| Functional. oxide thin films exhibit fascinating physical properties and phenomena compared with bulk materials, and have important potential application in miniaturization to nanoscale dimension of electronic and magnetic devices. Synergistic research effort of growth, microstructures, interfaces and physical properties will provide fundamental knowledge which in turn may help in optimizing the fabrication of high quality thin films for novel devices.The epitaxial oxide-on-silicon templates may help the integration of functional oxides (ferroelectric, ferromagnetic, piezoelectric.) on silicon platforms and the development of new classes of micro and nanosystems. A challenge issue, however, is the influence of interface structure and strain on the physical properties of epitaxial oxides. It is significant to understand the evolution of microstructures to exploit their physical properties for further applications. Because of the small quantity of material involved, the classical methods are not always adapted for the study of these two dimensional (2D) systems and in particular for their first stage of growth. Infrared and THz spectroscopy, combined with Density Functional Theory (DFT) calculation, can be a powerful and nondestructive technique for characterizing the structure and physicochemical phenomena of the epitaxial functional oxides and their formation.The main objectives of this thesis are (â…°) to develop a nondestructive technique, combining infrared spectroscopy with theoretical simulations, for the characterization and analysis of microstructure and physical properties of functional oxide thin films, and (â…±) to understand the relationships between microstructure, interface structure and optical properties of functional oxide thin films for design and quality control of novel functionalities based on oxide properties.(1) The structural and dynamical properties of SrTiO3/Si(001) epitaxial thin films are studied by infrared and THz spectroscopy. The crystalline structure of STO films and the nature of STO-Si interface are estimated using the phonon modes. The influences of epitaxial temperature, thickness and heat treatment on the local interatomic and interfacial structure are evidenced by the variation of phonon frequency and intensity. The best conditions for the epitaxial growth of SrTiO3/Si(001) are determined. The strain level of the various layers has been evaluated by the phonon shift compared with crystalline STO. The assignment and interpretation of IR spectra are clarified by comparing the experimental results with the DFT calculations.(2) The MITs of VO2thin films on Gd2O3/Si(111) template are investigated by and THz spectroscopy. The phonon modes and lattice modification of the monoclinic VO2are assigned and interpreted on the basis of DFT calculation. The optical and dielectric properties of VO2thin films across the MIT are estimated. The relationship between the electronic correlations and the structural phase transition are discussed, which may help to better understand the MIT in VO2thin film devices.(3) A comprehensive study of the alumina films formed from heating Fe3A1under different oxidizing atmospheres is conducted using Fourier Transform Infrared spectroscopy (FTIR) in the complete Mid Infrared (MIR) and Far Infrared (FIR) ranges. In addition, this experimental vibrational study is combined with DFT simulation to allow for the first measure of the crystalline structure of alumina thin films. The phase structure of alumina films is estimated and the2-D modification compared with the crystalline alpha-alumina structure is discussed. Furthermore, the dependence of film dynamical properties on oxygen and water partial pressure is addressed and the strain induced by the film growth on a metal substrate is evaluated.
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