| Summary: | 博士 === 國立臺灣大學 === 材料科學與工程學研究所 === 97 === In this thesis, the advanced lithography technology of nanoimprint, reversal nanoimprint and nanoshpere lithography are applied to fabricate patterns on functional materials, including ferroelectric materials, metal nanoparticles and carbon nanotubes (CNTs). The optical characteristics of surface plasmon resonance (SPR) and diffraction in these nanostructured materials are studied.
First, with chemical reduction method, I prepared gold nanoparticle-embedded lead zirconate titanate (PZT) films to study its surface plasmon resonance phenomenon. As the sintering temperature increases, the size of gold nanoparticles is increased thus induce red shifts of SPR wavelength. Second, I successfully obtain a periodical pattern using nanoimprint the gold/PZT bilayer structure. Third, I also discuss the optical characteristics of high absorbed CNTs. Using the reflectance spectra of TE and TM polarized light measured at different incident angles, I can obtain the equivalent anisotropic optical constants of a vertical-aligned carbon nanotubes (VA-CNT) thin film. Furthermore, using nanosphere lithography and reversal nanoimprint techniques, I can fabricate various patterns on CNT thin films, such as gratings, hexagonal holes and broccoli like arrays. Despite the light could be trapped in the CNT forest and the low refractive index contrast between air and a CNT film is low, iridescence phenomenon can be observed in patterned CNTs samples.
For the tuning wavelength study, I use two kinds of method, applying electric field or bending flexible substrates, to modulate the SPR or diffraction wavelength induced from the structured materials mentioned previously.
When an electric field is applied on gold nanoparticle-embedded PZT films, the refractive index of PZT is changed that induce the shifting of SPR wavelength. On the other hand, in the patterned PZT/gold/ PZT multilayer structures, I can control both the period of the gold/ PZT patterns and the refractive index of the PZT layer. Thus I can obtain a bi-directionally tunable SPR device. By bending the flexible substrates, I demonstrated the period and diffraction wavelength changed in the flexible samples coated with patterned CNTs. The diffraction wavelength can be dynamically modulated depending on the radius of curvature, as well as the type of convex or concave bending.
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