Ferroelectrics are a group of advanced electronic materialswith a wide variety of properties useful in applications suchas memory devices, resonators and filters, infrared sensors,microelectromechanical systems, and optical waveguides andmodulators. Among the oxide perovskite-structured ferroelectricthin film materials sodium potassium niobate or Na0.5K0.5NbO3(NKN) has recently emerged as one of the most promisingmaterials in microwave applications due to high dielectrictunability and low dielectric loss. This licentiate thesispresents results on growth and structural, optical, andelectrical characterization of Na0.5K0.5NbO3 thin films. Thefilms were deposited by rf-magnetron sputtering of astoichiometric, high density, ceramic Na0.5K0.5NbO3 target ontosingle crystal LaAlO3 and Al2O3, and polycrystalline Pt80Ir20substrates. By x-ray diffractometry, NKN films on c-axisoriented LaAlO3 substrates were found to grow epitaxially,whereas films on hexagonal sapphire and polycrystallinePt80Ir20 substrates were found to be preferentially (00l)oriented. Optical and waveguiding properties of theNa0.5K0.5NbO3/Al2O3 heterostructure were characterized using aprism-coupling technique. Sharp and distinguishable transversemagnetic (TM) and electric (TE) propagation modes wereobserved. The extraordinary and ordinary refractive indiceswere calculated to ne = 2.216±0.003 and no =2.247±0.002 for a 2.0 μm thick film at λ = 632.8nm. This implies a birefringence Δn = ne - no =-0.031±0.003 in the film. The ferroelectric state inNKN/Pt80Ir20 films at room temperature was indicated by apolarization loop with polarization as high as 33.4 μC/cm2at 700 kV/cm, remnant polarization of 9.9 μC/cm2 andcoercive field of 91 kV/cm. Current-voltage characteristics ofvertical Au/NKN/Pt80Ir20 capacitive cells and planar Au/NKN/LaAlO3 interdigital capacitors (IDCs) showed very goodinsulating properties, with the leakage current density for anNKN IDC on the order of 30 nA/cm2 at 400 kV/cm. Rf dielectricspectroscopy demonstrated low loss, low frequency dispersion,and high voltage tunability. At 1 MHz NKN/LaAlO3 showed adissipation factor tan δ of 0.010 and a tunability of 16.5% at 200 kV/cm. For the same structure the frequencydispersion, Δεr, between 1 kHz and 1 MHz was 8.5%. <b>Key words:</b>ferroelectrics, sodium potassium niobates,thin films, rf-magnetron sputtering, waveguiding, refractiveindex, prism coupling, dielectric tunability / NR 20140805

This past decade, 2D materials beyond graphene, and most specifically transition metal dichalcogenides (TMDCs) have gained remarkable attention due to their novel applications in electronics and optoelectronics applications. This work reports large-area growth and structural, optical, and electronic transport properties of few-layer MoS2 thin films fabricated using a hybrid approach based on the magnetron sputtering method. In the first part of this dissertation, properties of optimally annealed MoS2 on different substrates such as amorphous BN, SiO2, Si, Al2O3 are discussed using diffraction, spectroscopic, and transport techniques. Later, we show that the physical properties of large-area sputtered MoS2 thin films can be dramatically improved by an ex-situ high-temperature sulfurization process as it leads to the formation of defect-free MoS2 by removing sulfur vacancies. Sharp film-substrate interface along with high bulk structural order is demonstrated as inferred from diffraction and spectroscopic methods. We show that sulfur vacancies can obscure the MoS2 A-B exciton peaks along with a sharp increase in dc conductivity of MoS2. In the last part of my dissertation, we outline the growth of a novel thermoelectric material (SnSe) and new magnetic inverse-Heuslers (of nominal composition MnxFeSi) using the co-sputtering method. These are some of the first attempts, to our knowledge, to grow such materials in thin-film form. Detailed structure-property relations are thoroughly discussed.

High Power Impulse Magnetron Sputtering (HiPIMS) comes as a new and promising PVD method for the development of high-performance coatings for cutting applications. This technique utilizes high energy and ionization which can produce a denser and stronger ceramic in comparison to traditional deposition techniques. Important coating characteristics that arise from this method such as enhanced hardness, adhesion, and less defects, can be applied when machining hard-to-cut materials. In this study, investigation of tool life and wear mechanisms, mechanical and physical properties of AlTiN coatings deposited on carbide tools by HiPIMS and Cathodic Arc Evaporation (CAE) were analyzed when machining Inconel 718 and Stainless Steel 304. Experimental turning tests were performed to evaluate tool life, and the wear mechanisms were analyzed by optical and scanning electron microscopy. Nanohardness, scratch test, fracture toughness and other methods were carried out to evaluate the coating properties. Impedance experiments were performed to determine the coating porosity and resistance to corrosion. The results showed that HiPIMS coating presented higher hardness, toughness to fracture and adhesion to the substrate in comparison to CAE coatings. The HiPIMS coated tool substantially improved tool life when machining Inconel. The dominant wear mechanism found was abrasion, which is induced by the presence of hard carbides. The main wear patterns observed were flank, notch, and crater wear. The tool performance of HiPIMS was found to have enhanced mechanical properties, lower porosity, and form a larger amount of tribo-oxides when machining, in comparison to CAE. / Thesis / Master of Applied Science (MASc)

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Im Fokus der vorliegenden Arbeit lag die Untersuchung polykristalliner TiO2:Ta-Schichten, hergestellt mittels Gleichstrom-Magnetron-Sputtern durch Verwendung reduzierter keramischer Targets und anschließender thermischer Nachbehandlung im Vakuum der zunächst nichtleitfähigen amorphen Precursorschichten. Es wurden die physikalischen Zusammenhänge, welche die strukturellen, elektrischen und optischen Eigenschaften der kristallinen TiO2:Ta-Schichten beeinflussen analysiert und dabei eine empfindliche Abhängigkeit vom Sauerstofffluss während der Abscheidung festgestellt. Es zeigte sich, dass die Verringerung der kinetischen Energie der Plasmateilchen beim Magnetron-Sputtern durch die Erhöhung des Gesamtdruckes vorteilhaft ist, um das Wachstum des gegenüber Rutil besser leitfähigen Anatas in Verbindung mit dem für niedrige Widerstände notwendigen Sauerstoffdefizit zu realisieren. Bei einem Gesamtdruck von 2 Pa abgeschiedene polykristalline TiO2:Ta-Schichten haben einen spezifischen Widerstand von 1,5·10-3 Ωcm, eine hohe Ladungsträgermobilität (≈8 cm2V-1s-1) und einen geringen Extinktionskoeffizienten von 0,006. Die Abhängigkeit des elektrischen Widerstandes vom Sauerstoffdefizit in der TiO2:Ta-Schicht wurde unter dem Gesichtspunkt der Ladungsträgeraktivierung sowie der Bildung von Ti-Fehlstellen diskutiert, welche vermutlich zur Kompensation und Lokalisierung von freien Elektronen beitragen. Darüber hinaus wurde zur effizienteren Gestaltung der thermischen Nachbehandlung die konventionelle Vakuumtemperung erstmalig erfolgreich durch die Blitzlampentemperung ersetzt. / The work is focused on understanding the physical processes responsible for the modification of the structural, electrical and optical properties of polycrystalline TiO2:Ta films formed by vacuum annealing of initially not conductive amorphous films deposited by direct current magnetron sputtering. It is shown that the oxygen deficiency of amorphous and annealed TiO2:Ta films, respectively, is critical to achieve low resistivity and high optical transmittance of the crystalline films. Increasing the total pressure during magnetron sputter deposition is shown to be beneficial to achieve the desired oxygen deficient anatase growth, which is discussed in terms of energetic particle bombardment. Polycrystalline anatase TiO2:Ta films of low electrical resistivity (1,5·10-3 Ωcm), high free electron mobility (≈8 cm2V-1s-1), and low extinction (0,006) are obtained in this way at a total pressure of 2 Pa. The dependence of the polycrystalline film electrical properties on the oxygen content is discussed in terms of Ta dopant electrical activation as well as transport limiting processes taking into account the formation of Ti-vacancies. In addition, the conventional vacuum annealing has been successfully substituted by the flash lamp annealing in the millisecond range.

Un plasma est défini comme un gaz partiellement ou totalement ionisé. Bien que très présent dans l'univers visible, les plasmas naturels sont rares sur Terre. Cependant, ils représentent un intérêt majeur pour les industries et les instituts de recherche (traitement de surface, propulsion spatiale). Toutefois, la compréhension du comportement d'un plasma est complexe et fait appel à de nombreux domaines de la physique. De plus, ces plasmas peuvent être magnétisé i.e. lorsqu'un champ magnétique extérieur ou induit influence significativement la trajectoire des particules : r/L<1 où r est le rayon de Larmor et L la longueur caractéristique du système. Ce travail de thèse s'intéresse à la modélisation du comportement du plasma présent dans deux dispositifs : l'accélérateur de l'Injecteur de Neutres (IdN) rapides d'ITER et le magnétron en régime DC ou HiPIMS. La réalisation de la fusion nucléaire sur Terre fait actuellement l'objet de nombreuses recherche dans le monde. Du fait de l'énergie nécessaire au franchissement de la barrière de répulsion coulombienne, le plasma doit être confiné. Dans le cas d'ITER, le confinement est réalisé par de puissant champ magnétique. Cependant, pour atteindre les conditions nécessaires aux réactions de fusion, notamment en température, un injecteur de particules neutres à haute énergie (1MeV) est nécessaire. L'accélération de ces particules est une phase critique dans la création du faisceau de neutres et elle représente un défi technologique qui fait l'objet d'une étude dans ce travail de thèse. Le magnétron est un procédé industriel permettant la réalisation de couches minces par pulvérisation cathodique. Les ions créés par un plasma de décharge arrachent les atomes de la cathode qui se déposent sur l'anode. Le champ magnétique créé par des aimants permanents piège les électrons à proximité de la cathode augmentant l'efficacité du dispositif. Le comportement du plasma magnétron est ainsi étudié en régime continu ou pulsé ainsi que l'apparition de structures auto-organisées en rotation autour de l'axe du magnétron dans certaines conditions. Afin d'étudier ces dispositifs, plusieurs programmes de simulation numérique ont été développés. La méthode Paticle-In-Cell a été choisie car elle permet de prendre en compte la charge d'espace des particules de manière auto-cohérente. Diverses techniques (technique de collision nulle, Monte Carlo Collision, a posteriori Monte Carlo) et améliorations (maillage non uniforme, projections de charges au troisième ordre) ont été développées et implémentées. De plus, une méthode originale, Pseudo 3D, permettant un traitement à trois dimension du magnétron a été utilisées avec succès. Enfin, ces programmes ont été parallélisés afin de réduire le temps de calcul. / A plasma is defined as a partially or completely ionized gas. Even though, they are very present in the visible universe, natural plasmas are rare on Earth. However, they are a major interest for industries and research institutes (surface treatment, spatial propulsion). Nevertheless, the understanding of plasma behavior is complicated because of the numerous physical fields involved. Moreover, theses plasmas can be magnetized, i.e., a magnetic field, external or induced, affects significantly the particle trajectories: r/L<1 where r is the Larmor radius and L the typical length of the system. This thesis is focused on the plasma modeling in two device: the accelerator of the ITER's neutral beam injector (NBI) and the magnetron in DC or HiPIMS regime. The feasibility of nuclear fusion on Earth is subject of numerous research around the world. Because of the energy necessary to get over the Coulomb barrier, the plasma must be confined. For ITER, the confinement is achieved by intense magnetic fields. However, to reach the required conditions of nuclear fusion reactions, especially in temperature, a high energy (1MeV) neutral beam injector is needed. The particle acceleration is a critical part in the creation of the neutral beam and it represents a technical challenge which is studied in this thesis work. The magnetron is an industrial process for creating thin film by physical sputtering. The ions created by a plasma discharge tear the atoms out of the cathode which are then deposited on the anode. The magnetic field created by permanent magnets trap the electrons near the cathode improving the process efficiency. The plasma behavior inside the magnetron is studied in direct and pulsed current as well as the appearance of self-organized structures in rotation around the magnetron axis. To study these devices, several program of numerical simulation have been developed. The Particle-In-Cell methode has been chosen because it takes into account, self-consistently, the space charge of the particules. Several techniques (null collision technique, Monte Carlo Collision, a posteriori Monte Carlo) and improvement (Non uniform mesh, third order charge projection) have been developed and implemented. Moreover, an original method, Pseudo 3D, allowing a three dimensional study of the magnetron, has been used with success. Finally, these programs have been parallelized to reduce the computation time.

Neste trabalho é apresentado um estudo sobre a produção e caracterização do nitreto de alumínio (AlN) obtido pela técnica de r.f. Magnetron Sputtering reativo. Aqui reportamos o efeito dos parâmetros de deposição, como densidade de potência de r.f., temperatura e pressão de processo nas propriedades estruturais, morfológicas e elétricas dos filmes de AlN obtidos. Foram realizados estudos sobre os modos vibracionais, pela técnica de espectroscopia de infravermelho por transformada de Fourier (FTIR), das orientações cristalográficas por difração de raios X e da morfologia da superfície pela técnica de microscopia de força atômica (AFM). Estes estudos nos permitiram produzir filmes finos de AlN com uma alta orientação na direção cristalográfica [002] com uma potência de r.f. de 1,23 W/cm2 , uma temperatura de deposição de 200°C e uma pressão de processo de 2 mTorr. Este estudo nos permitiu fabricar filmes de AlN com alta orientação [002] à temperatura ambiente a partir de um alvo de Al. O coeficiente piezoelétrico d33 variou de aproximadamente 4 a 6 pm/V e o d31 2 a 3 pm/V para filmes cristalinos e d33 3 pm/V e d31 1,5 pm/V para filmes amorfos. Os coeficientes piezoelétricos d33 and d31 foram estimados pelo método capacitivo proposto por Mahmoud Al Ahmad and Robert Plana, através da variação das dimensões geométricas induzidas pelo campo elétrico aplicado. / In this work we present a study about the production and characterization of aluminum nitride (AlN) obtained by r.f. Reactive Magnetron Sputtering. Here we report the effect of the deposition parameters, such as r.f. power density, and deposition temperature and pressure, on the morphological, structural and electrical properties of the obtained AlN thin films. In this work we have performed studies concerning the vibrational modes by Fourier Transform Infrared Absorption technique (FTIR), the crystallographic orientations by X-ray diffraction and the surface morphology by Atomic Force Microscopy (AFM). This study allowed us to produce high oriented [002] AlN thin films with a r.f. power density of 1.23 W/cm2, a deposition temperature of 200ºC and a process pressure of 2 mTorr. This study allowed us to produce high oriented [002] AlN thin films at room temperature from a pure Al target. The piezoelectric coefficient d33 was around 4 to 6 pm/V and d31 2 to 3 pm/V to crystalline films and d33 3 pm/V and d31 1.5 pm/V amorphous ones. d33 and d31 piezoelectric coefficients were estimated by the capacitive method proposed by Mahmoud Al Ahmad and Robert Plana, through its geometrical dimensions variation.