Development of a Light Detection System Combined with a Transmission Electron Microscope

本研究的目的是开发一种结合透射电子显微镜的光探测系统，该系统具有纳米尺寸电子束的汇聚能力。利用单色计、光电倍增管和光子计数器可以获得从局部区域发射的光谱，并由微型计算机显示。计算机还通过TEM扫描系统控制电子束，并在显示器上获得单色光子图像。光子图像的空间分辨率小于0.1 μ m。该系统已应用于两个学科；切伦科夫辐射和跃迁辐射的研究，以及阴极发光的研究。主要结果如下：1)切伦科夫辐射和跃迁辐射：云母膜的正向辐射主要来自切伦科夫辐射，反向跃迁辐射也有相当大的贡献，由于干扰效应，在光谱中产生一组峰。跃迁辐射在半导体和金属薄膜的发射中占主导地位。在半导体薄膜的情况下，一些峰对应于介电函数的最大值，即带间跃迁。银薄膜的反向发射光谱包含一个特征峰，这是由于辐射表面等离子体模式（Ferrell模式）。单色光子图像揭示了特征峰与晶格缺陷、表面形貌等结构特征之间的关系。2)在GaAs衬底上生长ZnS MBE薄膜的阴极发光：在CL光谱中观察到与束缚激子和导电-受体跃迁相关的发光峰，并研究了发光的空间分布与卡滞缺陷等晶格缺陷的相关性。3)多孔硅的阴极发光：在420 nm波长附近出现一个宽发光峰，同时出现一个红色发射峰。横断面样品的CL图像显示了这些CL发射区域的不同空间分布。通过退火实验和红外吸收测试发现，420 nm峰与Si表面形成的Si- h化合物有关。少

The purpose of this research is to develop a light detection system combined with a transmission electon microscope which has a capability of converged electron beam of a nanometer size. A spectrum of light emitted from a localized region can be obtained by using a monochrometer, a photomultiplier tube and a photon counter and is displayd by a mini-computer. The computer also controls the electron beam through a TEM scanning system and a monochromatic photon image can be obtained in a monitor. The spatial resolution of the photon image is less than 0.1mum.This system has been applied to the two subjects ; the study of Cherenkov and transition radiation from thin films, and that of cathodoluminescence. The main results are as follows.1) Cherenkov and transition radiation : Emission from a mica film is contributed mainly from Cherenkov radiation in the forward direction, while transition radiation is also considerable in the backward direction, which gives set of peaks in a spectrum due … More to intereference effect. Transition radiation is dominant in emissions from semiconductor and metal films. In the case of a semiconductor film some peaks correspond to maximum of the dielectric function, i.e., the interband transition.The backward emission spectrum from a thin silver filn involves a characteristic peak due to a radiative surface plasmon mode (Ferrell mode). The monochromatic photon images reveal the relation between the characteristic peaks and structural features such as lattice defects and surface morphology.2) Cathodoluminescence of ZnS MBE grown films on GaAs substrates : The luminescence peaks associated with bound excitons and the conduction-acceptor transition were observed to appear in the CL spectra, and the correlation between spatial distribution of the luminescences and lattice deffects such as stucking fault were studied.3) Cathodoluminescence of porous silicon : A broad luminescence peak around a wavelength of 420 nm was observed to appear together with a red emission peak. CL images of a cross-sectional sample revealed different spatial distributions of those CL emission regions. It was found from the annealing experiment and the IR absorption measurment that the 420 nm peak is related to Si-H compounds formed on the Si surface. Less