周期性纳米金属粒子表面等离子体共振的调控及应用

发布时间：2018-06-27 01:45

本文选题：表面增强拉曼散射 + 光刻　；参考：《中国科学院研究生院(上海应用物理研究所)》2017年博士论文

【摘要】：在过去几十年,表面增强拉曼散射已经成为一种非常重要的化合物分析方法,在光谱分析、生物传感等领域有着广泛的应用。概括起来,一个高性能的表面增强拉曼散射基底应满足以下要求:一是具有较高的灵敏度,通过调控粒子的大小,形状和二个粒子的间距等要素,产生强大的电磁场增强,最终得到高灵敏度的拉曼信号;二是具有较好的均匀性,这就要求表面增强拉曼散射基底上各点的增强效果均匀一致。目前制备表面增强拉曼散射基底的方法主要分为二类,即自下而上和自上而下方法。目前,由于技术条件的限制难以制备小于10nm间距的大面积均匀阵列结构。因此很难实现同时具有高灵敏度和高重复性的表面增强拉曼散射基底。本论文的目的在于克服现有技术条件限制,改进纳米加工方法,制备出大面积、高密度、小间距、均匀稳定的纳米金属结构。使得基底产生更强更均匀的表面等离子体增强电场,并探索在光谱增强领域的应用。本文主要围绕光刻技术和新型的三明治结构,取得的主要成果如下:(1)利用电子束光刻直接扫描图形,制备了多种尺寸、形状以及构型的纳米阵列。此外,我们还利用同步辐射X射线干涉光刻方法快速制备具有大面积、小周期的纳米金属阵列,并将其应用于基于表面增强拉曼散射的分子探测领域。结果表明该表面增强拉曼散射基底具有高的灵敏度,较高的重复性和一致性,有望实现商业化应用。(2)提出了一种新型的纳米阵列-绝缘层-金属膜的三明治结构。这种基底同时具有较高的灵敏度和较好的均匀性。表面增强拉曼散射实验表明,相比常规在二氧化硅衬底,三明治结构的拉曼散射强度提高了一个量级,同时,也保持了周期性阵列带来的良好的均匀性。(3)研究发现,在几个纳米绝缘层的限制下,拉曼信号对于纳米金的尺寸也非常敏感。通过三明治结构中优化粒子的尺寸和薄膜的厚度,可以进一步提高表面增强拉曼散射信号的灵敏度。(4)系统地研究了三明治结构中各个变量对于表面等离子体共振位置的影响,详细地分析了三明治结构中的多种共振模式,并进行了理论推导和实验验证。三明治结构中共振效应可以分为局域表面激发等离子体共振和法布里珀罗多次干涉效应二种共振模式。(5)不同直径的纳米金圆盘会导致不同的共振模式出现。该共振模式可以认为是法布里珀罗共振模式,纳米圆盘的直径等效于法布里珀罗共振模型中腔体的长度。随着共振腔体的长度变化,会有更多高阶共振模式被激发,从而产生多波长共振现象。结果表明,在同一种三明治结构中产生的多波长共振可以实现三种入射光激发条件下均达到最优,使得该表面增强拉曼散射基底在多个波长下均可以有最优的性能。
[Abstract]:In the past few decades, surface-enhanced Raman scattering has become a very important method for the analysis of compounds, which has been widely used in the field of spectral analysis, biosensor and so on. To sum up, a high performance surface-enhanced Raman scattering substrate should meet the following requirements: first, it has a high sensitivity, by regulating the particle size, shape and the distance between the two particles, a powerful electromagnetic field is enhanced. Finally, the high sensitivity Raman signal is obtained, and the second is the good uniformity, which requires the enhancement effect on the surface enhanced Raman scattering substrate to be uniform. At present, the surface enhanced Raman scattering substrate is mainly divided into two categories: bottom-up and top-down methods. At present, it is difficult to fabricate large area uniform array structures which are smaller than 10nm spacing due to the limitation of technical conditions. Therefore, it is difficult to achieve a highly sensitive and reproducible surface-enhanced Raman scattering substrate. The purpose of this paper is to overcome the limitations of the existing technical conditions, improve the nanoprocessing method, and prepare large area, high density, small spacing, uniform and stable nanometallic structures. It makes the substrate produce stronger and more uniform surface plasma-enhanced electric field, and explores the application in the field of spectral enhancement. The main achievements of this paper are as follows: (1) Nano-arrays of various sizes, shapes and configurations have been prepared by direct scanning of electron beam lithography. In addition, we use synchrotron radiation X-ray interference lithography to rapidly fabricate nanometallic arrays with large area and small periods, and apply them to the field of molecular detection based on surface-enhanced Raman scattering. The results show that the surface-enhanced Raman scattering substrate has high sensitivity, high reproducibility and consistency. (2) A novel sandwich structure of nano-array-insulation-metal film is proposed. The substrate has high sensitivity and good uniformity. Surface-enhanced Raman scattering experiments show that the Raman scattering intensity of sandwich structure is increased by one order of magnitude compared with that of conventional silicon dioxide substrates, and the uniformity of periodic array is maintained. (3) the results show that, Raman signals are also sensitive to the size of nanocrystalline gold under the constraints of several nanocrystalline insulators. The sensitivity of surface enhanced Raman scattering signal can be further improved by optimizing the particle size and film thickness in sandwich structure. (4) the influence of various variables in sandwich structure on the surface plasmon resonance position is systematically studied. The resonance modes in sandwich structure are analyzed in detail, and the theoretical derivation and experimental verification are carried out. The resonance effect in sandwich structure can be divided into two resonance modes: local surface excited plasmon resonance and Fabry-Perot multiple interference. (5) different diameter of gold nanocrystalline disk will lead to different resonance modes. The resonance mode can be considered as the Fabry-Perot resonance mode, and the diameter of the nanodisc is equivalent to the length of the cavity in the Fabry-Perot resonance model. As the length of the resonator changes, more high-order resonant modes are excited, resulting in multi-wavelength resonance. The results show that the multi-wavelength resonance generated in the same sandwich structure can be optimized under three excitation conditions of incident light, which makes the surface-enhanced Raman scattering substrate have the best performance at multiple wavelengths.
【学位授予单位】：中国科学院研究生院(上海应用物理研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O657.37

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