Developemtn of High Resolution Scanning Transmission Electron Microscope through Spherical Aberration Correction by Means of a Foil Lens

箔透镜球差校正高分辨率扫描透射电子显微镜的研制

• 批准号: 61850069
• 负责人: HIBINO Michio
• 金额: $ 3.39万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Developmental Scientific Research
• 财政年份: 1986
• 资助国家: 日本
• 起止时间: 1986 至 1987
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-61850069/
• 关键词: Electron lens; Shperical aberration; Correction; Foil Lend; Electron Probe; Scanning Transmission Election Microscopy (STEM); Recolution; SN比; 球面収差補正

A foil lens was applied to a scanning transmission electron microscope(STEm) to attain higher resolving power through correction of spherical aberration of the probe-forming lens. Following new developments were achieved.1. Evacuating system of the STEM was improved to reduce the contamination rate onto the foil fo the foil lens, which determines the life time of the foil lens. The resultant clean vacuum allowed the use of the foil lens without obvious contrmination for about fifty hours.2. Characteristics of the foil lens were investigated numerically. The fifth order spherical aberration, which had been a limiting factor of the probe diameter obtained, was found bto be negligibly small when the foil lens was located near the principal plane of the probe-forming lens. A one foil lens was designed based on this result.3. In order remove a part of electrons scatterd in the foil, which result in increase of the back ground noise in STEM images, aperture diaphragms of various diameters were located at the conjugate of the specimen plane. When visual field was limited to 37 um by an small sperture diaphragm, 40% od scatters electrons were removed.4. For quantification if improvement of the image due to spherical berration correction,a system for the measutemetn of SN ratio of the image was constructed. The system computes the SN ratio from two digiralized STEM images of the same field by means of maximum likelifood method.5. Images of fine particles were taken with the foil lens. The measured SN ratio increased with the foil lens voltage, indeicating the effect of reduced spherical aberration.6. The errect on resolution of non-rotationally symmetrical aberrations was investigated. The result showed that ten times higher machining accuracy of the foil lens would achieve the STEM with the resolution comparable to conventionl transmission electron micrscopes.

将箔透镜应用于扫描透射电子显微镜（STEm），以通过校正探针形成透镜的球面像差来获得更高的分辨率。以下新的发展被公布。为了降低薄膜透镜的污染率，对STEM的抽真空系统进行了改进，这决定了薄膜透镜的寿命。由此产生的清洁真空允许使用箔透镜而没有明显的收缩约50小时。对薄膜透镜的特性进行了数值研究。当箔透镜位于形成探针的透镜的主平面附近时，五阶球面像差，这是获得的探针直径的限制因素，被发现是可以忽略不计的小。在此基础上设计了一种单箔透镜.为了去除部分散射在薄膜中的电子，使STEM图像中背景噪声增大，在样品平面的共轭处设置了不同直径的孔径光阑。当用小孔光阑将视野限制在37 μ m时，OD散射电子的去除率为40%.为了量化球面像差校正对图像质量的改善，建立了图像信噪比测量系统。该系统通过最大似然法计算同一视野的两幅数字化STEM图像的信噪比.用箔透镜拍摄微粒的图像。测得的SN比随着箔透镜电压的增加而增加，表明球差减少的效果。6.研究了非旋转对称像差分辨力的误差。结果表明，提高10倍的箔透镜加工精度，可以获得与传统透射电镜相当的分辨率。

项目成果

M.HIBINO: Journal of Electron Microscopy,Supplement. 35. 255-258 (1986)

M.HIBINO：电子显微镜杂志，增刊。

S.SUGIYAMA: Journal of Electron Microscopy,Supplement. 35. 429-430 (1986)

S.SUGIYAMA：电子显微镜杂志，增刊。

日比野 倫夫: 電子顕微鏡. 21. 99-104 (1986)

日比野道雄：电子显微镜。21. 99-104 (1986)

Michio Hibino: "Reduction of statistical Noise of Electrons in STEM" Proceedings og the 4th Asia-Pacific Conference on Electron Microscopy. (1988)

Michio Hibino：“减少 STEM 中电子统计噪声”第四届亚太电子显微镜会议论文集。

日比野 倫夫: Journal of Electron Microscopy, Supplement. 35. 225-258 (1986)

日比野道雄：《电子显微镜杂志》，增刊 35. 225-258 (1986)。