A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. / A quartz microbalance electrode (QME) was constructed for the investigation of the electrochemistry of electroless plating baths. To this end, the electronic oscillator circuitry required for the microbalance was developed from literature examples, and the techniques of forming electrodes and mounting the crystal in an appropriate holder were established. The device thus developed was compact, allowing for in situ frequency and electrochemical measurements to be made in a commercially available 100 mL Metrohm cell. The precision .and accuracy obtained with the home-built device were shown to be adequate for electrochemical research, and the sensitivity was found to be consistent with the value expected from the Sauerbrey equation.(Abbreviation abstract) / Andrew Chakane 2018

by Lam Ka. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 54-60). / Abstracts in English and Chinese. / ABSTRACT --- p.i / ACKNOWLEDGEMENT --- p.ii / TABLE OF CONTENT --- p.iii / LIST OF TABLES --- p.v / LIST OF FIGURES --- p.vii / Chapter CHAPTER ONE: --- INTRODUCTION --- p.1 / Chapter 1.1 --- Metal deposition --- p.1 / Chapter 1.2 --- Electroless Nickel Plating --- p.3 / Chapter 1.2.1 --- Historical Review and Applications --- p.3 / Chapter 1.2.2 --- General Chemical Principles --- p.5 / Chapter 1.2.3 --- Previous Studies --- p.7 / Chapter 1.3 --- Scope of Work --- p.12 / Chapter CHAPTER TWO: --- EXPERIMENTAL --- p.13 / Chapter 2.1 --- Bath Composition --- p.13 / Chapter 2.1.1 --- Theoretical Description --- p.13 / Chapter 2.2.2 --- Materials --- p.15 / Chapter 2.2 --- Procedure and Experimental Conditions --- p.17 / Chapter 2.3 --- Characterization of EN Coatings --- p.18 / Chapter 2.3.1 --- Theory --- p.18 / Chapter 2.3.1.1 --- Energy Dispersive X-ray Detection of Scanning Electron Microscopy --- p.18 / Chapter 2.3.1.2 --- Polycrystalline X-ray Diffraction --- p.18 / Chapter 2.3.1.3 --- X-ray Photoelectron Spectroscopy --- p.20 / Chapter 2.3.1.4 --- Microhardness --- p.22 / Chapter 2.3.1.5 --- Corrosion resistance --- p.23 / Chapter 2.3.1.6 --- Thickness Measurement --- p.23 / Chapter 2.4 --- Application --- p.24 / Chapter CHAPTER THREE: --- RESULTS AND DISCUSSION --- p.26 / Chapter 3.1 --- Appearance --- p.28 / Chapter 3.2 --- Microstructure --- p.30 / Chapter 3.2.1 --- Effect of Phosphorus Content --- p.30 / Chapter 3.2.2 --- Effect of heat treatment --- p.32 / Chapter 3.3 --- Corrosion Resistance --- p.37 / Chapter 3.3.1 --- Effect of Phosphorus Content --- p.37 / Chapter 3.3.2 --- Effect of Heat Treatment --- p.45 / Chapter 3.3.2.1 --- Temperature --- p.45 / Chapter 3.3.2.2 --- Cooling Rate --- p.47 / Chapter 3.4 --- Microhardness --- p.49 / Chapter 3.4.1 --- Effect of Phosphorus Content --- p.49 / Chapter 3.4.2 --- Effect of Heat Treatment --- p.49 / Chapter CHAPTER FOUR: --- CONCLUSION --- p.52 / REFERENCES --- p.54

The utilization of Electroless Nickel-Phosphorus (EN) coatings has witnessed a staggering increase during the last two decades. Many outstanding characteristics of the EN coating method have generated a lot of interest in various industries including oil and gas, electronic, chemical, automotive, aerospace, and mining. Some of the highlighted characteristics of EN coatings are superior corrosion and wear resistance especially in environments containing H2S and CO2, superior mechanical properties, uniform coating thickness, excellent surface finish properties, superb adhesion characteristics, and wide range of thickness. The EN coating process is based on a redox reaction in which a reducing agent is oxidized and Ni+2 ions are reduced on the surface of the substrate materials. Once the first layer of Ni is deposited, it acts as a catalyst for the process. Consequently, a linear relationship between coating thickness and time usually occurs. If the reducing agent is sodium hypophosphite, the deposit obtained will be a nickel-phosphorus alloy. The objective of this research was to evaluate various properties of three types of EN coatings, namely, low, medium, and high phosphorus. In the first phase of this work an automated prototype EN bath was designed and engineered. As a result, three types of EN coatings were deposited on various substrates. In the second phase of this research, various qualitative and quantitive methods were implemented to evaluate various properties of EN coatings. Also, the effects of various coating parameters including coating thickness and phosphorus content on properties of EN coatings were comprehensively investigated. Furthermore, the effect of post heat treatment on various properties of EN coatings was studied. Heat treatment on EN deposits in the range of 300-400 °C for one hour caused the hardness to increase due to the formation of various types of nickel phosphide (NixPy). The results of this study showed that various properties of EN coatings are directly related to the phosphorus content of the coatings. EN coatings with lower phosphorus content are crystalline, hard and brittle. As a result, they have superior wear resistance. On the other hand, EN coatings with higher phosphorus content are amorphous with superior corrosion resistance. iii EN coatings in general have excellent adhesion properties. However, the degree of adhesion is affected by several parameters including coating thickness, phosphorus content, post heat treatment, and ductility of the substrate. Moreover, it was shown that due their brittle nature EN coatings in general and heat-treated low phosphorus EN coating in particular have a detrimental effect on fatigue properties of their substrates. It was also shown that EN coatings in general, improve the kinetic coefficient of friction. In other words, EN coatings exhibit a self-lubricating behavior. Also, it was shown that EN coatings completely follow the surface profile of their substrate unlike conventional electroplating. Corrosion and wear studies on EN coatings revealed that EN coatings are excellent candidates for materials subjected to excessive corrosion and wear in a potash brine environment. Finally, the microstructure study of EN coatings using TEM and STEM electron microscopy revealed valuable information regarding the phase transformation during the heat treatment. It was shown that heat treatment at 400°C for one hour caused the precipitation of various nickel phosphide particles. As a result, significant changes in various properties of EN coatings occurred.

The utilization of Electroless Nickel-Phosphorus (EN) coatings has witnessed a staggering increase during the last two decades. Many outstanding characteristics of the EN coating method have generated a lot of interest in various industries including oil and gas, electronic, chemical, automotive, aerospace, and mining. Some of the highlighted characteristics of EN coatings are superior corrosion and wear resistance especially in environments containing H2S and CO2, superior mechanical properties, uniform coating thickness, excellent surface finish properties, superb adhesion characteristics, and wide range of thickness. The EN coating process is based on a redox reaction in which a reducing agent is oxidized and Ni+2 ions are reduced on the surface of the substrate materials. Once the first layer of Ni is deposited, it acts as a catalyst for the process. Consequently, a linear relationship between coating thickness and time usually occurs. If the reducing agent is sodium hypophosphite, the deposit obtained will be a nickel-phosphorus alloy. The objective of this research was to evaluate various properties of three types of EN coatings, namely, low, medium, and high phosphorus. In the first phase of this work an automated prototype EN bath was designed and engineered. As a result, three types of EN coatings were deposited on various substrates. In the second phase of this research, various qualitative and quantitive methods were implemented to evaluate various properties of EN coatings. Also, the effects of various coating parameters including coating thickness and phosphorus content on properties of EN coatings were comprehensively investigated. Furthermore, the effect of post heat treatment on various properties of EN coatings was studied. Heat treatment on EN deposits in the range of 300-400 °C for one hour caused the hardness to increase due to the formation of various types of nickel phosphide (NixPy). The results of this study showed that various properties of EN coatings are directly related to the phosphorus content of the coatings. EN coatings with lower phosphorus content are crystalline, hard and brittle. As a result, they have superior wear resistance. On the other hand, EN coatings with higher phosphorus content are amorphous with superior corrosion resistance. iii EN coatings in general have excellent adhesion properties. However, the degree of adhesion is affected by several parameters including coating thickness, phosphorus content, post heat treatment, and ductility of the substrate. Moreover, it was shown that due their brittle nature EN coatings in general and heat-treated low phosphorus EN coating in particular have a detrimental effect on fatigue properties of their substrates. It was also shown that EN coatings in general, improve the kinetic coefficient of friction. In other words, EN coatings exhibit a self-lubricating behavior. Also, it was shown that EN coatings completely follow the surface profile of their substrate unlike conventional electroplating. Corrosion and wear studies on EN coatings revealed that EN coatings are excellent candidates for materials subjected to excessive corrosion and wear in a potash brine environment. Finally, the microstructure study of EN coatings using TEM and STEM electron microscopy revealed valuable information regarding the phase transformation during the heat treatment. It was shown that heat treatment at 400°C for one hour caused the precipitation of various nickel phosphide particles. As a result, significant changes in various properties of EN coatings occurred.

In this study we present the results of electroless deposition of silver (Ag) and electrophoretic deposition (EPD) of Al2O3 layers on glass for application in thin film transistor (TFT). Since Ag exhibits excellent resistivity, it is selected to be the material of conductive layer. Ag thin film electrical and physical parameters are studied as a function of the deposition time and working temperature. We study the thin-film electrical and mechanical properties using 4-point Probe, surface analyzer and nano indenter. The Ag film, thicker than 200 nm, exhibited a specific electrical sheet resistivity of about 500 m£[/¡¼. We also study the thin-film morphology and composition using SEM and FTIR, respectively. In this study, Mechanism and kinetics of the electrophoretic process in an Al2O3 cell are also studied. Al2O3 concentration levels are set from 1.25 to 7.5%, and deposition time from 5~20 seconds. Deposition time and Al2O3 particle concentration is experimentally discussed and characterized. The result shows that a linear relationship between the deposition rate and applied voltage is obtained. Besides, in this study, deposition of conductive layer silver and insulating layer Al2O3 for TFT are studied. A new process to deposit Ag layer and Al2O3 layer to be the conductivity layer and insulating layer of TFT is presented. First, the circuit pattern is defined by lithography process. Then, Ag is deposited with thickness of 200 nanometers. Second, the wafer is immersed in the stripper solution to remove the resist. After the deposition of the Ag on glass is finished, Al2O3 nano-scale particle concentration is prepared for electrophoretic deposition.

Hydrogen is considered to be the fuel of the future as it is clean and abundant. Together with the rapidly developing fuel cell technology, it can sustain an environmentally sound and efficient energy supply system. Developing the technologies of palladium-based membrane for hydrogen separation and palladium nanostructured materials for hydrogen sensing and hydrogenation catalysts makes the "hydrogen economy" possible. This is because these technologies will allow for commercially viable production of comparatively cheap and high-quality hydrogen, and safety of its application. Based on the market requirements and interest in the development of a hydrogen economy, the purposes of this thesis are to develop thin palladium membrane for hydrogen separation and to explore an economic method for the synthesis of palladium nanowires in potential engineering applications. The original contributions of this thesis are outlined below: / The investigation of deposition progress of a palladium membrane on porous stainless steel substrate illustrates that palladium deposits will form a network structure on pore areas of the substrate surface in the initial stages. A bridge model is presented to describe the formation of a membrane. This model is confirmed from the cross-section of the deposited membranes. Based on the bridge model and the experimental measurements of palladium membranes deposited on the pore area of the substrates, the thickness of a palladium membrane deposited on 0.2 mum grade porous stainless steel substrate can be effectively controlled around 1.5∼2 mum, and the thickness of a palladium membrane deposited on 2 mum grade porous Inconel substrate can be effectively controlled around 7.5∼8 mum. Comparing the thickness and quality of palladium membranes deposited on the same substrates with the data in the literature, the thicknesses of the membranes prepared in this program are lower. The obtained result will be beneficial in the design and manufacture of suitable membranes using the electroless deposition process. / In the initial deposition stages, palladium nanoparticles cannot be deposited at the surface of the SiO2 inclusions that appear at the substrate surface. With the extension of deposition time, however, palladium nanoparticles gradually cover the SiO2 inclusions layer by layer due to the advance deposited palladium nanoparticles on the steel substrate surrounding them. The effect of the SiO2 inclusions on palladium deposits cannot be neglected when an ultra-thin membrane having the thickness similar to the size of inclusions is to be built. / The chemical reaction between phosphorus (or phosphate) and palladium at high temperature can take place. This reaction causes surface damage of the membranes. If palladium membranes are built on the porous substrates that contain phosphorus or phosphate used in the inorganic binders, they cannot be used over 550°C. This result also implies that palladium membranes cannot be employed on the work environment of phosphorus or phosphates. / Palladium nanowires are well arranged by nanoparticles at the rough stainless steel surface. The formation procedures consist of 3 stages. In the initial stage, palladium nanoparticles are aligned in ore direction, then the nanowire is assembled continuously using follow-up palladium deposits, and finally the nanowire is built smoothly and homogeneously. It is also found that palladium nanoparticles generated from the autocatalytic reaction are not wetting with the steel substrate and they are not solid and easily deformed due to the interfacial tension when they connect to each other. / Various palladium nanowire arrays possessing the morphologies of single wires, parallel and curved wires, intersections and network structures are illustrated. The results demonstrate that palladium nanowires can be built in a self-assembled manner by palladium nanoparticles in the initial deposition stages. Such self-assembled nanowires may attract engineering applications because electroless deposition process and preparation of a substrate are simple and inexpensive. / The diameter of palladium nanowires can be effectively controlled by the concentration of PdCl2 in the plating solution and deposition time. The size of palladium nanoparticles generated from the autocatalytic reaction is directly dependent on the concentration of PdCl2 in the plating solution. The higher the concentration of PdCl2 in the plating solution is, the smaller the deposited palladium nanoparticles are. The experimental results provide a controllable method for the fabrication of palladium nanowire arrays with potential engineering applications.

L’ABS est un copolymère de Acrylonitrile-Butadiène-Styrène utilisé industriellement et dont la surface peut être recouverte para un dépôt métallique. Le processus traditionnel pour déposer des films métalliques de manière auto catalytique est connu comme « Electroless ». Cependant, ce processus utilise un mélange sulfochromique dans l’étape de traitement préliminaire de la surface, contenant du Cr (VI), qui est dans la liste des contaminants toxiques qui doivent être substitués. Il est donc primordial de développer de nouveaux procédés de modification de surface de faible impact sur l’environnement. Dans ce travail de thèse, nous avons développé trois nouvelles techniques de modifications de la surface d’ABS. Les deux premières permettent une modification générale de la surface et la troisième une modification spécifique. La première méthode, par voie sèche basée sur l’application en alternance de décharges Corona et radiations ultra-violet, est appelée « Traitement Optophysique ». La deuxième méthode appelée « Traitement Photocatalytique » correspond à l’application des propriétés photocatalytiques de nanoparticules de TiO2 (30nm) en suspension sur la surface du polymère et soumis à une radiation ultra-violet. La troisième méthode appelée « Traitement Optothermique » permettant une modification sélective, est réalisée par ablation thermique laser» à partir d’une sensibilisation de la surface avec des nanoparticules de Palladium et des particules d’Argent. Postérieur à l’étape de traitement « Traitement Optophysique » ou « Traitement Photocatalytique », les substrats ont été pré-métallisés soit par le procédé « Electroless », soit par le procédé de «Dépôt Chimique Dynamique » (DCP). A différence du procédé « Electroless », le procédé « DCP » ne nécessite pas d’une étape antérieure d’activation de sites superficielles avec des ions palladium. Le dépôt métallique final est réalisé par voie électrolytique conventionnelle. Les surfaces prétraitées ont été analysées par des Mesures d’Angle de Contact et les techniques de spectroscopie FT-IR et XPS. La présence de charges superficielles a été évaluée par la Mesure de Potentielle de Surface et de Radiométrie des Photoporteurs. La morphologie des surfaces a été observée et mesurée par les techniques de SEM, AFM et AFAM. Les analyses de rugosité ont été faites par Senseur Mécanique, par Optique Interférentielle et par AFM. L’adhérence des dépôts métalliques a été mesurée par la méthode de la Bande Adhésive sur Coupe Croisée (ASTM D-3359), les essais Pull Off. (ASTM D4541-02) et Peel Off (ASTM B533 A). Les dépôts les plus adhérents ont été obtenus avec un prétraitement « Optophysique » et une pré-métallisation par « DCP ». Les valeurs d’adhérence obtenues sont supérieures à celle des dépôts obtenus para le procédé traditionnelle « Electroless ». Le « Traitement Optothermique » a permis une gravure sélective de la surface de l’ABS en utilisant des lasers de faible puissance. / The ABS is a copolymer formed by Acrylonitrile-Butadiene-Styrene used in industry whose surface can be coated with a metallic deposit. The traditional process for depositing metallic films in an auto-catalytic way is know as “Electroless”, However, this process uses a sulfo-chromic mixture in the preliminary stage of the surface treatment containing Cr (VI) which is a toxic, polluting agent that needs to be replaced. Therefore, it is necessary to develop new surface modification procedures with a lower environmental impact. Three new techniques for ABS surface modification have been developed in this study. The first two allow a general surface modification and the third one a specific surface modification. The first method, using a dry system, is based on alternating a corona discharge with ultraviolet radiation and is called the “Optophysique Treatment”. The second method involves the application of the photocatalytic properties of TiO2 nanoparticles in a suspension on the polymer surface under ultraviolet radiation and is called “Photocatalytic Treatment”. The third method allows a selective modification using thermal laser ablation which is accomplished with the ABS sensibilization with palladium and silver particles and is called “Optothermal Treatment”. After the “Optophysique” or “Photocatalytic” treatments, the substrates were treated either by the ¨Electroless¨ method or by the “Dynamic Chemical Deposit” method. Unlike the “Electroless” method, the “DCP” method does not need a preliminary step to activate the surface sites with palladium ions. The final metallic coating is accomplished by a conventional electrolytic method. The pre-treated surfaces were analyzed by Contact Angle Measurements and with the spectroscopy techniques FT-IR and XPS. The presence of surface changes was evaluated by Potential Measurement and Photocarrier Radiometry. The surface morphology was observed and measured by the following techniques: SEM, AFM, and AFAM. The surface roughness analysis was performed by Mechanical Sensors, Optical Interference and AFM. The adherence of the metallic deposits was measured by the Cross Cut Tape test (ASTM D-3359), and the Pull Off test (ASTM D4541-02) and the Peel Off test (ASTM B533 A). The deposits with greater adhesion were obtained with the “Optophysique” treatment using a pre-coating done by “DCP”. The adherence values obtained were higher than those for deposits obtained by the traditional “Electroless” process. The Optothermal treatment allowed the selective etching on the ABS surface using low power lasers. / El ABS es un copolímero formado por Acrilonitrilo-Butadieno-Estireno utilizado industrialmente, cuya superficie puede ser metalizada mediante un depósito metálico. El proceso tradicional para depositar películas metálicas de manera autocatalítica es conocido como “Electroless”. Sin embargo, este proceso utiliza una mezcla sulfocrómica en la etapa de tratamiento preliminar de la superficie, conteniendo Cr (VI), contaminante tóxico que debe ser sustituido. Por lo tanto, es primordial desarrollar nuevos procedimientos de modificación superficial de bajo impacto ambiental. En este trabajo de tesis, se han desarrollado tres nuevas técnicas de modificación de la superficie del ABS. Los dos primeros permiten una modificación general de la superficie y la tercera una modificación específica. El primer método, realizado por vía seca, consiste en la aplicación en alternancia de descargas corona y radiación ultravioleta, este método es llamado “Tratamiento Optofísico”. El segundo método llamado “Tratamiento Fotocatalítico” corresponde a la aplicación de propiedades fotocatalíticas de nanopartículas de TiO2 (30 nm) en suspensión sobre la superficie del polímero y sometidas a una irradiación ultravioleta. El tercer método es llamado “Tratamiento Optotérmico” permite una modificación selectiva y es realizado por “ablación térmica láser” a partir de una sensibilización de partículas de Paladio y Plata. Posterior al tratamiento “Optofísico” o “Fotocatalítico”, los sustratos fueron pre-metalizados ya sea por el método “Electroless”, o por el método de “Depósito Químico Dinámico” (DCP). A diferencia del método “Electroless”, el método “DCP” no necesita de una etapa anterior a la activación de sitios superficiales con iones de Paladio. El depósito metálico final es realizado por vía electrolítica convencional. Las superficies pre-tratadas fueron analizadas por Medición de Ángulo de Contacto y con las técnicas espectroscópicas FT-IR y XPS. Se evaluó la presencia de cargas superficiales por la medición de potencial y radiometría de fotoportadores. La morfología de las superficies fue observada y medida por las técnicas de SEM, AFM y AFAM. Los análisis de rugosidad se hicieron por Sensores Mecánicos, por Interferencia Óptica y por AFM. La adherencia de los depósitos metálicos fue medida por el método de Cinta de Corte Cruzado (ASTM D-3359), la prueba Pull Off (ASTM D4541-02) y Peel Off (ASTM B533 A). Los depósitos de mayor adherencia fueron obtenidos con el tratamiento “Optofísico” y con un pre-metalizado realizado con “DCP”. Los valores de adherencia obtenidos son superiores al de los depósitos obtenidos por el proceso tradicional “Electroless”. El tratamiento Optotérmico permitió realizar un grabado selectivo sobre la superficie del ABS usando láseres de bajas potencias.

No description available.

Le procédé de dépôt electroless de Cu permet la métallisation de substrats non-conducteurs en utilisant un électrolyte composé d’un agent réducteur et d’un sel de cuivre métallique complexé à pH basique. La réduction spontanée des ions cuivre dans l’électrolyte rend l’électrolyte métastable. Des stabilisants (SB) sont ajoutés pour ralentir la cinétique au sein de l’électrolyte et contrôler la vitesse de dépôt sur le substrat.Ce travail de thèse se concentre sur l’étude de la N,N’-diéthylthiourée (DETU), utilisée comme SB dans les électrolytes electroless de cuivre dans une gamme de concentration allant du µM au nM. Une faible variation de la concentration montre des effets prononcés sur la stabilité de l’électrolyte ainsi que sur la cinétique de dépôt et les propriétés du dépôt lui-même. C’est pour cela que la quantification des SB dans ces électrolytes est d’une importance majeure pour assurer la durabilité du procédé electroless. Le défi principal de ce travail est de développer une méthode de quantification de stabilisants (de 1 à 100 nM) dans les électrolytes electroless de cuivre.L’influence du DETU sur les propriétés du dépôt est étudiée pour différentes durées de dépôt. Le dépôt de cuivre est caractérisé en utilisant différentes techniques telles que les techniques DRX, MEB, AFM et XPS. La structure cristalline et la microstructure des couches de cuivre varient peu avec la concentration de DETU. Par contre, une augmentation de la teneur en nickel augmente la vitesse de dépôt et la taille des grains, rendant les couches déposées plus poreuses.La voltammétrie linéaire à balayage (LSV) sur une électrode d’or est utilisée pour étudier les réactions d’oxydation se déroulant à l’électrode et l’influence du SB. Toutes les signatures voltammétriques sont identifiées. Le profil LSV est sensible à la concentration de SB et la densité de courant globale diminue lorsque la concentration de SB augmente. Ceci est dû à l’adsorption du SB sur l’électrode, qui diminue la densité de sites actifs libres et par conséquent limite la vitesse d’oxydation. L’adsorption de SB sur l’électrode est modélisée en utilisant l’isotherme de Langmuir. La cinétique d’adsorption est étudiée pour des vitesses de balayage variables. Le taux de couverture total de l’électrode est discuté en fonction de la concentration, en faisant l’hypothèse que l’équilibre est atteint aux faibles vitesses de balayage de LSV. Une méthode de suivi des SBs dans les électrolytes de cuivre electroless est proposée. La limite de détection de concentration de DETU est 2 nM. Différents SB ainsi que des mélanges de SB peuvent également être analysés par cette méthode. / The Cu electroless process allows the plating of non-conductive substrates using an electrolyte composed of a reducing agent and a complexed copper metal salt at alkaline pH. Spontaneous reduction of copper ions to metallic copper in the electrolyte makes the process metastable. So called stabilizers (SB) are added to slow down the kinetics in the electrolyte and to control the plating rate.This work focuses on the study of N,N’-diethylthiourea (DETU), which is used as SB in electroless copper electrolytes in concentration ranging from µM to nM. A slight variation of concentration has a strong effect on the electrolyte stability as well as the deposition kinetics and deposit properties. Therefore, quantification of the SBs in the electrolyte is of primary importance for the sustainability of the electroless process. The main challenge of this work is to develop a quantification method of stabilizers (from 1 to 100 nM) in electroless copper electrolytes.The influence of DETU on the deposit properties is studied for various deposition times. The Cu-deposit is characterized using different techniques such as XRD, AFM, HRSEM and XPS. On one hand, the crystalline structure and the microstructure do not vary with the DETU concentration. On the other hand, higher nickel content is found to increase the deposition rate and the grain size, making the deposited layer more porous.Linear sweep voltammetry (LSV) on a gold rotating disk electrode is used to study the oxidation reactions occurring in the electrolyte and the influence of SB. Each voltammetric signature is assigned. The LSV profile is sensitive to SB concentration and the overall current density decrease for increasing SB concentrations. This is assigned to SB adsorption on the electrode, which decreases the density of active free sites and therefore limits the oxidation rate. Adsorption of SB on the electrode is described using the Langmuir isotherm model. Kinetics of adsorption is studied by varying the scan rate. Final electrode coverage is discussed as a function of concentration assuming equilibrium is reached at low LSV scan rates. An analytical method for monitoring SB in electroless copper electrolytes is proposed. The limit of detection for DETU is 2 nM. Various SB and SB mixtures can be monitored as well.

The ability to passivate metallic surfaces under non-UHV conditions is not only of fundamental interests, but also of growing practical importance in catalysis and microelectronics. In this work, the passivation effect of a surface iodine layer on air-exposed Ta for the copper electroless deposition was investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Although the passivation effect was seriously weakened by the prolonged air exposure, iodine passivates the Ta substrate under brief air exposure conditions so that enhanced copper wetting and adhesion are observed on I-passivated Ta relative to the untreated surface.