and vitreous chalcogenides is known as “photodoping”. Based on a series of experimental results, a model for photodoping was proposed. It was assumed in this model, that a junction barrier at the silver-chalcogenide interface worked for separating photocarriers. Holes are captured by metallic silver, and electrons are trapped by active or loosely bound chalcogen atoms after travel toward the interior of a glass layer. The Coulomb attraction field between ions thus formed is large enough to overcome the kinetic barrier in the process of silver diffusion. The square root dependence for the growth of the photodoped depth with exposure time has been explained in the light of this proposed model.

Photoconductivity of microcrystalline AgBr : I− emulsions

It is experimentally demonstrated that the photoelectron trap depth of AgBr : I− is unaffected by I− addition. The trap density increases with both I− content and with the size of the crystal. It is likely that the traps are on the surface of the microcrystals. Photoelectron decay data indicate that, after saturation of a few deep traps, the decay rate for temperatures above 60 K is determined by diffusion of interstitial silver ions (Ag+i) to the sites of trapped electrons. The activation energy for Ag+i diffusion in AgBr : I− is higher than in AgBr, and the concentration of Ag+i increases with both crystal size and I− content. These results are explained in terms of a more uniform Ag+i distribution and a probable localization of Ag+i near the I− impurity.

Modes in diffused optical waveguides (parabolic and Gaussian models)

A simple analytical description of diffused optical waveguides by a Gaussian refractive index profile is proposed and compared to a parabolic one. Propagation constants and fields are obtained in terms of well-known functions only. The models are experimentally verified by measuring the mode spectrum of waveguides formed by thermal diffusion of silver ions into glass. These models yield a method to obtain guide parameters from mode spectrum.

Diffusion of silver through epitaxial films of copper and nickel on silver (111): the formation of an equilibrium layer of silver

Thick (>2000 AA) epitaxial films of nickel and copper grown on silver (111) have been annealed in ultra-high vacuum at temperatures in the range 500-600K. This annealing procedure appears to cause diffusion of silver to the outer surface to take place, with the formation of an 'equilibrium layer' of silver. The silver layer appears to be strained in each case to give an integral ratio matching with the nickel or copper, the matching being 6:7 for Ag:Ni and 8:9 for Ag:Cu. A comparative study was made for thin films of silver deposited directly on to copper (111). LEED, RHEED and Auger spectroscopy were used throughout the study. Extra non-primary satellite beams in both LEED and RHEED from thin layers of Ag on Cu or Ni are believed to result from a combination of multiple diffraction and periodic deformations in the overlayer.

Diffusion, electric transport, and effect of a silver impurity on the electrical and optical properties of As2Se3

The diffusion and electric transport of silver in glassy As2Se3 was studied in the range 110 to 160 °C with the radioactive tracer 110mAg. It is shown, that the temperature dependence of the silver diffusivity can be described by the formula D = 5.9 × 10−6 exp (−0.41/kT), and that the effective mobility of the silver ions in the range 134 to 155 °C vary within (1.7 to 5.0) × 10−9 cm2/Vs. At temperatures below 134 °C silver is found to migrate in glass in the form of positive ions with an effective charge qeff ≧ + 1, the experimentally measured charge above 134 °C is qeff ≧ +2. This anomalous increase of qeff with temperature is shown to be associated with the formation of inclusions of a second phase (apparently Ag2Se, Ag3AsSe3, or AgAsSe2) in the course of the electric transport at T > 134 °C. A discussion based on the experimental data obtained is made of the mechanism of silver diffusion involving the migration of arsenic selenide through the interlayer space. Further an effect of white light illumination on the concentration profile of silver introduced by diffusion in As2Se3 is revealed. The results obtained are considered on the basis of photochemical reactions occurring at the silver–As2Se3 interface. A study is also made of the effect of silver impurities introduced by diffusion in As2Se3 glasses on the electrical and optical properties of this material. [Russian Text Ignored]

The isotope effect of silver diffusion in aluminium

The isotope effect of silver diffusion in aluminium is measured as function of diffusion temperature. The result agrees with impurity diffusion measurements of Peterson and Rothmann, giving no indication for a divacancy contribution to impurity diffusion. The activation energy of aluminium self-diffusion must be greater than 28.8 kcal/mol. Es wurde die Temperaturabhangigkeit des Isotopieeffekts der Silberdiffusion in Aluminium gemessen. In Ubereinstimmung mit den Fremddiffusionsmessungen von Peterson und Rothmann wurde kein Doppelleerstellenbeitrag zur Fremddiffusion gefunden. Die Aktivierungsenergie der Selbstdiffusion des Aluminiums mus groser als 28,8 kcal/Mol sein.