Advanced TEM imaging tools for materials science
Being able to directly relate the final properties with the intimate structure provides a unique insight into the functionality of materials and devices, especially when compared to the necessarily statistical nature of the information that can be retrieved by macroscopic measurements. In particular...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2015 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/395195 |
| Acceso en línea: | http://hdl.handle.net/10803/395195 |
| Access Level: | acceso abierto |
| Palabra clave: | Electrònica Electrónica Electronics Microscòpia electrònica de transmissió Microscopía electrónica de transmisión Transmission electron microscopy Ciència dels materials Ciencia de los materiales Materials science Nanociència Nanociencia Nanoscience Materials nanoestructurats Materiales nanoestructurados Nanostructured materials Ciències Experimentals i Matemàtiques 53 |
| Sumario: | Being able to directly relate the final properties with the intimate structure provides a unique insight into the functionality of materials and devices, especially when compared to the necessarily statistical nature of the information that can be retrieved by macroscopic measurements. In particular, the scale reduction associated with the Nanoscience and Nanotechnology revolution demands characterization tools capable of reaching an unprecedented resolution, in a wide range of fields, not only for standard quality control, but in order to understand the properties of matter at the nanoscale. Going from bigger to smaller devices, but also from elemental building blocks (even atoms) to bigger assemblies, basic properties and device functionalities meet. With its ability to provide different kinds of information at a very high spatial resolution, state-of-the-art TEM and related techniques are in the core of this multidisciplinary and rapidly growing field. The first major topic is related to the assessment of local atomic ordering/disordering phenomena in functional materials. A series of rare earth niobates (RE3NbO7) will be studied in order to understand the microstructural origin of their proton conduction properties, that make them excellent candidates to be used as electrode materials in solid oxide fuel cells. Also, single crystals of the tetragonal tungsten bronze (TTB) Sr0.33Ba0.66Nb2O6 (SBN-67) will be studied by different TEM techniques in order to assess the possible short range structural and/or chemical disorder. These features are thought to be responsible for the observed macroscopic uniaxial polarization vector of the material as well as its relaxor properties. A second major topic of interest will be the phenomena taking place at interfaces. This includes the characterization of a set of LaNiO3 perovskite thin films grown on different substrates (LAO, LSAT, STO, YAO). The effect of the substrate-induced compressive/tensile strain, given by lattice mismatch, on the structure of the films will be assessed and related to the observed electric transport properties. The interfaces in a GaN/InAlN multilayered system designed as a Bragg reflector for laser cavities applications will be investigated in order to account for a lower than expected reflectivity of the devices. The presence of structural defects and the detection of intergrowth of wurtzite and zinc blende phases of GaN in thin films will be addressed. Also regarding interfaces and strain conditions, the characterization of the free surface of Nb2O5 nanorods, as a key point for their humidity sensing properties. Expanding on this, the strain state of Nb2O5 when grown on SnO2 nanowires will also be studied. The coupling of the sensing capabilities of Nb2O5 with the electrical transport properties of SnO2 is of particular interest for functional sensing devices. Therefore, defects at the interface and strain state are of capital interest in order to understand the band structure alignment of the system. Interfaces in lower dimensionality systems will also be studied, as in the case of Ag@Fe3O4 dimers for applications in magnetoplasmonics. The epitaxial quality, strain, and the possible chemical diffusion through the contact surface of the two phases of the dimer are key aspects in order to properly tailor their optical properties. The last major topic is the mapping of magnetic fields at the nanoscale. The magnetic configurations of different geometric arrangements of magnetite Fe3O4 nanocubes will be studied. This characterization is aimed at obtaining enhanced responses in magnetic hyperthermia treatments for cancer. Given the strong interrelationship between the problems under study, the chapter structure follows the dimensionality of the systems under study (3D, 2D, 1D and 0D systems). |
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