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TUNABLE PHYSICAL PROPERTIES AND ROBUST THERMAL STABILITY OF METAL-OXIDE HYBRID THIN FILMS
thesisposted on 28.04.2021, 00:27 by Di Zhang
Functional metal-oxide hybrid thin films are of great research interests owing to the extraordinary physical properties and multifunctionalities beyond the naturally existing materials. Plasmonic metal-oxide metamaterials exhibit unprecedented optical properties due to the enhanced light-matter interactions at the metallic and dielectric interfaces, showing great promise in nanophotonic device applications. Precision control of the light-matter interactions at nanoscale within the hybrid metamaterial to achieve tunable optical responses in different wavelength regions is essential for various application needs.
In this dissertation, Au-BaTiO3 is chosen as a representative metal-oxide hybrid thin film system where plasmonic Au nanopillars are embedded within the ferroelectric BTO matrix. Through either geometry control of the Au phase by varying the film thickness, or growing complex 3D multilayer Au-BTO structure, highly tunable optical properties including localized surface plasmon resonance (LSPR) and hyperbolic dispersion wavelength tuning in the UV-vis-NIR region. The thermal stability of both single and multilayered Au-BTO hybrid films has been investigated via ex situ XRD, TEM and in situ TEM heating experiments, demonstrating the metal-oxide hybrid film remains quite stable when being heated up to 650oC. Lastly, an alloy-based Au0.4Ag0.6-BaTiO3 VAN thin film is integrated by a templated growth method in PLD. Owing to the change of electron density by adding Ag, the Au0.4Ag0.6-BaTiO3 film exhibits blue-shift of the LSPR and epsilon-near-zero (ENZ) in the UV-vis-NIR wavelength region and low-loss compared to that of the single layer Au-BTO film. The alloyed metallic-oxide film shows excellent thermal stability as well. The alloy-based metal-oxide hybrid thin film opens up enormous possibilities of design and integrating novel type of metallic-dielectric metamaterials towards electronic and nanophotonic applications.