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Improvement of Resolution of a Electron Microscope by Means of Correction of Spherical Aberration Using a Foil Lens

通过使用箔透镜校正球面像差来提高电子显微镜的分辨率

基本信息

批准号：
11650055
负责人：
HANAI Takaaki
金额：
$ 2.24万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

1. Development of a foil lens for the objective lens of a transmission electron microscope (TEM).In order to design the foil lens which enables us to correct the spherical aberration at a lower electrostatic field than 120 kV/mm, that is the known limit of self-supporting of the foil electrode, optical characteristics of the foil lens were numerically studied. It was found that that the correction is achieved by locating the foil lens at the position 3.6 mm lower from the center of the gap of the objective polepieces. The spherical aberration is corrected at the foil lens voltage of 550 V when the distance of the aperture and foil electrodes. An improved side-entry type foil lens was developed based on the calculation. The foil lens holder has the thickness of 1.7 mm, 0.3 mm thinner than previous one.2. Observation of crystal lattice images with the improved foil lens.The foil lens was incorporated with a commercial TEM and the images of Au fine particles were observed at the accelerating voltage of 200 kV. At the foil lens voltage of 300 V, (111) lattice images were observed at nearly in-focus condition where the contrast of the Fresnel fringe was weak. Such reduction of aretefacts shows an effect of correction of spherical aberration.3. Measurements of spherical aberration of the corrected objective lens.The spherical aberration was measured with a newly developed method, in which the spherical aberration coefficient and the defocus are simultaneously determined from the deviation of the dark-field TEM images of Au particles from the corresponding bright-field image. It was shown that the improved foil lend yields smaller spherical aberration coefficients than the previous one at the same foil lens voltage.

1. 透射电子显微镜 (TEM) 物镜用箔透镜的开发。为了设计能够在低于 120 kV/mm（箔电极自支撑的已知极限）的较低静电场下校正球面像差的箔透镜，对箔透镜的光学特性进行了数值研究。结果发现，通过将箔片透镜定位在距离物镜极片间隙中心低3.6mm的位置来实现校正。当孔径和箔电极的距离为550V时，球面像差在箔透镜电压下被校正。根据计算结果，开发了改进的侧入式箔片透镜。箔片镜架厚度为1.7毫米，比之前的薄0.3毫米。2。使用改进的箔透镜观察晶格图像。将箔透镜与市售TEM结合，在200 kV的加速电压下观察Au细颗粒的图像。在箔透镜电压为300 V时，在近焦状态下观察到(111)晶格图像，其中菲涅耳条纹的对比度较弱。这种伪影的减少显示了球差校正的效果。3．校正物镜的球差测量。球差采用新开发的方法测量，其中球差系数和散焦是根据Au颗粒的暗场TEM图像与相应的明场图像的偏差同时确定的。结果表明，在相同的箔片透镜电压下，改进的箔片透镜产生的球面像差系数比前一种更小。