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Thesis (M.S.) -- Worcester Polytechnic Institute. / Keywords: palladium composite membrane; leak formation. Includes bibliographical references (leaves 107-112).

Magister Philosophiae - MPhil / Pd based membranes are known for their incredible selectivity towards H2. In order for Pd membranes to display high H2 selectivity, a defect free layer of Pd needs to be deposited onto a support. Although various fabrication techniques do exist, many researchers have attempted to produce defect free Pd-based films, using electroless plating. The first step in the preparation technique involves “seeding” of the support structure. Even though these seeds, if well distributed and anchored to the support, are crucial in order to obtain the defect free Pd layer, they hardly ever received attention from the science community. This thesis reports findings on various seeding methods as well as the resulting microstructures of the Pd films formed as a result of the type of seeding method employed. Finally the quality of the membranes using the most promising seeding technique was determined by subjecting the membranes to permeance tests with N2 at both high and low temperatures as well as with H2 at high temperatures.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements of the degree of Master of Science. November 1995. / The preparation of supported cobalt and gold catalysts by the technique of electroless plating, and the establishment of the influence of synthesis variables on the physical properties of the supported catalyst, forms the basis of this dissertation. In both the cases of cobalt and gold supported on extruded cylindrical alumina pellets, the penetration profile of the metal into the support showed dependence on the pH of the activation solution, while the metal loading onto the same support showed no dependence on pH of the activation solution at all. The variables involved in the plating process of the activated pellets, namely: i) the concentration of the activation solution, ii) pH and temperature of the plating bath, iii) plating time, and Iv) variation of the concentrations of components of the plating bath all influenced the mass of metal loaded onto the support, but not the penetration characteristics. It is therefore possible to prepare a supported catalyst with very specific , properties using the above information. Under similar conditions, with extruded alumina pellets as support and with the specific plating formulations used, gold showed higher metal loadings at lower gold concentrations than cobalt.

This study focused on improvement of electroless plating methods by use of particular bath additives. The techniques developed here can enable us to plate very thin layers selectively on a nonconductive substrate and thus create metallized features on a nanoscale. Through the development of such bottom-up techniques this work contributes a key technology to achieving self-assembled nanocircuits. The use of additives in an electroless plating environment can modify the barriers to nucleation (or seeding) and growth. Two additives, namely 3-mercapto-1-propanesulfonic Acid (MPS) and 1,3-propanedisulfonic acid (PDS), notably increased the selectivity of electroless metallization on chemically modified surfaces, which can be used to create patterned structures. More specifically, the additives increased the growth rate of metal on an aminosilane-coated surface relative to an uncoated surface. This work includes an examination of metal layer thickness and conductivity in addition to selectivity. The layer thickness was determined through the use of atomic force microscopy on surfaces that exhibited conductivity. The conductivity of the surface metal was determined through a measurement on a four-point probe measurement. In this series of experiments, the disulfonate-containing additive PDS provided the highest nucleation density, highest conductivity and the best selectivity ratio. The palladium metal deposit on the PDS-treated surface was nearly uniform in height and its conductivity approached the bulk conductivity of palladium with a metal height of less than 30 nm. MPS-treated surfaces also provided increased nucleation density when used during the seeding step, but the resulting conductivity was less than that of the PDS treated samples. We recommend the use of PDS as an effective electroless plating additive for use in palladium electroless plating processes.

The concentration of tin and palladium in catalysts used in electroless copper plating have been determined by Rutherford backscattering spectrometry with high energy (2-5) MeV ⁴He⁺. The tin:palladium ratio in the catalyst decreases when exposed to an alkaline solution. X-ray photoelectron spectroscopy has confirmed this result and has shown the palladium in the catalyst is present as palladium metal and the tin is present, probably as an oxidized species, to a depth of about 30 Å. Catalysts for the electroless plating of copper are obtained by the reaction of Pd(II) and Sn(II). The extent of the reaction and the concentrations of the reaction products depend on the solution conditions. Conflicting results obtained in previous investigations of tin-palladium catalysts can be explained on this basis. Single crystals of gallium arsenide (GaAs(100)) were found to dissolve in synthetic lung fluid (Gamble solution). The concentrations of arsenic and gallium in the Gamble solution as well as the arsenic:gallium ratio on the GaAs surface increased continuously as the time of exposure to the Gamble solution increased. X-ray photoelectron spectroscopic studies of the gallium arsenide surface showed that arsenic migrated to the surface and it was oxidized to a species resembling As₂O₃ and finally solubilized by the Gamble solution. The solubility of gallium was governed primarily by the formation of stable complexes with the citrate and phosphate ions in the Gamble solution. Zinc that was present in the single crystals of gallium arsenide also migrated to the surface.

A study has been carried out to investigate the effects of heat treatment on microindentation hardness, abrasion and corrosion resistance of Electroless Nickel coatings. In particular, a proprietary coating system, NIKLAD 794 has been investigated. Samples of 4130 steel have been plated according to manufacturer's specifications. The plated samples have then been subjected to an array of heat treatment temperatures and times. Post heat treatment tests have been conducted including Taber Abrasion testing, salt fog chamber testing, and Knoop microindentation hardness testing. Results of the individual tests have been compared to determine the effects of heat treatment on, and the interactions between, the parameters examined.

by Chow Yeung Ming = 化學鍍鎳層的表面性質與焊接能力之關係 / 周洋明. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 62-65). / Text in English; abstracts in English and Chinese. / by Chow Yeung Ming = Hua xue du nie ceng de biao mian xing zhi yu han jie neng li zhi guan xi / Zhou Yangming. / Abstract --- p.i / 論文摘要 --- p.ii / Acknowledgements --- p.iii / Table of Contents --- p.v / List of Figures --- p.viii / List of Tables --- p.ix / Abbreviations --- p.x / Chapter Chapter 1 --- INTRODUCTION / Chapter 1.1 --- Electroless Plating (Autocatalytic Deposition) --- p.1 / Chapter 1.2 --- Electroless Nickel (EN) Plating --- p.2 / Chapter 1.3 --- Types of Electroless Nickel Deposits --- p.2 / Chapter 1.4 --- Properties of Electroless Nickel --- p.5 / Chapter 1.5 --- Applications of Electroless Nickel in Electronic Packaging Industry --- p.7 / Chapter 1.6 --- Importance of Solderability --- p.8 / Chapter 1.7 --- Literature Review of Solderability Studies of Electroless Nickel --- p.9 / Chapter 1.8 --- Motivations & Aims of Studies --- p.10 / Chapter Chapter 2 --- EXPERIMENTAL & INSTRUMENTATION / Chapter 2.1 --- Electroless Nickel Plating --- p.11 / Chapter 2.2 --- Solderability Measurements / Chapter 2.2.1 --- Soldering --- p.13 / Chapter 2.2.2 --- Various test methods for solderability --- p.13 / Chapter 2.2.3 --- Wetting balance method --- p.15 / Chapter 2.2.4 --- Solderability measurements of electroless nickel deposits --- p.17 / Chapter 2.2.5 --- Assessment of wetting curves --- p.19 / Chapter 2.3 --- Surface Oxidation Studies / Chapter 2.3.1 --- Use of X-ray photoelectron spectroscopy (XPS) in surface characterization --- p.19 / Chapter 2.3.2 --- XPS system --- p.22 / Chapter 2.3.3 --- Surface composition of electroless nickel deposits --- p.22 / Chapter 2.3.4 --- Oxide thickness characterization by angle-resolved XPS --- p.25 / Chapter 2.3.5 --- Oxide thickness characterization by XPS depth profiling with low-energy-ion sputtering --- p.28 / Chapter 2.4 --- Surface Morphology Studies / Chapter 2.4.1 --- Surface morphology studies by scanning Auger electron microscopy (SAM) & atomic force microscopy (AFM) --- p.28 / Chapter 2.4.2 --- SAM studies of electroless nickel surfaces --- p.29 / Chapter 2.4.3 --- AFM studies of electroless nickel surfaces --- p.29 / Chapter 2.5 --- Oxide Quality Studies --- p.31 / Chapter Chapter 3 --- RESULTS & DISCUSSIONS / Chapter 3.1 --- Solderability Measurements by the Wetting Balance Method --- p.33 / Chapter 3.2 --- Surface Oxidation Studies / Chapter 3.2.1 --- Surface composition of electroless nickel deposits --- p.36 / Chapter 3.2.2 --- Oxide thickness characterization by angle-resolved XPS --- p.38 / Chapter 3.2.3 --- Oxide thickness characterization by XPS depth profiling with low-energy-ion sputtering --- p.44 / Chapter 3.2.4 --- Conclusion --- p.47 / Chapter 3.3 --- Surface Morphology Studies / Chapter 3.3.1 --- SAM studies of electroless nickel surfaces --- p.49 / Chapter 3.3.2 --- AFM studies of electroless nickel surface --- p.49 / Chapter 3.3.3 --- Conclusion --- p.53 / Chapter 3.4 --- Interpretation of Wetting Kinetics of Electroless Nickel --- p.54 / Chapter Chapter 4 --- CONCLUSIONS & FURTHER STUDIES / Chapter 4.1 --- Conclusions --- p.59 / Chapter 4.2 --- Further Studies --- p.60 / Appendix --- p.61 / References --- p.62

When porous silicon is plated with a catalytic metal, the two materials can act together as a single entity whose electrical properties are sensitive to its environment – the sensing component of an electrochemical gas sensor. Etching pores into silicon is an electrochemical process; and which type of doped silicon used is one of its key parameters. For nearly all reported porous silicon gas sensors, the silicon has been of the p-doped variety – because p-doped porous etching is better understood and the layers that result from it are more predictable – despite n-doped silicon having potentially significant benefits in ease of fabrication and being more conducive to plating by a catalyst. This experiment is an attempt at creating a palladium plated n-doped porous silicon layer, and an examination into what differentiates this fabrication process and the layers that result from the traditional p-doped type. The porous layers to be plated are to be the same and would ideally have properties that are a close approximation to what a functional gas sensor would require. This experiment defined a process that fabricated this “ideal” layer out of N-type, , double polished silicon wafers with a resistance of 20 Ω cm. The wafers were subjected to the anodic etching method with an HF/ethanol mixture as the electrolyte; and only two (of among many) fabrication parameters were varied: HF concentration of the electrolyte and total etching time. We find that a concentration of 12% HF (by volume) and an etching time of 6 hours result in layers most appropriate to carry into plating. The anodization current density is 15 mA cm-2. Deposition of the catalyst, palladium, is done using the electroless method by immersing the porous layer in a .001M PdCl2 aqueous bath. Characterization of this Pd/Porous Silicon layer was done by measuring resistivity by four point probe and imaging through Scanning Electron Microscopy. It was found that layers of a maximum average of 63 ± 6% porosity were created using our fabrication method. There is evidence of palladium deposition, but it is spotty and irregular and is of no improvement despite the n-doping wafer makeup. Resistivity in well-plated regions was measured to be 7-10 Ωcm, while resistivity in regions not well-plated was measured to be 70-140 Ω cm. This is comparable to previous literature values, indicating n-silicon porous silicon can be fabricated and still have potential as a catalytic layer, should metal deposition methods improve.

<p>Patterning of multi crystalline silicon Solar cell is prepared with photolithography etching. Electroless plating is used to get metallization of Nickel contacts. SEM analysis of Nickel deposition and measurement of contact resistance for series and shunt resistance is done. To increase the fill factor, the screen printed electrodes are subjected to different firing temperatures there by increasing the efficiency of solar cell. Nickel-silicide formation at the interface between the Silicon and Nickel enhances stability and reduces the contact resistance, resulting in higher energy conversion efficiency.</p><p> </p>