Controlled Preparation And Optical Properties Of Zinc-oxide And Noble Metal Microstructures Based On Two-dimensional Colloidal Crystal Template

The studies of optical microstructures are currently one of the main research subjects in the areas of material science, photonics and their interdisciplines, aiming at controlling the light excitation, transport and radiation throught the designs of structures and physical properties. In recent years, the fabrications and their optical and electrical properties of ZnO nanostructures as well as their ordered arrays have received extensive attentions, due to their potential high-performance in photoelectric devices and bio-chemical sensing.In this thesis we reported the templating methods to fabricate ZnO and noble metal micro structures based on two-dimensional colloidal crystal (2D CC), explored experimental conditions to control the structural parameters of the artificial materials, and preliminarily studied their optical and electric properties. The thesis includes the following parts:1. Combined with electrodeposition technique and2D CC, we developed a template-directed preparation method to fabricated the ZnO nanowire array with controlled morphology, which is included two steps as follows. The first step is the preparation of gold (Au) half-shells array which would be used as a electrode for the following electrodeposition process, by nanosphere lithography through a physical deposition of thin Au layer on a self-assemblied2D CC. The second step is electrodeposition of ZnO nanowires on the Au half-shells electrode above mentioned. The preliminary optical and electric properties of ZnO nanowires array templated by Au half-shells covered2D CC was studied. A few attempts were made to alter the parameters of electrodeposition (i.e, the concentration of electrolyte, quantity of electric charge, temperature) to control the structural parameters of the ZnO nanowire array. We also posed a contrast among the ZnO nanowire morphologies and basic optic properties grown on different gold substrates, such as the gold plain substrate, nano-prism substrate and the curved half-shell substrate as well.2. Preparation of monocrystalline silver (Ag) nanowire using hydrothermal method combined with reduction of ethylene glycol (EG) was studied. Effects of various ions on the crystal growth of the Ag nanowire was investigated. It was presented that Copper ion (Cu2+), especially, would favour to remove the adsorbed oxygen from the surface of the Ag twin crystal and promote the growth of Ag nanowire. In addition, the crystallinity and optical properties of the nanowire were investigated as well. Our study opens a new way to low-cost metal nanowire with a wide range of chemical and biological sensing applications.3. The optical properties of a highly corrugated gold film was studied, which were prepared by coating PS2D CCs with a-SiO2layer, followed by a further deposition of thin gold films onto the top-most surface. It was shown that by introducing a dielectric layer between the up gold cover layer and the2D CC, the optical transmission properties can be effectively modulated by varying the thickness of the a-SiO2dielectric layer. We do numerical study by using the finite element method and find out that the simulated transmission spectra show good agreements to the experimental results. According to the modeled computational field analysis, we were able to pinpoint the underlying mechanism of resonant transmission of the system which relied on the coupling modes associated with intercalated dielectric layer.