L’un des enjeux relatif au déploiement des piles à combustible à oxyde solide comme système de production d’une énergie propre relève de la température de fonctionnement qui est actuellement autour de 1000°C. Abaisser cette température tout en préservant les performances afin de réduire les coûts de fabrication et d’augmenter la durée de vie des systèmes a été l’objectif dece travail de doctorat.Un coeur de pile à combustible (anode-électrolyte-cathode) élaboré avec des procédés physiques de dépôts (projection par plasma atmosphérique et pulvérisation cathodique magnétron) a été développé et optimisé sur un support métallique poreux. Les matériaux étudiés ont été un cermet en Nickel-Zircone stabilisée à l’Ytttrium (Ni-YSZ) pour l’anode, un électrolyte en YSZ avec ou sans couche de cérine gadoliniée (GDC) et les nickelates de terres rares comme cathode. La maitrise des procédés de revêtements a permis de réduire les épaisseurs de chaque couche et d’assurer la cohésion de l’ensemble des 3 couches avec des caractéristiques cristallographiques, microstructurales et de porosité adaptées. . Les performances électrochimiques ont été étudiées pour chaque élément du coeur de pile puis pour l’ensemble du système élaboré sur métal poreux. Même si les performances atteintes ne sont pas encore suffisantes, les procédés de revêtements optimisés pour recouvrir un support métallique poreux ont confirmé leur potentiel. / Energy production by a clean and environmental processes is a real challenge. Fuel cell technology is good candidate to answer this objective. The major problem of the Solid Oxide Fuel Cell is their high operating temperature (around 1000°C) for a massive industrialisation. Decreasing these temperature at 700°C allows a reduction of cost manufacturing and increase the lifetime, in this case the new challenge is to avoid the performances losses.During this phD work, dry surface treatment processes are employed for produce the fuel cell core. The thickness reduction of each part limit the performances decreasing generate by the modification of the temperature. The materials used is a Ni-Yttria stabilised zirconia cermet (Ni-YSZ) for the anode, YSZ with or without gadolinnia doped ceria (GDC) for electrolyte and rare earth nickelate for the cathode component. All material are a usual employed in the SOFC technology. All coating are synthesized and characterised separately. After a third generation of fuel cell is realized on ITM porous metal support produced by PLANSEE. The anode has been deposit by atmospheric plasma spray, the electrolyte and cathode have been synthesised by reactive magnetron sputtering.

Les travaux de recherches développés dans cette thèse concernent la réalisation de couchesminces, à partir de l’alliage à mémoire de forme (AMF) NiTi mécanoélaboré et de structurenanocristalline, en vue de leur intégration dans des microsystèmes. Le but est d’améliorer lespropriétés AMF de leurs homologues de structure microcristalline, dits conventionnels.Les techniques de caractérisation physico-chimiques (DRX, MET, MEB) nous ont permisd’une part, de suivre le mécanisme de formation de l’intermétallique B2-NiTi en fonction dutemps de broyage et d’autre part, de déterminer les paramètres microstructuraux à savoir, lataille des cristallites, le taux de microdéformations et la densité de dislocations des élémentspurs ainsi que ceux de la phase B2-NiTi. Ces paramètres révèlent le caractère nanocristallin etdésordonné des poudres broyées.Par ailleurs, nous avons fabriqué pour la première fois une cible B2-NiTi de structurenanocristalline, par l’intermédiaire d’une méthode alternative (mécanosynthèse et procédé deprojection à froid).Nous avons montré également qu’il est possible de déposer sous forme de couche mincel’intermétallique NiTi nanostructuré. Ce film mince d’épaisseur 447 nm a été déposé parpulvérisation cathodique à magnétron à partir de la cible élaborée par projection à froid (coldspray). / The research work developed in this thesis is related to preparing a thin film of NiTi shapememory alloy used to integrate into microsystems. The goal is to improve the properties oftheir counterparts of microcrystalline structure (conventional target).Physical and chemical techniques of characterization (XRD, TEM and SEM) have allowed onthe one hand, to follow the mechanism of intermetallic NiTi formation as a function ofmilling time and on the other hand, to determine the microstructural parameters : crystallitesize, the microstrain and dislocation density of the pure elements and the B2-NiTi phase.These parameters reveal the character of the disordered nanocrystalline of the milled powders.Furthermore, we fabricated a target of B2-NiTi nanocrystalline structure by an alternativemethod (mechanical alloying and cold spray).We also showed that it is possible to deposit the nanocrystalline NiTi intermetallic thin film.This film with a thickness of about 447 nm was deposited by magnetron sputtering techniquefrom the NiTi target.

Le couplage de la spectroscopie d’impédance électrochimique(EIS) et de la spectroscopie photoélectronique à rayonnement X(XPS) a permis d’étudier en profondeur le lien entre la structure etles propriétés électrochimiques d’électrolytes solides en couchesminces, ainsi que de l’interface formée avec le matériau d’électrodepositive LiCoO2. L’incorporation d’azote dans la structure duLiPON, électrolyte solide de référence dans les microbatteries, estcaractérisée par la formation de lacunes de lithium et d’oxygènesfavorables au transport des ions lithium. Un électrolyte solideLiPOS a été développé par pulvérisation cathodique radiofréquencevia l’incorporation de soufre dans la structure initiale Li3PO4. Laprésence d’une interface solide/solide entre le LiPON et LiCoO2 estcaractérisée par une réduction partielle du cobalt et une oxydationdu LiPON à son voisinage, vraisemblablement responsable del’augmentation de la résistance de transfert de charges entre lesdeux matériaux. / The link between the structure and the electrochemicalproperties of thin-film electrolytes and the interface formed withthe cathode material LiCoO2 has been intensively studied bycoupling Electrochemical Impedance Spectroscopy (EIS) and X-rayPhotoelectron Spectroscopy (XPS). Nitrogen incorporation intoLiPON, reference solid-state electrolyte for microbatteries, ischaracterized by the formation of lithium and oxygen vacancies,increasing the lithium ions transport. A sulfide based thin filmelectrolyte called LiPOS has been developed by radiofrequencysputtering, with the incorporation of sulfur into the initial Li3PO4structure. The solid/solid interface between LiPON and LiCoO2 ischaracterized by a partial reduction of cobalt and oxidation ofLiPON, which is in all probability responsible of the increase of thecharge transfer resistance between the two materials.

<p>This thesis report is focused on the growth of Pt/Mg multilayers and the studies of the sputter yield amplification effect in these. The main application is to use the multilayers as X-ray mirrors reflecting an X-ray wavelength of 17 Å. This wavelength is important for astronomical applications in general, and solar imaging applications in particular.</p><p>For periodic X-ray multilayer mirrors only a certain specific wavelength of X-rays can be reflected. What wavelength that is reflected depends on the individual layer thicknesses of the materials that are constituting the multilayer. These thicknesses can be determined using modified Bragg’s law and are approximately a quarter of the wavelength.</p><p>In order to obtain the exact desired layer thickness of each individual layer it is necessary to understand the growth processes and the effects that are going on during deposition of such multilayer mirrors. It has been shown that when depositing multilayers consisting of one very light and one very heavy material, like e.g. Pt and Mg, the deposition rate of the light element is non-linear with deposition time for thin layers. This is because of backscattered energetic neutrals from the heavy target material, which affects the growing film. Furthermore, a sputter yield amplification is present for thin layers when a light element is grown on top of a heavy element, i.e. for Mg on top of Pt.</p><p>Dual DC magnetron sputtering has been used to grow the Pt/Mg multilayers, and the influence of the backscattered energetic neutrals and the sputter yield amplification effect has been studied for Ar and Kr sputtering gases at pressures ranging from 3 up to 9 mTorr. The individual layer thicknesses have been obtained from simulations of hard X-ray reflectivity measurements using the IMD program. The number of backscattered energetic neutrals and their energies at the target have been calculated using the TRIM code.</p><p>Using the results obtained it is now possible to predict and compensate for the non-linear deposition rate of Mg.</p>

<p>This thesis reports on the development of low-temperature processes for transition metal carbide and MAX-phase thin film growth. Magnetron sputtering and evaporation, far from thermodynamical equilibrium, have been utilised to engineer the properties of the films by physical and chemical control. Deposition of W, W₂C and β-WC_1-x films with controlled microstructure, from nanocrystalline to epitaxial, is shown in the W-C system down to 100 ^oC. W films with upto 20 at% C exhibited an extreme solid-solution hardening effect, with a nanoindentation hardness maximum of 35 GPa. Furthermore, the design of epitaxial ternary carbide films is demonstrated in the Ti_1-xV_xC_y system in the form of controlled unit-cell parameters, strain-free films with a perfect match to the substrate, and ternary epitaxial gradient films. Moreover, phase stabilisation and pseudomorphic growth can be tuned in (Nb,Mo)C and (Ti,W)C films. The results obtained can be used for example to optimise electrical contacts in SiC high-power semiconductor devices. </p><p>A large part of this thesis focuses on the deposition of MAX-phases. These compounds constitute a family of thermally stable nanolaminates with composition M_n+1AX_n, n=1, 2 or 3, where M is an early transition metal, A is generally a group 13-14 element, and X is C or N. They show a combination of typical ceramic and metallic properties and are also machinable by virtue of the unique deformation behaviour observed only in laminates. So far, the MAX-phases have almost exclusively been prepared by high-temperature sintering and studied in bulk form. However, this thesis establishes a patented seed layer approach for successful MAX-phase thin film depositions down to 750 ^oC. For the first time, single-phase and epitaxial films of Ti₃SiC₂, Ti₃AlC₂ and Ti₂AlC have been grown. The method has also been used to synthesise a new MAX-phase, Ti₄SiC₃. In addition, two previously unreported intergrown MAX-type structures are presented, Ti₅Si₂C₃ and Ti₇Si₂C₅. Combined theoretical and experimental results show the possibility to deposit films with very low bulk resistivity and designed mechanical properties. Furthermore, the demonstration of MAX-phase and carbide multilayer films paves the way for macrostructure engineering, for example, in coatings for low-friction or wear applications.</p>

Microwave materials have been widely used in a variety of applications ranging from communication devices to military satellite services, and the study of materials properties at microwave frequencies and the development of functional microwave materials have always been among the most active areas in solid-state physics, materials science, electrical and electronic engineering. In recent years, the increasing requirements for the development of high speed, high frequency circuits and systems require complete understanding of the properties of materials function at microwave frequencies. Ferroelectric materials usually have high dielectric constant, and their dielectric properties are temperature and electric field dependent. The change in permittivity as a function of electric field is the key to a wide range of applications. Ferroelectric materials can be used to fabricate capacitors for electronic industry because of their high dielectric constant, and this is important in the trend toward miniaturization and high functionality of electronic products. The simple tunable passive component based on ferroelectric films is a varactor which can be made as a planar structure and used for electrically tunable microwave integrated circuits. It is an important task to sinter highly tunable and low loss ferroelectrics, fabricate and test the properties of microwave ferroelectric components. This thesis shows experimental results on growth, crystalline and microwave properties of Na0.5K0.5NbO3 (NKN), AgTa0.5Nb0.5O3 (ATN), Ba0.5Sr0.5TiO3 (BST) as well as AgTaO3 (ATO), and AgNbO3 (ANO) thin films. The films were grown by Pulsed Laser Deposition (PLD) and rf-magnetron sputtering techniques from stoichiometric high density ceramic NKN, ATN, ATO, ANO and BST targets onto LaAlO3 (LAO), Al2O3 (r-cut sapphire), Nd:YAlO3 single crystals and amorphous glass substrates. Advanced X-ray diffraction examinations showed NKN, ATN, BST films on LAO substrates grow epitaxially, whereas films on r-cut sapphire were found to be preferentially (00l) oriented. Coplanar waveguide 2 µm finger gap interdigital capacitor (CPWIDC) structures were fabricated by photolithography process and metal lift-off technique. On-wafer tests up to 40 GHz were performed to characterize microwave properties of the ferromagnetic film CPWIDC devices. The measurement setup is composed of network analyzer, probe station, and microwave G-S-G probes. External electric field was applied to planar capacitors to measure tunability. Original de-embedding technique has been developed to calculate capacitance, loss tan δ, and tunability of varactors from the measured S-parameters. NKN film interdigital capacitors on Nd:YAlO3 showed superior performance compared to ATN in the microwave range from 1 to 40 GHz. Within this range, the voltage tunability (40V, 200 kV/cm) was about 29%, loss tangent ~ 0.13, K-factor = tunability/tan δ from 152% @ 10GHz to 46% @ 40GHz. The ATN/sapphire CPWIDCs showed the lowest dispersion ~ 4.3% in whole frequency range from 1 to 40 GHz, voltage tunability 4.7% @ 20GHz and 200 kV/cm, lowest loss tangent ~ 0.068 @ 20GHz, K-factor = tunability/tan δ ranged from 124% @ 10GHz to 35% @ 40GHz. BST film CPWIDCs on sapphire showed frequency about 17%, the highest voltage tunability ~ 22.2%, loss tangent ~ 0.137 @ 20GHz, and K-factor = 281% @ 10GHz to 95% @ 40GHz. / QC 20100906

Ferroelectric oxides are a group of advanced electronic materials with a wide variety of properties useful in applications such as memory devices, resonators and filters, infrared sensors, microelectromechanical systems, and optical waveguides and modulators. Among the oxide perovskite-structured ferroelectric thin film materials, sodium potassium niobate or Na0.5K0.5NbO3 (NKN) has recently emerged as one of the most promising materials in radio frequency (rf) and microwave applications due to high dielectric tenability and low dielectric loss. This thesis presents results on growth and structural, optical, and electrical characterization of NKN thin films. The films were deposited by rf-magnetron sputtering of a stoichiometric, high density, ceramic Na0.5K0.5NbO3 target onto single crystal LaAlO3 (LAO), Al2O3 (sapphire), SrTiO3, and Nd:YAlO3, and polycrystalline Pt80Ir20 substrates. By x-ray diffractometry, NKN films on c-axis oriented LaAlO3, SrTiO3 and Nd:YAlO3 substrates were found to grow epitaxially, whereas films on r-cut sapphire and polycrystalline Pt80Ir20 substrates were found to be preferentially (00l) oriented. The surface morphology was explored using atomic force microscopy. Optical and waveguiding properties of the Na0.5K0.5NbO3/substrate heterostructures were characterized using prism-coupling technique. Sharp and distinguishable transverse magnetic and electric propagation modes were observed for NKN thicknesses up to 2.0 μm. The extraordinary and ordinary refractive indices were calculated together with the birefringence of the NKN material. The electro-optic effect in transverse geometry was measured in transmission, where the effective linear electro-optic response was determined to reff = 28 pm/V for NKN/Al2O3 with an applied dc field up to 18 kV/cm. The ferroelectric state in NKN films on Pt80Ir20 at room temperature was indicated by a polarization loop with saturated polarization as high as 33.4 μC/cm2 at 700 kV/cm, remnant polarization of 10 μC/cm2, and coercive field of 90 kV/cm. Current-voltage characteristics of vertical Au/NKN/PtIr capacitive cells and planar Au/NKN/LAO interdigital capacitors (IDCs) showed very good insulating properties, with the leakage current density for an NKN IDC on the order of 30 nA/cm2 at 400 kV/cm. Rf dielectric spectroscopy demonstrated low loss, low frequency dispersion, and high voltage tunability. At 1 MHz, NKN/LAO showed a dissipation factor tan δ = 0.010 and a tunability of 16.5 % at 200 kV/cm. For the same structure the frequency dispersion was Δεr = 8.5 % between 1 kHz and 1 MHz. / QC 20100928

This thesis report is focused on the growth of Pt/Mg multilayers and the studies of the sputter yield amplification effect in these. The main application is to use the multilayers as X-ray mirrors reflecting an X-ray wavelength of 17 Å. This wavelength is important for astronomical applications in general, and solar imaging applications in particular. For periodic X-ray multilayer mirrors only a certain specific wavelength of X-rays can be reflected. What wavelength that is reflected depends on the individual layer thicknesses of the materials that are constituting the multilayer. These thicknesses can be determined using modified Bragg’s law and are approximately a quarter of the wavelength. In order to obtain the exact desired layer thickness of each individual layer it is necessary to understand the growth processes and the effects that are going on during deposition of such multilayer mirrors. It has been shown that when depositing multilayers consisting of one very light and one very heavy material, like e.g. Pt and Mg, the deposition rate of the light element is non-linear with deposition time for thin layers. This is because of backscattered energetic neutrals from the heavy target material, which affects the growing film. Furthermore, a sputter yield amplification is present for thin layers when a light element is grown on top of a heavy element, i.e. for Mg on top of Pt. Dual DC magnetron sputtering has been used to grow the Pt/Mg multilayers, and the influence of the backscattered energetic neutrals and the sputter yield amplification effect has been studied for Ar and Kr sputtering gases at pressures ranging from 3 up to 9 mTorr. The individual layer thicknesses have been obtained from simulations of hard X-ray reflectivity measurements using the IMD program. The number of backscattered energetic neutrals and their energies at the target have been calculated using the TRIM code. Using the results obtained it is now possible to predict and compensate for the non-linear deposition rate of Mg.

Co-doped ZnO (ZnO:Co) thin film with room temperature ferromagnetism and spin polarized carriers is one of the advance materials and highly applicable in future development in spintronics. When ZnO:Co films deposited by a £_ growth method in a ion sputtering system, low solubility of Co (3.75%) limits further applications such that a single-guns sputtering thin film growth technique is employed in this study to outreach this limitation. A ZnO:Co bulk with 5 at% of Co was formed by a solid reaction method and used as a target. ZnO:Co films were grown in a single-gun RF sputtering system. However, all films grown at room temperature were insulator which might because sufficient oxygen content in the target and the negative charge of oxygen ion moving toward substrate making the films of full oxygen content. In this study, the post annealing in vacuum environment and the deposition of films in hydrogenation environment are conducted to try to produce various level of oxygen vacancies in the films for understanding the interplay between the oxygen vacancies and the electric transport and magnetic coupling. The present experiment contains two parts: (1) grow films with various thicknesses by controlling deposition time and then applying post annealing process, and (2) grow the films in oxygen reduced environment by introducing hydrogen during growth and taking out partial oxygen content in the plasma and the films. In the first part, the grain sizes of the films are near constant while the crystal quality is improved with the thickness of films. The worse crystal quality of grains, the better the electric transport and the stronger the magnetic coupling after post annealing processes. This indicates that the electric transport and magnetic coupling could be improved when the thin films was formed by crystals with certain disordering and contained a certain level of oxygen vacancies. In the second part, the introduced hydrogen may combine with the oxygen sputtered out from the target before deposition on substrates. It means that the films are grown in oxygen deficient conditions and result in various degrees of oxygen vacancies. Zn clusters precipitate in films when the concentration of hydrogen is over 20%, and at the meantime, they increase the conductivity and suppress the magnetic coupling in the films. These discoveries provide new perspective in understand the electric transport and ferromagnetism mechanics in DMS materials.

In der vorliegenden Arbeit wird das Wachstum von Ta- und TaN-Schichten auf Si- und SiO_2-Substraten untersucht Die Schichten werden dabei unter technologienahen Bedingungen mittels Magnetron-Sputtern abgeschieden. Die Untersuchungen erfolgen hauptsächlich mit winkelaufgelöster röntgenstrahlungsangeregter Photoelektronenspektroskopie (ARXPS). Die Analysen erfolgen in situ, ohne Unterbrechung des Ultrahochvakuums, um die Deposite vor Oxidation und Kontamination zu schützen. Zur zerstörungsfreien Tiefenprofilanalyse wird ein Quantifizierungsalgoritmus beschrieben und angewandt. Für die Kombination Ta/Si wird die Bildung einer zunächst unvollständigen TaSi_2-Schicht, danach das Aufwachsen von Ta auf diese Zwischenschicht beobachtet. Für die Kombination Ta/SiO_2 wird eine Reduktion des SiO_2-Substrates bei gleichzeitigem Aufwachsen von Ta-Oxiden beobachtet. Auf dem durchmischten Schichtstapel wächst danach Ta auf. Für die Kombination TaN/Si wird die Bildung einer Si-N-Zwischenschicht bei gleichzeitigem Wachsen einer TaN-Schicht beobachtet. Für die Kombination TaN/SiO_2 wird das Aufwachsen einer TaN-Schicht ohne Ausbilung von Zwischenschichten beobachtet. Das Wachstumsverhalten des Ta/Si-Systems wird zusätzlich mit in situ Rastertunnelmikroskopie und -spektroskopie untersucht. Es wurden Untersuchungen zur thermischen Stabilität von abgeschiedenen Schichten an den Systemen Ta/Si und TaN/SiO_2 durchgeführt. Als mögliche Alternative zur winkelaufgelösten XPS wurden Untersuchungen mittels synchrotronstrahlungsangeregter Photoelektronenspektroskopie bei variierter Anregungsenergie durchgeführt.