Nanostructured thin films : plasmon resonance phenomena
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NO FULL TEXT AVAILABLE. Access is restricted indefinitely. ----- Nanostructured thin films of conducting and insulating materials, produced by various techniques, were investigated. Different film structures were produced by: sputtering, or e-beam evaporation; de-alloying, anodisation or annealing; and specialised etching/filling techniques. The structures and materials investigated were as follows: porous anodic alumina - with silver filling, mesoporous gold, nano-grained vanadium dioxide - including doping, and multi-layer silver dielectric structures. The optical and electrical properties of the structures were both measured experimentally and modelled, relating the results back to the structure. Plasmonic responses and resonant behaviour have been observed and identified in each of the films. A simplified method for producing and filling porous anodic alumina on glass was developed. The resultant resonant structure was modelled using an effective medium approximation. Nanograined VO₂ thin films were produced on glass substrates via sputtering of metallic V, followed by an annealing process. Aluminium doping was achieved by co-deposition with Al₂O₃. Dual semiconductor-metallic behaviour was found for nanograin and doped VO₂ above the MIT temperature, with the observed character dependent on the frequency of the applied field. VO₂ grain size and doping was linked with the DC activation energy of the VO₂ samples. Two types of mesoporous gold structures were investigated. A modelling technique for the homogenised response of the void/conductor systems allowed determination of the observed effective plasma frequency and carrier effective mass, using the structural parameters and void content. An investigation of a new type of narrow band double cavity filter is presented, in which three silver and two alumina layers are used. Tuning of the filter is achieved by adjusting the matched oxide-pair thickness. Simple wedging of oxide thickness enabled production of linear variable filters.
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