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This work focuses on a simple template assisted approach for fabricating I-III-VI semiconductor nanowire arrays. Vertically aligned nanowires of p-CIS of controllable diameter and thickness are electrodeposited, from an acidic electrolyte solution, inside porous aluminum templates using a three electrode set up with saturated calomel electrode as the reference. AAO template over ITO-glass was used as starting template for the device fabrication. The deposited CIS is annealed at different temperatures in a reducing environment (95% Ar+ 5% H2) for 30 minutes. X-ray diffraction of the nanowires showed nanocrystalline cubic phase structures with a strong orientation in the <112> direction. The effective bandgap of the deposited CIS nanowires determined using the Near Infrared (NIR) Spectrometer was found to be 1.07eV. The type of CIS electrodeposited inside the porous alumina template is determined to be p-type from the Schottky diode obtained with ITO-CIS-Au structure. Schottky diodes were characterized and analyzed at room temperature.

Vertically aligned nanowire arrays of copper phthalocyanine (CuPc) and CuPc-Al Schottky diodes, of controllable diameter and length were fabricated by cathodic electrodeposition of CuPc into anodized alumina (AAO) templates, followed by annealing at 300 ºC in Argon. AAO over Aluminum tape and that over ITO-glass were both used as starting templates for the device fabrication. Depending on the dimensions of the starting AAO template, diameters of CuPc nanowires ranged from 30 nm to 40 nm and the lengths ranged from 500 nm to 1 μm. The temperature dependence of the phase and the absorption spectrum of the nanowires are reported. The electrodeposited nanowires (as prepared) had the preferred crystallite orientation of the α-phase. ITO formed the ohmic contact and Schottky contacts were formed between CuPc and aluminum. Insertion of a thin layer of PEDOT:PSS between CuPc nanowires and the ITO electrode improved the contact and reduced the series resistance by an order of magnitude. Schottky diodes were characterized and analyzed at room temperature and at cryogenic temperatures.

Face à une croissance effrénée de la demande en indium et aux enjeux à la fois socio-économiques et politiques potentiels qu'il représente, le recyclage de l'indium contenu dans les équipements en fin de vie reste la seule alternative pour remédier à des risques de pénuries. Au-delà des aspects économique et stratégique, le recyclage de l'indium peut permettre de préserver l'environnement en évitant l'exploitation à grande échelle des gisements de minerais contenant l'indium. Par ailleurs, la toxicité de l'indium justifie à elle seule le développement de procédés de traitement de déchets en contenant. Pourtant, la récupération de l'indium à partir de déchets électroniques est actuellement assez peu développée, mis à part au Japon, où plusieurs procédés existent à l'échelle industrielle. Ces procédés sont toutefois peu respectueux de l'environnement et fortement énergivores. Dans ce travail de doctorat, le recyclage de l'indium par extraction liquide/liquide dans un liquide ionique suivie de son électrodéposition in situ nous est apparu comme un procédé prometteur, permettant de s'affranchir de l'étape souvent difficile de dés-extraction du cation métallique. Parmi les liquides ioniques que nous avons synthétisés et caractérisés, en termes de structure et de propriétés physico-chimiques, le bis(trifluorométhylsulfonyl) amidure de 1-butyl-1-éthylpipéridinium (BEPipNTf2) s'est avéré le plus adapté du fait de sa bonne stabilité cathodique, de sa faible viscosité, de son caractère hydrophobe et peu hygroscopique. Nous avons montré qu'en synergie avec l'oxyde de trioctylphosphine (TOPO) comme extractant, il est possible d'extraire plus de 90% de l'indium contenu dans une phase aqueuse 10-2 M en HCl. Le système électrochimique In(III)/In(0) dans le BEPipNTf2 a alors été étudié en présence de chlorures, d'eau, d'oxygène et de TOPO, espèces présentes à l'issue de l'étape d'extraction liquide/liquide de l'In(III). Une étude détaillée de l'influence des ions chlorures a notamment été réalisée, mettant en évidence la formation de chlorocomplexes d'indium lors de l'application d'un potentiel cathodique de réduction de l'In(III), ce qui modifie considérablement les caractéristiques électrochimiques du système In(III)/In(0). Les résultats obtenus montrent qu'il est possible d'électrodéposer de l'In(III) sous sa forme métallique dans le domaine de stabilité électrochimique du liquide ionique, et ceci de façon non réversible en présence de TOPO, dont l'électroactivité dans le domaine de potentiel correspondant porte néanmoins à croire que la réduction pourrait entraîner la présence d'impuretés organiques dans le dépôt d'indium et limiter la quantité de métal déposée.

This thesis investigates the effect of microstructural strengthening mechanisms on the overall mechanical performance of micro-truss periodic cellular metals (PCMs). Prior to the author’s work, the primary design considerations of micro-truss PCMs had been topological issues, i.e. the architectural arrangement of the load-supporting ligaments. Very little attention had been given to investigate the influence of microstructural effects within the cellular ligaments. Of the four broad categories of strengthening mechanisms in metals, only solute and second phase strengthening had previously been used in micro-trusses; the potential for strengthening micro-truss materials by work-hardening or grain size reduction had not been addressed. In order to utilize these strengthening mechanisms in micro-truss PCMs, two issues needed to be addressed. First, the deformation-forming method used to produce the micro-trusses was analyzed in order to map the fabrication-induced (in-situ) strain as well as the range of architectures that could be reached. Second, a new compression testing method was developed to simulate the properties of the micro-truss as part of a common functional form, i.e. as the core of a light-weight sandwich panel, and test the effectiveness of microstructural strengthening mechanisms without the influence of typical high-temperature sandwich panel joining processes, such as brazing. The first strengthening mechanism was achieved by controlling the distribution of plastic strain imparted to the micro-truss struts during fabrication. It was shown that this strain energy can lead to a factor of three increase in compressive strength without an associated weight penalty. An analytical model for the critical inelastic buckling stress of the micro-truss struts during uniaxial compression was developed in terms of the axial flow stress during stretch forming fabrication. The second mechanism was achieved by electrodeposition of a high-strength nanocrystalline metal sleeve around the cellular ligaments, producing new types of hybrid nanocrystalline cellular metals. It was shown that despite the added mass, the nanocrystalline sleeves could increase the weight-specific strength of micro-truss hybrids. An isostrain model was developed based on the theoretical behaviour of a nanocrystalline metal tube network in order to predict the compressive strength of the hybrid materials.

Nowadays, the development of novel materials involves diverse branches of science as a consequence of the new requirements imposed by modern society. This includes aspects ranging from the optimization of the manufacturing processes to the durability of the materials themselves. Ideally, some synergism should exist between the durability, the properties of interest in the material. Although metals in their pure state are often desired, the best properties or combination of properties often cannot be satisfactorily achieved with a single metal. In these situations, the desired properties can be attained by the formation of alloys of these metals with others. Ni-Co alloys are no exceptions and so have received considerable attention especially in microsystem technology due to the magnetic properties of cobalt and the corrosion and wear resistance of nickel. Moreover, this interest has been further stimulated by its use in the manufacture of sensors, magnetic devices, microrelays, inductors, actuators, memory devices and hard drives. The fabrication of these alloys (particularly coatings) via electroplating has been shown to be techno-economically feasible in comparison with other processes: capability of high volume production, low cost and the ability to coat thin layers on non-planar substrates. In addition, the materials fabricated by this technology exhibit excellent characteristics such as refined grain structure, smoothness, low residual stress and coercivity, etc., making them advantageous to materials produced by other physical methods of deposition. Nevertheless, one of the biggest problems faced during the formation of Ni-Co alloys is its anomalous behavior whereby cobalt preferentially deposits over nickel under most conditions, even when the Ni(II) concentration is significantly higher than that of Co(II). This problem has complicated the prediction and control of the metal composition in these alloys during their production and as a consequence the ability to obtain the desirable properties associated with high nickel content. Although this problem is not recent, the studies that have been carried out so far to analyze this system have not always been as comprehensive as they could be in terms of the experimental conditions investigated or the reaction mechanisms and mathematical models developed to describe its behavior. Consequently, the origin of this behavior is still not completely understood. Thus, this work presents a contribution in terms of the analysis of the reaction mechanisms for single metal deposition of nickel and cobalt and for the formation of Ni-Co alloys in sulphate media with the intention of gaining a better understanding of the phenomena controlling the anomalous behavior of this system. Analyses of the single metal deposition of nickel and cobalt are first carried out to better understand their reaction mechanisms. Such an approach should allow the contributions of the reduction of each metal ion and interactions between the two systems during alloy co-deposition to be more clearly understood. In order to analyse the aforementioned systems, both steady state and transient techniques are employed. Among these techniques, electrochemical impedance spectroscopy (EIS) is employed since it is a robust and powerful method to quantitatively characterize the various relaxation phenomena occurring during the electrodeposition of metals. The experimental data acquired from this technique are analyzed with comprehensive physicochemical models and the electrochemical processes are quantified by fitting the models to these data to determine the kinetic parameters. During the development of the physicochemical models, several assumptions (e.g. neglect of convection, homogeneous reactions and single electron-transfer steps) made in former models are relaxed in order to investigate their combined impact on the predicted response of the system. Estimates of the kinetic parameters determined by EIS for the deposition of the single metals reveals that the first step of Co(II) reduction is much faaster tha the corresponding step of Ni(II) reduction. Some limitations of the EIS technique (i.e. analysis at high overpotentials) are exposed and compared in the case of the nickel deposition using linear sweep voltammetry (LSV). Likewise, physicochemical models accounting for most of the important phenomena are derived and fitted to experimental data. Ni-Co alloy formation is analyzed using LSV and steady state polarization experiments for different pH, current density and electrolyte composition. Current efficiencies for metal depsoition and alloy composition are also evaluated. To date, no experimental study considering all these variables has been reported in the literature. Then a steady state model is presented to describe the electrode response during alloy formation and used to provide insight into the anomalous behavior of this system. This model is based on information obtained from previous studies reported in the literature and from the current research. After being fitted to the experimental data, the model reveals that the anomalous behavior observed for this alloy is likely caused by the much faster charge-transfer of Co(II) reduction than that of Ni(II) reduction and not by other previously proposed mechanisms such as competition between adsorbed species for surface sites, formation of aqueous hydroxides (MeOH+) or mixed intermediate species (NiCo(III)ads) on the surface of the electrode.

Ferritic stainless steels are the most commonly used materials for solid oxide fuel cell interconnect application. Although these alloys may meet the criteria for interconnect application for short periods of service, their application is limited for long-term use (i.e., 40,000 h) due to poor oxidation behaviour that results in a rapid increase in contact resistance. In addition, volatile Cr species migrating from the chromia scale can poison the cathode resulting in a considerable drop in performance of the cell. Coatings and surface modifications have been developed in order to mitigate the abovementioned problems. In this study, composite electrodeposition of reactive element containing particles in a metal matrix was considered as a solution to the interconnect problems. Nickel and Co were used as the metal matrix and LaCrO3 particles as the reactive element containing particles. The role of the particles was to improve the oxidation resistance and oxide scale adhesion, while the role of Ni or Co was to provide a matrix for embedding of the particles. Also, oxidation of the Ni or Co matrix led to the formation of conductive oxides. Moreover, as another part of this study, the effect of substrate composition on performance of steel interconnects was investigated. Numerous experimental techniques were used to study and characterise the oxidation behaviour of the composite coatings, as well as the metal-oxide scale interface properties. Scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX), as well as surface analysis techniques including Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS), were used for the purpose of characterization. The substrate used for coating was AISI-SAE 430 stainless steel that is considered as a typical, formerly used interconnect material. Also, for the purpose of the metal-oxide scale interfacial study, ZMG232 stainless steel that is a specially designed interconnect alloy was used. It is shown that the composite coatings greatly reduce the contact resistance and effectively inhibit Cr outward migration. In addition, it was determined that the presence of impurities in the steel, especially Si, and the absence of reactive elements drastically contribute to interconnect degradation. / Materials Science and Engineering

In this work, all-copper connections between silicon microchips and substrates are developed. The semiconductor industry advances the transistor density on a microchip based on the roadmap set by Moore's Law. Communicating with a microprocessor which has nearly one billion transistors is a daunting challenge. Interconnects from the chip to the system (i.e. memory, graphics, drives, power supply) are rapidly growing in number and becoming a serious concern. Specifically, the solder ball connections that are formed between the chip itself and the package are challenging to make and still have acceptable electrical and mechanical performance. These connections are being required to increase in number, increase in power current density, and increase in off-chip operating frequency. Many of the challenges with using solder connections are limiting these areas. In order to advance beyond the limitations of solder for electrical and mechanical performance, a novel approach to creating all-copper connections from the chip-to-substrate has been developed. The development included characterizing the electroless plating and annealing process used to create the connections, designing these connections to be compatible with the stress requirements for fragile low-k devices, and finally by improving the plating/annealing process to become process time competitive with solder. It was found that using a commercially available electroless copper bath for the plating, followed by annealing at 180 C for 1 hour, the shear strength of the copper-copper bond was approximately 165 MPa. This work resulted in many significant conclusions about the mechanism for bonding in the all-copper process and the significance of materials and geometry on the mechanical design for these connections.

Η ρύπανση του περιβάλλοντος και η εξάντληση των ορυκτών καυσίμων έχουν φέρει την ανάγκη για νέες ανανεώσιμες πηγές καυσίμων, όπως το υδρογόνο ειδικά όταν παραχθεί με ηλεκτρολυτική μέθοδο. Σ' αυτήν την εργασία, παρασκευάσαμε και αξιολογήσαμε ηλεκτρόδια(λεπτά υμένια) για την αποτελεσματική παραγωγή υδρογόνου. Χρησιμοποιήσαμε την ηλεκτροαπόθεση για την παρασκευή των λεπτών υμενίων σε υπόστρωμα χαλκού. Πιο συγκεκριμένα αποθέσαμε λεπτά υμένια με βάση το νικέλιο. Τα υμένια Ni-Fe, Ni-Zn, Ni-Co-Zn, Ni-Mo-Zn, Ni-Mo-Fe και Ni-Mo-Fe-Zn παρασκευάστηκαν με ηλεκτροαπόθεση. Τα ηλεκτρόδια χρησιμοποιήθηκαν ως κάθοδοι σε μια συσκευή ηλεκτρόλυσης τύπου Hoffmann, ώστε να εξεταστούν ως προς την παραγωγή υδρογόνου. Για περαιτέρω χαρακτηρισμό των ηλεκτροδίων πραγματοποιήθηκαν μετρήσεις υπερδυναμικού για αρκετές πυκνότητες ρεύματος. Μέσω των διαγραμμάτων Tafel λάβαμε χρήσιμα πειραματικά αποτελέσματα όπως η κλίση Tafel και η πυκνότητα ρεύματος ανταλλαγής. Τέλος εικόνες SEM μας έδωσαν πληροφορίες για τη μορφολογια και τις ηλεκτροκαταλυτικές ιδιότητες των λεπτών φιλμ. / The environmental pollution and the depletion of fossil fuels have brought the need for new renewable fuels, such as hydrogen, especially when it has been produced with electrolytic process. In this work, we report on the preparation and evaluation of special electrodes (thin film alloys) for high efficiency H2 production. We are using the electrochemical deposition method copper is used as substrate. In particular we have deposited films of the transition metal Ni on copper substrates. films Ni-Fe, Ni-Zn, Ni-Co-Zn, Ni-Mo-Zn, Ni-Mo-Fe and Ni-Mo-Fe-Zn are produced using the electrochemical deposition method. These electrodes are used as cathodes in an electrolyte cell of the Hoffmann type in order to examine their efficiency in producing hydrogen. Furthermore, in order to consider the individual characteristics of the electrodes, measurements of overpotentional for several current densities were taken. In addition to the previous measurements, the Tafel plot has given useful experimental results. The most important from the Tafel plot, is the Tafel slope and the exchange current density. Finally SEM images gave more accurate results on the morphology and the electrocatalytic properties of the thin film alloys.