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Fundamental study on spherical aberration correction of the objective lens of an electron microscope using a foil lens

箔透镜电子显微镜物镜球差校正的基础研究

基本信息

批准号：
05650051
负责人：
HANAI Takaaki
金额：
$ 1.54万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
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 with the optimum characteristics in spherical aberration correction, spherical aberration coefficients were calculated for variable geometries of the foil lens. It was found that the correction is achieved by locating the foil lens close to the lower polepiece and making the diameter of the electrode aperture as small as 0.3mm. A side-entry type foil lens was developed based on the calculation. A device for heating the foil was incorporated to avoid contamination build-up on the foil due to intense transmitted electron beam focused on it.2. Measurements of spherical aberration of the corrected objective lens : The spherical aberration was measured from the deviation of dark-field TEM images of MgO particles from the corresponding bright-field image. The spherical aberration decreased as the foil lens voltage was increased up to 600 V and became negative at … More 800 V.A small spherical aberration caused around the optimum foil lens voltage, however, could not be measured because the dark-field image of MgO quickly fades out at high magnifications due to radiation damage. Fine gold particles which is not sensitive to electron irradiation, therefore, were observed around the optimum voltage at sufficiently high magnifications, which also enabled us to reduce the error in measured spherical aberrations caused by defocus because the defocus effect was detected from the phase contrast of the carbon supporting film. At the foil lens voltage of 615 V the deviation of the dark-field image disappeared, which proved the correction of spherical aberration.3. Construction of an optical Fourier transform system for measurements of spherical aberration coefficients. : In order to investigate the performance of the foil lens not only at single diffraction angle but over a wide range of the aperture angle, an optical Fourier transform system, which consists of a diffractmeter and a computer for data treatments, was constructed. The spherical aberration coefficients were accurately measured from spatial frequencies providing maxima and minima in the power spectrum of TEM images of thin carbon films. Less

1.透射式电子显微镜物镜用箔片透镜的研制：为了设计出具有最佳球差校正特性的箔片透镜，计算了不同几何形状的箔片透镜的球差系数。结果表明，通过将箔片透镜放置在靠近下极镜的位置，并将电极孔径缩小到0.3 mm，就可以实现校正。在此基础上研制了侧入口式箔片透镜。加入了一个加热铝箔的装置，以避免由于聚焦在其上的强烈透射式电子束而在铝箔上积聚污染。校正物镜球差的测量：球差的测量是根据氧化镁颗粒的暗场透射电子显微镜图像与相应的亮场图像的偏差来测量的。当箔透镜电压增加到600V时，球差减小，在…时球差变为负然而，在最佳箔片透镜电压附近产生的小球差不能测量到800V以上，因为由于辐射损伤，在高倍率下，氧化镁的暗场图像很快就消失了。因此，在足够高的放大率下，在最佳电压附近观察到对电子照射不敏感的细小的金粒子，这也使我们能够减少由于离焦引起的球差测量误差，因为离焦效应是从碳支撑膜的相位对比度中检测到的。当箔透镜电压为615V时，暗视场图像的偏差消失，证明了球差的校正。光学傅里叶变换球差系数测量系统的构建。为了研究箔片透镜在单一衍射角和较宽口径范围内的性能，建立了由衍射仪和数据处理计算机组成的光学傅里叶变换系统。球差系数的准确测量提供了空间频率的最大值和极小值的功率谱的薄膜碳膜。较少