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Zinc selenide (ZnSe) film is successfully deposited by the electrodeposition technology. Due to ZnSe with a direct band-gap of 2.7 eV, it is widely used for optoelectronic applications. Recently, it is used as the window layer to improve the open circuit voltage in solar cells. The ZnSe film was prepared with vacuum, high temperature, and high pressure was usually used. However, these disadvantages limited the cost down and time to market. Electrodeposition is an easy use and very simple technology proposed to grow large area of ZnSe films. In this study, the electrodeposition of ZnSe film has been accomplished in an aqueous bath (pH = 2) during electrochemical reduction of an electrolyte containing SeO2 (100 mM) and ZnSO4¡E7H2O (1 M) on a indium tin oxide glass substrate. Results clearly show that the film quality was strongly depend on the electrodeposited potential. The electro-potential is Indeed as a function of the substrate temperature, the concentration of solutes, and pH value of solution. The structure of as-deposited ZnSe thin film is polycrystalline measured by x-ray diffraction (XRD). The surface morphology of deposited films are investigated by Scanning electron microscopy (SEM). The high quality of film growth is achieved when the electro-potential applied is close to the electrodeposited potential of ZnSe. As the more negative of electrodeposited potential applied at room temperature, the growth rate, thickness and resistance of thin film are increase and the current is decrease. In addition, the i-t curve shows very rough due to the bubbles generated to disturb the solution while electrodeposited at the high temperature.

In the early years, DLC films was deposited at high voltage applied by electrochemical method. In this study, DLC film was deposited alternatively at low voltage applied using electrodeposition. The ITO glass substrate was used as the cathode, and graphite sheet was the anode. The electrolyte is a mixture of acetic acid with DI water. The applied voltage was mere 2.1 volt during the electrochemical process. For investigating the structure of deposited films, the deposited DLC layers were characterized by Fourier transform infrared (FTIR), Scanning electron microscope (SEM) and Raman spectrometer. The SEM results show that the DLC films have a rough surface and their roughness increased with longer in deposition time as well as raise applied voltage. The Raman spectra shows distinct broad characteristic peaks at ~ 1336 cm-1 (D-peak) and ~ 1601 cm-1 (G-peak), which indicate the disordered graphite-like structure and the graphite structure, respectively. While the bond angles occur to bend or the increase the content of sp3 bonds in DLC film, both the G-peak and the D-peak shift to the lower wave numbers. Peaks at ~ 2956 and ~ 2917 cm-1 found in FTIR measurement were used to recognize the existence of sp3 and sp2 combined carbon atoms in the films. Based on above results, it could conclude that the DLC film could be prepared by electrodeposition under low applied voltage.

The Diamond-like Carbon (DLC) films have numerous extraordinary advantages, such as high hardness, low friction factor, strong chemical stability, and high insulation properties for satisfying significant application in the industrial domain. In this study, DLC films are deposited by electrodeposition, which is different from the conventional technology of PVD and CVD. The methodology provides several advantages such as low voltage supply, low temperature electrodeposition, simple experimental steps and easy to operate, resulting in low costs. The experiment used ITO glass substrate covered with SnO2 as cathode, a thin graphite plate as anode, the voltage supply between the two poles is 2.1V ~ 50V, and the main components of electrolyte is the solution of acetic acid with deionized (DI) water. The property of Diamond-like Carbon films have been investigated to be associated with a variety of bias voltage, the concentration of acetic acid (electrolyte) during the process. As a result, the deposition rate and hardness of Diamond-like Carbon films increase with the bias voltage. However, the surface roughness tends to decrease, and the same outcomes manifested when the concentration of electrolyte increased. For the analysis of Raman Spectrum, the D peak and G peak were at 1350cm-1 and 1580cm-1 individually, which demonstrated the existence of Diamond-like Carbon films. Finally, of analyzing the SEM and AFM photograph, the surface morphology of Diamond-like Carbon films are used to correlate the deposited parameters for obtaining the best quality of DLC films.

No description available.

Cadmium coatings are currently applied to steel fasteners used in aerospace applications. At present there are growing concerns, based on cadmium's toxicity and carcinogenicity, which may lead to its eventual banning. The aim of this research, therefore, was to find a possible replacement to electrodeposited cadmium for use on aerospace fasteners. Any replacement coating system should have all of the relevant properties that make cadmium so attractive, but without its obvious shortcomings. These beneficial properties include excellent corrosion resistance in chloride containing media (such as seawater), the ability to offer sacrificial protection to steel, excellent galvanic compatibility with most aluminium alloys and an inherent lubricity. Alternatives proposed and produced in this research are electrodeposited composite coatings containing PTFE particles, based on zinc or zinc alloys. Extensive analysis was carried out in order to characterise the coatings. Composition was determined by a number of methods; gravimetric analysis was used to determine the percentage of codeposited PTFE, while X-ray and X-ray wavelength energy dispersive analysis were used to determine the percentage of alloy element present in these coatings. Coating morphology was investigated by scanning electron microscopy. The sacrificial corrosion performance of each coating in relation to steel was studied using neutral salt-spray tests, while linear polarisation resistance tests gave an indication of their barrier corrosion properties. Galvanic compatibility of the coatings with aerospace grade aluminium alloys was investigated using a zero resistance ammeter. Two different tribological tests, an inclined plane test and a reciprocating wear test, were used to determine the coefficient of friction for the coatings. Finally, linear sweep voltammetry was used to compare the kinetics of electrodeposition from dilute solutions and corrosion in aqueous media for each of the coating systems. The composite coatings were found to offer either similar or slightly reduced corrosion performance to conventional zinc and zinc alloy coatings, but were inferior to commercially electrodeposited cadmium. However, the tribological properties of these coatings demonstrated a marked improvement over cadmium.

Le silicium sous forme de nanofil peut être utilisé dans de nombreux domaines en raison de ses propriétés spécifiques et de son important rapport surface/volume : transistors à nanofil unique, anodes pour batteries Li-ion, capteurs... Ces applications restent cependant dans l'état actuel de simples prototypes en raison de la difficulté de transfert technologique dû au coût relativement important des voies de synthèse utilisées. C'est pourquoi nous avons choisi, au cours de ce travail, de mettre en place un protocole de synthèse innovant et bas-coût, permettant habituellement de synthétiser de nombreux types de matériaux : l'électrodépôt. Pour pouvoir électrodéposer le silicium, il a fallu attendre l'apparition d'une nouvelle catégorie de solvants appelés " liquides ioniques ", solvants qui possèdent une fenêtre électrochimique assez large et modulable, incluant le potentiel de dépôt relativement bas du silicium. Nous avons dû, dans une première étape, réaliser et étudier l'électrodépôt du silicium sous forme de films minces, afin de valider le procédé et de comprendre les mécanismes mis en jeu selon les paramètres de synthèse. Nous avons ensuite réalisé le dépôt de silicium au sein de membranes nanoporeuses dont la taille des pores est connue et contrôlée et qui nous ont permis d'obtenir des nanofils de silicium aux dimensions parfaitement définies et en grande densité. Lors du dépôt de nanofils selon certains paramètres nous avons aussi pu observer la présence de nanotubes à certains endroits de l'échantillon. Ceci nous a amené à ouvrir une étude prospective sur les paramètres de synthèse qui ont une influence déterminante sur la géométrie des nanotubes. Parallèlement nous avons mis en place, avec succès, un protocole de co-éléctrodépôt permettant d'obtenir des nanofils de silicium dopés erbium avec un contrôle du taux de dopage dépendant des concentrations utilisées et des potentiels de dépôt appliqués. Les résultats obtenus dans tous ces domaines ont été très positifs et permettront d'ouvrir de nouveaux champs de recherche en termes d'applications ou d'approfondissements théoriques. / Silicon nanowires can be used in a lot of different applications due to its specific properties and its high surface/volume ratio : single nanowire transistors, anode in Li-ion batteries, sensors and biosensors... All those examples are still prototypes because the technology transfer appear to be difficult, mainly due to the high cost of usual synthesis processes. We choose to develop a new, cheap method, usually allowing the elaboration of a lot of kind of materials which is called " electrodeposition ". In order to electrodeposit silicon, we had to work with a new kind of solvents called " Ionic Liquids ". Those solvents have a large electrochemical window allowing electrodeposition of silicon which usually occurs at very low potentials. The first step here was to validate the process and study the effect of synthesis parameters on the reaction mecanisms for silicon thin films. In a second part, we achieved the electrodeposition in a nanoporous membrane to elaborate silicon nanowires with controlled dimensions. We observed, by changing the synthesis parameters, the emerging of a large amount of nanotubes in the samples. That's why we also did a prospective study to understand which synthesis parameters control the silicon nanotube geometry. At the same time, we studied the possibility of doping the silicon nanowires by co-electrodepositing silicon with erbiium. We obtained erbium-doped silicon nanowires with an amount of erbium controlled by either the variation of concentrations or the applied potential. Results obtained during this work are very promising and can bring up to a lot of new research axes.

Ce manuscrit présente un procédé innovant d’élaboration de revêtements prothétiques phosphocalciques : l’électrodéposition. Un protocole original est développé, qui associe l’électrodéposition en mode courant pulsé et l’incorporation de peroxyde d’hydrogène (H2O2)dans la solution électrolytique. Ce protocole permet d’obtenir des revêtements phosphocalciques homogènes et compacts dont la composition chimique est contrôlée. Ils peuvent être constitués d’une hydroxyapatite déficitaire en calcium avec un déficit variable ou d’une hydroxyapatite stoechiométrique. La morphologie des revêtements élaborés est observée par MEB et MEBT, et leur composition chimique est étudiée par microanalyse X et par une méthode normalisée basée sur la DRX, en déterminant le rapport atomique Ca/P caractéristique de ces revêtements. L’étude du comportement en température des échantillons élaborés est présentée afin de déterminer la température optimale de traitement nécessaire pour obtenir une valeur suffisante de l’adhérence du revêtement phosphocalcique sur le substrat métallique. Malgré une limitation de cette température à 550°C lorsque le traitement est réalisé à l’air, la mesure de l’adhérence conduit à une valeur de 16,5 MPa qui répond aux critères normalisés pour les implants chirurgicaux. Par ailleurs, la bioactivité des revêtements élaborés est évaluée en milieu physiologique en étudiant d’une part leur comportement vis-àvis de la corrosion par la représentation de Tafel des courbes de polarisation et par spectroscopie d’impédance électrochimique, et en étudiant d’autre part les réactions de dissolution-précipitation qui interviennent lors d’une immersion prolongée. La formation d’une couche d’apatite osseuse à la surface du revêtement électrodéposé est alors observée.Le protocole d’élaboration développé permet de moduler l’intensité de ces comportements en milieu physiologique. Enfin, la flexibilité de l’électrodéposition est utilisée pour incorporer uniformément dans les revêtements phosphocalciques élaborés du strontium qui est un agent actif dont la cinétique de relargage en milieu physiologique peut être modulée. Une étude structurale de ces nouveaux revêtements permet d’observer que l’incorporation de cet élément modifie la proportion des phases constituant le revêtement après un traitement en température adéquate. La proportion des phases et la répartition uniforme du strontium sont également observées à une échelle submicrométrique par EELS. / This manuscript presents an innovative process to produce prosthetic calcium phosphate coatings: electrodeposition. An original protocol is developed, combining pulsed electrodeposition current mode and the incorporation of hydrogen peroxide (H2O2) into the electrolytic solution. This protocol leads to homogeneous and compact calcium phosphate coatings whose chemical composition is controlled. They may consist of a calcium-deficient hydroxyapatite with a variable deficit or of a stoichiometric hydroxyapatite. The morphology of the coatings is observed by SEM and STEM, and their chemical composition is studied by X-ray microanalysis and by a standardized method based on XRD, determining the characteristic Ca/P atomic ratio of these coatings. The study of the thermal behavior of the elaborated samples is performed in order to determine the optimal treatment temperature to obtain a sufficient value of the calcium phosphate coating adhesion onto the metallic substrate. Despite the limitation of this temperature to 550°C when the treatment is carried out in air, the measurement of the coating adhesion to the substrate leads to a value of 16.5 MPa that corresponds to the standardized criteria for the surgical implants. Furthermore, the bioactivity of the elaborated coatings is evaluated in a physiological environment by studying firstly their corrosion behavior using the Tafel representation of the polarization curves and the electrochemical impedance spectroscopy, and secondly by studying the dissolution precipitation reactions that occur during a prolonged immersion. The formation of a “bonelike” apatite layer on the surface of the electrodeposited coating is then observed. The elaboration protocol developed allows the modulation of these behaviors in physiological medium. Finally, the flexibility of the electrodeposition process is used to uniformly incorporate strontium in the calcium phosphate coating that is an active agent whose release in physiological medium can be modulated. A structural study is performed to observe that the incorporation of this element in the coating modifies the proportion of the phases that compose the coating after a suitable thermal treatment. The phase proportion and the uniform distribution of the strontium are also observed at the submicron scale by EELS.

Driven by the emerging interest in the design and realization of structures with co-existing micro- and nanoscale features, various nanofabrication approaches are being developed. We show that the selective, conformal growth of a multilayer structure is a promising route for the controlled realization of various structures with size-hierarchy, including both surface (i.e., the structures of which functionalities are characterized by the interaction between their surface, and external systems, such as self-cleaning, superhydrophic substrates with dual-scale topography), and volumetric (i.e. composite materials of which functionalities rely on the intrinsic properties of nanostructures distributed throughout their volume, such as giantmagnetoresistance sensors) structures. This is realized based on a sequential multilayer electrodeposition guided by an insulating substrate with predesigned topography, referred to as template-assisted multilayer electrodeposition process. Various multiscale, multidimensional surface and volumetric hierarchical structures are demonstrated of which size scale of the nanostructures are defined by the individual layer deposition parameters, while their position and overall geometry are defined by that of the template. These structures include (1) large area (> 1 cm^2), planar, or non-planar surfaces comprised of anisotropic, nanoscale surface relief structures of wide-ranging size scale (10 nm-1 micron); and (2) thick (10-100 micron), volumetric composite material in which individual metallic layers of micron, or submicron scale thicknesses are electrically insulated from the adjacent layers by interlamination insulating layers of similar thicknesses. The utility of the fabricated structures is evaluated in a few potential application domains, i.e., nanolithography, self-cleaning, and high frequency magnetic devices.

No description available.