Nucleation Of Copper Research Articles

Nucleation of electrodeposited copper on anodized titanium

A study has been made to determine the effect of an electrochemically produced titanium-oxide film on the nucleation of copper. The oxide films were made galvanostatically at 25°C in 1 M sulphuric acid on pure titanium metal. Potentiodynamic, potential step and current step experiments were performed in an additive-free copper sulphate-sulphuric acid electrolyte at 25°C. It was found that the oxide film played an important role during nucleation. By increasing the thickness of the anodic film it was possible to decrease the diameter and to increase the surface density of copper nuclei. The kinetics of nucleation and growth of the copper deposits were analysed. The deposits were examined by SEM.

Influence of ion beam activation on the mode of growth of Cu on Si(100)

The influence of simultaneous low-energy argon-ion bombardment on the initial nucleation and growth of sputter-deposited copper on Si(100) under ultrahigh vacuum conditions has been investigated using Auger electron spectroscopy. Argon-ion energies were either 500 or 1000 eV, with the ratio of ion arrival rate to copper atom arrival rate to the substrate ranging from 0.3 to 0.8. Proton-induced x-ray emission was used to measure the thickness (areal density) of the deposited copper. The intensities of the Si-LVV and Cu-LVV Auger transitions were measured as a function of film thickness and from those data it was possible to determine the mode of growth of the copper film. For the case of deposition without ion beam activation, an island growth mechanism was observed. For simultaneous bombardment with 500-eV Ar+ , a complete change to layer-by-layer growth was observed when the ion-to-atom arrival ratio was 0.8. For 1000-eV Ar+ bombardment, the results indicated an island growth mechanism for arrival rate ratios between 0.3 and 0.6, although the possibility of ion beam mixing between the overlayer and substrate, which would affect the interpretation of the data, cannot be discounted. Equilibrium sputtering yields for concurrent ion bombardment and film deposition were also measured and were found to be considerably less than those for equivalent Ar+ bombardment of bulk copper.

Electrochemical nucleation and growth of copper on polycrystalline palladium

The electrochemical nucleation of copper on palladium has been investigated by applying the potential step technique. The nucleation process was found to be progressive and interpretation of current-time transients over a wide overpotential interval made it possible to determine the overpotential dependence of the steady state nucleation rate, the size of the critical nucleus and the work of nucleation.

Blowholing in PTH Solder Fillets

Data from laboratory and production scale tests are given that show that the efficiency of catalyst adsorption controls the coverage by the electroless copper deposit in plated‐through‐holes in FR‐4 laminate, and that this, in turn, governs the outgassing performance of the finished board. The nature of electroless copper nucleation and growth is discussed and the reasons for the formation of voids in the deposit are identified.

The formation of copper fibers during the lime-enhanced hydrogen reduction of cuprous sulfide

Morphological features of the lime-enhanced hydrogen reduction of cuprous sulfide pellets were investigated as a function of temperature and time by scanning electron microscopy. Moderate temperatures of reduction (600–750°C) were found to result in the formation of fibers and loops of copper, whereas at high temperatures of reduction (900–1000°C) only sintered crusts of spongy copper were obtained. The sequence of nucleation and growth of copper fibers was found to be the formation of pits and pores on the sulfide particles, followed by the nucleation of copper preferentially in these pores, the emergence of copper hairs from the sulfide base, and the formation and thickening of loopy fibers. These events are explained on the basis of the reduction characteristics and nonstoichiometry of cuprous sulfide and its mismatch with the product metal. While lime enhances the bulk reduction rate of cuprous sulfide, it does not seem to affect the mechanism of copper fiber formation.

Study of the promoting influence of transition metals on the reduction of cupric oxide by temperature programmed reduction

Temperature programmed reduction (t.p.r.) has been used to study the hydrogen reduction of cupric oxide and the influence on the reduction of transition metals added to the bulk oxide. X.r.d. and X.p.s. were used to characterise the samples.For cupric oxide containing 2 mol% metal additive, three types of reduction behaviour were indicated. (i)For Cr, Mn, Fe, Co and Ni, a single reduction process some 30 K below that observed for pure CuO. (ii) For Pd and Ru, two reduction processes some 100 K below that observed for pure CuO. (iii) For Pt, Rh and Ir, complex reduction behaviour with the bulk of the reduction occurring some 100 K below that for CuO. For Ag and Au, similar complex behaviour with the main reduction some 30 K below that for CuO.A detailed study was made of the reduction of CuO containing Pd (0.05–4.0 mol%) and Pt (0.05–10 mol%).Measured activation energies were essentially independent of the metal additive indicating that rate limiting steps for the reductions involve the growth of metal nuclei.The promoting effects of metal additives are discussed in terms of their ability (i) to remain within the CuO lattice, (ii) to produce extra nucleation sites and (iii) to increase the concentration of surface hydrogen. Thus the first row transition metals produce extra copper nucleation sites by non-specific distortion of the CuO lattice. For Group VIII and Ib additives, the nucleation sites are provided by the preferential reduction of the additive ion. The Group VIII metals further promote the reduction of CuO by mechanisms involving hydrogen adsorption and spillover.

Characterization of copper nucleation and growth from aqueous solution on aluminum: A transmission electron microscopy study of copper cementation

A novel technique was developed for the direct observation of copper precipitate nuclei forming on aluminium surfaces by cementation. This technique involves the preparation of thin electron-transparent aluminum films by vapor deposition in vacuum onto cleaved NaCl crystal blanks. Following aqueous CuSO 4 solution contact of an exposed aluminum film surface area, the films with attached copper nuclei were examined by transmision and scanning electron microscopy. For conditions which promoted optimum deposit growth kinetics, the initial faceted polyhedral nuclei developed microdendritic precipatates which led to the growth of massive dendritic deposits. The details of microdendrite arm structures were directly observed in the transmission electron microscope. By systematically varying the residual grain structure of the aluminum films, it was demonstrated that grain size and grain structure do not affect the disposition and morphology of the initial precipitates. Furthermore, in single-crystal aluminum films containing dislocations it was not possible to show any consistent association of nucleation or nuclei with the emergence sites of individual dislocations. The principal feature of the substrate which influences precipitation as a result of the electrochemical cementation reaction seems to be crystallographic orientation, and this is consistent with observations of the growth and structure of conventional electrodeposits.

Electrochemical nucleation and growth of copper on iron and aluminum: A TEM study of industrial copper cementation

Georgius Agricola in 1556 in his classical book, “De Re Metallica”, mentioned a strange water drawn from a mine shaft near Schmölnitz in Hungary that eroded iron and turned it into copper. This precipitation (or cementation) of copper on iron was employed as a commercial technique for producing copper at the Rio Tinto Mines in Spain in the 16th Century, and it continues today to account for as much as 15 percent of the copper produced by several U.S. copper companies.In addition to the Cu/Fe system, many other similar heterogeneous, electrochemical reactions can occur where ions from solution are reduced to metal on a more electropositive metal surface. In the case of copper precipitation from solution, aluminum is also an interesting system because of economic, environmental (ecological) and energy considerations. In studies of copper cementation on aluminum as an alternative to the historical Cu/Fe system, it was noticed that the two systems (Cu/Fe and Cu/Al) were kinetically very different, and that this difference was due in large part to differences in the structure of the residual, cement-copper deposit.

Nucleation of Copper Electrodeposits on Thin (111) Films of Evaporated Copper

Electrodeposited nuclei and defect structures on thin (111) films of evaporated copper were studied by means of electron and optical microscopes and electron diffraction, as a part of an investigation of copper nucleation from sulfate baths. The roles of noncoherent twin boundaries on the films were of limited significance in the nucleation. Macroscopic defects such as notches and macrosteps on the surface with mirror luster were preferential nucleation sites. The rate of nucleation in the initial stage was evaluated under various overpotentials.

Electrolytic nucleation of copper and brass on platinum single crystal spheres

The nucleation of copper from cyanide electrolytes on platinum single crystal cathodes was investigated by a pulse method. Using pulse widths of 10 ms to 1 min the critical overvoltage for nucleation varies between 35 and 60 mV. The nucleation rate depends not only on the pulse width and amplitude but also to a high degree on the crystallographic orientation of the substrate. The Gibbs free energy of nucleation is about 3–7 kT and 1–7 atoms are in one nucleus. The deposition of copper-zinc alloys from cyanide solutions was also studied. It was found that the nucleation rate and the content of copper in the deposited brass crystals depend on the composition of the electrolyte solution, the electrode potential and the crystallographic orientation of the substrate.

A Quantitative Study of Nucleation and Growth of Copper I—Oxide on Copper Single Crystals

A microgravimetric study shows that the rate of oxidation of the (100) face of copper is convenient for the observation of the different steps of the process: induction, nucleation, and growth of the oxide particles. The rate of those steps and the number of nuclei depend upon crystallographic orientation of the metal, temperature of reaction, and pressure of oxygen. Sticking probabilities and activation energies of the different steps have been determined. Our results show under which conditions Rhead's theoretical scheme founded on surface diffusion remains valid.

Nucleation and crystal growth of copper(II) 8-hydroxyquinolinate precipitated from mixed solvents

The precipitation kinetics of copper(II) 8-hydroxyquinolinate, formed in water-acetone mixtures, have been studied in a stop-flow apparatus by spectrophotometric techniques. Three factors are found to be important in improving the physical characteristics of crystals precipitated from mixed solvents. Supersaturation and growth rate can be controlled uniformly by slow rate of change in solvent composition; the presence of acetone significantly reduces the number of effective nuclei; thirdly, large amounts of organic solvent cause a change in the crystal form and its growth mechanism. At room temperature, copper(II) 8-hydroxyquinolinate is precipitated as a dihydrate from water-acetone mixtures containing 0–60% acetone, and the crystal growth is limited by a diffusion-controlled process. Anhydrous copper(II) 8-hydroxyquinolinate is formed in 70% acetone solutions by a surface-controlled reaction.

Influence of Adsorbed Gas on Surface Diffusion and Nucleation

Experiments with the field-electron emission microscope show that residual gas pressures as low as 2×10−8 Torr increase the density of nucleation of copper on tungsten compared with the nucleation density at 4×10−10 Torr ambient pressure. The effect of adsorbed oxygen and nitrogen on the mobility of copper on tungsten depends on the relative amounts of gas and copper and on the local substrate crystallography. Generally stated, they increase the activation energy for surface diffusion.