Study On Optical Dielectric Properties And Plasmoncis Characters Of Metallic Alloy Films

Surface plasmon polariton phtonics or “Plasmonics” is considered for a promisingnew device technology that aims to exploit the unique optical properties of metallicnanostructures to enable routing and active manipulation of light at nanoscale. Thematerials with negative permittivity such as metals Ag and Au are the basic conditionfor the existence of plasmoncis. However, the large losses of metals arising from theohmic loss and interband transitions, seriously limit the applicability of plasmonics andmetamaterials. Therefore, more low-loss materials are needed for the development ofplasmonics. In this dissertation, the optical properties of metallic alloy films depositedby direct current magnetron sputtering are studied with variable angle spectroscopicellipsometry (VASE). The dielectric constants and band structure of metallic alloy flimsare analyzed in detail with the change of annealing temperature, composition and filmthickness, respectively. The key findings and conclusions of this dissertation are asfollows:A new method based on variable angle spectroscopic ellipsometry is used to studythe optical dielectric properties of metallic alloy films. The dielectric properties ofAl-Ag alloy films in optical range were studied with different annealing temperatureand composition. We also investigated the band structure and the microstructure of thealloy films. The results show that the grain size and the imaginary part of the dielectricfunctions for the Al-Ag alloy films are increased and decreased with the increase of theannealing temperature, respectively. A typical interband transition around1.5eV of theAl-Ag alloy films separately shift to the low and high energy part with the increae of theannealing temperature and the silver concentrations in aluminum. The permittivity ofalloy films was slightly changed to the same with increasing the film thickness. TheAl-Ag alloy films are good candidate for plasmonics.The optical dielectric constants of Ag-Pt alloy films were investigaged byellipsometry for the first time. The experiments show that the real and imaginary part ofdielectric constants are decreased and increased with improving the wavelength,respectively. By ananlyzing the joint density of states (JDOS) and fitting parameters ofthe model, we found that there are two typical interband transitions around1.9eV and3.1eV in the Ag-Pt alloy films. Furthermore, the centre of3.1eV transition shows a red shift and the imaginary part of permittivity is increased byincreasing the platinum addition in silver. The dielectric functions ofAg-25at%Pt alloy films annealed at300oC is clearly less than the one withother annealing temperature. Therefore, the quality factors of Ag-Pt alloy filmscan be greatly improved with the appropriate annealing effect.The optical dielectric properties and band structures of the silver copperand copper zinc alloy films are tunable with the change of annealingtemperature and film thickness. It has been shown that two typical interbandtransitions around1.7eV and3.5eV are presented in Ag-Cu alloy films. Withincreasing the copper composition in silver, the lattice constants of Ag-Cualloys are decreased and the interband transition at3.5eV shifts to high energy.In addition, the grain size and surface roughness of Ag-Cu alloy films aresimultaneously increased by increasing the annealing temperature. For thecopper zinc alloy films, there are two interband transtions around2.0eV and3.2eV which arising from the top of the d band to the Fermi level in the vicinity ofthe L point in the reciprocal space. The dielectric functions of the Cu-Zn alloyfilms are relative to the film thickness.