飛秒雷射激發下電漿子金屬奈米粒子輔助多光子聚合過程之資訊記錄

Abstract

在近場飛秒雷射激發下，電漿子共振所促成金屬奈米粒子吸收多光子而發生聚合反 應，是一個新的凝態化學基礎問題。本計畫目的在於以多種金屬奈米粒子與聚合物研究 電漿子輔助多光子聚合的機制，並在聚合薄膜中創造三維結構以用於記錄資訊。這種三 維結構在工業應用上相當有利，原因有二：(1)其尺寸遠小於傳統光學元件的繞射極限， 因此可在現有資訊媒材上達到更高記錄密度；(2)由於電漿子共振位置及周圍介質介電傳 導性不同，可在同一記錄空間中使用不同雷射波長進行多次記錄。此類三維結構的性質 將以近場顯微鏡（掃描穿隧式顯微鏡、原子力顯微鏡、近場掃瞄光學顯微鏡）、傅立葉 紅外光顯微鏡和電子顯微鏡研究。奈米粒子周邊的電場分佈，將利用自行研發的電腦軟 體，以有限差異時間域方法進行數值計算而得；奈米叢簇的電子結構則以量子化學方法 計算之。此外，叢簇中化學反應速率常數與聚合物片段和奈米粒子間相對位置的相關 性，亦將予以估算。這些理論計算結果都將與實驗所得數值比較。

Polymerization of metal nanoparticles caused by absorption of multiple photons from a femtosecond laser in near-field and assisted by plasmon resonance is a new fundamental problem of condensed-phase chemistry. The aim of this project is to study mechanisms of plasmon-assisted multiphoton photopolymerization using various types of metal nanoparticles and polymers, and to create 3D-structures in polymer films, which can be utilized for recording of information on an information medium. Such 3D-structures can be useful for industrial applications for two reasons: 1) their size is significantly smaller than the diffraction limit of the traditional optics making it possible to reach a recording density much higher than that achieved in the currently used information mediums; 2) due to different positions of the plasmon resonance and different dielectric conductivities of the surrounding medium, it is possible to record information more than once in the same volume using different laser wavelength. Properties of the 3D-structures will be studied by the near-field microscopy (scanning tunneling microscope (STM), atomic force microscope (AFM), near-field scanning optical microscope), Fourier IR microscopy, and electron microscopy. The electric field profile in a vicinity of nanoparticles will be calculated numerically by the FDTD (Finite Difference Time Domain) method using a self-developed computational package. The electronic structure of nanoclusters will be studied by quantum-chemical methods. In addition, the dependence of rate constants of chemical reactions in clusters on the relative positions of polymer fragments and nanoparticles will be evaluated. Results of the theoretical calculation will be compared with the experimental data.