應用先進微影技術製備具可調變光波長之奈米結構材料

Abstract

在本論文中，藉由奈米壓印、轉印、奈米球模板技術等先進微影技術在功能性材料，包括鐵電材料，奈米金屬粒子，奈米碳管中製作奈米結構或圖案，並探討其表面電漿共振與繞射之光學特性。 在鐵電材料中，利用簡單的化學合成方式，製備了含有奈米金粒子之鋯鈦酸鉛複合薄膜並使其誘發表面電漿共振現象。隨著燒結溫度的增加使奈米金粒子的大小增加，進而使表面電漿共振波長產生紅移。另一方面，利用奈米壓印的方式，可以直接壓印於金/鋯鈦酸鉛之雙層結構上，成功地製備週期性圖案並觀察到表面電漿共振的發生。此外，亦探討高吸收奈米結構材料，奈米碳管，其特殊結構所造成的光學行為。利用大角度入射的TE和TM的偏振光之反射光譜，來獲得垂直排列奈米碳管薄膜在該入射角時之等效非均向性光學常數。進一步，應用奈米球模板技術及奈米轉印技術等等技術，在可撓曲的基板上製備出不同圖案，例如光柵，六角形，花椰菜排列的奈米碳管薄膜。儘管奈米碳管會將入射光侷限於其中，而且與空氣的折射率對比很低，但經由圖案化後的奈米碳管，依舊可以觀察彩色影像。圖案化後的奈米碳管，其光學性質亦符合週期性結構之繞射現象。 之後更進一步，利用各種不同的方式，如外加電場或形變(彎曲)的方式，來調變各種不同的奈米結構材料所引發之特殊光波長。當施予外加電場於含金粒子之鋯鈦酸鉛複合薄膜時，鋯鈦酸鉛薄膜之折射率會隨之改變，進而造成表面電漿共振波長的偏移。另一方面，奈米圖案化之鋯鈦酸鉛/金/鋯鈦酸鉛多層結構，可以藉由外加電場來控制週期性圖案的週期與鋯鈦酸鉛薄膜的折射率，進而達到雙向調變表面電漿共振波長的元件。而利用彎曲的方式亦可以使得週期性圖案的週期改變，因而使得圖案化後的奈米碳管薄膜其繞射波長改變。因此，繞射之光學波長可以藉由彎曲的形式，如凸面或凹面，曲率半徑的大小，來進行動態的調變。

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.