Evaluation of probe size in STEM imaging at 30 and 60 kV

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• 作者：Takeo Sasaki^a ; ^d ; ^{tasasaki@jeol.co.jp} ; Hidetaka Sawada^a ; ^d ; Eiji Okunishi^a ; Fumio Hosokawa^a ; Toshikatsu Kaneyama^a ; ^d ; Yukihito Kondo^a ; Koji Kimoto^b ; ^d ; Kazu Suenaga^c ; ^d
• 关键词：Low-voltage electron microscopy ; Aberration-corrected scanning transmission electron microscopy ; Annular dark field imaging ; Multislice simulation ; Chromatic aberration ; Probe size
• 刊名：Micron
• 出版年：2012
• 期刊代码：37_09684328
• 类别：ph
• 出版时间：March, 2012
• 卷：43
• 期：4
• 页码：551-556
• 文件大小：1203 K

摘要

In order to estimate the probe size on the specimen surface in a newly developed low-acceleration-voltage (30-60 kV) atomic-resolution scanning transmission electron microscopy (STEM), we compared the intensity profiles of experimentally obtained annular dark field (ADF)-STEM images of Si-Si dumbbells and those of images simulated using a multislice method which takes chromatic aberration into account. However, the simulated ADF images at 30 and 60 kV were found not to match the corresponding experimental images. Subsequently, the simulated images were convolved with probe functions (normal distributions) of different widths until a good match was obtained between the images. This allowed the probe shapes corresponding to the experimental conditions to be determined. ADF-STEM images with chromatic aberration could then be calculated by an incoherent superposition of these probe functions over a range of energies. The full widths at half maximum for the probe functions were estimated to be 99.2 pm for 30 kV and 92.8 pm for 60 kV. The D59 diameters were calculated to be 154.0 pm for 30 kV and 127.8 pm for 60 kV. This means that the 30-kV probe has a larger tail than the 60-kV probe.