Study of Surface Plasmon by Electron Beam Induced Light Emission Technique

在本研究中，我们利用光探测系统和透射电子显微镜相结合，发展了电子束诱导光发射技术。这项技术使我们能够通过选择偏振方向来测量发射光谱，并在合适的波长下观察单色光子图。利用这种技术可以可视化金属纳米结构上的表面等离子体激元。本研究的目的是研究具有亚波长周期的金属纳米结构表面等离子体的物理性质，并寻找其产生的机制。我们对原有的阴极发光检测系统进行了改进，引入了一种高灵敏度的CCD探测器来测量发射光谱。还研制了角分辨测量装置。样品是条状结构及其一维阵列、二维金属颗粒阵列和带有纳米孔阵列的金属薄膜。观察到这些结构在电子束辐照后的发射光谱中出现了几个发射峰。这些峰值对应于周期结构中定域表面等离子体激元(LSP)的共振模式和表面等离子体激元(SPP)的驻波模式。从扫描电子束获得的光谱图像的角分辨测量结果中发现，跃迁辐射和表面等离子体诱导辐射之间的干涉主要导致光子图上的对比度。在表面平行电子束照射下光子晶体的电子束诱导发射和周期性金属表面的Smith-Purcell辐射的研究中也获得了新的信息。

In the present research, we have developed the electron beam induced light emission technique using a light detection systems combined with a transmission electron microscope. This technique enables us to measure an emission spectrum with choosing a polarization direction, and observe a monochromatic photon map at a proper wavelength. Surface plasmon on metallic nano-structures can be visualized by this technique. The purpose of the present research is to investigate physical properties of surface plasmon on metallic nano-structures with sub-wavelength periods and to find a mechanism of them. We improved the previous cathodoluminescence detection system, introducing a CCD detector to measure an emission spectrum with a high sensitivity. The set-up for angular resolved measurement has also been developed. Samples are a stripe structure and their 1D array, 2D array of metal particles and metal films with nano-hole arrays. Several emission peaks were observed to appear in the emission spectra from those structures irradiated by an electron beam. Those peaks correspond to resonant modes of the localized surface plasmon (LSP) and standing wave modes of surface plasmon polariton (SPP) in the periodic structures. From the result of angular resolved measurements of spectrum image taken by scanning the electron beam, it was found that the interference between the transition radiation and surface plasmon induced radiation mainly causes the contrast in the photon maps. New information was also obtained in the study of the electron beam induced emission from photonic crystals and Smith-Purcell radiation from a periodic metal surface under the surface parallel electron beam illumination.