ISBN 9783843914659

978-3-8439-1465-9, Reihe Anorganische Chemie

Raquel Fiz González
Vapor Phase Growth of Anisotropic Metal Oxide Heterostructures: Growth Models, and Energy & Sensor Applications

261 Seiten, Dissertation Universität Köln (2013), Softcover, A5

Zusammenfassung / Abstract

Fundamental research on novel nanostructured materials and their properties is essential for the next generation of highly efficient and inexpensive minituarized devices. The M2M strategy ("molecule to materials") uses bottom-up approaches to fabricate materials, whose properties can be tailored a priori at a molecular scale. In this thesis we show the potential of vapor phase methods such as chemical vapor deposition (CVD) and atomic layer deposition (ALD) for the fabrication of metal oxide nanostructures with a high degree of control over composition, size, morphology, and growth location, and which can be directly integrated in the final device platforms. The influence of the CVD parameters on the synthesis of V2O5, Nb2O5 and Ta2O5 nanostructured thin films is systematically investigated. The optimization of the deposition parameters can lead to the formation of one-dimensional (1D) metal oxide nanostructures (e.g. V2O5, Nb2O5, SnO2, Fe3O4). These 1D nanostructures grown in a first step can be further modified leading to the design of heterostructures with the desired properties in terms of crystal and band engineering concepts. SnO2-based heterostructures were also synthesized and integrated in different device concepts: lithium-ion batteries, conductometric gas sensors, photodiodes and in photocatalytic applications. The role of interfacial properties on the chemical potential, electronic barriers and modulation of junction characteristics is investigated. Besides the size (confinement) and surface effects, the functional properties are greatly enhanced by phase-boundaries, which can exist between the substrate and the growing material or between two phases. Whereas new concepts of material design offer opportunities to suppress or promote specific chemical interactions, the challenge associated with reproducible material synthesis, and integration into devices needs further attention.