Дисертації з теми "Oxide thin films and heterostructure"
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Glavic, Artur [Verfasser]. "Multiferroicity in oxide thin films and heterostructures / Artur Glavic." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2012. http://d-nb.info/1025883497/34.
Повний текст джерелаVaghefi, Seyedeh Pegah Mirzadeh. "Structural and physical properties studies on multiferroic oxide films and heterostructures." Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/18502.
Повний текст джерелаO presente trabalho de doutoramento é um estudo de propriedades físicas e aspectos estruturais de filmes de óxidos e heteroestruturas multiferróicas, englobando técnicas de caracterização do nível macroscópico ao microscópico. O objectivo principal é a compreensão de novas heteroestruturas epitaxiais multifuncionais e as suas interfaces para junções de túnel magnetoelétricas e filtros de spin. Os principais materiais em estudo foram manganitas à base de La dopadas com iões divalentes (ba, Sr), apresentando efeito magnetoelétrico, sendo preparadas em diferentes substratos e diferentes técnicas de crescimento, optimizadas para epitaxia e qualidade de interface. O estudo combinado de propriedades eléctricas e magnéticas permitiu estabelecer as condições necessárias para a aplicação dos materiais multiferróicos em estudo, por técnicas experimentais apresentadas neste trabalho. O trabalho consistiu no estudo sistemático de microestrutura de filmes finos de La0:7Sr0:3MnO3 em substratos de SrTiO3, preparados por pulsed laser deposition, o filme fino de La0:9Ba0:1MnO3 e a heteroestrutura La0:9Ba0:1MnO3/BaTiO3/La0:9Ba0:1MnO3 em substrato de Al2O3, e filme fino de La0:9Ba0:1MnO3, BaTiO3 e heteroestrutura de La0:9Ba0:1MnO3/BaTiO3/La0:9Ba0:1MnO3 em substrato de Si, preparado por RF magnetron sputtering. A caracterização estrutural das amostras foi feita principalmente por difracção de raio-X (XRD) convencional e de alta resolução e Microscopia de Transmissão de Alta Resolução (HRTEM). A composição química foi analisada por Electron Dispersion Spectroscopy (EDS), Rutherford backscattering spectroscopy (RBS) e energy filtered transmission electron microscopy (EFTEM). As medidas de magnetização forram realizada com a um magnetómetro superconducting quantum interference device (SQUID). A análise da topografia e efeitos locais foi realizada por microscopia de varimento de ponta usando microscopia da Força Atómica (AFM) e de resposta piezoeléctronica (PFM). Os resultados mostram claramente uma evolução da microestrutura dos filmes finos de La0:7Sr0:3MnO3, á medida que aumenta a sua espessura, passando de uma estrutura policristalina no filme mais fino (13.5 nm) a colunar inclinado (45 nm e 200 nm), a uma estrutura ramificada no filme mais espesso (320 nm). A alteração na estrutura do filme é devida à tensão pelo substrato e deformação da estrutura nas etapas iniciais de crescimento, onde se detectaram fronteiras anti-phase e maclas. A evolução da estrutura modificou as propriedades magnéticas dos filmes a baixa temperatura (abaixo da temperatura de transição estrutural do substrato de SrTiO3), mostrando magnetização em excesso e defeito, para espessuras abaixo e acima de 100 nm, respectivamente. Análises STEM-EELS e EFTEM mostraram a diferença em composição elementar dos filmes perto das fronteiras e na interface com o substrato.No âmbito do plano de trabalhos de doutoramento, o segundo substrato consiste em estudar as propriedades físicas e estruturais de filmes finos de La0:9Ba0:1MnO3 e heteroestruturas La0:9Ba0:1MnO3/BaTiO3/La0:9Ba0:1MnO3 em substratos de Al2O3, revelando estruturas altamente orientadas. A razão La/Ba do filme e heteroestrutura é drasticamente diferente do alvo providenciado, La0:7Ba0:3MnO3, como provado por XRD, RBS e transições de fase magnéticas. As propriedades magnéticas e eléctricas das estruturas mostraram uma forte dependência na cristalinidade do filme e da heteroestrutura. A parte final do trabalho é dedicada aos filmes de La0:9Ba0:1MnO3, BaTiO3 e a heteroestrutura de La0:9Ba0:1MnO3/BaTiO3/La0:9Ba0:1MnO3 em substrato de Si, que em comparação com as estruturas em substrato de ALO, provaram o efeito da cristalinidade nas propriedades magnéticas, eléctricas e de magneto-resistência do filme e heteroestrutura. Foi mostrado que um grau superior de cristalinidade leva a uma mais elevada magnetização, reduzindo a resistividade das estruturas. Pela primeira vez, um estudo de deformação de topografia por aplicação de uma tensão dc externa foi feito num filme fino de BaTiO3 em Si, usando uma técnica de poling num microscópio de força piezoresponse. Os resultados mostraram a capacidade de uma modificação controlada da superfície, por aplicação de uma voltagem externa nointervalo 14V < Vapp < 20V. Abaixo destes valores, não se observou alguma deformação na topografia, enquanto acima deste intervalo, a 30V, a superfície foi completamente danificada. A mudança topográfica produzida mostrou estabilidade no tempo, onde após a aplicação de 20V, a área modificada alcançou 83% da altura as-poled ( 9 nm) em 90 minutos, a 7,4 nm. A resposta assimétrica de piezoresponse da área poled foi associada à existência de um campo eléctrico interno na amostra, que foi também provado através de medidas de espectroscopia de switching no filme fino. A heteroestrutura no substrato de Si mostraram o mesmo fenómeno que a mono-camada de BaTiO3, onde o arranjo de heteroestrutura realça o efeito de voltagem aplicada na topografia. Aplicando 10V, a estrutura da superfície foi alterada na heteroestrutura e houve uma modificação visível da camada de BaTiO3, alterando também a topografia da camada superior de La0:9Ba0:1MnO3.
This present PhD work made a study of structural aspects and physical properties of the oxide films and multiferroic heterostructures, encompassing the techniques from macroscopic level to microscopic description. The understanding of novel multifunctional epitaxial heterostructures and their interfaces for magneto-electrically driven tunnel junctions and spin-filters is the central objective. The main materials in study were La based doped manganites with magnetoelectric effect prepared on different substrates and growth conditions, optimized for epitaxy and interface quality. The combined study of electric and magnetic properties allowed us examining the conditions required for application of the studied multiferroic materials and experimental techniques are presented in this work. The work consists of three main substrates, a systematic study of microstructure of La0:7Sr0:3MnO3 thin films on SrTiO3 substrate, prepared by pulsed laser deposition, the La0:9Ba0:1MnO3 thin film and La0:9Ba0:1MnO3/BaTiO3/La0:9Ba0:1MnO3 heterostructure on Al2O3 substrate, and the La0:9Ba0:1MnO3 thin film, BaTiO3 and La0:9Ba0:1MnO3/BaTiO3/La0:9Ba0:1MnO3 heterostructure on Si substrate, prepared by RF magnetron sputtering. Main structural characterization of samples was performed by conventional and high resolution X-Ray Diffraction (XRD), High Resolution Transmission Electron Microscopy (HRTEM); chemical composition was determined by Electron Dispersion Spectroscopy (EDS), Rutherford Backscattering Spectroscopy (RBS) and Energy Filtered Transmission Electron Microscopy (EFTEM); Magnetization measurements done with a Superconducting Quantum Interface Device (SQUID) magnetometer. Surface probing of topography and local effects was performed, using Atomic Force (AFM) and Piezo-Response (PFM) Microscopy. Results clearly showed that there is an evolution in the microstructure of the La0:7Sr0:3MnO3 thin films, by increasing their thickness, changing from polycrystalline structure in the thinnest film (13.5 nm) to tilted columnar structure(45 nm and 200 nm) and to a branched structure in the thickest film (320 nm). The change in the structure of the film is due to the strain from the substrate and deformation of the structure in the early stages of the growth, where anti-phase boundaries and twinning were detected. The evolution of the structure modified the low temperature (below structural phase transition of SrTiO3 substrate) magnetic properties of the films, showing in-excess and in-defect magnetization, below and above 100 nm thickness, respectively. Also, STEM-EELS and EFTEM analysis showed the difference in the elemental composition of the films near the boundaries and interface with the substrate.In the scope of the PhD work plan, the second substrate consists of studying the structural and physical properties of La0:9Ba0:1MnO3 thin film and La0:9Ba0:1MnO3/BaTiO3/La0:9Ba0:1MnO3 heterostructure on Al2O3 substrate, where they showed highly oriented structure. The La/Ba ratio of the single layer film and heterostructure is drastically different from the target, La0:7Ba0.3MnO3, proven by XRD, RBS, and magnetic phase transitions. The magnetic and electrical properties of the structures showed strong dependence on the crystallinity of the samples. The final part of the work is devoted to the La0:9Ba0:1MnO3 and BaTiO3 thin films and La0:9Ba0:1MnO3/BaTiO3/La0:9Ba0:1MnO3 heterostructure on Si substrate, which in comparison with the structures on Al2O3 substrate, highlights the influence of crystallinity on magnetic, ferro-electrical and magnetoresistance properties of the film and heterostructure. It is shown that higher degree of crystallinity leads to higher magnetization and lowers the resistivity. For the first time, a study of the topography deformation by applying a dcexternal voltage was done on BaTiO3 thin film on Si, using a poling technique in a piezoresponse force microscope. The results show the ability of controlled modification of the surface, by applying an external voltage/electric field in the range of 14V< Vapp<20V. Below this range, no deformation is observed on the topography, and above this interval, at 30V, the surface is completely damaged. The produced topographical change show stabilization in respect to time, where after applying 20V, the modified area reaches its 83% of the as-poled height ( 9nm) in 90 minutes, to 7.4 nm. The asymmetrical response in the piezoresponse of the poled area is related to the existence of an internal built-in electric field in the sample, which is also confirmed by performing switching spectroscopy measurements on the single layer. The heterostructure on the Si substrate shows the same phenomena, as the BTO single layer, where the heterostructure arrangement enhances the applied voltage effect on the topography. With applying 10V, the structure of the surface changes in the heterostructure and a visible modification of BaTiO3 layer, changing also the topography of La0:9Ba0:1MnO3 top layer is observed.
Leung, Gong Wai. "Magnetic semiconducting oxide thin films and heterostructures by pulsed laser deposition." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609286.
Повний текст джерелаWang, Chao-Hsiung. "The growth of thin film epitaxial oxide-metal heterostructures." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368667.
Повний текст джерелаLüders, Ulrike Anne. "Development and integration of oxide spinel thin films into heterostructures for spintronics." Doctoral thesis, Universitat Autònoma de Barcelona, 2005. http://hdl.handle.net/10803/3373.
Повний текст джерелаHemos descubierto que el crecimiento epitaxial permite estabilizar fases nuevas del óxido NiFe2O4, fases que no existen en la forma másiva, y que tienen propiedades remarcablemente distintas. Como por ejemplo: un aumento dramático de la magnetización o la posibilidad de modificar drásticamente sus propiedades de transporte, pudiéndose obtener capas aislantes -como es en forma cerámica- o conductivas. Se ha realizado un estudio sistemático de los efectos del espesor de la capa y de las condiciones de crecimiento sobre las propiedades de magnetotransporte y los mecanismos de crecimiento.
Argumentamos que el aumento de la magnetización es debido a la estabilización de una fase NiFe2O4 espinela que es parcialmente inversa, en la que los iones Ni2+ están distribuidos entre las dos posiciones disponibles (tetraédrica y octaédrica) de la estructura. En la forma masiva del material los iones Ni solo se encuentran en los sitios octaédricos. La introducción adicional de vacantes de oxígeno es probablemente la causa de la existencia de una configuración electrónica mixta Fe2+/3+ en la subred octaédrica y de la alta conductividad de las capas.
Hemos aprovechado la capacidad de obtener epitaxias de NiFe2O4 ferrimagnéticas conductoras o aislantes para integrarlas en dos distintos dispositivos magnetoelectrónicos: una unión túnel magnética y un filtro de spin.
Las capas conductoras de NiFe2O4 se han empleado como electrodos ferrimagnéticos-metálicos en uniones túnel. El otro electrodo magnético es (La,Sr)MnO3 y la barrera túnel SrTiO3. Se ha podido medir una magnetoresistencia túnel importante hasta temperaturas tan altas como 280K. Los valores de magnetoresistencia corresponden a una polarización de spin del NiFe2O4 de aproximadamente un 40%, que es prácticamente independiente de la temperatura. Estos resultados sugieren que la nueva fase conductora que hemos estabilizado es un candidato interesante como fuente de corriente polarizada en spin.
Por otra parte, el NiFe2O4 aislante se ha implementado, por primera vez, como barrera túnel en una heteroestructura de filtro de spin. El electrodo magnético es (La,Sr)MnO3 y el electrodo no magnético Au. Hemos observado una magnetoresistencia túnel que alcanza valores de hasta un 50%. A partir de estas medidas, hemos deducido detalles relevantes de la estructura electrónica de la fase parcialmente inversa de NiFe2O4.
Hemos crecido el óxido CoCr2O4 sobre distintos substratos, tales como MgO(001) y MgAl2O4(001). Hemos podido comprobar que este óxido presenta una pronunciada tendencia a un crecimiento 3D. Por esta razón, las superficies de la capa no son nunca suficientemente planas y no se pueden usar en heteroestructuras túnel.
Sin embargo hemos aprovechado esta característica para controlar el crecimiento de estas estructuras 3D y hemos conseguido la formación de objetos submicrónicos, autoorganizados con formas piramidales muy bien definidas. El estudio detallado del efecto de los parámetros de crecimiento nos ha permitido por una parte, dilucidar cuales son los mecanismos que llevan a una autoorganización tan perfecta y por otra determinar que, en las condiciones adecuadas, se pueden obtener templates totalmente faceteados con múltiples posibilidades para futuras aplicaciones.
In this thesis the growth of thin films of NiFe2O4 and CoCr2O4 by RF sputtering on different oxide substrates and the characterization of their magnetic and electric properties is reported. The aim is to integrate the films into spintronic devices namely magnetic tunnel junctions and spin filter.
It was found that the epitaxial growth of these films permits to stabilize new phases of NiFe2O4, which are not found for the bulk material and which show remarkably distinct properties. A strong enhancement of the saturation magnetization was found as well as the possibility to tune the electric behaviour of the films from insulating - like in bulk NiFe2O4 - to conducting. A systematic study of the influence of the film thickness and growth parameters on the properties of the films was carried out.
The enhancement of the saturation magnetization can be explained by a partially inversed spinel structure, where the Ni2+ ions are distributed over both available sites (octahedral and tetrahedral) of the structure, whereas in bulk NiFe2O4 the Ni2+ ions are only located on the octahedral sites of the structure. An additional introduction of oxygen vacancies causes the formation of mixed valence Fe2+/3+ chains on the octahedral sites and thus a hopping conductivity.
We have taken advantage of our ability to obtain epitaxial ferromagnetic NiFe2O4 films of insulating or conducting character to integrate them in two different spintronic devices: the magnetic tunnel junction and the spin filter.
The conducting NiFe2O4 was integrated in a magnetic tunnel junction as a magnetic electrode, with a (La,Sr)MnO3 counterelectrode and a SrTiO3 barrier. A magnetoresistance was measured up to a temperature of 280K. The values of the magnetoresistance correspond to a spin-polarization of 40%, which is basically constant in temperature. This results show that the conductive phase of NiFe2O4 is an interesting candidate for the application as a source of highly spin-polarized current.
On the other hand the insulating NiFe2O4 has been integrated into a spin filter as the magnetic barrier. The magnetic electrode was again (La,Sr)MnO3 and the counter electrode Au. A magnetoresistance up to 50% was observed. It was possible to deduce the band structure of NiFe2O4 from these measurements.
Thin films of CoCr2O4 were grown on different substrates like MgO(001) or MgAl2O4(001). It was found that the material shows a pronounced tendency to grow in a three dimensional manner. Thus the surface of these films is not sufficiently smooth to integrate them into tunnel contacts.
However, we were able to control the growth and morphology of the three dimensional structures leading to the formation of submicron self-organized pyramids with a square or elongated base. By a detailed study of the influence of the growth parameters it was possible to elucidate the underlying growth mechanisms and to obtain a fully faceted surface, which can be used in different applications.
Luders, Ulrike. "Development and integration of oxide spinel thin films into heterostructures for spintronics." Phd thesis, INSA de Toulouse, 2005. http://tel.archives-ouvertes.fr/tel-00011342.
Повний текст джерелаIl a été montré que la croissance épitaxiale permet la stabilisation de nouvelles phases de NiFe2O4 qui n'existent pas sous forme massive. Ces phases présentent une augmentation forte du moment magnétique ou la possibilité d'ajuster les propriétés électriques du matériaux. Nous expliquons l'augmentation du moment magnétique par une inversion partielle des sites cationiques du NiFe2O4, matériau dans lequel les ions Ni2+ sont répartis entre les deux sites de la structure spinelle. Les lacunes en oxygène sont susceptibles de favoriser un comportement conducteur en induisant des états de valence mixte Fe2+/3+ dans les sites octaédriques.
Des couches minces de NiFe2O4 conducteur ont été utilisées comme électrodes ferrimagnétiques dans des jonctions tunnel. Une magnétorésistance significative a été mesurée, correspondant à une polarisation de spin de 40% du NiFe2O4 pratiquement constante en température. Le NiFe2O4 isolant a été incorporé avec succès en tant que barrière tunnel ferrimagnétique au sein de jonctions de type "filtre à spin", ce qui en fait la première structure de ce type réalisée avec des oxydes complexes.
Il a été mis en évidence que les couches minces de CoCr2O4 ont une tendance forte à croître de manière tridimensionnelle de la forme des objets pyramidaux aux facettes parfaitement définies. Cette croissance auto-organisée de nano-objets et sa dépendance à l'égard des conditions de dépôt été étudie en detail.
Sacco, Chiara. "Growth and characterization of epitaxial oxide-based electron and hole-doped thin films and their heterostructures." Doctoral thesis, Universita degli studi di Salerno, 2018. http://hdl.handle.net/10556/3180.
Повний текст джерелаThe main goal of this dissertation is the study of the effects induced by quantum confinement in transition-metal oxides quantum wells (QWs). The field of possible applications of oxide-based heterostructures (oxide-based nanoelectronics, spintronics, quantum computation, excitonic devices, energy conversion in solar cells, etc.) is very ample and growing, thanks to the many fascinating and exotic properties of transition-metal oxides and their versatility as well. p-type SrMnO3/La0.7Sr0.3MnO3/SrMnO3 QWs and n-type SrCuO2/Sr0.9La0.1CuO2/SrCuO2 QWs have been studied. The first part of my work has been devoted to the investigation of quantum confinement achievement using a Mott insulator with a small band gap. The observed results suggest that this type of material can be successfully used in QWs. As a final result of my work, the achievement of dimensional effects induced by the layering on the normal state of both investigated systems (n and p-doped) has been assessed. In addition, the layering has been shown to influence the superconducting state of the investigated n-doped QWs and on the metal-to-insulator transition of the p-doped QWs. The investigation of the behavior of each layer constituent the QW (both n and p-doped) is relevant in view of future growth of proximate p-n doped systems. Part of my work, therefore, has been devoted to the study of the properties of (Sr,La)CuO2 thin films. The study of electrical transport properties of SLCO thin films as a function of the doping has allowed to relate the presence of the low temperature upturn in the (Sr,La)CuO2 resistivity versus temperature curves the quantum interference effects produced by weak localization effects. Furthermore, the presence of low temperature Fermi liquid behaviors in SLCO thin films has also been observed... [edited by Author]
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Mirjolet, Mathieu. "Transparent Conducting Oxides Based on Early Transition Metals: From Electrical and Optical Properties of Epitaxial Thin Films, to Integration in All-Oxide Photoabsorbing Heterostructures." Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/673687.
Повний текст джерелаLos óxidos conductores transparentes (TCO) son esenciales en dispositivos tecnológicos. Su capacidad para combinar alta conductividad eléctrica y transparencia óptica a la luz visible los hace particularmente útiles en una gran variedad de dispositivos: pantallas, células solares, ventanas inteligentes, etc. El óxido de indio y estaño (ITO) es hasta ahora el TCO más extendido. Un gran inconveniente del ITO es su alto coste ya que el indio, su componente principal, es un material escaso. Por otro lado, algunos óxidos metálicos intrínsecos de metales de transición también son transparentes. En estos materiales, la banda (3,4)d es estrecha y parcialmente llena. Es la responsable de la alta densidad de portadores libres y su masa efectiva grande hace que la luz no se refleje en el visible y que el borde de reflexión (frecuencia de plasma) esté en la región del IR cercano. En esta tesis, hemos explorado las propiedades de las películas delgadas de óxidos metálicos (SrVO3 (SVO; 3d1) y SrNbO3 (SNO; 4d1)) crecidas por deposición de láser pulsado (PLD). Dado que la calidad epitaxial es fundamental para obtener buenas propiedades funcionales, el primer paso consistió en optimizar los parámetros de crecimiento de las películas SVO/SNO. Las películas deben crecerse en ultra alto vacío (UHV) para estabilizar el estado de oxidación 4+ de V/Nb y usar temperaturas de depósito altas (700-800°C) para permitir la movilidad de las especies sobre el sustrato. Sin embargo, la ablación en UHV y la expansión de la pluma del PLD, muy enérgica, provocan la creación de defectos puntuales en las películas. Hemos resuelto este problema utilizando un gas inerte durante el crecimiento, que controla la expansión de la pluma. Finalmente, hemos estudiado el impacto de la deformación epitaxial en la conductividad eléctrica y la transparencia óptica. Se obtuvieron películas con una conductividad mayor que ITO y una transparencia similar. Por otra parte, la observación de que la frecuencia de plasma en estos materiales esté en el IR cercano, se atribute comúnmente a un aumento de la masa efectiva de los electrones debido a las correlaciones e-e dentro de la banda estrecha 3d. Tras un análisis sistemático de los datos de transporte de SVO llegamos a la conclusión de que la teoría del líquido de Fermi no puede explicar el aumento de la masa efectiva de los portadores. En cambio, hemos sugerido que el acoplamiento electrón-fonón y el carácter 2D de la superficie de Fermi juegan un papel importante. Además, hemos demostrado que la imagen clásica de banda rígida, de un electrón libre que evoluciona en una banda 3d-t2g es solo una aproximación, como lo demuestra la hibridación observada de los orbitales V-3d y O-2p. Hemos observado también que la tensión epitaxial, afecta a la hibridación, el orden orbital y últimamente a la resistividad de las capas. Hemos podido observar y explicar que a la frecuencia de plasma se excitan, en las condiciones de iluminación adecuadas, pasmones de volumen. Una observación y descripción poco frecuentes y que, en esencia, están relacionadas con la componente π de la polarización de la luz y el gradiente de carga en la superficie del material. Finalmente, hemos probado la idoneidad de SVO como electrodo en heteroestructuras fotoabsorbentes “todo-óxido”. Hemos observado la respuesta fotovoltaica, usando capas epitaxiales de LaFeO3 como absorbente y hemos puesto de relieve el papel de la función de trabajo del electrodo en el rendimiento del dispositivo. Como perspectiva, hemos demostrado que los electrodos transparentes SVO y SNO, al tener funciones de trabajo distintas, podrán permitir ajustar y optimizar los dispositivos. Este trabajo aporta un nuevo conocimiento fundamental de las propiedades de óxidos y demuestra su versatilidad en componentes fotovoltaicos.
Transparent conducting oxides (TCOs) are key elements to many technological devices. Their ability to combine high electrical conductivity and high optical transparency to visible light, make them particularly useful in a myriad of devices such as displays, solar cells, smart windows, etc. Indium tin oxide (ITO) is so far the most widespread TCO. By Sn-doping, this wide band gap In2O3 semiconductor can reach low resistivity (only about two orders of magnitude above conventional metals) while preserving its transparency. A major drawback of ITO is its high cost as indium, its main component, is a scarce material. Moreover, due to its nature of doped-semiconductor, some physical limits impose that its properties cannot be further improved. On the other hand, some intrinsic metallic oxides composed of early transition metals also turn out to be transparent. In these materials, the partially filled narrow d band is responsible for high density of free carriers with increased effective mass, thus bringing the reflection edge down to the near-IR region. In this thesis, we were interested in exploring the properties of metallic oxide thin films grown by pulsed laser deposition (PLD), namely SrVO3 (SVO; 3d1) and SrNbO3 (SNO; 4d1). As high epitaxial quality is essential to obtain good functional properties, the first step consisted in optimizing the growth parameters for single phase and flat SVO/SNO films, displaying high crystallinity, conductivity and transparency. As anticipated, films need to be grown in ultra-high vacuum (UHV) to stabilize the 4+ oxidation state of V/Nb and using a high substrate temperature (700-800°C) to allow good mobility of the species on the substrate. However, the deposition in UHV and its subsequent highly energetic PLD plasma plume lead to a high concentration of point defects. We have solved this issue by using an inert background gas. Finally, we have studied the impact of epitaxial strain on the electrical conductivity and optical transparency window. All in all, it turned out that optimal films display larger conductivity than ITO, for a similar transparency. Conventional wisdom would suggest that a low plasma frequency would be due to the electron-electron correlations within the narrow nd1 band. In a systematic analysis of SVO transport data (temperature-dependent resistivity, etc.), we have concluded that the Fermi liquid theory alone cannot account for the carrier mass enhancement. Instead, we have suggested that the 2D-like Fermi surface and the electron-phonon coupling play a major role. In addition, we have shown that the classical rigid band picture, of one free electron evolving in a 3d-t2g band is only a rough approximation, as attested by the observed hybridization of the V 3d and O 2p orbitals. Moreover, strain affects this hybridization by modifying the orbital hierarchy and covalency which could be responsible for the observed strain-dependent resistivity and effective mass. By appropriate optical measurements, we have also discussed the nature of the plasmonic excitations at plasma frequency in SNO and SVO films. Interestingly, the possibility of exciting volume plasmons in these TCOs gives a glimpse on their potential applications in the field of plasmonics. Finally, we have tested the suitability of SVO as electrode in photoabsorbing all-oxide heterostructures. In particular, we have successfully observed a photovoltaic effect in LaFeO3-based capacitors and disclosed the important role of the electrode work function on the device performances. As outlook, we have concluded that SVO and SNO, by having distinct work functions, could allow to tune any device properties. This work demonstrates the suitability and high potential of this whole new category of TCOs as electrode material in all-oxide devices. We are convinced that it opens the way to a plethora of possible devices, photovoltaic-wise or other.
Universitat Autònoma de Barcelona. Programa de Doctorat en Física
Mukherjee, Devajyoti. "Growth and Characterization of Epitaxial Thin Films and Multiferroic Heterostructures of Ferromagnetic and Ferroelectric Materials." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3622.
Повний текст джерелаDRERA, GIOVANNI. "ELECTRONIC STRUCTURE OF TIO2 THIN FILMS AND LAALO3-SRTIO3 HETEROSTRUCTURES: THE ROLE OF TITANIUM 3D1 STATES IN MAGNETIC AND TRANSPORT PROPERTIES." Doctoral thesis, Università degli Studi di Milano, 2012. http://hdl.handle.net/2434/168728.
Повний текст джерелаMeng, Keng-Yuan. "Magnetic Skyrmions in Oxide Thin Film Heterostructures." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1562856036665345.
Повний текст джерелаAeschlimann, Raphaël. "Magnetic and transport properties of rare-earth titanate thin films and heterostructures." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS142.
Повний текст джерелаTransition metal oxides possess a broad range of functionalities (superconductivity, magnetism, ferroelectricity, multiferroicity) stemming from the interplay between structural effects and electronic correlations. Recent work has revealed exciting physics at their interfaces, including conductivity and superconductivity in the two-dimensional electron system (2DES) that forms at the interface between two band insulators, LaAlO₃ and SrTiO₃. However, to embrace the immense potential of oxide interfaces and unveil unprecedented electronic phases, combining insulators with stronger electronic correlations is necessary. At the crossroad between strongly correlated electron physics, magnetism and spintronics, the present thesis project aims to harness electronic and magnetic instabilities in correlated oxides to craft new electronic phases controllable by external stimuli. We investigated rareearth titanates RTiO₃, a relatively unexplored family of Mott insulating perovskites with a crossover between antiferromagnetic and ferromagnetic orders upon changing the rare-earth size. Contrary to most previous works, we focused on ferromagnetic compounds, and their integration in 2DES. The thesis developed along two main axes. First, we explored several members of the rare-earth titanates family in epitaxial thin film form. We highlighted the presence of a magnetically active dead layer at the surface of thin films and established its origin as due to the overoxidation of titanium ions. We also studied the presence of an unexpected orbital moment carried by the titanium in some compounds, and discussed it in the light of the non-collinear spin arrangement promoted by the rare-earth orbital moment and of a structural gradient evidenced by transmission electron microscopy. In a second stage, we combined DyTiO₃ with SrTiO₃ to stabilize a conducting interface with puzzling magnetotransport properties that we interpreted with a model involving spin-orbit coupling as well as induced magnetism
Wallace, Anthony James. "Tin oxide thin films." Thesis, Brunel University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294556.
Повний текст джерелаHu, Xiao. "Ultra-thin oxide films." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:d7373376-84f1-459e-bffb-f16ce43f02b7.
Повний текст джерелаZhao, Haibin. "Optical characterization of ferromagnetic heterostructure *interfaces and thin films." W&M ScholarWorks, 2006. https://scholarworks.wm.edu/etd/1539623494.
Повний текст джерелаД`яченко, Олексій Вікторович, Алексей Викторович Дьяченко, Oleksii Viktorovych Diachenko, Анатолій Сергійович Опанасюк, Анатолий Сергеевич Опанасюк, Anatolii Serhiiovych Opanasiuk, D. Nam, and H. Cheong. "Characterization Cupper Oxide thin films." Thesis, Львівський національний університет ім. Івана Франка, 2015. http://essuir.sumdu.edu.ua/handle/123456789/48287.
Повний текст джерелаCrumlin, Ethan J. "Fundamental studies of heterostructured oxide thin film electrocatalysts for oxygen reduction at high temperatures." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74904.
Повний текст джерелаCataloged from PDF version of thesis.
Includes bibliographical references.
Searching for active and cost-effective catalysts for oxygen electrocatalysis is essential for the development of efficient clean electrochemical energy technologies. Perovskite oxides are active for surface oxygen exchange at evaluated temperatures and they are used commonly in solid oxide fuel cells (SOFC) or electrolyzers. However, the oxide surface chemistry at high temperatures and near ambient oxygen pressure is poorly understood, which limits the design of highly active catalysts. This work investigates heterostructured interfaces between (Lai. xSrx)CoO 3-3 (where x = 0.2 and 0.4, LSC80-2011 3 and LSC60-40 113 respectively) and (Lao. 5 Sro.5 )2CoO 4 ,3 (LSC2 14) enhanced ORR catalytic activity 1) via electrochemical impedance spectroscopy, atomic force microscopy, scanning electron microscopy, scanning transmission electron microscopy, and high resolution X-ray diffraction (HRXRD) and 2) using in situ ambient pressure X-ray photoelectron spectroscopy (APXPS) and in situ HRXRD. Here we show that the ORR of epitaxial LSC80-20 1 3 and LSC60-40113 is dramatically enhanced (~3-4 orders of magnitude above bulk LSC113) by surface decorations of LSC214 (LSC 1 31214) with coverage in the range from ~0.1 to ~15 nm. Such high surface oxygen kinetics (~ 110-5 cm-s1 at 550 C) are among the most active SOFC cathode materials reported to date. Although the mechanism for ORR enhancement is not yet fully understood, our results to date show that the observed ORR enhancement can be attributed to highly active interfacial LSCn 13/LSC214 regions, which were shown to be atomically sharp. Using in situ HRXRD and APXPS we show that epitaxial LSC80-20n3 thin films have lower coverage of surface secondary phases and higher Strontium enrichment in the perovskite structure, which is attributed to its markedly enhanced activity relative to LSC80-20113 powder. APXPS temperature cycling of epitaxial LSC80-20113 APXPS reveled upon heating to 520 *C the initial Sr enrichment which is irreversible, however subsequent temperature cycling demonstrates a small amount of reversible Sr enrichment. With applied potentials LSC80- 2013/214 shows significant Sr enrichment greater then LSC80-20 113, and the ability to stabilize high concentrations of both lattice and surface Sr which we hypothesize is a very important factor governing LSC80-2011 3214 enhanced ORR activity.
by Ethan Jon Crumlin.
Ph.D.
Wu, Chen. "Elemental growth of oxide thin films." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:ac82a52f-bb62-41d0-a604-3cf7a95e5aaf.
Повний текст джерелаYang, Zheng. "Doping in zinc oxide thin films." Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3359913.
Повний текст джерелаIncludes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 12, 2010). Includes bibliographical references. Also issued in print.
MARTINEZ, POZZONI UMBERTO LUIGI. "Oxide ultra-thin films on metals." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2009. http://hdl.handle.net/10281/7463.
Повний текст джерелаKiisk, Valter. "Optical investigation of metal-oxide thin films /." Online version, 2006. http://dspace.utlib.ee/dspace/bitstream/10062/115/1/kiiskvalter.pdf.
Повний текст джерелаHolden, Anthony Peter. "Tunnelling studies of very thin oxide films." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336960.
Повний текст джерелаPonja, Sapna D. "Metal oxide thin films for optoelectronic applications." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10045545/.
Повний текст джерелаSilverman, Lee Arnold 1959. "Sol-gel derived tantalum oxide thin films." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14835.
Повний текст джерелаOwens, Jessica Margaret. "The sputter deposition of oxide thin films." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627173.
Повний текст джерелаJames, Amy Frances. "Tin-oxide thin films by thermal oxidation." University of Western Cape, 2021. http://hdl.handle.net/11394/8239.
Повний текст джерелаTin dioxide (SnO2) thin films are a worthy candidate for an electron transport layer (ETL) in perovskite solar cells, due to its suitable energy level, high electron mobility of 240 cm2 v-1 s- 1, desirable band gap of 3.6 - 4.0 eV, and ultimately proves to be suited for a low temperature thermal oxidation technique for ETL production. A variety of methods are available to prepare SnO2 thin films such as spin and dip coating and chemical bath deposition. However, the customary solid-state method, which incorporates thermal decomposition and oxidation of a metallic Sn precursor compound in an oxygen abundant atmosphere prevails to be low in cost, is repeatable and allows for large-scale processing.
Khokhlova, Mariya. "Interactions of cells with oxide thin films." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMC241.
Повний текст джерелаIn the present work we demonstrate how oxide thin films can be used as bioactive surfaces, a field of research which is still underexplored. For this purpose, thin films of TiO2, Al2O3, VOx and some others were deposited on glass substrates using the Pulsed Laser Deposition (PLD) technique, and adhesion, proliferation and differentiation of human bone marrow-derived mesenchymal stem cells were evaluated. Cell behavior was analyzed with respect to the various key surface parameters such as chemistry, wettability, morphology and the thickness of films.Our results indicate that thin films of TiO2 and Al2O3 can not only support mesenchymal stem cells adhesion and growth, but also can be used to influence osteogenic and chondrogenic differentiation path. Additionally, effect of oxide thin films on adhesion and growth of cancer cell lines was studied. We showed that culturing these cell lines on thin films affects their growth and, therefore, could be a valuable method to perform screening tests with drugs.This work will provide a better understanding of correlation between surface chemistry and cellular response, which has a high significance in the field of biomaterials fabrication
Isukapati, Sundar Babu. "Gallium Oxide Thin Films for Optoelectronic Applications." Youngstown State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1527125539086742.
Повний текст джерелаDulal, Prabin. "Optoelectronic Characteristics of Indium Oxide Thin Films." Bowling Green State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1562680154150056.
Повний текст джерелаWang, Hao. "Cathodic electrodeposition of thin ceramic oxide films." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/11950.
Повний текст джерелаJiang, Fang-Xing. "Tantalum oxide thin films for microelectronic applications /." Online version of thesis, 1995. http://hdl.handle.net/1850/11925.
Повний текст джерелаHuang, Bin. "Mechanical characterization of thin films /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?MECH%202005%20HUANG.
Повний текст джерелаHan, Sanggil. "Cu2O thin films for p-type metal oxide thin film transistors." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/285099.
Повний текст джерелаGhasemi, Arsham. "Atomic structure of thin films and heterostructure of Bi2Te3 and Bi2Se3 topological insulators." Thesis, University of York, 2017. http://etheses.whiterose.ac.uk/18907/.
Повний текст джерелаYoon, Jongsik. "Nanostructured thin films for solid oxide fuel cells." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3164.
Повний текст джерелаBackholm, Jonas. "Electrochromic Properties of Iridium Oxide Based Thin Films." Doctoral thesis, Uppsala universitet, Fasta tillståndets fysik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8505.
Повний текст джерелаGarg, Ashish. "Growth and characterization of epitaxial oxide thin films." Thesis, University of Cambridge, 2001. https://www.repository.cam.ac.uk/handle/1810/34609.
Повний текст джерелаMolapo, David Theko. "Infrared studies of oxide catalysts and thin films." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ32452.pdf.
Повний текст джерелаVonk, Vedran. "Growth and structure of complex oxide thin films." Enschede : University of Twente [Host], 2006. http://doc.utwente.nl/57134.
Повний текст джерелаUnsworth, Larry David Brash J. L. "Protein adsorption to chemisorbed polyethylene oxide thin films." *McMaster only, 2005.
Знайти повний текст джерелаDepaz, Michael. "Processing and characterization of zinc oxide thin films." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002235.
Повний текст джерелаMurphy, Thomas Patrick. "Electrochromic properties of tin-nickel oxide thin films." Thesis, Oxford Brookes University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284756.
Повний текст джерелаHilou, H. W. "Electrical properties of R.F. sputtered thin oxide films." Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355425.
Повний текст джерелаElfallal, Ibrahim Abdel-Wahab. "A study of indium tin oxide thin films." Thesis, University of Salford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261449.
Повний текст джерелаRauf, Ijaz Ahmad. "Structure and properties of indium oxide thin films." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358371.
Повний текст джерелаHou, Ya-Ching. "Surface far-infrared emission from oxide thin films." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616237.
Повний текст джерелаHong, Yuanjia. "Magnetic and Transport Properties of Oxide Thin Films." ScholarWorks@UNO, 2007. http://scholarworks.uno.edu/td/615.
Повний текст джерелаLopez, Mark Gerard. "Aspects of electroforming in silicon oxide thin films." Thesis, Keele University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385191.
Повний текст джерелаDyachenko, A. V. "Spray pyrolysis deposition of magnesium oxide thin films." Thesis, Сумський державний університет, 2014. http://essuir.sumdu.edu.ua/handle/123456789/34844.
Повний текст джерелаVemuri, Venkata Rama Sesha Ravi Kumar. "Fabrication and characterization of zirconium oxide thin films." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
Повний текст джерела